水稻白叶枯病菌hrcU基因缺失突变体构建及功能研究

Site-Directed Mutagenesis and Functional Analysis of hrcU Gene from Rice Pathogen Xanthomonas oryzae pv. oryzae

通过基因敲除方式,构建了水稻白叶枯病菌hrcU基因的缺失突变体。突变体丧失了在水稻上的致病性和在非寄主植物上的过敏反应。携带hrcU基因的黏粒完全互补了hrcU突变菌株的表型,互补菌在水稻组织中的生长能力也与野生型菌株相当。免疫杂交结果显示,hrcU基因突变后,水稻白叶枯病菌的Harpin蛋白Hpa1不能从细胞内分泌到胞外。这些结果表明,水稻白叶枯病菌hrcU基因的主要功能是形成Ⅲ型分泌系统,将效应分子分泌到病原细菌胞外,从而决定了在非寄主上的过敏反应和在水稻上的致病性。

The hrp gene cluster is composed of 27 members in rice pathogen Xanthomonas oryzae pv.oryzae（Xoo）.To analyze the function of hrcU gene,the hrcU gene was knocked out by allelic exchange.The resulting hrcU mutant lost the pathogenicity in rice and the ability to trigger hypersensitive response in nonhost plant tobacco.The sole hrcU gene fully restored the phenotypic alterations in pathogenicity in rice,hypersensitive response in tobacco,and bacterial growth in rice.Western blot displayed that the typeⅢ secretion system was destroyed in hrcU mutant in which the T3S effectors Hpa1 could not be secreted into extracellular.This indicates that the hrcU gene of Xoo was essential for type Ⅲ secretion system to deliver effectors into plants.