ABA-Hypersensitive germination3 encodes a protein phosphatase 2C (AtPP2CA) that strongly regulates abscisic acid signaling during germination among Arabidopsis protein phosphatase 2Cs
ABA-Hypersensitive germination3 encodes a protein phosphatase 2C (AtPP2CA) that strongly regulates abscisic acid signaling during germination among Arabidopsis protein phosphatase 2Cs
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DOI：
10.1104/pp.105.070128
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发表时间：
2006-01-01
期刊：
影响因子：
7.4
通讯作者：
Hirayama, T
中科院分区：
文献类型：
--
作者：
Yoshida, T;Nishimura, N;Hirayama, T
植物激素脱落酸 (ABA) 调节重要的生理发育过程和应激反应。之前，我们报道了拟南芥（Arabidopsis thaliana）L. Heynh。 ahg 突变体，在发芽和早期生长过程中对 ABA 高度敏感。其中，ABA超敏萌芽3（ahg3）表现出最强的ABA超敏性。在这项研究中，我们发现 AHG3 基因与 AtPP2CA 相同，后者编码蛋白磷酸酶 2C (PP2C)。尽管根据反向遗传学方法获得的结果，AtPP2CA 被报道参与 ABA 反应，但其在 ABA 反应中的生理相关性尚未阐明。我们在体外和体内证明 ahg3-1 错义突变会导致 PP2C 活性丧失，这为 PP2C 在 ABA 信号传导中充当负调节因子提供了具体的证据。此外，我们还比较了拟南芥中8个结构相关的PP2C基因（包括ABI1、ABI2、HAB1和HAB2）的破坏突变体的影响，发现AHG3/AtPP2CA的破坏突变体在发芽过程中具有最强的ABA超敏性，但在成年植株中没有表现出任何显着的表型。 Northern 印迹分析清楚地表明，AHG3/AtPP2CA 是种子中 PP2C 基因中最活跃的。这些结果表明，AHG3/AtPP2CA 在种子 ABA 反应中的 PP2C 中发挥着重要作用，并且这些 PP2C 的功能重叠，但它们独特的组织或发育特异性表达在 ABA 反应中赋予了独特且不可或缺的生理功能。
The phytohormone abscisic acid (ABA) regulates physiologically important developmental processes and stress responses. Previously, we reported on Arabidopsis (Arabidopsis thaliana) L. Heynh. ahg mutants, which are hypersensitive to ABA during germination and early growth. Among them, ABA-hypersensitive germination3 (ahg3) showed the strongest ABA hypersensitivity. In this study, we found that the AHG3 gene is identical to AtPP2CA, which encodes a protein phosphatase 2C (PP2C). Although AtPP2CA has been reported to be involved in the ABA response on the basis of results obtained by reverse-genetics approaches, its physiological relevance in the ABA response has not been clarified yet. We demonstrate in vitro and in vivo that the ahg3-1 missense mutation causes the loss of PP2C activity, providing concrete confirmation that this PP2C functions as a negative regulator in ABA signaling. Furthermore, we compared the effects of disruption mutations of eight structurally related PP2C genes of Arabidopsis, including ABI1, ABI2, HAB1, and HAB2, and found that the disruptant mutant of AHG3/AtPP2CA had the strongest ABA hypersensitivity during germination, but it did not display any significant phenotypes in adult plants. Northern-blot analysis clearly showed that AHG3/AtPP2CA is the most active among those PP2C genes in seeds. These results suggest that AHG3/AtPP2CA plays a major role among PP2Cs in the ABA response in seeds and that the functions of those PP2Cs overlap, but their unique tissue- or development-specific expression confers distinct and indispensable physiological functions in the ABA response.