Abscisic acid-activated SNRK2 protein kinases function in the gene-regulation pathway of ABA signal transduction by phosphorylating ABA response element-binding factors
Abscisic acid-activated SNRK2 protein kinases function in the gene-regulation pathway of ABA signal transduction by phosphorylating ABA response element-binding factors
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DOI：
10.1111/j.1365-313x.2005.02583.x
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发表时间：
2005-12-01
期刊：
影响因子：
7.2
通讯作者：
Hattori, T
中科院分区：
文献类型：
--
作者：
Kobayashi, Y;Murata, M;Hattori, T
植物激素脱落酸（阿坝）通过ABA调节基因启动子中的ABA反应元件（ABRE）诱导基因表达。一组bZIP蛋白已被鉴定为ABRE结合因子（ABF），其通过该顺式元件激活转录。水稻ABF，TRAB1，已被证明是通过ABA依赖性磷酸化激活。虽然大量的信号转导因子已被确定参与阿坝调节ABA，相对较少的是已知的ABA信号通路，导致基因表达。我们最近发现，水稻SnRK2蛋白激酶家族的三个成员，SAPK8，SAPK9和SAPK10，被阿坝信号以及高渗胁迫激活。在这里，我们表明，这些ABA激活的SnRK2蛋白激酶在培养的细胞原生质体中的瞬时过表达导致ABRE调节的启动子的激活，这表明这些激酶参与阿坝信号的基因调控途径。我们进一步展示了几条证据，这些ABA激活的SnRK2蛋白激酶直接磷酸化TRAB 1响应阿坝。SAPK10激活和TRAB1磷酸化的动力学分析表明，后者紧随前者。TRAB 1不仅在阿坝的作用下发生磷酸化，而且在高渗胁迫下也发生磷酸化，这被解释为高渗激活的SAPKs磷酸化TRAB 1的结果。TRAB1和SAPK10在体内的物理相互作用通过免疫共沉淀实验证明。最后，TRAB 1在体外被ABA激活的SnRK2蛋白激酶在Ser102处磷酸化，Ser102在体内响应阿坝而磷酸化，并且对于激活功能至关重要。
The plant hormone abscisic acid (ABA) induces gene expression via the ABA-response element (ABRE) present in the promoters of ABA-regulated genes. A group of bZIP proteins have been identified as ABRE-binding factors (ABFs) that activate transcription through this cis element. A rice ABF, TRAB1, has been shown to be activated via ABA-dependent phosphorylation. While a large number of signalling factors have been identified that are involved in stomatal regulation by ABA, relatively less is known about the ABA-signalling pathway that leads to gene expression. We have shown recently that three members of the rice SnRK2 protein kinase family, SAPK8, SAPK9 and SAPK10, are activated by ABA signal as well as by hyperosmotic stress. Here we show that transient overexpression in cultured cell protoplasts of these ABA-activated SnRK2 protein kinases leads to the activation of an ABRE-regulated promoter, suggesting that these kinases are involved in the gene-regulation pathway of ABA signalling. We further show several lines of evidence that these ABA-activated SnRK2 protein kinases directly phosphorylate TRAB1 in response to ABA. Kinetic analysis of SAPK10 activation and TRAB1 phosphorylation indicated that the latter immediately followed the former. TRAB1 was found to be phosphorylated not only in response to ABA, but also in response to hyperosmotic stress, which was interpreted as the consequence of phosphorylation of TRAB1 by hyperosmotically activated SAPKs. Physical interaction between TRAB1 and SAPK10 in vivo was demonstrated by a co-immunoprecipitation experiment. Finally, TRAB1 was phosphorylated in vitro by the ABA-activated SnRK2 protein kinases at Ser102, which is phosphorylated in vivo in response to ABA and is critical for the activation function.