Abstract
The CYP707As encode ABA 8'-hydroxylases, the key regulatory enzymes in ABA catabolism. To reveal the roles of four Arabidopsis CYP707As (CYP707A1-A4) in seeds, we analyzed the expression and mutant phenotypes of these genes. Previous study has demonstrated that CYP707A2 is the major isoform for the ABA catabolism after seed imbibition. Interestingly, the cyp707a1 dry seed accumulated higher ABA levels compared to the cyp707a2. Expression analysis during seed development revealed that CYP707A1 and CYP707A2 were differentially expressed at mid-maturation and late-maturation stage, respectively. The mutant analysis demonstrated that degree of seed dormancy was correlated with the ABA levels in imbibed seed rather than those in dry seed. Among cyp707a mutants examined, ABA-hypersensitivity was most prominent in the cyp707a2 during germination, whereas the cyp707a1 was most strongly inhibited by exogenous ABA during early seedling growth, indicating CYP707A1 acts as the major player for ABA catabolism in postgermination growth.
