Polymorphic residues in rice NLRs expand binding and response to effectors of the blast pathogen

First author: Juan Carlos De la Concepcion; Affiliations: John Innes Centre (约翰英纳斯中心): Norwich, UK

Corresponding author: Mark J. Banfield 

Accelerated adaptive evolution is a hallmark (特点) of plant-pathogen interactions. Plant intracellular immune receptors (NLRs) often occur as allelic series with differential pathogen specificities. The determinants of this specificity remain largely unknown. Here, we unravelled the biophysical and structural basis of expanded specificity in the allelic rice NLR Pik, which responds to the effector AVR-Pik from the rice blast pathogen (稻瘟病菌) Magnaporthe oryzae. Rice plants expressing the Pikm allele resist infection by blast strains expressing any of three AVR-Pik effector variants, whereas those expressing Pikp only respond to one. Unlike Pikp, the integrated heavy metal-associated (HMA) domain of Pikm binds with high affinity to each of the three recognized effector variants, and variation at binding interfaces between effectors and Pikp-HMA or Pikm-HMA domains encodes specificity. By understanding how co-evolution has shaped the response profile of an allelic NLR, we highlight how natural selection drove the emergence of new receptor specificities. This work has implications for the engineering of NLRs with improved utility in agriculture.

植物与病原菌之间的互作会加速适应性进化。植物细胞内的免疫受体NLRs经常会有一系列的等位基因变异，并且具有不同的病原菌特异性。而决定这些NLR的病原菌特异性的机制还不清楚。本文的研究揭示了水稻中响应稻瘟病真菌Magnaporthe oryzae效应物AVR-Pik的等位NLR Pik特异性增加的生物物理和结构基础。表达Pikm等位基因的水稻植株会对能够产生三种AVR-Pik效应物任何一种的水稻稻瘟病菌株产生抗性，而表达Pikp的却只能抵抗其中一种。与Pikp不同，整合了重金属相关结构域HMA的Pikm能够高亲和地结合到任何三种能够识别的效应物上，并且在效应物与Pikp-HMA或者Pikm-HMA结合处具有突变的变种导致了特异性的产生。本文的研究通过理解共进化如何改变一个等位NLR的响应谱进一步揭示了自然选择如何驱动新的受体特异性的出现。本文的工作对于农业中的NLR基因工程用于遗传育种改良具有重要提示作用。

通讯：Mark J. Banfield (https://www.jic.ac.uk/directory/mark-banfield/)

研究方向：植物-病原菌互作。

doi: https://doi.org/10.1038/s41477-018-0194-x

Journal: Nature Plants

Published date: 09 July, 2018

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