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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(約翰英納斯中心):Norwich, UK

Corresponding author:Mark J. Banfield

Accelerated adaptive evolution is a hallmark (特點) 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 thePikmallele resist infection by blast strains expressing any of three AVR-Pik effector variants, whereas those expressingPikponly 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.

植物與病原菌之間的互作會加速適應性進化。植物細胞內的免疫受體NLRs經常會有一系列的等位基因變異，並且具有不同的病原菌特異性。而決定這些NLR的病原菌特異性的機制還不清楚。本文的研究揭示了水稻中響應稻瘟病真菌Magnaporthe oryzae效應物AVR-Pik的等位NLR Pik特異性增加的生物物理和結構基礎。表達Pikm等位基因的水稻植株會對能夠產生三種AVR-Pik效應物任何一種的水稻稻瘟病菌株產生抗性，而表達Pikp的卻只能抵抗其中一種。與Pikp不同，整合了重金屬相關結構域HMA的Pikm能夠高親和地結合到任何三種能夠識別的效應物上，並且在效應物與Pikp-HMA或者Pikm-HMA結合處具有突變的變種導致了特異性的產生。本文的研究通過理解共進化如何改變一個等位NLR的響應譜進一步揭示了自然選擇如何驅動新的受體特異性的出現。本文的工作對於農業中的NLR基因工程用於遺傳育種改良具有重要提示作用。

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

研究方向：植物-病原菌互作。

Journal:Nature Plants

Published date: 09 July, 2018

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