Gibberellic acid (GA)-mediated cell expansion initiates the seed-to-seedling transition in plants and is repressed by DELLA proteins .

Using digital single-cell analysis , we identified a cellular subdomain within the midhypocotyl , whose expansion drives the final step of this developmental transition under optimal conditions .

Using network inference , the transcription factor ATHB5 was identified as a genetic factor whose localized expression promotes GA-mediated expansion specifically within these cells .

Both this protein and its putative growth-promoting target EXPANSIN3 are repressed by DELLA , and coregulated at single-cell resolution during seed germination .

The cellular domains of hormone sensitivity were explored within the Arabidopsis ( Arabidopsis thaliana ) embryo by putting seeds under GA-limiting conditions and quantifying cellular growth responses .

The middle and upper hypocotyl have a greater requirement for GA to promote cell expansion than the lower embryo axis .

Under these conditions , germination was still completed following enhanced growth within the radicle and lower axis .

Under GA-limiting conditions , the athb5 mutant did not show a phenotype at the level of seed germination , but it did at a cellular level with reduced cell expansion in the hypocotyl relative to the wild type .

These data reveal that the spatiotemporal cell expansion events driving this transition are not determinate , and the conditional use of GA-ATHB5-mediated hypocotyl growth under optimal conditions may be used to optionally support rapid seedling growth .

This study demonstrates that multiple genetic and spatiotemporal cell expansion mechanisms underlie the seed to seedling transition in Arabidopsis .


Bensulfuron-methyl ( BSM ) is widely used in paddy soil for weed control .

BSM residue in the soil has been known to inhibit the growth of sensitive crop plants .

However , it is unknown whether BSM residue can affect the agrosystem in general .

In this study , we have found significant effects of BSM on the infestation of Bemisia tabaci , Myzus persicae , and Tobacco mosaic virus ( TMV ) in Nicotiana tabacum .

The soil was treated with BSM before the pest inoculation .

The herbicide-treated tobaccos showed resistance to B. tabaci , but this resistance could not be detected until 15-day post-infestation when smaller number of adults B. tabaci appeared .

In M. persicae assay , the longevity of all development stages of insects , and the fecundity of insects were not significantly affected when feeding on BSM-treated plants .

In TMV assay , the BSM treatment also reduced virus-induced lesions in early infection time .

However , the titer of TMV in BSM treated plants increased greatly over time and was over 40-fold higher than the mock-infected control plants after 20 days .

Further studies showed that BSM treatment increased both jasmonic acid ( JA ) and salicylic acid ( SA ) levels in tobacco , as well as the expression of target genes in the JA and SA signaling pathways , such as NtWIPK , NtPR1a , and NtPAL .

NtPR1a and NtPAL were initially suppressed after virus-inoculation , while NtRDR1 and NtRDR6 , which play a key role in fighting virus infection , only showed up- or were down-regulated 20 days post virus-inoculation .

Taken together , our results suggested that BSM residue in the soil may affect the metabolism of important phytohormones such as JA and SA in sensitive plants and consequently affect the plant immune response against infections such as whitefly , aphids , and viruses .


Germination of Amaranthus caudatus is inhibited by light , far-red being the most effective part of the spectrum .

At temperatures of 25 ° and below there is a low final germination percentage under continuous far-red whereas above 25 ° there is only a delaying effect .

In the presence of a saturating concentration of gibberellic acid ( GA3 ) at 25 ° seeds germinate under continuous far-red although they are delayed .

At 25 ° seeds exposed to 48 hr far-red fail to germinate when transferred to darkness .

This induced dormancy can be broken by a single short exposure to red light given at any time after the far-red illumination .

This effect of short red can be reversed by a subsequent short period of far-red indicating that the seeds are phytochrome controlled .

Although most seeds have escaped from the reversing effect of short far-red after an intervening dark period of 5 hours , germination is greatly reduced by continuous far-red at this time .

Results of exposing seeds to varying periods of far-red before and after dark imbibition are interpreted in terms of a continual production of phytochrome in its active P fr form and a requirement for P fr action over a long period of time .

Effects of intermittent and continuous low intensity far-red on the inhibition of germination provides further evidence for a low energy photoreaction involving phytochrome .

Effects on Germination Index of continuous illumination with various light sources maintaining different P fr /P total ratios have been investigated .

The results suggest that the proportion of phytochrome in the P fr form is the most important factor in the regulation of germination .

A scheme for the phytochrome control of germination in Amaranthus caudatus is presented and possible explanations for the dependence on P fr /P total ratio are discussed .


Acer pseudoplatanus seeds are characterized by a deep physiological embryo dormancy that requires a few weeks of cold stratification in order to promote germination .

Understanding the function of proteins and their related metabolic pathways , in conjunction with the plant hormones implicated in the breaking of seed dormancy , would expand our knowledge pertaining to this process .

In this study , a proteomic approach was used to analyze the changes occurring in seeds in response to cold stratification , which leads to dormancy release .

In addition , the involvement of abscisic ( ABA ) and gibberellic acids ( GA ) was also examined .

Fifty-three proteins showing significant changes were identified by mass spectrometry .

An effect of ABA on protein variation was observed at the beginning of stratification , while the influence of GA on protein abundance was observed during the middle phase of stratification .

The majority of proteins associated with dormancy breaking in the presence of only water , and also ABA or GA , were classified as being involved in metabolism and genetic information processing .

For metabolic-related proteins , the effect of ABA on protein abundance was stimulatory for half of the proteins and inhibitory for half of the proteins .

On the other hand , the effect on genetic information processing related proteins was stimulatory .

GA was found to upregulate both metabolic-related and genetic information processing-related proteins .

While seed dormancy breaking depends on proteins involved in a variety of processes , proteins associated with methionine metabolism ( adenosine kinase , methionine synthase ) and glycine-rich RNA binding proteins appear to be of particular importance .


The pentose phosphate pathway ( PPP ) plays an important role in plant growth and development , and plant responses to biotic and abiotic stresses .

Yet , whether the PPP regulates plant defenses against herbivorous insects remains unclear .

In this study , we cloned a rice cytosolic 6-phosphogluconate dehydrogenase gene , Os6PGDH1 , which encodes the key enzyme catalyzing the third step in the reaction involving the oxidative phase of the PPP , and explored its role in rice defenses induced by brown planthopper ( BPH ) Nilaparvata lugens .

Levels of Os6PGDH1 transcripts were detected in all five examined tissues , with the highest in outer leaf sheaths and lowest in inner leaf sheaths .

Os6PGDH1 expression was strongly induced by mechanical wounding , infestation of gravid BPH females , and jasmonic acid ( JA ) treatment .

Overexpressing Os6PGDH1 ( oe6PGDH ) decreased the height of rice plants and the mass of the aboveground part of plants , but slightly increased the length of plant roots .

In addition , the overexpression of Os6PGDH1 enhanced levels of BPH-induced JA , jasmonoyl-isoleucine ( JA-Ile ) , and H(2)O(2 ) , but decreased BPH-induced levels of ethylene .

Bioassays revealed that gravid BPH females preferred to feed and lay eggs on wild-type ( WT ) plants over oe6PGDH plants ; moreover , the hatching rate of BPH eggs raised on oe6PGDH plants and the fecundity of BPH females fed on these were significantly lower than the eggs and the females raised and fed on WT plants .

Taken together , these results indicate that Os6PGDH1 plays a pivotal role not only in rice growth but also in the resistance of rice to BPH by modulating JA , ethylene , and H(2)O(2 ) pathways .


Isolated thylakoids from halophytic Eutrema salsugineum ( Thellungiella salsuginea ) produces more H2O2 in comparison to glycophytic Arabidopsis thaliana .

The first objective of this study was to verify whether this feature is relevant also to the intact chloroplasts and leaves .

Enhanced H2O2 levels in chloroplasts and leaves of E. salsugineum were positively verified with several methods ( electron microscopy , staining with Amplex Red and with diaminobenzidine ) .

This effect was associated with a decreased ratio of [ Formula : see text]/H2O2 in E. salsugineum in comparison to A. thaliana as detected by electron paramagnetic resonance method .

As a next step , we tested how this specific ROS signature of halophytic species affects the antioxidant status and down-stream components of ROS signaling .

Comparison of enzymatic antioxidants revealed a decreased activity of ascorbate peroxidase ( APX ) , enhanced activity of glutathione peroxidase , and the presence of thylakoid-bound forms of iron superoxide dismutase ( FeSOD ) and APX in E. salsugineum .

These cues were , however , independent from application of salt stress .

The typical H2O2-dependent cellular responses , namely the levels of glucosinolates and stress-related hormones were determined .

The total glucosinolate content in E. salsugineum water-treated leaves was higher than in A. thaliana and increased after salinity treatment .

Treatment with salinity up-regulated all of tested stress hormones , their precursors and catabolites [ abscisic acid ( ABA ) , dihydrophaseic acid , phaseic acid , 1-aminocyclopropane-1-carboxylic acid , salicylic acid , jasmonic acid , cis-(+)-12-oxo-phytodienoic acid and jasmonoyl-L-isoleucine ] in A. thaliana , whereas in E. salsugineum only a stimulation in ethylene synthesis and ABA catabolism was noted .

Obtained results suggest that constitutively enhanced H2O2 generation in chloroplasts of E. salsugineum might be a crucial component of stress-prepardeness of this halophytic species .

It shapes a very efficient antioxidant protection ( in which glucosinolates might play a specific role ) and a fine tuning of hormonal signaling to suppress the cell death program directed by jasmonate pathway .


Grain quality is an important agricultural trait that is mainly determined by grain size and composition .

Here , we characterize the role of the rice transcription factor ( TF ) SALT-RESPONSIVE ERF1 ( SERF1 ) during grain development .

Through genome-wide expression profiling and chromatin immunoprecipitation , we found that SERF1 directly regulates RICE PROLAMIN-BOX BINDING FACTOR ( RPBF ) , a TF that functions as a positive regulator of grain filling .

Loss of SERF1 enhances RPBF expression resulting in larger grains with increased starch content , while SERF1 overexpression represses RPBF resulting in smaller grains .

Consistently , during grain filling , starch biosynthesis genes such as GRANULE-BOUND STARCH SYNTHASEI ( GBSSI ) , STARCH SYNTHASEI ( SSI ) , SSIIIa , and ADP-GLUCOSE PYROPHOSPHORYLASE LARGE SUBUNIT2 ( AGPL2 ) are up-regulated in SERF1 knockout grains .

Moreover , SERF1 is a direct upstream regulator of GBSSI .

In addition , SERF1 negatively regulates germination by controlling RPBF expression , which mediates the gibberellic acid (GA)-induced expression of RICE AMYLASE1A ( RAmy1A ) .

Loss of SERF1 results in more rapid seedling establishment , while SERF1 overexpression has the opposite effect .

Our study reveals that SERF1 represents a negative regulator of grain filling and seedling establishment by timing the expression of RPBF .


cDNA clones encoding three additional serine carboxypeptidases ( Ser-CPs ) have been isolated from a gibberellic acid-induced barley aleurone cDNA library .

