白叶枯病菌效应子XopN在拥有OsSWEET11同源基因的水稻品种上发挥毒性作用  

Effector XopN of Xanthomonas oryzae pv.oryzae Plays a Virulent Role in Rice Varieties Harboring OsSWEET11 Homologs

作　　者：李丽 莫旭艳 李甜甜 张丽媛 董汉松 LI Li;MO Xuyan;LI Tiantian;ZHANG Liyuan;DONG Hansong(College of Plant Protection,Shandong Agricultural University,Taian 271018,China;College of Plant Protection,Nanjing Agricultural University,Nanjing 210095,China;State Key Laboratory of Crop Biology,Taian 271018,China)

机构地区：[1]山东农业大学植物保护学院,山东泰安271018 [2]南京农业大学植物保护学院,南京210095 [3]作物生物学国家重点实验室,山东泰安271018

出　　处：《中国水稻科学》2020年第4期368-382,共15页Chinese Journal of Rice Science

基　　金：国家自然科学基金面上项目(31772247);国家重点研发计划资助项目(2017YFD0200901)。

摘　　要：【目的】黄单胞菌细胞外泌蛋白质(Xanthomonas outer proteins,Xops)是植物病原黄单胞菌高度保守的毒性效应子或毒性辅助组分,通过细菌Ⅲ型分泌系统分泌到细菌细胞外部,然后转入植物细胞而发挥病理作用。水稻黄单胞菌水稻致病变种即水稻白叶枯病菌的标准菌株PXO99^A分泌的XopN是一种毒性效应子,通过影响寄主免疫反应而使水稻发病。但是,XopN对病菌毒性的影响是否因水稻品种的不同而异,还有待研究。【方法】利用同源双交换技术,先敲除了PXO99^A的XopN基因,获得了ΔXopN突变体,又经过遗传互补,得到了回补菌株ΔXopN/XopN。通过营养肉汤液体培养,测定了XopN对病菌繁殖能力的影响;根据文献选用14个水稻品种,通过接种实验,测定了PXO99^A对这些品种的毒性与XopN敲除或回补的影响;在XopN发挥毒性作用的水稻品种上,测定了隐性抗病基因OsSWEET11/xa13与显性感病基因OsSWEET11/Xa13受病菌侵染而表达的情况,分析了XopN敲除或回补的影响。【结果】在营养肉汤液体培养过程中,病菌突变体菌株ΔXopN的繁殖速度明显低于野生型PXO99^A。PXO99^A、ΔXopN和ΔXopN/XopN接种水稻后,根据其在水稻叶片组织内的繁殖量及随后产生的白叶枯病症状的严重程度,将供试的14个水稻品种分为两种情况。一是感病程度与病菌XopN是否敲除或回补无关,这有10个水稻品种(IRBB1、IRBB3、IRBB8、IRBB10、IRBB14、IR24、IRBB203、IRBB204、IRBB205和IRBB211),PXO99^A、ΔXopN和ΔXopN/XopN对它们的毒性无明显差别。二是XopN对病菌毒性发挥作用的水稻品种,包括高度感病的3个品种(IRBB208、Asominori和日本晴)和低感品种IRBB13。与PXO99^A或ΔXopN/XopN相比,ΔXopN对这4个水稻品种的毒性大为降低。在IRBB13上,病菌侵染对隐性抗病基因OsSWEET11/xa13在叶片内的表达发生抑制作用,这一效应与XopN的毒性功能相关。相反,日本晴显性感病基因OsSWEET11/Xa13却受【Objective】Xanthomonas outer proteins(Xops)are conservatively virulent effectors or virulence-assistant components secreted by the typeⅢsecretion system in plant-pathogenic bacteria that falls into the Xanthomonas genus,including the rice bacterial blight pathogen.Xops were secreted to the outside of bacterial cells,and then transported to plant cells to play a pathological role.One of these proteins,XopN,secreted by the standard strain PXO99^A of the rice pathogen,has been implicated in the bacterial virulence by subverting plant immunity,but the specificity in the virulence role of XopN is unclear.【Method】By using the double crossover homologous-recombination technique,the XopN gene-knockout mutantΔXopN and genetically complemented strainΔXopN/XopN were generated under the background of the bacterial wild-type strain PXO99^A.By comparing both recombinant strains with PXO99^A in terms of bacterial multiplication in nutrition broth,the role of XopN in the bacterial multiplication was evaluated.Based on literatures,14 varieties of rice were chosen for experimental assessments on the contribution of XopN to the spectrum of the bacterial virulence.By quantitative analyses of gene expression,the virulence of XopN was related to the effects of bacterial infection on foliar expression of the OsSWEET11 gene or its homologs in different rice varieties.【Result】The bacteria gain better multiplication in the medium with the presence of the XopN gene,in contrast to the gene-knockout mutation,which highly impairs the bacterial propagation level.Based on bacterial populations of PXO99^A,ΔXopN andΔXopN/XopN multiplied in rice leaves,as well as severities of subsequently developed leaf blight symptoms,the 14 rice varieties fall into two categories.1)Ten of the rice varieties(IRBB1,IRBB3,IRBB8,IRBB10,IRBB14,IR24,IRBB203,IRBB204,IRBB205 and IRBB211)display similar susceptibility to the bacteria no matter whether the XopN gene is present or not.2)By contrast,the bacteria depend on XopN to cause strong virulence on

关 键 词：水稻白叶枯病菌 XopN 细菌繁殖 毒性 OsSWEET11 

分 类 号：S435.111.47[农业科学—农业昆虫与害虫防治] Q943[农业科学—植物保护]