Autophosphorylation of Specific Threonine and Tyrosine Residues in Arabidopsis CERK1 is Essential for the Activation of Chitin-Induced Immune Signaling
Autophosphorylation of Specific Threonine and Tyrosine Residues in Arabidopsis CERK1 is Essential for the Activation of Chitin-Induced Immune Signaling
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DOI：
10.1093/pcp/pcw150
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发表时间：
2016-11-01
影响因子：
4.9
通讯作者：
Shibuya, Naoto
中科院分区：
文献类型：
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作者：
Suzuki, Maruya;Shibuya, Masatoshi;Shibuya, Naoto
植物细胞表面的模式识别受体介导微生物/损伤相关分子模式(MAMPs/DAMP)的识别，并激活下游的免疫信号。信号受体样激酶的自动磷酸化是激活下游反应的关键事件，但每个磷酸化位点在免疫信号调节中的作用尚不清楚。在这项研究中，41个Ser/Thr/Tyr和15个Ser/Thr残基被鉴定为拟南芥CERK1的体外和体内自磷酸化位点，这是几丁质信号转导所必需的。对Cerk1-2背景中每个磷酸化位点表达突变的CERK1基因的转基因植物的综合分析表明，位于催化环上游的T479和Y428的磷酸化对于激活甲壳素触发的防御反应是重要的。T573的磷酸化对甲壳素反应的贡献也被提出。体外活性测定表明，T479和T573的磷酸化直接参与CERK1的活性调节，而Y428的磷酸化调节几丁质信号，而不依赖于激酶活性的调节。这些结果表明，激酶结构域中特定残基的磷酸化可能通过调节蛋白的活性或通过不同的机制，如调节蛋白-蛋白质的相互作用，参与下游信号的调节。
Pattern recognition receptors on the plant cell surface mediate the recognition of microbe/damage-associated molecular patterns (MAMPs/DAMPs) and activate downstream immune signaling. Autophosphorylation of signaling receptor-like kinases is a critical event for the activation of downstream responses but the function of each phosphorylation site in the regulation of immune signaling is not well understood. In this study, 41 Ser/Thr/Tyr and 15 Ser/Thr residues were identified as in vitro and in vivo autophosphorylation sites of Arabidopsis CERK1, which is essential for chitin signaling. Comprehensive analysis of transgenic plants expressing mutated CERK1 genes for each phosphorylation site in the cerk1-2 background indicated that the phosphorylation of T479 in the activation segment and Y428 located upstream of the catalytic loop is important for the activation of chitin-triggered defense responses. Contribution of the phosphorylation of T573 to the chitin responses was also suggested. In vitro evaluation of kinase activities of mutated kinase domains indicated that the phosphorylation of T479 and T573 is directly involved in the regulation of kinase activity of CERK1 but the phosphorylation of Y428 regulates chitin signaling independently of the regulation of kinase activity. These results indicated that the phosphorylation of specific residues in the kinase domain contributes to the regulation of downstream signaling either through the regulation of kinase activity or the different mechanisms, e.g. regulation of protein-protein interactions.