昆虫因子调控南方水稻黑条矮缩病毒利用管状结构在介体内有效扩散的机制

Southern rice black-streaked dwarf virus (SRBSDV), a plant reovirus, has been epidemic in rice field in southern China. Basing on our previous investigations about the spread mechanism of plant reoviruses during their infection in insect vectors, we propose the “actin-based tubule motility (ABTM)” spread model (Annu Rev Phytopathol, 2016). However, it still remains unclear how the vector factors are involved in the virus-mediated ABTM to overcome vector tissues or membrane barriers. Based on our previous data that insect vector factors including B-cell receptor-associated protein 31-like, myosin and DNA-J have been identified to interact with SRBSDV tubular protein P7-1, we use various technology systems such as vector cell culture, transient expression vector transfection, immunofluorescence labeling and RNA interference, etc, to reveal how these vector factors positively or negatively modulate the spread ability of P7-1 tubules for maintaining the suitable viral accumulation in insects. We further investigate whether the involvement of vector factors in the spread of P7-1 tubules could mediate the persistent and highly efficient transmission of viruses by vectors. Results would improve and perfect the ABTM model, and solid the theoretical base for developing effective prevention and control strategies.

属于植物呼肠孤病毒的南方水稻黑条矮缩病毒（SRBSDV）近年来在我国南方稻区暴发流行。团队在前期对这类病毒在介体昆虫体内扩散机制的研究提出了actin-based tubule motility（ABTM）模型（Annu Rev Phytopathol, 2016）。然而，介体因子如何调控ABTM介导的病毒突破介体组织或膜屏障的机制并不清楚。本项目拟在鉴定与SRBSDV小管蛋白P7-1互作的介体因子B-cell receptor-associated protein 31-like、myosin和DNA-J的基础上，利用介体细胞培养、瞬时表达载体转染、免疫荧光标记、RNA干扰等技术体系，解析这些介体因子如何通过正负调控P7-1小管在介体中的扩散能力，维持病毒在介体内的适度积累，从而介导介体持久高效传播病毒的机制。研究结果将完善ABTM模型，为制定通过阻断病毒经介体传播的防控策略奠定基础。

南方水稻黑条矮缩病毒 (Southern rice black-streaked dwarf virus, SRBSDV) 是一种由介体白背飞虱 (Sogatella furcifera) 以持久增殖型方式传播的水稻呼肠孤病毒，自发现以来该病毒一直影响着我国南方稻区的水稻安全生产，目前仍属于最严重的水稻病毒病害之一。SRBSDV非结构蛋白P7-1诱导介体形成小管结构是病毒突破介体组织屏障，快速扩散的重要因素。针对近年来在我国发生的SRBSDV，按计划开展了介体昆虫因子调控SRBSDV利用管状结构在介体内有效扩散的机制探索。经过4年的持续研究，发现SRBSDV通过非结构蛋白P7-1与介体内质网相关降解通路（ERAD）相关因子BAP31、DNAJB11、myosin、DNAJB12和Hsc70互作。首先，揭示了SRBSDV在气候炎热的中国南部和越南北部地区流行，并随温度升高其侵染效率和传播效率增加的分子机制是介体BAP31和DNAJB11调控P7-1小管的组装，而高温可以显著上调DnaJB11的表达，抑制BAP31的表达，从而促进P7-1小管的组装，有利于SRBSDV P7-1病毒小管的组装。其次，解析了P7-1与ERAD的两个重要因子DNAJB12和胞质伴侣Hsc70直接互作。新生成的P7-1通过DNAJB12被募集并滞留于内质网中，然后通过DNAJB12的J结构域将胞质Hsc70招募至内质网，在Hsc70的ATP酶功能域活性作用下促进P7-1小管组装，并增强P7-1小管由内质网向胞质和胞外释放，从而促进病毒有效传播。由此本项目揭示了介体昆虫传播的植物病毒劫持昆虫ERAD相关因子DNAJB12-Hsc70伴侣复合体参与P7-1由内质网向胞质的转运，调控DNAJB11和BAP31在高温环境下参与P7-1小管的形成，从而使SRBSDV适应于高温环境高效增殖和传播的分子机制。此外，本项目建立了成熟的白背飞虱细胞培养体系，为SRBSDV的研究奠定了优越的技术平台。.本项目研究成果在PLoS Pathogens、Molecular Plant Pathology和Methods in Molecular Biology期刊发表3篇高质量的SCI论文，培养1名博士和2名硕士。