西瓜噬酸菌hflX基因功能分析

为明确GTP结合蛋白基因hflX在西瓜噬酸菌Acidovorax citrulli中的功能尤其是对该菌致病力的影响,以西瓜噬酸菌Aac5菌株为材料获得hflX基因的缺失突变菌株及互补菌株,通过对致病力等表型以及相关基因表达量的测定初步探究西瓜噬酸菌hflX基因的功能。结果显示,同野生型菌株Aac5相比,缺失突变菌株的致病力显著下降,III型分泌系统基因hrpG和hrpE的表达量显著下调,仅为野生型菌株表达量的54.99%和27.39%;hflX基因的缺失并未影响其引起烟草过敏性坏死反应的能力;但缺失突变菌株的运动能力显著下降,鞭毛基因fliR和fliC的表达量显著下调,仅分别为野生型菌株的37.04%和29.68%。此外,缺失突变菌株的生物膜形成能力相较于野生型菌株显著增强了26.32%,同时,其体外生长能力也有所增强。表明hflX基因可能通过调控III型分泌系统基因hrpG和hrpE、鞭毛基因fliR和fliC的表达以及运动能力来影响西瓜噬酸菌Aac5菌株的致病力。

Functional analysis of fruit blotch pathogen hflX in Acidovorax citrulli

In order to clarify the function of GTP-binding protein gene hflX in fruit blotch pathogen Acidovorax citrulli and its effect on pathogenicity, A. citrulli Aac5 strain was used as wild-type strain, resulting in a hflX-deletion mutant and its complementary strain. Compared with the wild-type strain Aac5, hflX mutant showed significantly reduced virulence, and the expression levels of type III secretion system genes hrpG and hrpE decreased significantly, only 54.99% and 27.39% of the wild-type strain. Deletion of hflX did not influence the bacterial ability to trigger hypersensitive response on non-host Nicotiana tabacum var. Samsun; the swimming motility significantly reduced, the expression levels of flagellar genes fliR and fliC decreased significantly, only 37.04% and 29.68% of the wild-type strain. In addition, the biofilm formation ability of hflX mutant strain was 26.32% higher than that of the wild strain, and enhanced significantly. The growth ability in vitro of hflX mutant strain had also been enhanced. The results indicated that hflX might regulate virulence of A. citrulli Aac5 strain by expression of type III secretion system genes hrpG and hrpE, flagellar genes fliR and fliC, and swimming motility.