sentence: CaHSL1 exhibited transcriptional upregulation in pepper plants exposed to HTHH , CaHSL1 silenced pepper plants by VIGS showed decreased both basal and acquired thermotolerance and optimal / maximal photochemical efficiency of PSII in the dark ( Fv / Fm ) , and downregulation of the thermotolerance-associated gene CaHSP24 ( Heckathorn et al ., 1996 ; Pivovarova et al ., 2005 ) .