水稻细菌性条斑病菌中一个调控致病性的DNA结合蛋白负调控胞外酶活性  

A DNA-binding protein required for virulence negatively regulates the activity of extracellular enzymes in Xanthomonas oryzae pv.oryzicola

作　　者：李瑞芳[1,2] 覃祚树 王欣欣 陈小林[1] 岑贞陆[1] 颜群[1] 晏卫红[1] 韦善富[1,3] 陆光涛[3] LI Rui-fang;QIN Zuo-shu;WANG Xin-xin;CHEN Xiao-lin;CEN Zen-lu;YAN Qun;YAN Wei-hong;WEI Shan-fu;LU Guang-tao(Plant Protection Research Institute,Guangxi Academy of Agricultural Sciences,Nanning 530007,China;Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests,Nanning 530007,China;State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources,College of Life Science and Technology,Guangxi University,Nanning 530007,China)

机构地区：[1]广西农业科学院植物保护研究所,南宁530007 [2]广西作物病虫害生物学重点实验室,南宁530007 [3]广西大学亚热带农业生物资源保护与利用国家重点实验室/生命科学与技术学院,南宁530007

出　　处：《植物病理学报》2021年第4期572-582,共11页Acta Phytopathologica Sinica

基　　金：国家自然科学基金(31660506);广西自然科学基金(2015GXNSFBA139110);广西作物病虫害生物学重点实验室系统课题(2019-ST-07);国家重点研发计划课题(2018YFD0200306);广西农业科学院团队项目(2015YT36)。

摘　　要：原核革兰氏阴性菌稻黄单胞菌稻生致病变种(又称水稻细菌性条斑病菌,Xanthomonas oryzae pv.oryzicola,Xoc)是引起水稻细菌性条斑病的病原物,该病是水稻粮食生产中的严重病害之一。我们的前期工作对广西农科院分离到的Xoc菌株GX01进行基因组序列分析,发现一个编号为gx01_0566的基因可能编码一个Fis家族的DNA结合蛋白。本工作采用自杀质粒pK18mobsacB介导的方法来构建该基因的缺失突变体,并对突变体进行反式互补。表型分析发现,gx01_0566基因的突变体在寄主水稻日本晴上的致病力显著下降,但其胞外多糖产量与野生型基本一致,胞外酶尤其是胞外纤维素酶活性却大幅度提高。为进一步研究gx01_0566基因在Xoc中调控胞外纤维素酶的机理,我们对该基因的产物进行过量表达和纯化,并通过凝胶阻滞实验和实时定量PCR实验分析,发现gx01_0566编码产物能够结合在一些编码纤维素酶的基因的启动子上,负调控这些纤维素酶基因的表达。The prokaryotic Gram-negative bacterium Xanthomonas oryzae pv.oryzicola(Xoc)is the causal agent of bacterial leaf streak disease of rice.In our previous work,a scanning of the genome sequence of the Xoc wild type strain GX01 isolated from Guangxi,China,revealed that a gene named gx010566 might encode a DNA-binding protein belonging to the Fis family.To facilitate the characterization of gx010566,a deletion mutant was constructed by using the suicide vector pK18 mobsacB and complemented in trans.Phenotypic analysis revealed that the virulence of the gx010566 mutant in the host plant Japonica cultivar Nipponbare was greatly reduced compared with wild-type,while the exopolysaccharide production of the gx010566 mutant is comparable to that of the wild-type.Interestingly,activities of the exoenzymes such as the endoglucanase increased greatly in the gx010566 mutant strain compared with the wild-type.To further investigate the role of the gx010566 gene in regulation of the endoglucanase activity,gx010566 protein was overproduced and purified.Electrophoresis mobility shift assays indicated that gx010566 protein binds to the promoter of certain endoglucanases-encoding genes such as gx010026 and gx014282.Furthermore,quantitative real-time PCR revealed that the expression level of several endoglucanase-encoding genes was enhanced greatly in the mutant compared with the wild-type,implying that the gx010566 protein represses the expression of these endoglucanases encoding genes via directly binding to their promoters.

关 键 词：水稻细菌性条斑病菌 DNA结合蛋白 胞外酶纤维素酶 致病性 

分 类 号：S432.42[农业科学—植物病理学]