水稻白叶枯病菌群体感应系统对T3SS基因表达的调控作用分析  

Regulation of expression of type Ⅲ secretion system-encoded hrp genes of Xanthomonas oryzae pv. oryzae by diffusible signal factor-mediated quorum sensing

作　　者：霍欢[1] 孙蕾[1] 田芳[1] 陈华民[1] 何晨阳[1] 

机构地区：[1]中国农业科学院植物保护研究所、植物病虫害生物学国家重点实验室,北京100193

出　　处：《植物病理学报》2012年第6期620-625,共6页Acta Phytopathologica Sinica

基　　金：国家"973"项目(2011CB100701);国家自然科学基金资助项目(31100947)

摘　　要：为了阐明水稻白叶枯病菌(Xanthomonas oryzae pv.oryzae,Xoo)利用DSF信号群体感应(QS)系统对毒性表达进行调控的机理,本研究对编码QS的rpf基因进行了分子鉴定,分析了Δrpf基因突变体在水稻叶组织中的种群量变化,利用RT-qPCR方法定量测定了编码T3SS的hrp基因转录本以及rpf基因自身表达。结果表明,rpfF、rpfC和rpfG基因与几种主要植物病原黄单胞菌同源序列高度保守;RpfF是烯脂酰辅酶A水合酶家族成员之一,RpfC含有组氨酸磷酸激酶结构域(His-KA)和磷酸受体结构域(REC),RpfG含有REC和HD-GYP结构域;Δrpf突变体在水稻叶组织中的种群量及其扩展能力均明显下降;hrp基因转录显著地受到QS调控;rpf基因表达与Xoo种群密度密切相关。因此,Xoo QS系统显著地调控了hrp基因的表达,在QS与T3SS表达之间存在一个信号通路。Bacterial virulence of Xanthomonas oryzae pv. oryzae （Xoo） was previously shown to be regulated by the diffusible signal factor （DSF）-mediated quorum sensing （QS）. To further elucidate the regulatory mech- anisms, structural features of QS-encoded rpf genes was identified through the bioinfomatic analysis, bacterial population of △rpf mutants in the infacted leaf tissues of rice was detected, and transcription leavels of type Ⅲ secretion system （T3SS）-encoded hrp genes were measured via RT-qPCR assays in this study. The results showed that rpf genes were found to be highly conserved in plant-pathogenic Xanthomonas spp. RpfF was one of enoyl-CoA hydratase family members, RpfC was structurally featured in N-terminal histidine kinase domain and C-terminal receiver （REC） domain, while RpfG contained REC and HD-GYP domains. Significant decreases in bacterial population and spread in the rice leaf tissues of △rpf mutants were observed compared with wild-type strain PXO99A. Transcription of hrp genes was significantly regulated by QS. Expression of rpf genes was regu- lated by Rpf proteins and bacterial density-dependent. Therefore, it might be suggested that QS regulated T3SS expression via the DSF/c-di-GMP-mediated signaling pathway（s）.

关 键 词：水稻白叶枯病菌 群体感应 DSF HRP基因 调控 

分 类 号：S435.111.47[农业科学—农业昆虫与害虫防治]