西瓜噬酸菌hpaB基因的功能研究

The function of hpaB gene of Acidovorax citrulli

瓜类细菌性果斑病(Bacterial fruit blotch,BFB)是西瓜、甜瓜等葫芦科植物上的重要病害,是一种世界范围内重要的检疫性、种传病害,病原菌为西瓜噬酸菌(Acidovorax citrulli)。Ⅲ型分泌系统(type Ⅲ secretion system,T3SS)是西瓜噬酸菌致病过程中的关键毒力因子,参与调节细胞的多种生理生化反应。hpa(hrp-associated)基因是植物病原细菌Ⅲ型分泌系统hrp基因簇的重要组成部分,T3SS分泌蛋白在分泌过程中通常需要hpa基因编码的蛋白质介导,这些蛋白通常有利于植物病原细菌发挥其致病性。为了探究Ⅲ型分泌系统hpaB基因在西瓜噬酸菌致病过程中的功能,以西瓜噬酸菌Ⅱ型菌株Aac5为研究对象,构建hpaB基因缺失突变菌株及其互补菌株,并对致病力、致病相关表型以及相关基因表达量进行测定。结果表明:hpaB基因缺失后,对寄主植物西瓜和甜瓜的致病力显著减弱,并丧失了诱导非寄主烟草HR应答能力,运动能力减弱,生物膜形成能力增强。荧光定量结果表明:hpaB基因缺失后,影响T3SS相关基因及其他致病相关基因的表达。研究表明hpaB基因在西瓜噬酸菌致病过程中起到了重要的作用。

Bacterial fruit blotch(BFB)is an important disease in cucurbitaceous plants such as watermelon and melon,and is an important quarantine and seed-borne disease around the world,the pathogenic bacterium of which is Acidovorax citrulli.Type Ⅲ secretion system(T3SS)is a key virulence factor affecting the pathogenic process of Acidovorax citrulli,participating in regulating a variety of physiological and biochemical reactions in cells.The hpa(hrp-associated)gene is an important part of hrp gene cluster of the type Ⅲ secretion system in plant pathogenic bacteria.The secreted proteins of T3SS usually need to be mediated by proteins encoded by the hpa gene during secretion.These proteins are usually beneficial for plant pathogenic bacteria to exert their pathogenicity.In order to investigate the biological functions of the typeⅢsecretion system hpaB in Acidovorax citrulli,the Aac5 strain was used as the research object in this study.The hpaB deletion mutant strain and its complementary strain were constructed,and the pathogenicity,pathogenic-related phenotypes and related gene expression levels were determined.The results showed that after the deletion of hpaB,the pathogenicity of host plants watermelon and melon were significantly reduced,and the ability to induce HR response of non-host tobacco was lost,the swimming ability was weakened,and the biofilm formation ability was enhanced.Realtime quantitative PCR analysis showed that hpaB affected type Ⅲ secretion system and other pathogenic related genes in the expression levels.It indicated that hpaB plays an important role in the pathogenic process of Acidovorax citrulli.