对虾AHPND致病性弧菌毒力基因pirAB及其载体质粒的水平传播机制与进化关系研究

Acute hepatopancreatic necrosis disease (AHPND) is a newly emerged shrimp disease caused by pathogenic vibrios, which has brought about a sharp decline in global prawn production and significant economic loss. Various AHPND pathogenic vibrios found in different countries and regions host a large plasmid pVH (about 70 Kbp) encoding the toxic gene pirAB. In this project, we mainly explore whether pirAB genes are subject to horizontal gene transfer under the mediating of functional Tn903 composite transposon; Whether horizontal transfer and spread of AHPND plasmid pVH results from conjugation in different vibrio species, such as V. owensii, V. campbellii, V. parahaemolyticus; and what bacterial host is responsible for the “birth” of plasmid pVH as well as how is the affinity and evolutionary relationship between pVH and other plasmids. The results will shed light on the occurrence and spread mechanisms of AHPND, and contribute to either improving the available or establishing new AHPND disease prevention and control strategies. Additionally, it also paves a way for evaluating the increasing risk of disease spread to other vibrios due to pirAB insert to other plasmids via transposon as well as to integration into the host bacterial chromosome DNA.

急性肝胰腺坏死病（AHPND）是由致病性弧菌引起的一种新型虾病，其爆发造成了全球对虾养殖产量急剧下降和重大经济损失。在不同国家和地区发现的多种AHPND致病性弧菌均携带一个编码有毒力基因pirAB的大质粒pVH（约70 Kbp）。本项目研究主要探索毒力基因pirAB能否在功能性Tn903复合转座子的介导下进行水平基因转移；AHPND质粒pVH通过接合的方式在不同种近亲弧菌间（比如V. owensii、V. campbellii、V. parahaemolyticus）进行水平转移和扩散的可能性；质粒pVH的原发性宿主菌探究以及揭示pVH与其它质粒的亲缘与进化关系。预期的研究结果将增进对AHPND形成和传播机制的认知，有助于改进或建立新的AHPND疾病防控策略。同时，也为评估pirAB借助转座子插入到其它质粒，并扩散到其它弧菌以及整合到宿主菌染色体DNA上而加大疾病扩散风险提供理论基础。

急性肝胰腺坏死病（AHPND）是由致病性弧菌引起的一种新型虾病，其爆发造成了全球对虾养殖产量急剧下降和重大经济损失。在不同国家和地区发现的多种AHPND致病性弧菌均携带一个编码有毒力基因pirAB的大质粒pVH（约70 Kbp）。本项目研究主要探索毒力基因pirAB能否在功能性Tn903复合转座子的介导下进行水平基因转移；AHPND质粒pVH通过接合的方式在不同种近亲弧菌间（比如V. owensii、V. campbellii、V. parahaemolyticus）进行水平转移和扩散的可能性；质粒pVH的原发性宿主菌探究以及揭示pVH与其它质粒的亲缘与进化关系。通过项目研究，我们证实复合转座子pirAB-Tn903通过特异性双位点插入转座；成功构建含氯霉素（chloramphenicol，Cm）抗性基因（Cmr）的重组毒力质粒pVHvo-Cmr且其可水平转入非AHPND致病菌V. owensii 051011B；揭示了PirAB蛋白及其同源蛋白结构与功能；阐明了AHPND毒力质粒pVH同源基因及其宿主的关系，AHPND毒力质粒pVH的起源与进化。预期的研究结果增进了学术界对AHPND毒力质粒pVH的起源、进化与传播研究的科学认知以及对AHPND形成和传播机制的认知，有助于改进或建立新的AHPND疾病防控策略。同时，也为评估pirAB借助转座子插入到其它质粒，并扩散到其它弧菌以及整合到宿主菌染色体DNA上而加大疾病扩散风险提供理论基础。