论文部分内容阅读
水稻自叶枯病菌(Xanthomonas oryzae pv.oryzae,Xoo)和条斑病菌(X.oryzae pv.oryzicola,Xoc)在非寄主烟草上产生过敏反应(HR)和在寄主水稻上具有致病性,是由hrp致病岛决定的,其中HrppG为关键调控因子。Xoo和Xoc侵染水稻途径和在水稻上产生病害症状的不同,是否与hrpG基因有关,还不清楚。本研究利用反向遗传学方法获得了Xoo和Xoc的hrpG突变体:P△hrpG和R△hrpG,并用hrpG_(Xoo)基因和hrpG_(Xoc)基因分别互补上述2个突变体,获得了相应的互补菌株。致病性测定结果显示,P△hrpG和R△hrpG突变体丧失了在水稻上的致病性和在非寄主烟草上产生HR的能力,而hrpG_(Xoo)基因和hrpG_(Xoc)基因可分别互补上述突变体至野生型水平。利用GUS报告基因检测基因启动子活性发现,hrpG_(Xoo)和hrpG_(Xoc)的启动子活性没有显著差别;RT-PCR和Western杂交结果显示,hrpG基因交叉互补菌株中HrpG调控的下游基因hrpX、hpaR、hrcT、hpa2和hrpD6的表达没有差异,且Ⅲ型分泌系统分泌蛋白Hpa2的分泌性没有受到影响。这些结果表明,稻黄单胞菌hrpG基因可在Xoo和Xoc中交叉互置,位于其上游和下游的调控途径可能相似,而决定Xoo和Xoc在水稻上的侵染途径以及所致病害症状差异可能与hrpG基因位点无关。
Xanthomonas oryzae pv. Oryzae (Xoo) and X. oryzae pv.oryzicola (Xoc) produce anaphylactic reaction (HR) on non-host tobacco and pathogenicity on host rice, and are Hrp pathogenic island determined by the HrppG as a key regulatory factor. It is unclear whether the differences between Xoo and Xoc’s pathogenicity to rice and the disease symptoms on rice are related to the hrpG gene. In this study, the hrpG mutants of Xoo and Xoc were obtained by reverse genetics: PΔhrpG and RΔhrpG. The two mutants were complemented by hrpG_ (Xoo) gene and hrpG_ (Xoc) gene, respectively, Complementary strains. The results of pathogenicity test showed that the PΔhrpG and RΔhrpG mutants lost their pathogenicity on rice and their ability to produce HR on non-host tobacco, while the hrpG_ (Xoo) and hrpG_ (Xoc) Mutant above mutants to wild-type level. The promoters of hrpG_ (Xoo) and hrpG_ (Xoc) showed no significant difference using the GUS reporter gene promoter assay. The results of RT-PCR and Western blot showed that the hrpG, The expression of hpaR, hrcT, hpa2 and hrpD6 were not different, and the secretion of Hpa2 secreted by the type Ⅲ secretion system was not affected. These results indicate that the hrpG gene of Y. difficile can be cross-coupled in Xoo and Xoc, and the upstream and downstream regulatory pathways may be similar, which determines the pathways of Xoo and Xoc infection in rice and the differences in disease symptoms It may not be related to the hrpG gene locus.