The Arabidopsis mitogen-activated protein kinase kinase MKK3 is upstream of group C mitogen-activated protein kinases and participates in pathogen signaling
The Arabidopsis mitogen-activated protein kinase kinase MKK3 is upstream of group C mitogen-activated protein kinases and participates in pathogen signaling
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DOI：
10.1105/tpc.106.050039
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发表时间：
2007-10-01
期刊：
影响因子：
11.6
通讯作者：
Hirt, Heribert
中科院分区：
文献类型：
--
作者：
Doczi, Robert;Brader, Gunter;Hirt, Heribert
虽然拟南芥基因组中含有编码20种丝裂原活化蛋白激酶（MAPK）和10种MAPK激酶（MAPK）的基因，但其中大多数基因的功能尚不清楚。在这项工作中，我们分析了B组MAPK激酶MKK 3的功能。转基因ProMKK 3：GUS株系在维管组织中表现出基础表达，其强烈诱导假单胞菌番茄致病变种DC 3000（Pst DC 3000）感染，但不受非生物胁迫。强毒Pst DC 3000的生长在mkk 3敲除植物中增加，而在MKK 3过表达植物中减少。此外，MKK 3过表达株系显示几个PR基因的表达增加。通过酵母双杂交分析，免疫共沉淀和蛋白激酶测定，MKK 3被揭示为C组MAPK MPK 1，MPK 2，MPK 7和MPK 14的上游激活剂。鞭毛蛋白衍生的flg 22肽强烈激活MPK 6，但导致MPK 7的弱激活。相比之下，MPK 6和MPK 7都被H2 O2激活，但只有MPK 7的激活被MKK 3增强。与MKK 3调节PR基因表达的观点一致，MKK 3-MPK 7的共表达强烈增强了ProPR 1：GUS的表达。我们的研究结果表明，MKK 3途径在病原体防御中发挥作用，并进一步强调了MAPK信号转导在植物胁迫反应中的重要性和复杂性。
Although the Arabidopsis thaliana genome contains genes encoding 20 mitogen-activated protein kinases (MAPKs) and 10 MAPK kinases (MAPKKs), most of them are still functionally uncharacterized. In this work, we analyzed the function of the group B MAPK kinase, MKK3. Transgenic ProMKK3:GUS lines showed basal expression in vascular tissues that was strongly induced by Pseudomonas syringae pv tomato strain DC3000 (Pst DC3000) infection but not by abiotic stresses. The growth of virulent Pst DC3000 was increased in mkk3 knockout plants and decreased in MKK3-overexpressing plants. Moreover, MKK3 overexpression lines showed increased expression of several PR genes. By yeast two-hybrid analysis, coimmunoprecipitation, and protein kinase assays, MKK3 was revealed to be an upstream activator of the group C MAPKs MPK1, MPK2, MPK7, and MPK14. Flagellin-derived flg22 peptide strongly activated MPK6 but resulted in poor activation of MPK7. By contrast, MPK6 and MPK7 were both activated by H2O2, but only MPK7 activation was enhanced by MKK3. In agreement with the notion that MKK3 regulates the expression of PR genes, ProPR1:GUS expression was strongly enhanced by coexpression of MKK3-MPK7. Our results reveal that the MKK3 pathway plays a role in pathogen defense and further underscore the importance and complexity of MAPK signaling in plant stress responses.