The three deduced Ser-CPs belong to the two-chain subfamily of Ser-CPs ; they are synthesized as precursors with a putative signal peptide , propeptide , and linker peptide between the A and B chains .

Their identification provides the proof for the existence of more than three Ser-CPs in cereal grains , and , based on their sequences , they may exhibit new substrate specificities .

The expression of these and of the three previously isolated Ser-CPs from barley grains ( CP-MI , CP-MII , and CP-MIII ) has been investigated by Northern and Western analysis and RNA PCR .

CP-MII is the only Ser-CP to be expressed and accumulate in the developing grain and is stored in its active form in the mature grain .

All six Ser-CPs are expressed de novo in the germinating grain , in the scutellum , and/or in the aleurone .

Furthermore , at least CP-MI , CP-MII , and CP-MIII are secreted into the endosperm .

In addition , all Ser-CPs ( except CP-MI ) are also expressed in the roots and shoots of the growing seedling .

This enzyme family thus appears to be ubiquitous in the barley plant , which suggests that Ser-CPs play additional roles besides their participation in the mobilization of storage proteins .


Jasmonic acid ( JA ) is a fatty acid-derived signaling molecule that regulates a broad range of plant defense responses against herbivores and some microbial pathogens .

Molecular genetic studies have established that JA also performs a critical role in several aspects of plant development .

Here , we describe the characterization of the Arabidopsis mutant jasmonic acid-hypersensitive1 - 1 ( jah1 - 1 ) , which is defective in several aspects of JA responses .

Although the mutant exhibits increased sensitivity to JA in root growth inhibition , it shows decreased expression of JA-inducible defense genes and reduced resistance to the necrotrophic fungus Botrytis cinerea .

Gene cloning studies indicate that these defects are caused by a mutation in the cytochrome P450 protein CYP82C2 .

We provide evidence showing that the compromised resistance of the jah1 - 1 mutant to B . cinerea is accompanied by decreased expression of JA-induced defense genes and reduced accumulation of JA-induced indole glucosinolates ( IGs ) .

Conversely , the enhanced resistance to B. cinerea in CYP82C2-overexpressing plants is accompanied by increased expression of JA-induced defense genes and elevated levels of JA-induced IGs .

We demonstrate that CYP82C2 affects JA-induced accumulation of the IG biosynthetic precursor tryptophan ( Trp ) , but not the JA-induced IAA or pathogen-induced camalexin .

Together , our results support a hypothesis that CYP82C2 may act in the metabolism of Trp-derived secondary metabolites under conditions in which JA levels are elevated .

The jah1 - 1 mutant should thus be important in future studies toward understanding the mechanisms underlying the complexity of JA-mediated differential responses , which are important for plants to adapt their growth to the ever-changing environments .


Staphylococcus aureus is a ubiquitous gram-positive bacterium that can cause superficial to serious systemic infections in animals and humans .

Here we report the development of a plant infection model to study the pathogenesis of this bacterium .

Three global regulatory mutants , RN6911 ( agr- ) , ALC 488 ( sarA- ) ALC 842 ( sarA-/agr- ) and an alpha-toxin mutant defective in biofilm formation ( DU1090 ) which are attenuated in animal pathogenesis , were also attenuated in their ability to infect plants , suggesting that these regulators that mediate synthesis of virulence factors essential for animal pathogenesis are also required for plant pathogenesis .

Further , using Arabidopsis plants altered in defense responses such as the transgenic lines NahG [ defective in salicylic acid ( SA ) accumulation ] , and 35S-LOX2- ( defective in jasmonic acid production and hyper-accumulator of SA ) , and mutants ics1 ( depleted in SA accumulation ) , and npr1 - 1 ( non-expressor of pathogenesis-related protein ) we show that resistance of Arabidopsis to typical plant pathogens and the animal pathogen S. aureus is conserved and is mediated by SA .

The data presented here suggest that Arabidopsis thaliana resistance to S. aureus is mediated either by a direct effect of SA on the pathogen , specifically one that affects the attachment/aggregate formation on the root surface and reduces the pathogen 's virulence , or by SA-dependent , NPR1-independent host responses .


BACKGROUND : Wheat stem rust , caused by Puccinia graminis f. sp. tritici , is a major wheat disease which is mainly controlled through the release of resistant cultivars containing one or several resistance genes .

Considerable effort has been put into the discovery of new resistance genes , but knowledge of their mechanisms of action is often lacking .

In this study , the mechanism of resistance conferred by a recently discovered stem rust resistance locus on wheat chromosome 7AL was investigated through microscopic observations and RNA-sequencing , using the susceptible line Columbus and the independent , backcrossed , resistant lines Columbus-NS765 and Columbus-NS766 .

RESULTS : Microscopic observations of infected leaves revealed that the resistance conferred by the 7AL resistance locus was initiated 2 days post-inoculation , upon the fungus entry into the plant through the stoma .

Resistance was manifested by death of guard and epidermal cells adjacent to an infection site .

Occasionally , similar observations were made in the susceptible line , suggesting that the resistance response was the same in all genotypes , but enhanced in the resistant lines .

Transcriptomic analysis , combined with assignment of genes to wheat chromosomes , revealed a disproportionately high number of differentially expressed genes were located on chromosomes 7AL and 6A .

A number of genes annotated as cysteine-rich receptor-like kinases were located on chromosome 7AL .

Closer investigation indicated that the encoded proteins were in fact putative receptor-like cytoplasmic kinases .

One of the putative RLCK genes contained a SNP marker previously shown to co-segregate with the 7AL resistance locus .

The results also indicated the presence of a large introgression on chromosome 6A in both resistant lines , but whether it has any role in the resistance response is unclear .

CONCLUSIONS : This study represents the first investigation on the resistance mechanism conferred by the wheat 7AL stem rust resistance locus .

The resistance response was associated with pre-haustorial cell death , and the transcriptome analysis suggested putative receptor-like cytoplasmic kinases as candidate resistance genes for further investigation .


Fungal elicitor prepared from the cell walls of Aspergillum niger induces multiple responses of Hypericum perforatum cells , including nitric oxide ( NO ) generation , jasmonic acid ( JA ) biosynthesis , and hypericin production .

Pretreatment of the cells with cPITO and JA biosynthesis inhibitors suppresses not only the elicitor-induced NO generation and JA accumulation but also the elicitor-induced hypericin production , which suggests that both NO and JA are involved in elicitor-induced hypericin biosynthesis .

External application of NO via its donor sodium nitroprusside induces hypericin production in the absence of fungal elicitor .

Sodium-nitroprusside-induced hypericin production is blocked by JA biosynthesis inhibitors , showing that JA biosynthesis is essential for NO-induced hypericin production .

The results demonstrate a causal relationship between elicitor-induced NO generation , JA biosynthesis , and hypericin production in H. perforatum cells and indicate a sequence of signaling events from NO to hypericin production , within which NO mediates the elicitor-induced hypericin biosynthesis at least partially via a JA-dependent signaling pathway .


The genes of the gibberellin ( GA ) biosynthesis pathway in Gibberella fujikuroi are organized in a gene cluster consisting of at least seven genes .

Here we report the cloning and characterization of smt , a gene encoding a membrane transporter of the major facilitator super-family 1 , which is located next to the GA gene cluster .

Since pathway-specific transporters occur frequently in prokaryotic and fungal antibiotic and toxin clusters , smt was thought to be involved in GA secretion .

The gene is expressed in mycelium grown under GA-production conditions , but not when the GA biosynthesis is repressed by high amounts of ammonium .

To investigate the function of SMT , gene replacement experiments were performed .

The smt-mutants did not show any reduction in the GA yield ; and gibberellic acid or its precursors did not influence the gene expression .

However , sugar alcohols , such as myo-inositol , sorbitol and mannitol , induced the expression of smt .

The results demonstrate that the smt gene does not play an essential role in biosynthesis and secretion of GAs in G. fujikuroi , despite the location adjacent to the GA gene cluster .


Gibberellic acid ( GA3 ) , a plant growth regulator , is widely used in agriculture in many countries to accelerate the growth of fruits and vegetables .

We designed histological , immunohistochemical , and biochemical studies to evaluate the deleterious effects of GA3 on the livers of adult pregnant rats and their offspring and to assess the possible ameliorative effect of Nigella sativa Linn . ( NsL.oil ) against these effects .

Twenty-four pregnant albino rats were utilized , randomly divided into four groups : The first group was used as a negative control group , while the second group ( positive control group ) was provided NsL.oil at a dose of 100 mg/kg of bodyweight .

Animals in the third group ( GA3 group ) were provided 200 ppm of GA3 dissolved in distilled water from the 7th day of pregnancy until 1 day after delivery .

Animals in the last group ( GA3 + NsL.oil group ) were provided GA3 and NsL-oil at the same doses as mentioned above .

One day after delivery , each group of lactating mothers and their pups were sacrificed .

Liver specimens were subjected to histopathological , immunohistochemical , and biochemical examinations .

The livers of rats from the GA3 group showed various degenerative changes , being predominant in the livers of the mothers compared with the offspring .

The pathological changes in the livers of the offspring suggested transplacental passage of GA3 .

The results reveal that GA3 ingestion induced a significant increase in alanine aminotransferase ( ALT ) and aspartate transaminase ( AST ) activities in the serum of both groups of mothers and their pups , with a significant increment in lipid peroxidation as evidenced by enhanced malondialdehyde ( MDA ) levels with significant decrements in superoxide dismutase ( SOD ) , catalase ( CAT ) , and glutathione peroxidase ( GPx ) enzymatic activities in comparison with control groups in the liver of mothers and their offspring .

Histopathological examination showed hydropic degeneration and inflammatory cellular infiltration .

Additionally , there was fibrosis around the portal area .

Moreover , immunolocalization revealed downregulation of the expression of the antiapoptotic marker Bcl-2 in hepatocytes and upregulation of the expression of the apoptotic marker Bax in the treated group .

Concomitant use of NsL.oil along with GA3 exerted a considerable reversing effect on histopathological and biochemical changes in the livers of mother groups and their pups .

The results of the present study highlight the consequences of exposure to GA3 during pregnancy on hepatic tissue in both mothers and their offspring .

Furthermore , the study suggests use of NsL.oil as a potential protective strategy against GA3-induced liver toxicity .


Calmodulin ( CaM ) plays an important role in sensing and transducing changes in cellular Ca2 + concentration in response to several biotic and abiotic stresses .

Although CaM is implicated in plant-pathogen interactions , its molecular targets and their role in defense signaling pathway(s ) are poorly understood .

To elucidate the signaling pathways that link CaM to defense responses , we screened a cDNA library constructed from bean leaves undergoing a hypersensitive response ( HR ) with radiolabeled CaM isoforms .

A total of 26 putative CBPs were identified .

Sequencing of the cDNAs revealed that they represent 8 different genes .

They are homologues of previously identified CaM-binding proteins ( CBPs ) in other systems .

