水稻白叶枯病菌鞭毛基体基因fliExoo缺失突变分析

Deletion analysis of fliExoo,the gene encoding a flagellar base body protein in Xanthomonas oryzae pv.oryzae

为了阐明水稻白叶枯病菌(Xanthomonas oryzae pv.oryzae,简称Xoo)鞭毛基体组分蛋白基因fliExoo的生物学功能,本研究用GmR抗性基因标记交换法成功构建了基因缺失突变体△fliExoo。与野生型菌株PXO99A相比,△fliExoo鞭毛缺失,菌体易沉降,在0.3%半固体培养基上运动能力明显降低;尽管生长速率和胞外纤维素酶活性无明显变化,但胞外多糖产生和生物膜形成能力明显下降;对水稻品种日本晴的致病性和对非寄主烟草的致敏性反应明显减弱。基因互补可以使上述突变表型恢复。因此,鞭毛基因fliExoo突变不仅影响了细菌鞭毛依赖的运动性,而且对病原菌毒性相关的表型也产生了影响。

To elucidate the function of fliExoo gene encoding a putative flagellar base body protein in Xanthomonas oryzae pv. oryzae （Xoo）, the gene deletion mutant △fliExoo was generated by the Gm^R marker exchange from the wild-type strain PXO99^A. Non-flagellum, cell precipitation in the culture and significantly attenuated motility on 0.3% semi-solid medium were observed in △fliExoo compared to those of PXO99^A. While there were no apparent alterations in bacterial growth and activity of cellulase in vitro, significant decreases in extracellular polysaccharide （EPS） production and biofilm formation were found in △fliExoo. The pathogenicity on rice （Oryza sativa L cv. Nipponbare） and induction of hypersensitive response （HR） on tobacco （Nicotiana tabacum L.） were attenuated in △fliExoo. △fliExoo-C, the complementation strain restored the phenotypes of the mutant △fliExoo partially or completely. As a result, the fliExoo mutation not only influenced on flagellar motility,but also virulence-related phenotypes in Xoo.