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| Subject Categories: Cellular Metabolism | Plant Biology |
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| The EMBO Journal
(2004) 23, 1647–1656, doi:10.1038/sj.emboj.7600121 Published online 25 March 2004 |
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| The Arabidopsis cytochrome P450 CYP707A encodes ABA 8'-hydroxylases: key enzymes in ABA catabolism |
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| Tetsuo Kushiro1, 5, Masanori Okamoto1, 2, 5, Kazumi Nakabayashi1, Kazutoshi Yamagishi1, 6, Sayaka Kitamura1, Tadao Asami3, Nobuhiro Hirai4, Tomokazu Koshiba2, Yuji Kamiya1 and Eiji Nambara1 |
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1 Plant Science Center, RIKEN, Yokohama, Japan 2 Department of Biological Sciences, Tokyo Metropolitan University, Hachioji-shi, Japan 3 Plant Functions Laboratory, RIKEN, Wako, Japan 4 International Innovation Center, Kyoto University, Kyoto, Japan To whom correspondence should be addressed Eiji Nambara, Lab for Reproductive Growth Regulation, Plant Science Center, RIKEN, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan. Tel.: +81 45 503 9666; Fax: +81 45 503 9665; E-mail: nambara@postman.riken.go.jp 5 These authors contributed equally to this work 6 Present address: The Special Division for Human Life Technology, National Institute of Advanced Industrial Science and Technology (AIST), Ikeda 563-8577, Japan Received 30 September 2003; Accepted 9 January 2004; Published online 25 March 2004. |
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| Abstract |
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| The hormonal action of abscisic acid (ABA) in plants is controlled by the precise balance between its biosynthesis and catabolism. In plants, ABA 8'-hydroxylation is thought to play a predominant role in ABA catabolism. ABA 8'-hydroxylase was shown to be a cytochrome P450 (P450); however, its corresponding gene had not been identified. Through phylogenetic and DNA microarray analyses during seed imbibition, the candidate genes for this enzyme were narrowed down from 272 Arabidopsis P450 genes. These candidate genes were functionally expressed in yeast to reveal that members of the CYP707A family, CYP707A1–CYP707A4, encode ABA 8'-hydroxylases. Expression analyses revealed that CYP707A2 is responsible for the rapid decrease in ABA level during seed imbibition. During drought stress conditions, all CYP707A genes were upregulated, and upon rehydration a significant increase in mRNA level was observed. Consistent with the expression analyses, cyp707a2 mutants exhibited hyperdormancy in seeds and accumulated six-fold greater ABA content than wild type. These results demonstrate that CYP707A family genes play a major regulatory role in controlling the level of ABA in plants. |
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| Keywords: abscisic acid, Arabidopsis, catabolism, P450 |
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