However , some CBPs are novel members of known CBP families .

The proteins encoded by these clones bound CaM in a Ca2 + -dependent manner .

To determine if these CBPs are involved in plant defense responses , we analyzed their expression in bean leaves inoculated with compatible , incompatible and nonpathogenic bacterial strains .

Expression of three CBPs including an isoform of cyclic nucleotide-gated channels ( PvCNGC-A ) and two hypothetical proteins ( PvCBP60-C and PvCBP60-D ) was induced whereas the expression of two other isoforms of CNGCs ( PvCNGC-B and PvCNGC-C ) was repressed in response to incompatible pathogens .

The expression of the rest , a small auxin up RNA ( PvSAUR1 ) and two hypothetical proteins ( PvCBP60-A and PvCBP60-B ) , was not changed .

The expression of most of the pathogen-regulated genes was also affected by salicylic acid , jasmonic acid , hydrogen peroxide and a fungal elicitor , which are known to induce defense responses .

Our results strongly suggest that at least five bean CBPs are involved in plant defense responses .


KEY MESSAGE : Arabidopsis gulliver3 - D/dwarf4 - D displays growth-promoting phenotypes due to activation tagging of a key brassinosteroid biosynthetic gene DWARF4 .

In gul3-D/dwf4-D , the Jasmonate and Salicylate signaling pathways were relatively activated and suppressed , respectively .

Energy allocation between growth and defense is elegantly balanced to achieve optimal development in plants .

Brassinosteroids ( BRs ) , steroidal hormones essential for plant growth , are regulated by other plant hormones , including auxin and jasmonates ( JA ) ; auxin stimulates the expression of a key brassinosteroid ( BR ) biosynthetic gene , DWARF4 ( DWF4 ) , whereas JA represses it .

To better understand the interaction mechanisms between growth and defense , we isolated a fast-growing mutant , gulliver3-D ( gul3-D ) , that resulted from the activation tagging of DWF4 , and examined the response of this mutant to defense signals , including JA , Pseudomonas syringae pv . tomato ( Pst DC3000 ) infection , and wounding .

The degree of root growth inhibition following MeJA treatment was significantly decreased in gul3 - 1D/dwf4 - 5D relative to the wild type , suggesting that JA signaling is partially desensitized in gul3 - 1D .

Quantitative RT-PCR analysis of the genes involved in JA and salicylic acid ( SA ) responses , including MYC2 , PDF1.2 , CORI3 , PR1 , and PR2 , revealed that JA signaling was preferentially activated in gul3 - 1D , whereas SA signaling was suppressed .

As a result , gul3 - 1D was more susceptible to a biotrophic pathogen , Pst DC3000 .

Based on our results , we propose a model in which BR and JA cooperate to balance energy allocation between growth and defense responses .

In ambient conditions , BRs promote plant growth ; however , when stresses trigger JA signaling , JA compromises BR signaling by downregulating DWF4 expression .


NaCl alleviates Cd toxicity in Sesvium portulacastrum by maintaining plant water status and redox balance , protecting chloroplasts structure and inducing some potential Cd ( 2 + ) chelators as GSH and proline .

It has been demonstrated that NaCl alleviates Cd-induced growth inhibition in the halophyte Sesuvium portulacastrum .

However , the processes that mediate this effect are still unclear .

In this work we combined physiological , biochemical and ultrastructural studies to highlight the effects of salt on the redox balance and photosynthesis in Cd-stressed plants .

Seedlings were exposed to different Cd concentrations ( 0 , 25 and 50 µM Cd ) combined with low ( 0.09 mM ) ( LS ) , or high ( 200 mM ) NaCl ( HS ) in hydroponic culture .

Plant-water relations , photosynthesis rate , leaf gas exchange , chlorophyll fluorescence , chloroplast ultrastructure , and proline and glutathione concentrations were analyzed after 1 month of treatment .

In addition , the endogenous levels of stress-related hormones were determined in plants subjected to 25 µM Cd combined with both NaCl concentrations .

In plants with low salt supply ( LS ) , Cd reduced growth , induced plant dehydration , disrupted chloroplast structure and functioning , decreased net CO2 assimilation rate ( A ) and transpiration rate ( E ) , inhibited the maximum potential quantum efficiency ( Fv/Fm ) and the quantum yield efficiency ( Φ PSII ) of PSII , and enhanced the non-photochemical quenching ( NPQ ) .

The addition of 200 mM NaCl ( HS ) to the Cd-containing medium culture significantly mitigated Cd phytotoxicity .

Hence , even at similar internal Cd concentrations , HS-Cd plants were less affected by Cd than LS-Cd ones .

Hence , 200 mM NaCl significantly alleviates Cd-induced toxicity symptoms , growth inhibition , and photosynthesis disturbances .

The cell ultrastructure was better preserved in HS-Cd plants but affected in LS-Cd plants .

The HS-Cd plants showed also higher concentrations of reduced glutathione ( GSH ) , proline and jasmonic acid ( JA ) than the LS-Cd plants .

However , under LS-Cd conditions , plants maintained higher concentration of salicylic acid ( SA ) and abscisic acid ( ABA ) than the HS-Cd ones .

We conclude that in S. portulacastrum alleviation of Cd toxicity by NaCl is related to the modification of GSH and proline contents as well as stress hormone levels thus protecting redox balance and photosynthesis .


OBJECTIVES : This study investigated , whether the growth rate of Lemna gibba L. ( duckweed ) can be influenced by the application of homeopathic potencies of gibberellic acid , kinetin , argentum nitricum , and lemna minor .

METHODS : Duckweed was grown in either potencies ( 14x-30x , decimal steps ) or water controls ( unsuccussed and succussed ) over seven days .

Frond ( leaf-like structure ) growth was measured using a non-destructive image analysis system .

Growth rates were calculated for three time intervals ( 0 - 7 , 0 - 3 , 3 - 7 days ) .

Five to six independent , randomized and blinded experiments were analysed for each of the four tested substances .

Water control experiments were performed repeatedly to test the reliability of the experimental set-up ( systematic negative controls ) .

RESULTS : The systematic negative control experiments did not yield any significant effects .

Hence , false positive results could be excluded .

The test system had a low coefficient of variation ( 1.5 % ) .

Out of the four tested substances gibberellic acid had the most pronounced effect ( p=0.0002 , F-test ) on the main outcome parameter frond growth rate ( r(area ) day 0 - 7 ) .

Potency levels 15x , 17x , 18x , 23x and 24x reduced growth rate of Lemna gibba ( p<0.05 against the pooled water control , LSD test ) .

CONCLUSIONS : Lemna gibba may be considered as a suitable test organism for further studies on the efficacy of homeopathic potencies .

Evidence accumulates , that adjacent potency levels may strongly differ in their biological activity .

Potential consequences for therapeutical application might be worth investigating .


In plants , ethylene and jasmonate control the defense responses to multiple stressors , including insect predation .

Among the defense proteins known to be regulated by ethylene is maize insect resistance 1-cysteine protease ( Mir1-CP ) .

This protein is constitutively expressed in the insect-resistant maize ( Zea mays ) genotype Mp708 ; however , its abundance significantly increases during fall armyworm ( Spodoptera frugiperda ) herbivory .

Within 1 h of herbivory by fall armyworm , Mir1-CP accumulates at the feeding site and continues to increase in abundance until 24 h without any increase in its transcript ( mir1 ) levels .

To resolve this discrepancy and elucidate the role of ethylene and jasmonate in the signaling of Mir1-CP expression , the effects of phytohormone biosynthesis and perception inhibitors on Mir1-CP expression were tested .

Immunoblot analysis of Mir1-CP accumulation and quantitative reverse-transcriptase polymerase chain reaction examination of mir1 levels in these treated plants demonstrate that Mir1-CP accumulation is regulated by both transcript abundance and protein expression levels .

The results also suggest that jasmonate functions upstream of ethylene in the Mir1-CP expression pathway , allowing for both low-level constitutive expression and a two-stage defensive response , an immediate response involving Mir1-CP accumulation and a delayed response inducing mir1 transcript expression .


A wheat ethylene receptor homologue ( W-er1 ) was isolated from a wheat stem cDNA library using the Arabidopsis ETR1 cDNA as a probe .

The predicted amino acid sequence of W-er1 is over 70 % similar to ERS1 from Arabidopsis and exhibits homology to bacterial two-component response regulators within the histidine kinase domain .

Northern hybridization demonstrated that W-er1 was expressed in stem , leaf and root tissues .

Treatments known to induce senescence of detached leaves including jasmonate , abscisic acid and wounding , increased the accumulation of W-er1 mRNA , while benzyladenine treatment did not .

These data suggest that W-er1 may play a role in the process of leaf senescence .


Jasmonates ( JAs ) regulate Arabidopsis thaliana wound and defence responses , pollen development , and stress-related growth inhibition .

Significantly , each of these responses requires COI1 , an F-box protein .

Other F-box proteins interact with SKP1 and cullin proteins to form SCF complexes that selectively recruit regulatory proteins targeted for ubiquitination .

To determine whether COI1 also functions in an SCF complex , we have characterized Arabidopsis proteins that bind to COI1 .

An Arabidopsis cDNA expression library was screened in yeast for clones that produce proteins which can bind to COI1 .

We recovered two SKP1 homologues and a histone deacetylase .

The Arabidopsis F-box protein TIR1 interacted with SKP1 proteins , but not with the histone deacetylase .

Mutant COI1 proteins revealed that the F-box is required for interaction with SKP1s , but that sequences in leucine-rich repeat domains are required for interaction with the histone deacetylase .

Epitope-tagged COI1 was introduced into Arabidopsis plants and cell cultures .

Co-immunoprecipitation experiments confirmed the interaction in planta of COI1 with SKP1-like proteins and histone deacetylase , and also indicated that COI1 interacted with cullin .

These results suggest that COI1 forms an SCFCOI1 complex in vivo .

COI1 is therefore expected to form a functional E3-type ubiquitin ligase in plants and to regulate expression of jasmonate responsive genes , possibly by targeted ubiquitination of a histone deacetylase .


Nitrogen dioxide ( NO(2 ) ) forms in plants under stress conditions , but little is known about its physiological functions .

Here , we explored the physiological functions of NO(2 ) in plant cells using short-term fumigation of Arabidopsis ( Arabidopsis thaliana ) for 1 h with 10 µL L(-1 ) NO(2 . ) Although leaf symptoms were absent , the expression of genes related to pathogen resistance was induced .

Fumigated plants developed basal disease resistance , or pattern-triggered immunity , against the necrotrophic fungus Botrytis cinerea and the hemibiotrophic bacterium Pseudomonas syringae Functional salicylic acid and jasmonic acid ( JA ) signaling pathways were both required for the full expression of NO(2)-induced resistance against B. cinerea An early peak of salicylic acid accumulation immediately after NO(2 ) exposure was followed by a transient accumulation of oxophytodienoic acid .

