Zur参与大豆斑疹病菌在寄主上的致病性和在非寄主上的过敏性反应  

Xanthomonas axonopodis pv.glycines Zur is involved in pathogenicity in host and hypersensitive responses in nonhosts

作　　者：林思怡 郑银邦 练梦洁 金罗佳 耿慧雅 徐江玲 纪志远[2] 郭威[1] LIN Siyi;ZHENG Yinbang;LIAN Mengjie;JIN Luojia;GENG Huiya;XU Jiangling;JI Zhiyuan;GUO Wei(College of Life Sciences,Zhejiang Normal University,Jinhua 321004,Zhejiang,China;National Key Facility for Crop Gene Resources and Genetic Improvement,Institute of Crop Sciences,Chinese Academy of Agricultural Sciences,Beijing 100081,China)

机构地区：[1]浙江师范大学生命科学学院,浙江金华321004 [2]中国农业科学院作物科学研究所农作物基因资源与基因改良国家重大科学工程,北京100081

出　　处：《生物工程学报》2024年第10期3603-3618,共16页Chinese Journal of Biotechnology

基　　金：国家大学生创新创业训练计划(202210345031);浙江省大学生科技创新活动计划(2023R404037)。

摘　　要：锌吸收调控蛋白(zinc uptake regulator,Zur)在植物病原黄单胞菌中的序列高度保守,但其在不同菌株或小种中的功能却差异显著。为阐明Zur在大豆斑疹病菌(Xanthomonas axonopodis pv.glycines,Xag)中的功能,本研究利用同源重组策略获得了zur基因的缺失突变株(△zur)。该突变株在寄主大豆上的致病性和在非寄主(烟草、番茄、辣椒和茄子)上激发超敏反应(hypersensitive responses,HR)能力相较于野生型均显著减弱。此外,与野生型菌株相比,突变株△zur的胞内锌稳态失衡,细胞外多糖(extracellularpolysaccharide,EPS)产量和胞外水解酶(纤维素酶、内切葡聚糖酶、淀粉酶和蛋白酶)表达均大幅降低,而且其对Zn^(2+)、Fe^(3+)和Cu^(2+)的敏感性显著增强。功能互补可将突变株△zur的上述缺陷性表型恢复至野生型水平。荧光定量PCR结果表明,zur基因受Zn^(2+)诱导表达;且zur基因突变大幅降低hrp基因簇代表性基因(hrpB1、hrpD6、hrpE、hrcV和hrcC)、胞外水解酶编码基因(engXCA、egl2、pro1、pra2、pro8、pro11和alpha1)和EPS合成基因(gumB、gumD、gumK、gumM、gumG和gumH)的表达水平。这些结果表明,Zur可能通过调控毒性因子合成和hrp基因表达,从而参与Xag在寄主大豆上的致病性和在非寄主植物上激发HR能力。本研究为进一步解析Zur在黄单胞菌-植物互作中的作用机制奠定了基础。The zinc uptake regulator(Zur)has highly conserved sequences in the plant pathogen Xanthomonas,while its functions are diverse in different strains or races.To elucidate the functions of Zur in Xanthomonas axonopodis pv.glycines(Xag),we constructed a zur-deleted mutant(Δzur)by homologous recombination.Compared with the wild type,Δzur demonstrated reduced pathogenicity in the host soybean and reduced ability to trigger hypersensitive responses(HR)in nonhosts such as tobacco,tomato,chili pepper,and eggplant.Additionally,the deletion of zur significantly enhanced Xag’s sensitivity to Zn^(2+),Fe^(3+),and Cu^(2+),induced an imbalance in intracellular zinc homeostasis,decreased extracellular polysaccharide(EPS)production,and down-regulated the expression of extracellular hydrolases(cellulase,endo-glucanase,amylase,and protease).Functional complementation restored the defective properties ofΔzur to the wild-type levels.The qRT-PCR results showed that zur expression was remarkably induced by Zn^(2+).Moreover,the deletion of zur evidently reduced the expression levels of hrp representative genes(hrpB1,hrpD6,hrpE,hrcV,and hrcC),extracellular hydrolase encoding genes(engXCA,egl2,pro1,pro2,pro8,pro11,and alpha1),and EPS synthesis genes(gumB,gumD,gumK,gumM,gumG,and gumH)relative to the wild type.In summary,the results suggested that Zur may be involved in pathogenicity in the host soybean and in triggering HR in nonhosts of Xag by regulating the synthesis of virulence factors and the expression of hrp genes.This laid a foundation for further analysis of the mechanism of Zur in Xanthomonas-plant interaction.

关 键 词：大豆斑疹病菌 锌吸收调控蛋白 致病性 过敏性反应 

分 类 号：S435.651[农业科学—农业昆虫与害虫防治]