sentence: Collectively , these observations suggest that down-regulation of CYCA1 / CDK complexes , caused in part by reduced cyclin availability ( Fig. 1 ) and by inhibition mediated by ICK / KRP-type CKIs ( Coelho et al. 2005 ) , could be involved in regulating the transition from a mitotic to an endoreduplication cell cycle in maize endosperm.In comparison to CYCA1-associated kinase activity , that associated with CYCB1 ;3 , CYCD5 and CYCD2 ; 1 did not decline with the onset of endoreduplication .