The simultaneous NO(2)-induced expression of genes involved in jasmonate biosynthesis and jasmonate catabolism resulted in the complete suppression of JA and JA-isoleucine ( JA-Ile ) accumulation , which was accompanied by a rise in the levels of their catabolic intermediates 12-OH-JA , 12-OH-JA-Ile , and 12-COOH-JA-Ile .

NO(2)-treated plants emitted the volatile monoterpene α-pinene and the sesquiterpene longifolene ( syn . junipene ) , which could function in signaling or direct defense against pathogens .

NO(2)-triggered B. cinerea resistance was dependent on enhanced early callose deposition and CYTOCHROME P450 79B2 ( CYP79B2 ) , CYP79B3 , and PHYTOALEXIN DEFICIENT3 gene functions but independent of camalexin , CYP81F2 , and 4-OH-indol-3-ylmethylglucosinolate derivatives .

In sum , exogenous NO(2 ) triggers basal pathogen resistance , pointing to a possible role for endogenous NO(2 ) in defense signaling .

Additionally , this study revealed the involvement of jasmonate catabolism and volatiles in pathogen immunity .


Jasmonic acid ( JA ) and nitric oxide ( NO ) are well-characterized signaling molecules in plant defense responses .

However , their roles in plant defense against root-knot nematode ( RKN , Meloidogyne incognita ) infection are largely unknown .

In this study , we found that the transcript levels of the JA- and NO-related biosynthetic and signaling component genes were induced after RKN infection .

Application of exogenous JA and sodium nitroprusside ( SNP ; a NO donor ) significantly decreased the number of egg masses in tomato roots after RKN infection and partially alleviated RKN-induced decreases in plant fresh weight and net photosynthetic rate .

These molecules also alleviated RKN-induced increases in root electrolyte leakage and membrane peroxidation .

Importantly , NO scavenger partially inhibited JA-induced RKN defense .

The pharmacological inhibition of JA biosynthesis significantly increased the plants ' susceptibility to RKNs , which was effectively alleviated by SNP application , showing that NO may be involved in the JA-dependent RKN defense pathway .

Furthermore , both JA and SNP induced increases in protease inhibitor 2 ( PI2 ) gene expression after RKN infestation .

Silencing of PI2 compromised both JA- and SNP-induced RKN defense responses , suggesting that the PI2 gene mediates JA- and NO-induced defense against RKNs .

This work will be important for deepening the understanding of the mechanisms involved in basal defense against RKN attack in plants .


• Arsenic ( As ) contamination of rice ( Oryza sativa ) is a worldwide concern and elucidating the molecular mechanisms of As accumulation in rice may provide promising solutions to the problem .

Previous studies using microarray techniques to investigate transcriptional regulation of plant responses to As stress have identified numerous differentially expressed genes .

However , little is known about the metabolic and regulatory network remodelings , or their interactions with microRNA ( miRNA ) in plants upon As(III ) exposure .

• We used Illumina sequencing to acquire global transcriptome alterations and miRNA regulation in rice under As(III ) treatments of varying lengths of time and dosages .

• We found that the response of roots was more distinct when the dosage was varied , whereas that of shoots was more distinct when the treatment time was varied .

In particular , the genes involved in heavy metal transportation , jasmonate ( JA ) biosynthesis and signaling , and lipid metabolism were closely related to responses of rice under As(III ) stress .

Furthermore , we discovered 36 new As(III)-responsive miRNAs , 14 of which were likely involved in regulating gene expression in transportation , signaling , and metabolism .

• Our findings highlight the significance of JA signaling and lipid metabolism in response to As(III ) stress and their regulation by miRNA , which provides a foundation for subsequent functional research .


Biosynthesis of nicotine in tobacco requires N-methylputrescine oxidase ( MPO ) , which belongs to the copper-containing amine oxidase superfamily .

Previous studies identified tobacco MPO1 and its close homolog NtDAO1 ( formerly called MPO2 ) , of which MPO1 has been shown preferentially to oxidize N-methylated amines .

We show here that NtDAO1 , as well as a homologous Arabidopsis diamine oxidase ( DAO ) , accept non-N-methylated amines more efficiently than their corresponding N-methylated amines .

MPO1 is coordinately regulated with other nicotine biosynthesis genes with regard to COI1-MYC2-dependent jasmonate induction and its dependence on nicotine-specific ERF transcription factors , whereas NtDAO1 is constitutively expressed at low basal levels in tobacco plants .

Both MPO1 and NtDAO1 are targeted to peroxisomes by their C-terminal motifs , and the peroxisomal localization of MPO1 is required for it to function in nicotine biosynthesis in jasmonate-elicited cultured tobacco cells .

Restricted occurrence of the MPO subfamily in Nicotiana and Solanum indicates that , during the formation of the Solanaceae , MPO has evolved from a DAO , which functions in polyamine catabolism within peroxisomes , by optimizing substrate preference and gene expression patterns to be suitable for alkaloid formation .


Poplar trees synthesize flavan-3-ols ( catechin and proanthocyanidins ) as a defense against foliar rust fungi , but the regulation of this defense response is poorly understood .

Here , we investigated the role of hormones in regulating flavan-3-ol accumulation in poplar during rust infection .

We profiled levels of defense hormones , signaling genes , and flavan-3-ol metabolites in black poplar leaves at different stages of rust infection .

Hormone levels were manipulated by external sprays , genetic engineering , and drought to reveal their role in rust fungal defenses .

Levels of salicylic acid ( SA ) , jasmonic acid , and abscisic acid increased in rust-infected leaves and activated downstream signaling , with SA levels correlating closely with those of flavan-3-ols .

Pretreatment with the SA analog benzothiadiazole increased flavan-3-ol accumulation by activating the MYB-bHLH-WD40 complex and reduced rust proliferation .

Furthermore , transgenic poplar lines overproducing SA exhibited higher amounts of flavan-3-ols constitutively via the same transcriptional activation mechanism .

These findings suggest a strong association among SA , flavan-3-ol biosynthesis , and rust resistance in poplars .

Abscisic acid also promoted poplar defense against rust infection , but likely through stomatal immunity independent of flavan-3-ols .

Jasmonic acid did not confer any apparent defense responses to the fungal pathogen .

We conclude that SA activates flavan-3-ol biosynthesis in poplar against rust infection .


Proteomics has contributed to defining the specific functions of genes and proteins involved in plant-pathogen interactions .

Proteomic studies have led to the identification of many pathogenicity and defense-related genes and proteins expressed during phytopathogen infections , resulting in the collection of an enormous amount of data .

However , the molecular basis of plant-pathogen interactions remains an intensely active area of investigation .

In this review , the role of differential analysis of proteins expressed during fungal , bacterial , and viral infection is discussed , as well as the role of JA and SA in the production of stress related proteins .

Resistance acquired upon induction of stress related proteins in intact plant leaves is mediated by potentiation of pathogens via signal elicitors .

Stress related genes extensively used in biotechnology had been cited .

Stress related proteins identified must be followed through for studying the molecular mechanism for plant defense against pathogens .


Phytohormones regulate diverse aspects of plant growth and environmental responses .

Recent high-throughput technologies have promoted a more comprehensive profiling of genes regulated by different hormones .

However , these omics data generally result in large gene lists that make it challenging to interpret the data and extract insights into biological significance .

With the rapid accumulation of theses large-scale experiments , especially the transcriptomic data available in public databases , a means of using this information to explore the transcriptional networks is needed .

Different platforms have different architectures and designs , and even similar studies using the same platform may obtain data with large variances because of the highly dynamic and flexible effects of plant hormones ; this makes it difficult to make comparisons across different studies and platforms .

Here , we present a web server providing gene set-level analyses of Arabidopsis thaliana hormone responses .

GSHR collected 333 RNA-seq and 1,205 microarray datasets from the Gene Expression Omnibus , characterizing transcriptomic changes in Arabidopsis in response to phytohormones including abscisic acid , auxin , brassinosteroids , cytokinins , ethylene , gibberellins , jasmonic acid , salicylic acid , and strigolactones .

These data were further processed and organized into 1,368 gene sets regulated by different hormones or hormone-related factors .

By comparing input gene lists to these gene sets , GSHR helped to identify gene sets from the input gene list regulated by different phytohormones or related factors .

Together , GSHR links prior information regarding transcriptomic changes induced by hormones and related factors to newly generated data and facilities cross-study and cross-platform comparisons ; this helps facilitate the mining of biologically significant information from large-scale datasets .

The GSHR is freely available at http://bioinfo.sibs.ac.cn/GSHR/.


In response to infestation by herbivores , rice plants rapidly biosynthesize defense compounds by activating a series of defense-related pathways .

However , which defensive compounds in rice are effective against herbivores remains largely unknown .

We found that the infestation of white-backed planthopper ( WBPH ) Sogatella furcifera gravid females significantly increased levels of jasmonic acid ( JA ) , jasmonoyl-isoleucine ( JA-Ile ) and H(2)O(2 ) , and reduced the level of ethylene in rice ; levels of 11 of the tested 12 phenolamides ( PAs ) were subsequently enhanced .

In contrast , WBPH nymph infestation had no effect on levels of JA , JA-Ile , ethylene and H(2)O(2 ) in rice , and enhanced levels of only 2 of 12 PAs .

Moreover , infestation by brown planthopper Nilaparvata lugens gravid females also affected the production of these PAs differently .

Bioassays revealed that 4 PAs - N-feruloylputrescine , N-feruloyltyramine , feruloylagmatine and N1,N10-diferuloylspermidine - were toxic to newly emerged WBPH female adults .

Our results suggest that WBPH- or BPH-induced biosynthesis of PAs in rice seems to be shaped primarily by the specific profile of defense-related signals elicited by the herbivore and that PAs play a role in conferring the resistance to WBPH on rice .


Infection by necrotrophs is a complex process that starts with the breakdown of the cell wall ( CW ) matrix initiated by CW-degrading enzymes and results in an extensive tissue maceration .

Plants exploit induced defense mechanisms based on biochemical modification of the CW components to protect themselves from enzymatic degradation .

The pectin matrix is the main CW target of Botrytis cinerea , and pectin methylesterification status is strongly altered in response to infection .

The methylesterification of pectin is controlled mainly by pectin methylesterases ( PMEs ) , whose activity is posttranscriptionally regulated by endogenous protein inhibitors ( PMEIs ) .

Here , AtPMEI10 , AtPMEI11 , and AtPMEI12 are identified as functional PMEIs induced in Arabidopsis ( Arabidopsis thaliana ) during B. cinerea infection .

AtPMEI expression is strictly regulated by jasmonic acid and ethylene signaling , while only AtPMEI11 expression is controlled by PME-related damage-associated molecular patterns , such as oligogalacturonides and methanol .

The decrease of pectin methylesterification during infection is higher and the immunity to B. cinerea is compromised in pmei10 , pmei11 , and pmei12 mutants with respect to the control plants .

A higher stimulation of the fungal oxalic acid biosynthetic pathway also can contribute to the higher susceptibility of pmei mutants .

