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eLife：植物NLR免疫受体蛋白N端功能保守性MADA基序作用于植物免疫

已有 3309 次阅读 2019-11-28 17:15 |个人分类:每日摘要|系统分类:论文交流

An N-terminal motif in NLR immune receptors is functionally conserved across distantly related plant species

First author: Hiroaki Adachi; Affiliations: University of East Anglia (东英吉利大学): Norwich, UK

Corresponding author: Sophien Kamoun

The molecular codes underpinning the functions of plant NLR immune receptors are poorly understood. We used in vitro Mu transposition to generate a random truncation library and identify the minimal functional region of NLRs. We applied this method to NRC4—a helper NLR that functions with multiple sensor NLRs within a Solanaceae receptor network. This revealed that the NRC4 N-terminal 29 amino acids are sufficient to induce hypersensitive cell death. This region is defined by the consensus MADAxVSFxVxKLxxLLxxEx (MADA motif) that is conserved at the N-termini of NRC family proteins and ~20% of coiled-coil (CC)-type plant NLRs. The MADA motif matches the N-terminal a1 helix of Arabidopsis NLR protein ZAR1, which undergoes a conformational switch during resistosome activation. Immunoassays revealed that the MADA motif is functionally conserved across NLRs from distantly related plant species. NRC-dependent sensor NLRs lack MADA sequences indicating that this motif has degenerated in sensor NLRs over evolutionary time.

植物NLR免疫受体发挥功能的分子基础还有待深入研究。本文中，作者使用体外Mu转座来产生一个随机的截短文库，从而鉴定NLR基因最小的功能区域。作者利用该方法研究了一个茄科受体网络中与多个感应NLRs（sensor NLRs）共同发挥作用的辅助NLR（a helper NLR），即NRC4蛋白。作者的研究揭示了NRC4蛋白的N端29个氨基酸足以诱导超敏细胞死亡。该区域具有一个保守的MADA基序（MADAxVSFxVxKLxxLLxxEx），该基序在所有的NRC家族蛋白和20%的CC类植物NLRs（CNLs）中都比较保守。MADA基序与拟南芥NLR蛋白ZAR1上N端的一个a1螺旋能够配对上，而该蛋白在抗病小体激活时会经历构想转变。免疫试验揭示了MADA基序在不同的远缘植物物种NLRs之间具有功能保守性。NRC依赖性感应NLRs中缺失了MADA基序，说明该基序在感应NLRs演化过程中丢失。