Activation of a mitogen-activated protein kinase cascade induces WRKY family of transcription factors and defense genes in tobacco
Activation of a mitogen-activated protein kinase cascade induces WRKY family of transcription factors and defense genes in tobacco
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DOI：
10.1111/j.1365-313x.2004.02033.x
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发表时间：
2004-04-01
期刊：
影响因子：
7.2
通讯作者：
Zhang, SQ
中科院分区：
文献类型：
--
作者：
Kim, CY;Zhang, SQ
丝裂原活化蛋白激酶（MAPK）级联是真核细胞中重要的信号传导模块，其将从受体/传感器产生的信号转化为细胞应答。激活后，MAPK可以易位到细胞核中，在那里它们磷酸化转录因子，这反过来激活基因表达。我们最近确定NtMEK 2，烟草MAPK激酶，作为上游激酶的SIPK和WIPK，两个充分表征烟草胁迫响应的MAPK。在转NtMEK 2（DD）基因烟草中，NtMEK 2（DD）通过激活内源SIPK和WIPK，诱导产生了多组防御基因，包括3-羟基-3-甲基戊二酰辅酶A还原酶（HMGR）、基本致病相关基因（PR）、系统获得性抗性基因8.2（Sar 8.2）和harpin诱导基因1（Hin 1）。为了鉴定参与这些防御基因激活的转录因子，我们使用NtMEK 2（DD）植物的核提取物进行凝胶迁移率变动测定。在防御相关基因启动子中存在的常见顺式作用元件中，我们观察到NtMEK 2（DD）植物核提取物中W盒的结合活性强烈增加，但对照NtMEK 2（KR）植物没有。核提取物中升高的W-box结合活性不能被磷酸酶处理逆转，排除了由SIPK/WIPK直接磷酸化调节WRKY转录因子的可能性。相反，我们观察到NtMEK 2（DD）植物中几个WRKY基因的表达迅速增加。这些结果表明，W-box结合活性的增加后，SIPK/WIPK激活是WRKY基因激活的结果，NtMEK 2-SIPK/WIPK级联参与调节基因的表达，从转录因子到防御基因在植物防御反应的进一步下游。
Mitogen-activated protein kinase (MAPK) cascades are important signaling modules in eukaryotic cells that convert signals generated from the receptors/sensors to cellular responses. Upon activation, MAPKs can be translocated into nuclei where they phosphorylate transcription factors, which in turn activate gene expression. We recently identified NtMEK2, a tobacco MAPK kinase, as the upstream kinase of SIPK and WIPK, two well-characterized tobacco stress-responsive MAPKs. In the conditional gain-of-function NtMEK2(DD) transgenic tobacco plants, the activation of endogenous SIPK and WIPK by NtMEK2(DD) induces several groups of defense genes, including 3-hydroxy-3-methlyglutaryl CoA reductase (HMGR), basic pathogenesis related (PR) genes, systemic acquired resistance gene 8.2 (Sar 8.2), and harpin-induced gene1 (Hin1). To identify the transcription factor(s) involved in the activation of these defense genes, we performed gel-mobility shift assays using nuclear extracts from NtMEK2(DD) plants. Among the common cis-acting elements present in the promoters of defense-related genes, we observed a strong increase in the binding activity to the W box in nuclear extracts from the NtMEK2(DD) plants but not the control NtMEK2(KR) plants. The elevated W-box-binding activity in the nuclear extracts cannot be reversed by phosphatase treatment, excluding the possibility of a direct phosphorylation regulation of WRKY transcription factors by SIPK/WIPK. Instead, we observed a rapid increase in the expression of several WRKY genes in the NtMEK2(DD) plants. These results suggest that the increase in W-box-binding activity after SIPK/WIPK activation is a result of WRKY gene activation, and the NtMEK2-SIPK/WIPK cascade is involved in regulating the expression of genes ranging from transcription factors to defense genes further downstream during plant defense responses.