The lack of PMEI expression does not affect hemicellulose strengthening , callose deposition , and the synthesis of structural defense proteins , proposed as CW-remodeling mechanisms exploited by Arabidopsis to resist CW degradation upon B. cinerea infection .

We show that PME activity and pectin methylesterification are dynamically modulated by PMEIs during B. cinerea infection .

Our findings point to AtPMEI10 , AtPMEI11 , and AtPMEI12 as mediators of CW integrity maintenance in plant immunity .


Leaf angle is an important agronomic trait in cereals and shares a close relationship with crop architecture and grain yield .

Although it has been previously reported that ZmCLA4 can influence leaf angle , the underlying mechanism remains unclear .

In this study , we used the Gal4-LexA/UAS system and transactivation analysis to demonstrate in maize ( Zea mays ) that ZmCLA4 is a transcriptional repressor that regulates leaf angle .

DNA affinity purification sequencing ( DAP-Seq ) analysis revealed that ZmCLA4 mainly binds to promoters containing the EAR motif ( CACCGGAC ) as well as to two other motifs ( CCGARGS and CDTCNTC ) to inhibit the expression of its target genes .

Further analysis of ZmCLA4 target genes indicated that ZmCLA4 functions as a hub of multiple plant hormone signaling pathways : ZmCLA4 was found to directly bind to the promoters of multiple genes including ZmARF22 and ZmIAA26 in the auxin transport pathway , ZmBZR3 in the brassinosteroid signaling pathway , two ZmWRKY genes involved in abscisic acid metabolism , ZmCYP genes ( ZmCYP75B1 , ZmCYP93D1 ) related to jasmonic acid metabolism , and ZmABI3 involved in the ethylene response pathway .

Overall , our work provides deep insights into the ZmCLA4 regulatory network in controlling leaf angle in maize .


Certain plant growth promoting bacteria have ability to ameliorate abiotic and/or biotic stressors , which can be exploited to enhance plant growth and productivity of the plants under stress conditions .

Therefore , the present study aimed to examine the role of a rhizospheric bacterial isolate SBP-9 isolated from Sorghum bicolor ( i ) in promoting the wheat plant growth under salinity stress , and ( ii ) in enhancing the defense response in wheat against fungal pathogen " Fusarium graminearum . " The test isolate possessed plant growth promoting ( PGP ) traits including ACC deaminase ( ACCD ) , gibberellic acid , indole acetic acid ( IAA ) , siderophore , and inorganic phosphate solubilization .

Under salt ( NaCl ) stress , inoculation of this isolate to wheat plant significantly increased plant growth in terms of various growth parameters such as shoot length/root length ( 20 - 39 % ) , fresh weight/dry weight ( 28 - 42 % ) , and chlorophyll content ( 24 - 56 % ) following inoculation of test isolate SBP-9 .

Bacterial inoculation decreased the level of proline , and malondialdehyde , whereas elevated the antioxidative enzymatic activities of superoxide-dismutase ( SOD ; 28 - 41 % ) , catalase ( CAT ; 24 - 56 % ) , and peroxidase ( POX ; 26 - 44 % ) .

Furthermore , it also significantly decreased the Na(+ ) accumulation in both shoot and roots in the range of 25 - 32 % , and increased the K(+ ) uptake by 20 - 28 % , thereby favoring the K(+)/Na(+ ) ratio .

On the other hand , the test isolate also enhanced the level of defense enzymes like β-1 , 3 glucanase , phenylalanine ammonia lyase ( PAL ) , peroxidae ( PO ) , and polyphenol oxidase ( PPO ) , which can protect plants from the infection of pathogens .

The result of colonization test showed an ability of the test isolate to successfully colonize the wheat plants .

These results indicate that Stenotrophomonas maltophilia SBP-9 has potential to promote the wheat growth under biotic and abiotic ( salt ) stressors directly or indirectly and can be further tested at field level for exploitation as bioinoculant .


Gibberellin ( GA ) , a diterpene hormone , plays diverse roles in plant growth and development , including seed germination , stem elongation , and flowering time . Although it is known that GA accelerates flowering through degradation of transcription repressors , DELLAs , the underlying mechanism is poorly understood .

We show here that DELLA directly binds to microRNA156 (miR156)-targeted SQUAMOSA PROMOTER BINDING-LIKE ( SPL ) transcription factors , which promote flowering by activating miR172 and MADS box genes .

The interaction between DELLA and SPL interferes with SPL transcriptional activity and consequently delays floral transition through inactivating miR172 in leaves and MADS box genes at shoot apex under long-day conditions or through repressing MADS box genes at the shoot apex under short-day conditions .

Our results elucidate the molecular mechanism by which GA controls flowering and provide the missing link between DELLA and MADS box genes .


Gibberellic acid was found to have no significant effect on amylase activity in attached or detached cotyledons of peas .


Solanum laciniatum Aiton treated with Gibberellic acid ( GA3 ) , [2-chloroethyl]-trimethyl ammonium chloride ( CCC ) , and their combinations at early and late stages of growth showed that early application of 2000 ppm CCC produced the greatest stem , leaves , and whole plant dry weight , followed by the combination of early application of 1000 ppm CCC and late application of 100 ppm GA3 ; whereas all GA3 treatments decreased the dry weight production compared with the controls .

Regarding the glyco-alkaloids , the highest percentage was obtained from the whole plant by early applications of both strengths of GA3 compared with other treatments or the controls .

On the other hand , early application of 1000 ppm CCC and also late application of 50 ppm GA3 when combined with early application of either 1000 ppm or 2000 ppm CCC produced greater alkaloid percentage yields in stem , leaves , and whole plants more than other treatments or the controls .

However , early application of 2000 ppm CCC produced the highest content of alkaloids in leaves and whole plants ; this was followed by yields from early application of 2000 ppm CCC and 50 ppm GA3 ; yields from early application of 100 ppm GA3 and 1000 ppm CCC ; and yields from early application of 1000 ppm CCC + 50 ppm GA3 .


Multiple isoforms of chitinases participate in plant defense against outside invaders .

However , the functions of hydrolase family 19 ( GH19 ) chitinases on pest control remain largely unknown .

Here we reported the isolation and functional analysis of a gene CsChi19 , which encodes a GH19 endochitinase protein of 332 amino acid residues from tea plant ( Camellia sinensis ) .

CsChi19 expression levels were upregulated in response to mechanical wounding , infestation by two important pests : the tea geometrid Ectropis grisescens and the tea green leafhopper Empoasca ( Matsumurasca ) onukii , a fungal pathogen Colletotrichum fructicola , and treatment with two phytohormones : jasmonic acid ( JA ) and salicylic acid .

CsChi19 was heterologously expressed in Escherichia coli , and its catalytic function was further elucidated .

The protein could hydrolyze colloidal chitin , and the optimum temperature and pH for its activity was 40 ° C and pH 5.0 .

CsChi19 were found to be toxic to tea pests when they were fed on artificial diets containing this protein .

Interestingly , the regurgitant derived from E. grisescens fed with artificial diets containing CsChi19 protein induced stronger expression of CsMPK3 , more JA burst , more accumulation of defense-related secondary metabolites , and more emission of volatiles than the regurgitant derived from E. grisescens fed only with artificial diets .

Our results provide first evidence that CsChi19 is involved in mediating a novel defense mechanism of tea plant through altering the composition of the regurgitant .


Rice OsEDR1 is a sequence ortholog of Arabidopsis EDR1 .

However , its molecular function is unknown .

We show here that OsEDR1-suppressing/knockout ( KO ) plants , which developed spontaneous lesions on the leaves , have enhanced resistance to Xanthomonas oryzae pv . oryzae ( Xoo ) causing bacterial blight disease .

This resistance was associated with increased accumulation of salicylic acid ( SA ) and jasmonic acid ( JA ) , induced expression of SA- and JA-related genes and suppressed accumulation of 1-aminocyclopropane-1-carboxylic acid ( ACC ) , the direct precursor of ethylene , and expression of ethylene-related genes .

OsEDR1-KO plants also showed suppressed production of ethylene .

Knockout of OsEDR1 suppressed the ACC synthase ( ACS ) gene family , which encodes the rate-limiting enzymes of ethylene biosynthesis by catalysing the formation of ACC .

The lesion phenotype and enhanced bacterial resistance of the OsEDR1-KO plants was partly complemented by the treatment with ACC .

ACC treatment was associated with decreased SA and JA biosynthesis in OsEDR1-KO plants .

In contrast , aminoethoxyvinylglycine , the inhibitor of ethylene biosynthesis , promoted expression of SA and JA synthesis-related genes in OsEDR1-KO plants .

These results suggest that ethylene is a negative signalling molecule in rice bacterial resistance .

In the rice-Xoo interaction , OsEDR1 transcriptionally promotes the synthesis of ethylene that , in turn , suppresses SA- and JA-associated defence signalling .


Selected strains of nonpathogenic rhizobacteria can reduce disease in foliar tissues through the induction of a defense state known as induced systemic resistance ( ISR ) .

Compared with the large body of information on ISR in dicotyledonous plants , little is known about the mechanisms underlying rhizobacteria-induced resistance in cereal crops .

Here , we demonstrate the ability of Pseudomonas fluorescens WCS374r to trigger ISR in rice ( Oryza sativa ) against the leaf blast pathogen Magnaporthe oryzae .

Using salicylic acid (SA)-nonaccumulating NahG rice , an ethylene-insensitive OsEIN2 antisense line , and the jasmonate-deficient mutant hebiba , we show that this WCS374r-induced resistance is regulated by an SA-independent but jasmonic acid/ethylene-modulated signal transduction pathway .

Bacterial mutant analysis uncovered a pseudobactin-type siderophore as the crucial determinant responsible for ISR elicitation .

Root application of WCS374r-derived pseudobactin ( Psb374 ) primed naive leaves for accelerated expression of a pronounced multifaceted defense response , consisting of rapid recruitment of phenolic compounds at sites of pathogen entry , concerted expression of a diverse set of structural defenses , and a timely hyperinduction of hydrogen peroxide formation putatively driving cell wall fortification .

Exogenous SA application alleviated this Psb374-modulated defense priming , while Psb374 pretreatment antagonized infection-induced transcription of SA-responsive PR genes , suggesting that the Psb374- and SA-modulated signaling pathways are mutually antagonistic .

Interestingly , in sharp contrast to WCS374r-mediated ISR , chemical induction of blast resistance by the SA analog benzothiadiazole was independent of jasmonic acid/ethylene signaling and involved the potentiation of SA-responsive gene expression .

Together , these results offer novel insights into the signaling circuitry governing induced resistance against M. oryzae and suggest that rice is endowed with multiple blast-effective resistance pathways .


Maize ( Zea mays L. ) suspension-cultured cells with up to 70 % less cellulose were obtained by stepwise habituation to dichlobenil ( DCB ) , a cellulose biosynthesis inhibitor .

Cellulose deficiency was accompanied by marked changes in cell wall matrix polysaccharides and phenolics as revealed by Fourier transform infrared ( FTIR ) spectroscopy .

