Activation of MAPK Kinase 9 Induces Ethylene and Camalexin Biosynthesis and Enhances Sensitivity to Salt Stress in Arabidopsis*
Activation of MAPK Kinase 9 Induces Ethylene and Camalexin Biosynthesis and Enhances Sensitivity to Salt Stress in Arabidopsis*
复制标题
DOI：
10.1074/jbc.m801392200
复制
发表时间：
2008-10
影响因子：
4.8
通讯作者：
Juan Xu;Yuan Li;Ying Wang;Hongxia Liu;L. Lei;Hailian Yang;Guoqin Liu;D. Ren
中科院分区：
文献类型：
--
作者：
Juan Xu;Yuan Li;Ying Wang;Hongxia Liu;L. Lei;Hailian Yang;Guoqin Liu;D. Ren
丝裂原活化蛋白激酶（MAPK）级联在调节植物生长、发育以及对各种环境刺激的响应中发挥重要作用。我们证明了MKK9（一种MKK）在体外和植物体内都是MPK3和MPK6这两种MPK的上游激活因子。活性MKK9蛋白在转基因植物中的表达通过激活内源性MPK3和MPK6激酶诱导乙烯和卡马雷辛的合成。结果，多个负责乙烯生物合成、乙烯响应以及卡马雷辛生物合成的基因的转录被协同上调。MKK9的激活抑制黄化幼苗下胚轴的伸长。MKK9介导的对下胚轴伸长的影响可被乙烯生物合成抑制剂氨基乙氧基乙烯基甘氨酸和乙烯受体拮抗剂Ag⁺阻断。活性MKK9蛋白的表达增强转基因幼苗对盐胁迫的敏感性，而MKK9活性的缺失降低盐敏感性，这表明MKK9在盐胁迫响应中起作用。此处报道的结果揭示MKK9 - MPK3/MPK6级联参与乙烯和卡马雷辛生物合成的调节，并且可能是拟南芥胁迫响应中的一个重要轴心。
Mitogen-activated protein kinase (MAPK) cascades play important roles in regulating plant growth, development, and responses to various environmental stimuli. We demonstrate that MKK9, an MKK, is an upstream activator of the MPKs MPK3 and MPK6 both in vitro and in planta. Expression of active MKK9 protein in transgenic plants induces the synthesis of ethylene and camalexin through the activation of the endogenous MPK3 and MPK6 kinases. As a consequence, transcription of multiple genes responsible for ethylene biosynthesis, ethylene responses, and camalexin biosynthesis is coordinately up-regulated. The activation of MKK9 inhibits hypocotyl elongation in the etiolated seedlings. MKK9-mediated effects on hypocotyl elongation were blocked by the ethylene biosynthesis inhibitor, aminoethoxyvinylglycine, and ethylene receptor antagonist, Ag+. Expression of active MKK9 protein enhances the sensitivity of transgenic seedlings to salt stress, whereas loss of MKK9 activity reduces salt sensitivity indicating a role for MKK9 in the salt stress response. The results reported here reveal that the MKK9-MPK3/MPK6 cascade participates in the regulation of the biosynthesis of ethylene and camalexin and may be an important axis in the stress responses of Arabidopsis.