24. シロイヌナズナABA 8'-水酸化酵素CYP707A2の生化学的解析 : 種子生理における役割

概要

論文の詳細を見る
Abscisic acid (ABA) controls many aspects of physiological processes including seed dormancy and acquisition of drought tolerance. The hormonal action of ABA depends on the endogenous level of ABA, which is controlled by the precise balance between its biosynthesis and catabolism. Recently, Arabidopsis cytochrome P450 CYP707A1-A4 genes have been shown to encode the ABA 8'-hydroxylase that catalyzes the committed step in the predominant catabolic pathway. CYP707A catalyzes a reaction for the conversion of ABA to 8'-hydroxy ABA, which is then spontaneously isomerized to form phasesic acid (PA). Expression analysis of CYP707A1-A4 revealed that CYP707A2 is responsible for the rapid decrease in ABA level after seed imbibition. To access its role in seed physiology, we performed biochemical analysis of CYP707A2 in terms of temperature dependence of its enzyme activity and the substrate specificity. PA forming activity from the microsomal fraction of CYP707A2 expressing yeast was observed at all physiological temperatures examined (4℃-37℃), although a significant reduction in the activity was found at 4℃ and 37℃. This result suggests that CYP707A2 is possibly involved in seed physiology to control the endogenous ABA level such as stratification and high-temperature induced dormancy. Indeed, among CYP707A genes, only CYP707A2 was upregulated during imbibition at 4℃ in the dark. In addition, CYP707A2 failed to hydroxylate ABA methyl ester, suggesting that this enzyme cannot use ABA conjugates as the substrate. We are currently measuring the contents of ABA and PA in Arabidopsis seed upon stratification, and the role of CYP707A2 in seed germination will be discussed.
植物化学調節学会の論文
2004-10-13

24. シロイヌナズナABA 8'-水酸化酵素CYP707A2の生化学的解析 : 種子生理における役割

スポンサーリンク

概要

著者

関連論文

スポンサーリンク