Cell wall compositional analysis indicated that the cellulose-deficient cell walls showed an enhancement of highly branched and cross-linked arabinoxylans , as well as an increased content in ferulic acid , diferulates and p-coumaric acid , and the presence of a polymer that stained positive for phloroglucinol .

In accordance with this , cellulose-deficient cell walls showed a fivefold increase in Klason-type lignin .

Thioacidolysis/GC-MS analysis of cellulose-deficient cell walls indicated the presence of a lignin-like polymer with a Syringyl/Guaiacyl ratio of 1.45 , which differed from the sensu stricto stress-related lignin that arose in response to short-term DCB-treatments .

Gene expression analysis of these cells indicated an overexpression of genes specific for the biosynthesis of monolignol units of lignin .

A study of stress signaling pathways revealed an overexpression of some of the jasmonate signaling pathway genes , which might trigger ectopic lignification in response to cell wall integrity disruptions .

In summary , the structural plasticity of primary cell walls is proven , since a lignification process is possible in response to cellulose impoverishment .


The wound response of tomato plants has been extensively studied , and provides a useful model to understand signal transduction events leading from injury to marker gene expression .

The principal markers that have been used in these studies are genes encoding proteinase inhibitor ( pin ) proteins .

Activation of pin genes occurs in the wounded leaf and in distant unwounded leaves of the plant .

This paper reviews current understanding of signalling pathways in the wounded leaf , and in the systemically responding unwounded leaves .

First , the nature of known elicitors and their potential roles in planta are discussed , in particular , oligogalacturonides , jasmonates and the peptide signal , systemin .

Inhibitors of wound-induced proteinase inhibitor ( pin ) expression are also reviewed , with particular reference to phenolics , sulphydryl reagents and fusicoccin .

In each section , results obtained from the bioassay are considered within the wider context of data from mutants and from transgenic plants with altered levels of putative signalling components .

Following this introduction , current models for pin gene regulation are described and discussed , together with a summary for the involvement of phosphorylation-dephosphorylation in wound signalling .

Finally , a new model for wound-induced pin gene expression is presented , arising from recent data from the author 's laboratory .


High-frequency bud break and multiple shoots were induced in apical shoot buds and nodal explants ofMorus cathayana , M. lhou andM. serrata on Murashige and Skoog ( MS ) medium containing 0.5 - 1.0 mg/l 6-benzylaminopurine ( BAP ) .

Addition of gibberellic acid ( 0.4 mg/l ) along with BAP induced faster bud break both in apical shoot buds and nodal explants and also enhanced the frequency of bud break in all three species .

Shoot culture initiation was greatly influenced by explant type , explant age and explanting season .

The shoots were successfully rooted on half-strength MS medium containing a combination of indole-3-acetic acid , indole-3-butyric acid and indole-3-propionic acid , each at 1.0 mg/l .

The plantlets were successfully acclimated and eventually established in soil .


Lettuce ( Lactuca sativa L. ) endosperm cell walls isolated prior to radicle emergence underwent autohydrolysis , the rate of which was correlated with whether radicle emergence would subsequently occur .

Extraction of endosperm cell walls with 6 M LiCl suppressed autohydrolysis , and the desalted extract possessed activity that was capable of hydrolyzing purified locust bean galactomannan but not arabinogalactan , carboxymethylcellulose , glucomannan , polygalacturonic acid , tomato galactomannan , or native lettuce endosperm cell walls .

Some hydrolytic activity was detected on endosperm cell walls if they were modified by partial trifluoroacetic acid hydrolysis or pretreatment with guanidinium thiocyanate .

In extended incubations the cell wall enzyme extract released only large molecular mass fragments from locust bean galactomannan , indicating primarily endo-activity .

Galactomannan-hydrolyzing activity in the cell wall extract increased as a function of imbibition time and was greatest just prior to radicle emergence .

Thermoinhibition ( imbibition at 32[deg]C ) or treatment with abscisic acid at a temperature optimal for germination ( 25[deg]C ) suppressed both germination and endosperm cell wall mannanase activity , whereas alleviation of thermoinhibition with gibberellic acid was accompanied by significant enhancement of mannanase activity .

We conclude that a cell wall-bound endo-[beta]-mannanase is expressed in lettuce endosperm prior to radicle emergence and is regulated by the same conditions that govern germination .


GP-1 , a novel glycoprotein from Streptomyces sp. ZX01 has a plant immunity-inducing effect .

GP-1-treated plants exhibited enhanced systemic resistance with a significant reduction in TMV lesions on tobacco leaves , but its antiviral mechanism remains unclear .

In this study , early plant defense-related responses , such as Ca(2 + ) influx , callose apposition , oxidative burst , hypersensitive response , programmed cell death , increase in nitric oxide ( NO ) , and stomatal closure , were investigated under GP-1 treatment , and the mechanism of how GP-1 induces viral resistance in Nicotiana benthamiana was studied .

Results showed that GP-1 induced [Ca(2+)](cyt ) rapidly in tobacco leaves and suspended cells , followed by reactive oxygen species ( ROS ) and NO elevation .

Transcriptome analysis showed significant differences in expression levels between the GP-1-treated N. benthamiana and the control and showed significantly upregulated and enriched pathways including defense and immune reaction .

Similar to typical pathogen-associated molecular patterns , GP-1 induced callose deposition and stomatal closure to form defense barriers against pathogen invasion .

The expression of defense-related genes further confirmed the above conclusions .

By analyzing transcriptome in N. benthamiana and the contents of salicylic acid ( SA ) and jasmonic acid ( JA ) , GP-1 enhanced viral resistance of tobacco by improving the SA and JA contents , strengthening plant secondary metabolites activities , promoting systemic accumulation of pathogenesis-related proteins in TMV- inoculated tobacco there by producing antiviral activity .


SPINDLY ( SPY ) is an important regulator of plant development , and consists of an N-half tetratricopeptide repeat ( TPR ) domain containing 10 TPR motifs and a C-half catalytic domain , similar to O-GlcNAc transferase ( OGT ) of animals .

The best characterised role of SPY is a negative regulator of GA signalling , and all known spy alleles have been isolated based on increased GA response .

Of the eight alleles that directly affect the TPR domain , all alter TPRs 6 , 8 and/or 9 .

To test the hypothesis that a subset of TPRs , including 6 , 8 and 9 , are both essential and sufficient for the regulation of GA response , we overexpressed the full-length barley ( Hordeum vulgare L. ) SPY protein ( HvSPY ) and several deletion mutants in barley aleurone cells and in Arabidopsis wild type ( WT ) and spy-4 plants .

Transient assays in barley aleurone cells , that also express endogenous HvSPY , demonstrated that introduced HvSPY and HvTPR inhibited GA(3)-induced alpha-amylase expression .

With the exception of HvSPYDelta1 - 5 , the other deletion proteins were partially active in the barley assay , including HvSPYDelta6 - 9 which lacks TPRs 6 , 8 and 9 .

In Arabidopsis , analysis of seed germination under a range of conditions revealed that 35S : HvSPY increased seed dormancy .

Hvspy-2 , which lacks parts of the eighth and ninth TPRs , was able to partially complement all aspects of the spy-4 phenotype .

In the presence of AtSPY , 35S : HvTPR caused some phenotypes consistent with a decrease in GA signalling , including increased seed sensitivity to paclobutrazol and delayed flowering .

These plants also possessed distorted leaf morphology and altered epidermal cell shape .

Thus , despite genetic analysis demonstrating that TPRs 6 , 8 and 9 are required for regulation of GA signalling , our results suggest that these TPRs are neither absolutely essential nor sufficient for SPY activity .


In tobacco , two mitogen-activated protein ( MAP ) kinases , designated salicylic acid (SA)-induced protein kinase ( SIPK ) and wounding-induced protein kinase ( WIPK ) are activated in a disease resistance-specific manner following pathogen infection or elicitor treatment .

To investigate whether nitric oxide ( NO ) , SA , ethylene , or jasmonic acid ( JA ) are involved in this phenomenon , the ability of these defense signals to activate these kinases was assessed .

Both NO and SA activated SIPK ; however , they did not activate WIPK .

Additional analyses with transgenic NahG tobacco revealed that SA is required for the NO-mediated induction of SIPK .

Neither JA nor ethylene activated SIPK or WIPK .

Thus , SIPK may function downstream of SA in the NO signaling pathway for defense responses , while the signals responsible for resistance-associated WIPK activation have yet to be determined .


Plant phospholipase Ds ( PLDs ) , essential regulators of phospholipid signaling , function in multiple signal transduction cascades ; however , the mechanisms regulating PLDs in response to pathogens remain unclear .

Here , we found that Arabidopsis ( Arabidopsis thaliana ) PLDδ accumulated in cells at the entry sites of the barley powdery mildew fungus , Blumeria graminis f. sp hordei Using fluorescence recovery after photobleaching and single-molecule analysis , we observed higher PLDδ density in the plasma membrane after chitin treatment ; PLDδ also underwent rapid exocytosis .

Fluorescence resonance energy transfer with fluorescence lifetime imaging microscopy showed that the interaction between PLDδ and the microdomain marker AtREMORIN1.3 ( AtREM1.3 ) increased in response to chitin , indicating that exocytosis facilitates rapid , efficient sorting of PLDδ into microdomains upon pathogen stimulus .

We further unveiled a trade-off between brefeldin A (BFA)-resistant and -sensitive pathways in secretion of PLDδ under diverse conditions .

Upon pathogen attack , PLDδ secretion involved syntaxin-associated VAMP721/722-mediated exocytosis sensitive to BFA .

Analysis of phosphatidic acid ( PA ) , hydrogen peroxide , and jasmonic acid ( JA ) levels and expression of related genes indicated that the relocalization of PLDδ is crucial for its activation to produce PA and initiate reactive oxygen species and JA signaling pathways .

Together , our findings revealed that the translocation of PLDδ to papillae is modulated by exocytosis , thus triggering PA-mediated signaling in plant innate immunity.plantcell;31/12/3015/FX1F1fx1 .


Genetic and biochemical dissection of signaling pathways regulating plant pathogen defense has revealed remarkable similarities with the innate immune system of mammals and Drosophila .

Numerous plant proteins resembling eukaryotic receptors have been implicated in the perception of pathogen-derived signal molecules .

Receptor-mediated changes in levels of free calcium in the cytoplasm and production of reactive oxygen species and nitric oxide constitute early events generally observed in plant-pathogen interactions .

Positive and negative regulation of plant pathogen defense responses has been attributed to mitogen-activated protein kinase cascades .

In addition , salicylic acid , jasmonic acid and ethylene are components of signaling networks that provide the molecular basis for specificity of plant defense responses .

This article reviews recent advances in our understanding of early signaling events involved in the establishment of plant disease resistance .


Ethylene responsive factors ( ERFs ) are a large family of plant-specific transcription factors that are involved in the regulation of plant development and stress responses .

However , little to nothing is known about their role in herbivore-induced defense .

