摘要
水稻白叶枯病菌(Xanthomonas oryzae pv.oryzae,Xoo)引起的白叶枯病(bacterial leaf blight,BLB)是水稻上最严重的细菌病害之一。Xoo与寄主水稻的互作依赖由hrp基因编码的Ⅲ型分泌系统(Type Ⅲ secretion system,T3SS),将效应蛋白(T3SS effectors,T3SEs)注射入水稻细胞,引起BLB症状的扩展。HrpG是hrp基因转录表达的主要调控因子。为了鉴定未知的hrpG调控子,本研究在以hrpG∷gusA为报道基因构建的转座子突变体库中,筛选获得4个候选的hrpG负调控子突变体G24-46、G48-22、G19-14和G57-41。GUS活性测定、荧光定量PCR以及烟草组织的GUS染色试验均显示,在这些突变体中hrpG的表达显著增加。Southern杂交结果显示,突变体中转座子均为单一位点的插入。插入位点分析结果显示,在G24-46、G48-22、G57-41和G19-14中转座子分别插入在minD、pilA、metB和wxoB基因中。毒性测定结果显示,这4个突变体在水稻上的毒性显著降低。这些hrpG调控子基因的鉴定为进一步解析稻黄单胞菌hrpG上游调控网络提供了新的科学线索。
Xanthomonas oryzae pv. oryzae （Xoo）, causes bacterial leaf blight （BLB） in rice （Oryza sativa）, which is one of the most serious bacterial diseases in rice. The Xoo-rice pathosystem mainly depends on a type 1II secretion system （T3SS） encoded by a hrp gene cluster to inject T3SS effectors （T3SEs） into rice ceils for BLB disease development. HrpG is a major regulator to control the expression of hrp genes. To determine unknown regulators controlling the expression of hrpG, four mutants G24-46, G48-99, G19-14 and G57-41 were screened from a transposon-inserted library of Xoo by using a hrpG ：： gusA fusion as a reporter. The results from GUS activity assays, real-time quantitative PCR and an in situ GUS staining experiment demonstrated that the hrpG expression in these four mutants was dramatically increased when compared to the wild-type strain. Southern blotting and sequencing analysis showed that the single transposon was inserted in minD, pilA, metB and woxB genes, in the mutants G24-46, G48-22, G57-41 and G19-14, respectively. Virulence assays displayed that the mutation in these four genes led the pathogen less virulent in rice compared to the wild-type. Therefore, identification of these hrpG regulator genes would provide some new threads to elucidate the regulation network upstream the hrpG gene in X. oryzae.
出处
《植物病理学报》
CAS
CSCD
北大核心
2015年第2期130-138,共9页
Acta Phytopathologica Sinica
基金
国家自然科学基金资助项目(31371905)
公益性行业(农业)科研专项(201303015-02)
