State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou, China.
J Exp Bot. 2019 Oct 15;70(19):5507-5516. doi: 10.1093/jxb/erz313.
LysM receptor-like kinases (LYKs) of Arabidopsis thaliana (namely LYK1, LYK4 and LYK5) play a major role in chitin perception and immunity against pathogenic fungi. Chitin-induced heterodimerization of LYK1 and LYK5 has been previously reported, but protein interaction partners of LYK4 have not yet been identified. In this study, by analysing mutants we confirmed a role of LYK4 in chitin perception, and found that the ectodomain of LYK4 homodimerizes and also interacts with the ectodomain of LYK5 in vitro. Pull-down experiments with proteins expressed in protoplasts indicated LYK4-LYK4 and LY4-LYK5 interactions in planta. When protoplasts were treated with chitoheptaose or chitin, a protein complex was immunoprecipitated that appeared to be composed of LYK1, LYK4, and LYK5. Similar experiments with proteins expressed in lyk mutant plants suggested that elicitor treatment induced a physical interaction between LYK1 and LYK5 but not between LYK1 and LYK4. Bimolecular fluorescence complementation experiments substantiated these findings. Overall, our data suggest that LYK4 functions as a LYK5-associated co-receptor or scaffold protein that enhances chitin-induced signaling in Arabidopsis.
拟南芥中的溶菌酶受体样激酶（LYK）（即 LYK1、LYK4 和 LYK5）在几丁质感知和对病原真菌的免疫中起主要作用。先前已经报道了 LYK1 和 LYK5 的几丁质诱导的异二聚化，但 LYK4 的蛋白相互作用伙伴尚未被鉴定。在这项研究中，通过分析突变体，我们证实了 LYK4 在几丁质感知中的作用，并发现 LYK4 同源二聚体的细胞外结构域在体外与 LYK5 的细胞外结构域相互作用。用原生质体中表达的蛋白质进行的下拉实验表明 LYK4-LYK4 和 LY4-LYK5 相互作用在植物体内。当用壳七糖或几丁质处理原生质体时，免疫沉淀的蛋白质复合物似乎由 LYK1、LYK4 和 LYK5 组成。用在 lyk 突变体植物中表达的蛋白质进行的类似实验表明，激发子处理诱导了 LYK1 和 LYK5 之间的物理相互作用，但 LYK1 和 LYK4 之间没有。双分子荧光互补实验证实了这些发现。总的来说，我们的数据表明 LYK4 作为 LYK5 的相关共受体或支架蛋白发挥作用，增强了拟南芥中几丁质诱导的信号转导。
