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Plant Cell | 中科院遗传所周俭民课题组揭示植物防卫反应MAPK级联作用新机制

【PDF原文: Receptor-like Cytoplasmic Kinases Directly Link Diverse Pattern Recognition Receptors to the Activation of Mitogen-activated Protein Kinase Cascades in Arabidopsis

植物进化出大量的锚定在细胞表面的模式识别受体 (pattern-recognition receptors, PRRs)来感受病原菌侵染时释放特异的分子模式 (molecular patterns),诱发PTI (pattern-triggered immunity)进程造成一系列反应,例如Ca2+流爆发、ROS增多及MAPK激活等等。已有研究表明,几乎所有的PRR都可以激活植物体内MPK3/4/6的激酶活性,这是植物建立抗病防卫系统的关键。MEKK1参与调控MPK4的活性的分子机制已被报道,但PRR介导的MAPKKK对MPK3/6的调控机制及MAPKKK如何被PRR激活等问题仍未解决。


2018年6月6日,The Plant Cell 在线发表了中国科学院遗传与发育生物学研究所周俭民课题组一篇题为“Receptor-like Cytoplasmic Kinases Directly Link Diverse Pattern Recognition Receptors to the Activation of Mitogen-activated Protein Kinase Cascades in Arabidopsis”的研究论文,报道了拟南芥中两个高度相关的激酶MAPKKK3和MAPKKK5参与调控至少4个PRR蛋白引发的MPK3/6激酶活性,并调控拟南芥对细菌和真菌病原菌的抗性。


该研究发现,类受体胞质激酶(receptor-like cytoplasmic kinases VII, RLCK Ⅶ )作用于PRR下游,可直接磷酸化MAPKKK5的Ser599。该磷酸化位点对分子模式引发的MPK3/6的激活、防卫反应下游基因的表达及植物抗病性起到关键性作用。有意思的是,这条途径存在正反馈机制,即激活的MPK6会进一步磷酸化MAPKKK5的Ser682和Ser692激活MPK3/6的磷酸化活性和抗病性。最终,MEKK1的Ser603被RLCK Ⅶ与MPK4磷酸化,这是激活分子模式引发的MPK4激酶活性的关键步骤。综上所述,该研究揭示了多种PRR蛋白介导的MAPK级联反应激活并使植物获得抗病性的作用机制。


Abstract

Plants deploy numerous cell surface-localized pattern-recognition receptors (PRRs) to perceive host- and microbe-derived molecular patterns that are specifically released during infection and activate defense responses. The activation of the mitogen-activated protein kinases MPK3, MPK4 and MPK6 (MPK¾/6) is a hallmark of immune system activation by all known PRRs and is crucial for establishing disease resistance. The MAP kinase kinase kinase (MAPKKK) MEKK1 controls MPK4 activation, but the MAPKKKs responsible for MPK3/6 activation downstream of diverse PRRs and how the perception of diverse molecular patterns leads to the activation of MAPKKKs remain elusive. Here we show that two highly related MAPKKKs, MAPKKK3 and MAPKKK5, mediate MPK3/6 activation by at least four PRRs and confer resistance to bacterial and fungal pathogens in Arabidopsis thaliana. The receptor-like cytoplasmic kinases VII (RLCK VII), which act downstream of PRRs, directly phosphorylate MAPKKK5 Ser599, which is required for pattern-triggered MPK3/6 activation, defense gene expression, and disease resistance. Surprisingly, MPK6 further phosphorylates MAPKKK5 Ser682 and Ser692 to enhance MPK3/6 activation and disease resistance, pointing to a positive feedback mechanism. Finally, MEKK1 Ser603 is phosphorylated by both RLCK VII and MPK4, which is required for pattern-triggered MPK4 activation. These findings illustrate central mechanisms by which multiple PRRs activate MAPK cascades and disease resistance.

  • Received December 22, 2017.
  • Accepted May 30, 2018.

【PDF原文: Receptor-like Cytoplasmic Kinases Directly Link Diverse Pattern Recognition Receptors to the Activation of Mitogen-activated Protein Kinase Cascades in Arabidopsis

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