Structural basis for specific self-incompatibility response in Brassica
Structural basis for specific self-incompatibility response in Brassica
复制标题
芸苔属特定自交不亲和反应的结构基础
DOI：
10.1038/cr.2016.129
复制
发表时间：
2016-12-01
期刊：
影响因子：
44.1
通讯作者：
Chai, Jijie
中科院分区：
文献类型：
--
作者：
Ma, Rui;Han, Zhifu;Chai, Jijie
自交不亲和性(SI)是开花植物中普遍存在的一种阻止自交受精和近交的机制。在油菜中，高度多态的S座位富含半胱氨酸的蛋白(Scr；或S座位蛋白11)被类似多态的S座位受体激酶识别，这决定了SI的特异性。在这里，我们报道了SRK9胞外区(ESRK9)与白菜SCR9形成的复合体的晶体结构。SCR9结合诱导eSRK9同源二聚，形成2：2的eSRK：SCR异构体，形状如字母“A”。对SCR9的特异性识别是通过eSRK9的三个高变区(Hv)介导的。每个SCR9同时与来自一个eSRK9单体的HVI和一半的HvII以及来自第二个eSRK9单体的另一半的HvII相互作用，在介导SRK9同源二聚过程中发挥主要作用，而不涉及两个SCR9分子之间的相互作用。对eSRK9-SCR9相互作用至关重要的残基的单一突变会破坏它们在体外的结合。我们的研究使SRK对SCR的特异性识别的数据更加合理，并为理解SRK和SCR之间的共同进化提供了一个结构模板。
Self-incompatibility (SI) is a widespread mechanism in flowering plants which prevents self-fertilization and inbreeding. In Brassica, recognition of the highly polymorphic S-locus cysteine-rich protein (SCR; or S-locus protein 11) by the similarly polymorphic S-locus receptor kinase (SRK) dictates the SI specificity. Here, we report the crystal structure of the extracellular domain of SRK9 (eSRK9) in complex with SCR9 from Brassica rapa. SCR9 binding induces eSRK9 homodimerization, forming a 2: 2 eSRK: SCR heterotetramer with a shape like the letter “A”. Specific recognition of SCR9 is mediated through three hyper-variable (hv) regions of eSRK9. Each SCR9 simultaneously interacts with hvI and one-half of hvII from one eSRK9 monomer and the other half of hvII from the second eSRK9 monomer, playing a major role in mediating SRK9 homodimerization without involving interaction between the two SCR9 molecules. Single mutations of residues critical for the eSRK9-SCR9 interaction disrupt their binding in vitro. Our study rationalizes a body of data on specific recognition of SCR by SRK and provides a structural template for understanding the co-evolution between SRK and SCR.