卵黄原蛋白介导水稻矮缩病毒利用共生菌突破介体经卵传播屏障的机制

The mechanism of transovarial transmission is a subject under intensive investigation in virology. Rice dwarf virus (RDV) is the first recorded plant virus to be transovarially transmitted by leafhopper. Vitellogenin (Vg) of vector insect is synthesized in the hemocoel and then enters the ovary to provide nutritive material for ovarian development. Symbiotic bacteria of insect have ancient paths for entry into oocyte. In the long term of co-evolution, viruses, Vg and symbiotic bacteria may have formed a mutualistic relationship. Previously, we have determined that symbiotic bacterium Sulcia was exploited for transovarial transmission of RDV is mediated by an interaction of RDV coat protein and Sulcia outer membrane protein (OMP). Recently, we have further found that Vg and symbiotic bacteria were co-located in insect ovary, suggesting that Vg may mediate the transovarial transmission of RDV by exploiting symbiotic bacteria. In this project, the methods including cell biology, protein interaction, antibody blocking and RNA interference will be used to investigate the interaction among Vg, OMP and RDV coat proteins, and to establish a new model for Vg-mediated synergistic transovarial transmission of RDV and symbiotic bacteria. We will also study the relationship among RDV, symbiotic bacterium and Vg to clarify the mutualistic relationship of Vg-symbiotic bacteria-RDV during the transovarial transmission of RDV. The results will improve our understanding of the transovarial transmission of vector-transmitted viruses and provide an important theoretical basis for the design of strategies by blocking the vertical transmission of viruses.

病毒的经卵传播机制是病毒学研究的热点和难点科学问题。水稻矮缩病毒（RDV）是最早发现的通过介体叶蝉经卵传播至子代昆虫的植物病毒，而介体昆虫体内合成的卵黄原蛋白（Vg）从血淋巴入卵为卵巢发育提供营养物质，同时介体昆虫共生细菌也具有古老的入卵通道，三者殊途同归，极可能进化为互惠共生的关系。前期发现RDV外壳蛋白通过与共生细菌Sulcia外膜蛋白（OMP）的互作介导共生菌携带病毒入卵，且Vg可以与共生菌在卵巢中结合在一起，推测Vg可能介导了共生菌携带病毒入卵的过程。本项目拟利用细胞生物学、蛋白互作、抗体阻断和RNA干扰等手段，明确Vg与共生菌OMP及RDV外壳蛋白间的互作关系，建立Vg介导共生菌和RDV协同入卵新模式；分析RDV、共生菌及Vg三者间的关系，阐明三者形成互惠关系协同入卵的机制。研究成果将拓宽人们对虫媒病毒经卵传播的新认识，为探索阻断病毒垂直传播的有效策略提供重要理论依据。

黑尾叶蝉传播的水稻矮缩病毒（RDV）是最早发现可经卵传播的病毒。在介体黑尾叶蝉体内，不仅RDV需经卵传播到子代昆虫，昆虫体内的初生共生菌也需经卵传播到子代昆虫。同时，大量卵黄原蛋白（Vg）被摄入卵母细胞为卵巢发育提供营养物质。因此病毒、共生菌和Vg三者在昆虫卵巢组织内殊途同归。本项目在前期揭示RDV外壳蛋白通过与黑尾叶蝉共生菌Sulcia外膜蛋白的互作介导共生菌携带RDV从上皮鞘侵入卵母细胞的基础上，利用细胞生物学、蛋白互作和RNA干扰等手段，对Vg、共生菌和RDV侵入卵母细胞的机制进行研究。一方面发现RDV可以通过病毒外壳蛋白P8与共生细菌Nasuia的孔蛋白直接互作而粘附在共生菌表面，然后借助共生菌Nasuia的入卵途径侵入卵母细胞；另一方面发现Vg也可借助共生菌Nasuia进入卵母细胞，且共生菌对Vg的携带间接促进了卵的发育，更加有利于共生菌和病毒的垂直传播。因此在介体昆虫体内，病毒、共生菌和Vg三者间形成了互惠共生的关系。.研究成果在Philosophical Transactions of Royal Society of London series B、mBio、Nature Communications和Frontiers in Microbiology期刊发表4篇高质量的SCI 论文，获得第十四届福建省自然科学优秀学术论文一等奖1项，培养2名博士，2 名硕士。研究成果拓宽了人们对Vg与病毒及共生菌协同经卵传播的新认识，为探索阻断病毒垂直传播的有效策略提供了重要的理论依据。