维氏气单胞菌是造成水产养殖巨大危害的病原菌，致病机制尚不清楚。已知反式翻译和铁硫簇合成对于病原菌致病性极其重要。我们近期研究发现，维氏气单胞菌中反式翻译缺陷，其生长、毒力未受显著影响，氧化应激能力增强；转录组分析发现，sRNA AsrA可能负调控铁硫簇合成调控因子IscR，介导氧化应激响应。我们提出致病性分子模型，即SmpB-AsrA-IscR构成信号通路，通过激活铁硫簇合成及毒力途径，维持致病性，补偿反式翻译功能丧失。本项目拟采用Northern blot和RACE鉴定AsrA转录本；用荧光定量PCR、双质粒系统、凝胶迁移、RNA toeprinting、MST和定点突变，分析其对IscR的调控方式和位点；观察重组菌株胁迫响应性，结合动物实验，解析该信号通路调控致病性的分子机理。研究成果深入诠释sRNA的功能，对阐明致病性调控机制、寻找新药物靶点、防治细菌病害都具有重要理论和实际意义。

Aeromonas veronii is a virulent pathogen that causes great threats to aquatic products, of which the mechanism of pathogenesis remains unclear. It has been verified that trans-translation and Fe-S cluster biosynthesis are both closely related to bacterial pathogenesis. Our recent studies found that, a mutant of A. veronii, in which the important core factor SmpB of trans-translation was deleted, exhibited moderate changes in growth and virulence, as well as enhanced resistance to oxidative stress. Using transcriptomic analysis, we also found that, a novel small RNA AsrA might negatively regulate the essential regulator IscR for Fe-S cluster biosynthesis and mediate the oxidative resistance. We proposed a new action model. That is, the SmpB-AsrA-IscR constitutes a signal pathway, which could mediate the maintance of bacterial pathogenesis by activating the Fe-S cluster biosynthesis and the virulence of the bacteria in the absence of trans-translation. This project aims to identify the transcript of AsrA using Northern blot and RACE; to investigate the regulation mode and interaction sites between AsrA and IscR mRNA using the techniques including real-time PCR, double-plasmid detection system,electrophoretic mobility shift assay, RNA toeprinting, MST, and site-directed mutagenesis; and to investigate the molecular mechanism of the bacterial pathogenesis through characterizations of the responses of recombinant strains against stresses, in combination with animal infection experiments. The results of this project would provide a new insight on the function of small RNA in bacteria, and have theoretical and practical significance for uncovering the molecular mechanism of pathogenesis in Ameromonas veronii, seeking novel therapeutic targets for bacterial disease treatments, and overcoming recurrent infections in aquaculture.