Abstract
The key enzyme for ABA catabolism is ABA 8'-hydroxylase. In Arabidopsis , four ABA 8'-hydroxylases (CYP707A1-4) have been identified. To reveal the role of each CYP707A, we analyzed ABA contents and phenotypes in mutants and examined their expression site by using CYP707A promoter::GUS. In vegetative tissue, ABA level and drought tolerance of cyp707a1 and cyp707a3 were increased compared to those of wild type. Moreover, its double mutant exhibited even stronger tolerance to drought stress. These results indicate that CYP707A1 and CYP707A3 play an important role during drought stress. Although only CYP707A2 has thought to play an important role in seed, ABA level in cyp707a1 was higher than that in cyp707a2. Moreover, cyp707a1cyp707a2 exhibited increased hyperdomancy and accumulated 50-fold more ABA content than wild type. These results suggest that both CYP707A1 and CYP707A2 are indispensable for regulating ABA levels before germination.
