摘要
The phytohormones gibberellic acid （GA） and abscisic acid （ABA） antagonistically control seed germina- tion. High levels of GA favor seed germination, whereas high levels of ABA hinder this process. The direct relationship between GA biosynthesis and seed germina- tion 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 germina- tion, 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 GA^2. Hence, our characterization of GIM2 demonstrates that it plays a role in seed germination by affecting the GA metabolic pathway in Arabidopsis.
The phytohormones gibberellic acid （GA） and abscisic acid （ABA） antagonistically control seed germina- tion. High levels of GA favor seed germination, whereas high levels of ABA hinder this process. The direct relationship between GA biosynthesis and seed germina- tion 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 germina- tion, 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 GA^2. Hence, our characterization of GIM2 demonstrates that it plays a role in seed germination by affecting the GA metabolic pathway in Arabidopsis.
基金
the ‘Large-scale Instrument and Equipment Sharing Foundation of Wuhan University’ for supporting the use of the instruments in the College of Life Sciences in Wuhan University
supported by grants to Y.W. from Nation Natural Science Foundation of China (31270333 and 90817013)
the Major State Basic Research Program from the Ministry of Science and Technology of China (2013CB126900)
