中文摘要：

水稻条斑病菌（Xanthomonas oryzaepv.oryzicola）hrcQ基因在动植物病原细菌中高度保守。不同植物病原细菌的HrcQ蛋白因在N端有变化,推测可能与分泌的效应分子特异性有关。但水稻条斑病菌HrcQ蛋白对Ⅲ型分泌系统（typeⅢsecretion system,T3SS）的形成以及对效应分子的分泌性影响还不清楚。为弄清HrcQ蛋白在此方面的作用,利用同源重组方式获得了水稻条斑病菌hrcQ基因的敲除突变体,该突变体丧失了在烟草上激发过敏性反应的能力和在水稻上的致病性。hrcQ基因与水稻细胞互作时受诱导表达。蛋白质-蛋白质互作结果显示,HrcQ可分别与Hpa1、HrcN、HrpB5和HrpB2互作。分泌性检测发现,HrcQ不通过T3SS分泌至胞外。hrcQ基因突变,影响Hpa1和HrpB2蛋白分泌。这些结果表明,HrcQ蛋白是形成Ⅲ型分泌系统的基本组分,并通过帮助Hpa1和HrpB2等T3SS效应因子的分泌,从而影响病菌在非寄主上的过敏性反应和在水稻上的致病性。这为进一步分析水稻黄单胞菌T3SS的形成和分泌机制奠定了基础。

英文摘要：

hrcQ gene of Xanthomonas oryzae pv.oryzicola（Xoc） is highly conserved in the animal and plant pathogens.It has been postulated that the differentiation at the N-terminal of HrcQ proteins in different plant pathogenic bacteria is related to the secretion of specific effectors through type Ⅲ secretion system（T3SS）.However,it is unclear whether HrcQ affects the formation of T3SS and the secretion of T3SS effectors.To understand the effect of HrcQ on the formation of T3SS and the secretion of T3SS effectors,hrcQ mutant of Xoc was generated by knocking-out mutagenesis through allelic exchange.Pathogenicity assays verified that the hrcQ mutant lost the ability to trigger hypersensitive response（HR） in nonhost tobacco and pathogenicity in host rice.The expression of hrcQ was induced when the pathogen interacted with rice cells.The protein-protein interaction assay by yeast two-hybrid system showed that HrcQ could interact with Hpa1,HrcN,HrpB5 and HrpB2.Immunobloting assay confirmed that HrcQ was not secreted through T3SS,whereas the mutation of hrcQ led to no secretion of Hpa1 and HrpB2 through T3SS.These results suggest that HrcQ is the core component of T3SS helping Hpa1 and HrpB2 secret through T3SS to determine HR in tobacco and pathogenicity in rice.All the above also provides a basis for further understanding of the secretion mechanisms by X.oryzae pv.oryzicola T3SS.