We discovered a nucleus-localized ERF gene in rice ( Oryza sativa ) , OsERF3 , that was rapidly up-regulated in response to feeding by the rice striped stem borer ( SSB ) Chilo suppressalis .

Antisense and over-expression of OsERF3 revealed that it positively affects transcript levels of two mitogen-activated protein kinases ( MAPKs ) and two WRKY genes as well as concentrations of jasmonate ( JA ) , salicylate ( SA ) and the activity of trypsin protease inhibitors ( TrypPIs ) .

OsERF3 was also found to mediate the resistance of rice to SSB .

On the other hand , OsERF3 was slightly suppressed by the rice brown planthopper ( BPH ) Nilaparvata lugens ( Stål ) and increased susceptibility to this piercing sucking insect , possibly by suppressing H(2)O(2 ) biosynthesis .

We propose that OsERF3 affects early components of herbivore-induced defense responses by suppressing MAPK repressors and modulating JA , SA , ethylene and H(2)O(2 ) pathways as well as plant resistance .

Our results also illustrate that OsERF3 acts as a central switch that gears the plant 's metabolism towards an appropriate response to chewing or piercing/sucking insects .


Plants counteract attack by herbivorous insects using a variety of inducible defence mechanisms .

The production of toxic proteins and metabolites that instantly affect the herbivore 's development are examples of direct induced defence .

In addition , plants may release mixtures of volatile organic compounds ( VOCs ) that indirectly protect the plant by attracting natural enemies of the herbivore .

Recent studies suggest that these VOCs can also prime nearby plants for enhanced induction of defence upon future insect attack .

However , evidence that this defence priming causes reduced vulnerability to insects is sparse .

Here we present molecular , chemical and behavioural evidence that VOC-induced priming leads to improved direct and indirect resistance in maize .

A differential hybridization screen for inducible genes upon attack by Spodoptera littoralis caterpillars identified 10 defence-related genes that are responsive to wounding , jasmonic acid ( JA ) , or caterpillar regurgitant .

Exposure to VOCs from caterpillar-infested plants did not activate these genes directly , but primed a subset of them for earlier and/or stronger induction upon subsequent defence elicitation .

This priming for defence-related gene expression correlated with reduced caterpillar feeding and development .

Furthermore , exposure to caterpillar-induced VOCs primed for enhanced emissions of aromatic and terpenoid compounds .

At the peak of this VOC emission , primed plants were significantly more attractive to parasitic Cotesia marginiventris waSPS .

This study shows that VOC-induced priming targets a specific subset of JA-inducible genes , and links these responses at the molecular level to enhanced levels of direct and indirect resistance against insect attack .


The role of ethylene ( ET ) signaling in the responses of two hybrid aspen ( Populus tremula L. x P. tremuloides Michx . ) clones to chronic ozone ( O(3 ) ; 75 nL L(-1 ) ) was investigated .

The hormonal responses differed between the clones ; the O(3)-sensitive clone 51 had higher ET evolution than the tolerant clone 200 during the exposure , whereas the free salicylic acid concentration in clone 200 was higher than in clone 51 .

The cellular redox status , measured as glutathione redox balance , did not differ between the clones suggesting that the O(3 ) lesions were not a result of deficient antioxidative capacity .

The buildup of salicylic acid during chronic O(3 ) exposure might have prevented the up-regulation of ET biosynthesis in clone 200 .

Blocking of ET perception with 1-methylcyclopropene protected both clones from the decrease in net photosynthesis during chronic exposure to O(3 ) .

After a pretreatment with low O(3 ) for 9 d , an acute 1.5-fold O(3 ) elevation caused necrosis in the O(3)-sensitive clone 51 , which increased substantially when ET perception was blocked .

The results suggest that in hybrid aspen , ET signaling had a dual role depending on the severity of the stress .

ET accelerated leaf senescence under low O(3 ) , but under acute O(3 ) elevation , ET signaling seemed to be required for protection from necrotic cell death .


How plants perceive insect attacks is an area of active research .

Numerous studies have shown that regurgitant from feeding insects elicits a defense response in plants , which is often assumed to be distinct from a wound response .

We have characterized the inducible defense response in hybrid poplar and found it to be qualitatively similar between wounding and application of regurgitant from forest tent caterpillar .

We suggest that this is likely attributable to our wounding treatment which is much more intense compared to most other studies .

These overlapping responses appear to be activated via jasmonic acid signaling , and we speculate that they are both triggered by elicitors of plant origin .

Wounding would release such elicitor molecules when leaf cells are disrupted , and regurgitant may contain them in a modified or processed form .

This hypothesis could explain why some other necrosis-inducing stresses also induce herbivore defense genes .


Brassinosteroids ( BRs ) are a group of naturally occurring plant steroidal compounds with wide-ranging biological activity that offer the unique possibility of increasing crop yields through both changing plant metabolism and protecting plants from environmental stresses .

In recent years , genetic and biochemical studies have established an essential role for BRs in plant development , and on this basis BRs have been given the stature of a phytohormone .

A remarkable feature of BRs is their potential to increase resistance in plants to a wide spectrum of stresses , such as low and high temperatures , drought , high salt , and pathogen attack .

Despite this , only a few studies aimed at understanding the mechanism by which BRs promote stress resistance have been undertaken .

Studies of the BR signaling pathway and BR gene-regulating properties indicate that there is cross-talk between BRs and other hormones , including those with established roles in plant defense responses such as abscisic acid , jasmonic acid , and ethylene .

Recent studies aimed at understanding how BRs modulate stress responses suggest that complex molecular changes underlie BR-induced stress tolerance in plants .

Analyses of these changes should generate exciting results in the future and clarify whether the ability of BRs to increase plant resistance to a range of stresses lies in the complex interactions of BRs with other hormones .

Future studies should also elucidate if BRI1 , an essential component of the BR receptor , directly participates in stress response signaling through interactions with ligands and proteins involved in plant defense responses .


Thellungiella , an Arabidopsis ( Arabidopsis thaliana)-related halophyte , is an emerging model species for studies designed to elucidate molecular mechanisms of abiotic stress tolerance .

Using a cDNA microarray containing 3,628 unique sequences derived from previously described libraries of stress-induced cDNAs of the Yukon ecotype of Thellungiella salsuginea , we obtained transcript profiles of its response to cold , salinity , simulated drought , and rewatering after simulated drought .

A total of 154 transcripts were differentially regulated under the conditions studied .

Only six of these genes responded to all three stresses of drought , cold , and salinity , indicating a divergence among the end responses triggered by each of these stresses .

Unlike in Arabidopsis , there were relatively few transcript changes in response to high salinity in this halophyte .

Furthermore , the gene products represented among drought-responsive transcripts in Thellungiella associate a down-regulation of defense-related transcripts with exposure to water deficits .

This antagonistic interaction between drought and biotic stress response may demonstrate Thellungiella 's ability to respond precisely to environmental stresses , thereby conserving energy and resources and maximizing its survival potential .

Intriguingly , changes of transcript abundance in response to cold implicate the involvement of jasmonic acid .

While transcripts associated with photosynthetic processes were repressed by cold , physiological responses in plants developed at low temperature suggest a novel mechanism for photosynthetic acclimation .

Taken together , our results provide useful starting points for more in-depth analyses of Thellungiella 's extreme stress tolerance .


We have examined the effect of gibberellic acid ( GA(3 ) ) on the distribution of the enzyme responsible for mobilizing storage triacylglycerol in aleurone cells of Hordeum vulgare L. cv Himalaya .

Using cellular fractionation techniques , we find that , in cells that have not been exposed to hormone , neutral lipase activity is principally associated with a pellet containing the membranes of protein bodies .

If the cells are exposed to GA(3 ) for at least 1 hour , the majority of the lipase activity becomes associated with the lipid body fraction .

The nature of the in vivo association between lipid bodies and protein bodies was examined using ultrarapid freezing followed by freeze-fracture electron microscopy .

Our analysis indicates that the phospholipid monolayer surrounding the lipid body is directly continuous with the outer leaflet of the bilayer surrounding the protein body .

Based on our data , we propose that lipase can be transferred from protein bodies ( storage form ) to lipid bodies ( active form ) by lateral diffusion within the plane of the fused phospholipid monolayer , and that the transfer can be controlled by gibberellic acid by an unknown mechanism .


Nodulation outer proteins secreted via type 3 secretion systems are involved in the process of symbiosis between legume plants and rhizobia .

To study the function of NopT in symbiosis , we mutated nopT in Mesorhizobium amphore CCNWGS0123 ( GS0123 ) , which can nodulate black locust ( Robinia pseudoacacia ) .

The nopT mutant induced higher levels of jasmonic acid , salicylic acid , and hydrogen peroxide accumulation in the roots of R. pseudoacacia compared with wild-type GS0123 .

The ΔnopT mutant induced higher disease-resistant gene expression 72 hours post-inoculation ( hpi ) , whereas GS0123 induced higher disease-resistant gene expression earlier , at 36 hpi .

Compared with the nopT mutant , GS0123 induced the up-regulation of most genes at 36 hpi and the down-regulation of most genes at 72 hpi .

Proteolytically active NopT_GS0123 induced hypersensitive responses when expressed transiently in tobacco leaves ( Nicotiana benthamiana ) .

Two NopT_GS0123 targets in R. pseudoacacia were identified , ATP-citrate synthase alpha chain protein 2 and hypersensitive-induced response protein .

Their interactions with NopT_GS0123 triggered resistance by the plant immune system .

In conclusion , NopT_GS0123 inhibited the host plant immune system and had minimal effect on nodulation in R. pseudoacacia .

Our results reveal the underlying molecular mechanism of NopT function in plant-symbiont interactions .


Bacterial wilt caused by the bacterial pathogen Ralstonia solanacearum is one of the most devastating crop diseases worldwide .

The molecular mechanisms controlling the early stage of R. solanacearum colonization in the root remain unknown .

Aiming to better understand the mechanism of the establishment of R. solanacearum infection in root , we established four stages in the early interaction of the pathogen with Arabidopsis roots and determined the transcriptional profiles of these stages of infection .

A total 2,698 genes were identified as differentially expressed genes during the initial 96 h after infection , with the majority of changes in gene expression occurring after pathogen-triggered root-hair development observed .

Further analysis of differentially expressed genes indicated sequential activation of multiple hormone signaling cascades , including abscisic acid ( ABA ) , auxin , jasmonic acid , and ethylene .

Simultaneous impairment of ABA receptor genes promoted plant wilting symptoms after R. solanacearum infection but did not affect primary root growth inhibition or root-hair and lateral root formation caused by R. solanacearum .

This indicated that ABA signaling positively regulates root defense to R. solanacearum .

Moreover , transcriptional changes of genes involved in primary root , lateral root , and root-hair formation exhibited high temporal dynamics upon infection .

Taken together , our results suggest that successful infection of R. solanacearum on roots is a highly programmed process involving in hormone crosstalk .


