禽致病性大肠杆菌（APEC）是家禽最重要的三大传染病病原之一，主要引起家禽的呼吸道疾病、生产性能下降甚至死亡，每年造成数百万美元的损失。深入、全面地认识APEC的致病机制对于防控该类疫病意义重大。近年来研究表明sRNAs可作为大肠杆菌毒力调控的关键因子，但其调控APEC典型毒力基因尤其是荚膜相关基因的机制尚未有报道。申请者通过转录组筛选并鉴定出一个与APEC毒力相关的新型小RNA ecsr1，本项目将对ecsr1的生物学功能及调控APEC毒力的分子机制进行研究。首先通过细胞试验和动物试验揭示ecsr1的生物学功能和对APEC毒力的贡献。利用生物信息学分析结合蛋白组学的方法筛选靶基因。通过双质粒荧光报告系统和Northern Blot等研究ecsr1对靶基因的调控机制。本研究将首次阐明sRNAs调控APEC荚膜等相关毒力基因的分子机制，丰富APEC致病机制的研究，为防控该类疫病提供理论基础。

Avian pathogenic Escherichia coli (APEC) is one of the three most important infectious diseases of poultry. It mainly causes respiratory diseases, poor performance and even death of poultry, and results in millions of dollars in losses every year. Thorough and comprehensive understanding of the pathogenic mechanism of APEC is of great significance for the prevention and control of this epidemics. In recent years, sRNAs have been proved to play important roles in the virulence regulation of Escherichia coli. But its mechanism of regulating APEC classical virulence genes, especially capsular associated genes, is not yet clear. A novel small RNA ecsr1was screened by RNA-sequencing and identified by Northern Blot. This project aims to explore the biological function of ecsr1 and its molecular mechanism for regulating the virulence of APEC. Firstly, the biological function of ecsr1 and its contribution to APEC virulence will be studied by in vitro cell tests and in vivo animal experiments. Target genes of ecsr1 will be screened by bioinformatics analysis and proteome. The regulatory mechanism of ecsr1 on target genes will be studied by dual plasmid fluorescence system and Northern Blot. This study will elucidate the molecular regulation mechanism of sRNAs on capsular-associated virulence genes in APEC for the first time, enrich the research on the pathogenic mechanism of APEC, and provide a theoretical basis for the prevention and control of this disease.