From defense to symbiosis: limited alterations in the kinase domain of LysM receptor-like kinases are crucial for evolution of legume-Rhizobium symbiosis
From defense to symbiosis: limited alterations in the kinase domain of LysM receptor-like kinases are crucial for evolution of legume-Rhizobium symbiosis
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DOI：
10.1111/j.1365-313x.2010.04411.x
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发表时间：
2011-01-01
期刊：
影响因子：
7.2
通讯作者：
Kouchi, Hiroshi
中科院分区：
文献类型：
--
作者：
Nakagawa, Tomomi;Kaku, Hanae;Kouchi, Hiroshi
豆科植物与根瘤菌之间的固氮共生是由宿主植物识别根瘤菌结瘤因子（NFs）而启动的。核因子是几丁质寡糖的二硫键修饰衍生物，几丁质寡糖是一种诱导植物防御反应的真菌激发子。最近的证据表明，核因子和几丁质激发子都被结构相关的LysM受体激酶所识别。莲藕转录组分析表明，NF不仅激活共生基因，而且通过NF受体瞬时激活防御相关基因。相反，几丁质寡糖能够独立于NF受体激活共生基因。使用由莲花NF受体NFR 1的LysM受体结构域和拟南芥几丁质受体CERK 1的激酶结构域组成的嵌合基因进行的分析表明，用来自NFR 1相应区域的氨基酸序列YAQ取代CERK 1中的α EF螺旋的一部分，使L. nfr1突变体与中慢生根瘤菌loti建立共生关系。我们还发现，两个莲花LysM受体激酶，Lys6和Lys7，也具有YAQ序列的激酶结构域，抑制nfr 1的共生缺陷。这些结果强烈表明，除了适应细胞外LysM结构域的NF，几丁质受体的激酶结构域的有限的改变，在转移细胞内信号从防御反应的共生发挥了至关重要的作用，从而构成了一个关键的遗传事件在豆科植物根瘤共生的进化。
P>Nitrogen-fixing symbiosis between legumes and rhizobia is initiated by the recognition of rhizobial Nod factors (NFs) by host plants. NFs are diversely modified derivatives of chitin oligosaccharide, a fungal elicitor that induces defense responses in plants. Recent evidence has shown that both NFs and chitin elicitors are recognized by structurally related LysM receptor kinases. Transcriptome analyses of Lotus japonicus roots indicated that NFs not only activate symbiosis genes but also transiently activate defense-related genes through NF receptors. Conversely, chitin oligosaccharides were able to activate symbiosis genes independently of NF receptors. Analyses using chimeric genes consisting of the LysM receptor domain of a Lotus japonicus NF receptor, NFR1, and the kinase domain of an Arabidopsis chitin receptor, CERK1, demonstrated that substitution of a portion of the alpha EF helix in CERK1 with the amino acid sequence YAQ from the corresponding region of NFR1 enables L. japonicus nfr1 mutants to establish symbiosis with Mesorhizobium loti. We also showed that the kinase domains of two Lotus japonicus LysM receptor kinases, Lys6 and Lys7, which also possess the YAQ sequence, suppress the symbiotic defect of nfr1. These results strongly suggest that, in addition to adaptation of extracellular LysM domains to NFs, limited alterations in the kinase domain of chitin receptors have played a crucial role in shifting the intracellular signaling to symbiosis from defense responses, thus constituting one of the key genetic events in the evolution of root nodule symbiosis in legume plants.