BACKGROUND : Fusarium head blight ( FHB ) caused by Fusarium species like F. graminearum is a devastating disease of wheat ( Triticum aestivum ) worldwide .

Mycotoxins such as deoxynivalenol produced by the fungus affect plant and animal health , and cause significant reductions of grain yield and quality .

Resistant varieties are the only effective way to control this disease , but the molecular events leading to FHB resistance are still poorly understood .

Transcriptional profiling was conducted for the winter wheat cultivars Dream ( moderately resistant ) and Lynx ( susceptible ) .

The gene expressions at 32 and 72 h after inoculation with Fusarium were used to trace possible defence mechanisms and associated genes .

A comparative qPCR was carried out for selected genes to analyse the respective expression patterns in the resistant cultivars Dream and Sumai 3 ( Chinese spring wheat ) .

RESULTS : Among 2,169 differentially expressed genes , two putative main defence mechanisms were found in the FHB-resistant Dream cultivar .

Both are defined base on their specific mode of resistance .

A non-specific mechanism was based on several defence genes probably induced by jasmonate and ethylene signalling , including lipid-transfer protein , thionin , defensin and GDSL-like lipase genes .

Additionally , defence-related genes encoding jasmonate-regulated proteins were up-regulated in response to FHB .

Another mechanism based on the targeted suppression of essential Fusarium virulence factors comprising proteases and mycotoxins was found to be an essential , induced defence of general relevance in wheat .

Moreover , similar inductions upon fungal infection were frequently observed among FHB-responsive genes of both mechanisms in the cultivars Dream and Sumai 3 .

CONCLUSIONS : Especially ABC transporter , UDP-glucosyltransferase , protease and protease inhibitor genes associated with the defence mechanism against fungal virulence factors are apparently active in different resistant genetic backgrounds , according to reports on other wheat cultivars and barley .

This was further supported in our qPCR experiments on seven genes originating from this mechanism which revealed similar activities in the resistant cultivars Dream and Sumai 3 .

Finally , the combination of early-stage and steady-state induction was associated with resistance , while transcript induction generally occurred later and temporarily in the susceptible cultivars .

The respective mechanisms are attractive for advanced studies aiming at new resistance and toxin management strategies .


Nonspecific lipid transfer proteins ( nsLTPs ) are small , basic cystein-rich proteins believed to be involved in plant defense mechanisms .

Three cDNAs coding nsLTPs from grape ( Vitis vinifera sp. ) were cloned by reverse-transcriptase-polymerase chain reaction ( RT-PCR ) and PCR .

The expression of nsLTP genes was investigated in 41B-rootstock grape cell suspension , in response to various defense-related signal molecules .

Ergosterol ( a fungi-specific sterol ) and a proteinaceous elicitor purified from Botrytis cinerea strongly and rapidly induced the accumulation of nsLTP mRNAs .

Jasmonic acid , cholesterol , and sitosterol also promoted nsLTPs mRNA accumulation , although to a lesser extent , whereas salicylic acid had no effect .

High performance liquid chromatography analysis indicated that the amounts of three LTP isoforms ( previously named P1 , P2 , and P4 ) were increased by ergosterol .

None of the four isoforms displayed any significant antifungal properties , with the exception of the P4 isoform , which reduced Botrytis mycelium growth in vitro , but only in calcium-free medium .

The results are discussed in the context of plant-pathogen interactions .


Plants are continually exposed to pathogen attack but usually remain healthy because they can activate defences upon perception of microbes .

However , pathogens have evolved to overcome plant immunity by delivering effectors into the plant cell to attenuate defence , resulting in disease .

Recent studies suggest that some effectors may manipulate host transcription , but the specific mechanisms by which such effectors promote susceptibility remain unclear .

We study the oomycete downy mildew pathogen of Arabidopsis , Hyaloperonospora arabidopsidis ( Hpa ) , and show here that the nuclear-localized effector HaRxL44 interacts with Mediator subunit 19a ( MED19a ) , resulting in the degradation of MED19a in a proteasome-dependent manner .

The Mediator complex of ∼25 proteins is broadly conserved in eukaryotes and mediates the interaction between transcriptional regulators and RNA polymerase II .

We found MED19a to be a positive regulator of immunity against Hpa .

Expression profiling experiments reveal transcriptional changes resembling jasmonic acid/ethylene ( JA/ET ) signalling in the presence of HaRxL44 , and also 3 d after infection with Hpa .

Elevated JA/ET signalling is associated with a decrease in salicylic acid (SA)-triggered immunity ( SATI ) in Arabidopsis plants expressing HaRxL44 and in med19a loss-of-function mutants , whereas SATI is elevated in plants overexpressing MED19a .

Using a PR1::GUS reporter , we discovered that Hpa suppresses PR1 expression specifically in cells containing haustoria , into which RxLR effectors are delivered , but not in nonhaustoriated adjacent cells , which show high PR1::GUS expression levels .

Thus , HaRxL44 interferes with Mediator function by degrading MED19 , shifting the balance of defence transcription from SA-responsive defence to JA/ET-signalling , and enhancing susceptibility to biotrophs by attenuating SA-dependent gene expression .


The phytoalexin-deficient Arabidopsis mutant pad3 - 1 , which is affected in the production of the indole-type phytoalexin camalexin , has previously been shown not to display altered susceptibility to either the bacterium Pseudomonas syringae ( Glazebrook & Ausubel 1994 ; Proc .

Acad . Sci . USA , 91 : 8955 - 8959 ) or the biotrophic fungi Peronospora parasitica ( Glazebrook et al. 1997 ; Genetics , 146 : 381 - 392 ) and Erysiphe orontii ( Reuber et al. 1998 ; Plant J. 16 : 473 - 485 ) .

We now show that this mutant is markedly more susceptible than its wild-type parental line to infection by the necrotrophic fungus Alternaria brassicicola , but not to Botrytis cinerea .

A strong camalexin response was elicited in wild-type plants inoculated with either Alternaria brassicicola or Botrytis cinerea , whereas no camalexin could be detected in pad3 - 1 challenged with these fungi .

Hence , PAD3 appears to be a key determinant in resistance to at least A. brassicicola .

The induction of salicylate-dependent and jasmonate/ethylene-dependent defense genes was not reduced in Alternaria-challenged pad3 - 1 plants compared to similarly treated wild-type plants .

Camalexin production could not be triggered by exogenous application of either salicylate , ethylene or jasmonate and was not , or not strongly , reduced in mutants with defects in perception of these defense-related signal molecules .

Camalexin-production appears to be controlled by a pathway that exhibits little cross-talk with salicylate- , ethylene- and jasmonate-dependent signalling events .


Fourteen chemically defined hydrolyzable tannins and six impure mixtures of either condensed or hydrolyzable tannins were found to inhibit the gibberellin-induced growth of light-grown dwarf pea seedlings .

The highest ratio of tannins to gibberellic acid tested ( 1000 : 1 by weight ) inhibited from 80 to 95 % of the induced growth for all tannins tested except for two monogalloyl glucose tannins which inhibited only 50 % of the induced growth .

The lowest ratio tested ( 10 : 1 ) inhibited the induced growth by less than 25 % except for the case of terchebin where 50 % inhibition was found .

The inhibition of gibberellin-induced growth was found to be completely reversed by increasing the amount of gibberellin in three cases tested .

Tannins alone did not inhibit endogenous growth of either dwarf or nondwarf pea seedlings .

Eight compounds related to tannins , including coumarin , trans-cinnamic acid , and a number of phenolic compounds were also tested as gibberellin antagonists .

Most of these compounds showed some inhibition of gibberellin-induced growth , but less than that of the tannins .

At the highest ratio ( 1000 : 1 ) the greatest inhibition was 55 % ; at the lowest ratio ( 10 : 1 ) no more than 17 % was observed .

These compounds did not inhibit endogenous growth , and the inhibition of gibberellin-induced growth could be reversed by increasing the amount of gibberellin in two cases tested .

Six chemically defined tannins were found to inhibit hypocotyl growth induced by gibberellic acid in cucumber seedlings .

Growth induced by indoleacetic acid in the same test was not inhibited .

The highest ratio of tannin to promotor tested gave strong inhibition of gibberellic acid-induced growth , but actually enhanced the growth induced by indoleacetic acid .

This difference in action suggests a specificity between the tannins and gibberellic acid .


Although the roles of salicylate ( SA ) and jasmonic acid ( JA ) have been well-characterized in Fusarium head blight (FHB)-infected cereals , the roles of other phytohormones remain more ambiguous .

Here , the association between an array of phytohormones and FHB pathogenesis in wheat is investigated .

Comprehensive profiling of endogenous hormones demonstrated altered cytokinin , gibberellic acid ( GA ) , and JA metabolism in a FHB-resistant cultivar , whereas challenge by Fusarium graminearum increased abscisic acid ( ABA ) , JA , and SA in both FHB-susceptible and -resistant cultivars .

Subsequent investigation of ABA or GA coapplication with fungal challenge increased and decreased FHB spread , respectively .

These phytohormones-induced effects may be attributed to alteration of the F. graminearum transcriptome because ABA promoted expression of early-infection genes , including hydrolases and cytoskeletal reorganization genes , while GA suppressed nitrogen metabolic gene expression .

Neither ABA nor GA elicited significant effects on F. graminearum fungal growth or sporulation in axenic conditions , nor do these phytohormones affect trichothecene gene expression , deoxynivalenol mycotoxin accumulation , or SA/JA biosynthesis in F. graminearum-challenged wheat spikes .

Finally , the combined application of GA and paclobutrazol , a Fusarium fungicide , provided additive effects on reducing FHB severity , highlighting the potential for combining fungicidal agents with select phytohormone-related treatments for management of FHB infection in wheat .


WRKY proteins form a large family of plant transcription factors implicated in the modulation of numerous biological processes , such as growth , development and responses to various environmental stresses .

However , the roles of the majority WRKY family members , especially in non-model plants , remain poorly understood .

Transient expression in onion epidermal cells showed that CaWRKY40 can be targeted to nuclei and activates expression of a W-box-containing reporter gene .

CaWRKY40 transcripts are induced in pepper by Ralstonia solanacearum and heat shock .

To assess roles of CaWRKY40 in plant stress responses we performed gain- and loss-of-function experiments .

Overexpression of CaWRKY40 enhanced resistance to R. solanacearum and tolerance to heat shock in tobacco .

In contrast , silencing of CaWRKY40 enhanced susceptibility to R. solanacearum and impaired thermotolerance in pepper .

Consistent with its role in multiple stress responses , we found CaWRKY40 transcripts to be induced by signalling mechanisms mediated by the stress hormones salicylic acid ( SA ) , jasmonic acid ( JA ) and ethylene ( ET ) .

Overexpression of CaWRKY40 in tobacco modified the expression of hypersensitive response (HR)-associated and pathogenesis-related genes .

Collectively , our results suggest that CaWRKY40 orthologs are regulated by SA , JA and ET signalling and coordinate responses to R. solanacearum attacks and heat stress in pepper and tobacco .