Qiu Jin-Long, Zhou Lu, Yun Byung-Wook, Nielsen Henrik Bjørn, Fiil Berthe Katrine, Petersen Klaus, Mackinlay Jim, Loake Gary J, Mundy John, Morris Peter C
Department of Biology, University of Copenhagen, 2200 Copenhagen N, Denmark.
Plant Physiol. 2008 Sep;148(1):212-22. doi: 10.1104/pp.108.120006. Epub 2008 Jul 3.
The Arabidopsis (Arabidopsis thaliana) MKK1 and MKK2 mitogen-activated protein kinase kinases have been implicated in biotic and abiotic stress responses as part of a signaling cascade including MEKK1 and MPK4. Here, the double loss-of-function mutant (mkk1/2) of MKK1 and MKK2 is shown to have marked phenotypes in development and disease resistance similar to those of the single mekk1 and mpk4 mutants. Because mkk1 or mkk2 single mutants appear wild type, basal levels of MPK4 activity are not impaired in them, and MKK1 and MKK2 are in part functionally redundant in unchallenged plants. These findings are confirmed and extended by biochemical and molecular analyses implicating the kinases in jasmonate- and salicylate-dependent defense responses, mediated in part via the MPK4 substrate MKS1. In addition, transcriptome analyses delineate overlapping and specific effects of the kinases on global gene expression patterns demonstrating both redundant and unique functions for MKK1 and MKK2.
拟南芥（Arabidopsis thaliana）的促分裂原活化蛋白激酶激酶MKK1和MKK2作为包括MEKK1和MPK4在内的信号级联反应的一部分，参与了生物和非生物胁迫反应。在此，MKK1和MKK2的双功能缺失突变体（mkk1/2）在发育和抗病性方面表现出与单基因mekk1和mpk4突变体相似的显著表型。由于mkk1或mkk2单突变体表现为野生型，其MPK4活性的基础水平未受损，并且在未受胁迫的植物中，MKK1和MKK2在功能上部分冗余。这些发现通过生化和分子分析得到证实和扩展，这些分析表明这些激酶参与了茉莉酸和水杨酸依赖性防御反应，部分是通过MPK4底物MKS1介导的。此外，转录组分析描绘了这些激酶对全局基因表达模式重叠和特定的影响，证明了MKK1和MKK2具有冗余和独特的功能。
