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J Integr Plant Biol, 60 (4): 276-291, Research Article
The dioxygenase GIM2 functions in seed germination by altering gibberellin production in Arabidopsis
Wei Xiong1, Tiantian Ye1,2, Xuan Yao1, Xiong Liu1, Sheng Ma1, Xi Chen1, Ming-Luan Chen2, Yu-Qi Feng2 and Yan Wu1*
1State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China 2Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), Department of Chemistry, Wuhan University, Wuhan 430072, China *Correspondence: Email: Yan Wu (wuy@whu.edu.cn)
Abstract

The phytohormones gibberellic acid (GA) and abscisic acid (ABA) antagonistically control seed germination. High levels of GA favor seed germination, whereas high levels of ABA hinder this process. The direct relationship between GA biosynthesis and seed germination ability need further investigation. Here, we identified the ABA‐insensitive gain‐of‐function mutant germination insensitive to ABA mutant 2 (gim2) by screening a population of XVE T‐DNA‐tagged mutant lines. Based on two loss‐of‐function gim2‐ko mutant lines, the disruption of GIM2 function caused a delay in seed germination. By contrast, upregulation of GIM2 accelerated seed germination, as observed in transgenic lines overexpressing GIM2 (OE). We detected a reduction in endogenous bioactive GA levels and an increase in endogenous ABA levels in the gim2‐ko mutants compared to wild type. Conversely, the OE lines had increased endogenous bioactive GA levels and decreased endogenous ABA levels. The expression levels of a set of GA‐ and/or ABA‐related genes were altered in both the gim2‐ko mutants and the OE lines. We confirmed that GIM2 has dioxygenase activity using an in vitro enzyme assay, observing that GIM2 can oxidize GA12. Hence, our characterization of GIM2 demonstrates that it plays a role in seed germination by affecting the GA metabolic pathway in Arabidopsis.

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Received: 19 October 2017      Published: 20 April 2018
© 2018 Institute of Botany, Chinese Academy of Sciences
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