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十字花科作物黑腐病,又称为野油菜黄单胞菌野油菜变种(Xanthomonas campestris pv.campestris,简称Xcc),该细菌是引起十字花科作物等植物发生黑腐病的病原菌,同时该细菌也是人们研究寄主与病原微生物相互作用的具体分子机理的模式菌之一。在Xcc 8004菌株基因组中,XC_2304编码的产物为一个趋化性蛋白。由于细菌的趋化性在病原学方面的意义是非常重要的,为评估XC_2304的功能,本研究利用p K18mob Sac B对XC_2304进行缺失突变,获得缺失突变体DM2304。植株试验发现,突变体DM2304对寄主植物的致病力下降约30%,其互补菌株CDM2304的致病力基本恢复至野生型水平,这表明XC_2304与Xcc致病力有关。利用毛细管法检测DM2304对18种物质的趋化性,结果表明突变体对木糖、苯丙氨酸、精氨酸、蔗糖以及核糖的趋化性比野生型弱。运动性分析发现,DM2304在含有0.3%、0.6%琼脂的NYGA板的游动性稍微降低,表明XC_2304与游动性有关。而DM2304的胞外纤维素酶、胞外蛋白酶、胞外淀粉酶、EPS产量、HR与野生型菌株相比均没有明显差异。本研究为十字花科黑腐病菌中其它与趋化性相关基因提供实验思路,对病原菌如何趋利避害的机制的研究具有一定的意义。
Cruciferae crop black rot disease, also known as Xanthomonas campestris pv. Campestris (referred to as Xcc), the bacteria is cruciferous crops and other plants caused by black rot pathogens, at the same time Bacteria are also one of the specific molecular mechanisms by which people study the interaction of host and pathogenic microorganisms. In the genome of Xcc 8004 strain, the product encoded by XC_2304 is a chemotactic protein. Because of the etiological importance of bacteria in the etiology is very important, in order to assess the function of XC_2304, the study of pK18mob Sac B XC_2304 deletion mutation, deletion mutant DM2304 was obtained. Plant tests showed that the virulence of mutant DM2304 to host plants decreased by about 30%, and the virulence of its complementary strain CDM2304 returned to wild-type levels, indicating that XC_2304 is associated with the virulence of Xcc. The chemotaxis of DM2304 to 18 substances was detected by capillary method. The results showed that the mutants had weaker chemotaxis to xylose, phenylalanine, arginine, sucrose and ribose than wild type. Motility analysis found that the mobility of DM2304 in NYGA plates containing 0.3% and 0.6% agar decreased slightly, indicating that XC_2304 is related to motility. The DM2304 extracellular cellulase, extracellular protease, extracellular amylase, EPS production, HR and wild-type strains compared no significant difference. This study provides experimental ideas for other genes related to chemotaxis in the cruciferous black rot pathogen and is of great significance to the research on the mechanism of how pathogens can reduce the risk.