The 9- <i>cis</i> -epoxycarotenoid cleavage reaction is the key regulatory step of abscisic acid biosynthesis in water-stressed bean
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- Xiaoqiong Qin
- Departments of Energy Plant Research Laboratory and Botany and Plant Pathology, Michigan State University, East Lansing, MI 48824
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- Jan A. D. Zeevaart
- Departments of Energy Plant Research Laboratory and Botany and Plant Pathology, Michigan State University, East Lansing, MI 48824
抄録
<jats:p> Abscisic acid (ABA), a cleavage product of carotenoids, is involved in stress responses in plants. A well known response of plants to water stress is accumulation of ABA, which is caused by <jats:italic>de novo</jats:italic> synthesis. The limiting step of ABA biosynthesis in plants is presumably the cleavage of 9- <jats:italic>cis</jats:italic> -epoxycarotenoids, the first committed step of ABA biosynthesis. This step generates the C <jats:sub>15</jats:sub> intermediate xanthoxin and C <jats:sub>25</jats:sub> -apocarotenoids. A cDNA, <jats:italic>PvNCED1</jats:italic> , was cloned from wilted bean ( <jats:italic>Phaseolus vulgaris</jats:italic> L.) leaves. The 2,398-bp full-length <jats:italic>PvNCED1</jats:italic> has an ORF of 615 aa and encodes a 68-kDa protein. The PvNCED1 protein is imported into chloroplasts, where it is associated with the thylakoids. The recombinant protein PvNCED1 catalyzes the cleavage of 9- <jats:italic>cis</jats:italic> -violaxanthin and 9′- <jats:italic>cis</jats:italic> -neoxanthin, so that the enzyme is referred to as 9- <jats:italic>cis</jats:italic> -epoxycarotenoid dioxygenase. When detached bean leaves were water stressed, ABA accumulation was preceded by large increases in <jats:italic>PvNCED1</jats:italic> mRNA and protein levels. Conversely, rehydration of stressed leaves caused a rapid decrease in <jats:italic>PvNCED1</jats:italic> mRNA, protein, and ABA levels. In bean roots, a similar correlation among <jats:italic>PvNCED1</jats:italic> mRNA, protein, and ABA levels was observed. However, the ABA content was much less than in leaves, presumably because of the much smaller carotenoid precursor pool in roots than in leaves. At 7°C, <jats:italic>PvNCED1</jats:italic> mRNA and ABA were slowly induced by water stress, but, at 2°C, neither accumulated. The results provide evidence that drought-induced ABA biosynthesis is regulated by the 9- <jats:italic>cis</jats:italic> -epoxycarotenoid cleavage reaction and that this reaction takes place in the thylakoids, where the carotenoid substrate is located. </jats:p>
収録刊行物
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- Proceedings of the National Academy of Sciences
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Proceedings of the National Academy of Sciences 96 (26), 15354-15361, 1999-12-21
Proceedings of the National Academy of Sciences
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詳細情報 詳細情報について
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- CRID
- 1360574095755704064
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- NII論文ID
- 80011668787
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- ISSN
- 10916490
- 00278424
- http://id.crossref.org/issn/00278424
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