Department of Entomology, The Volcani Center, Bet Dagan, Israel.
J Virol. 2014 May;88(10):5652-60. doi: 10.1128/JVI.00071-14. Epub 2014 Mar 5.
Numerous animal and plant viruses are transmitted by arthropod vectors in a persistent, circulative manner. Tomato yellow leaf curl virus (TYLCV) is transmitted by the sweet potato whitefly Bemisia tabaci. We report here that infection with Rickettsia spp., a facultative endosymbiont of whiteflies, altered TYLCV-B. tabaci interactions. A B. tabaci strain infected with Rickettsia acquired more TYLCV from infected plants, retained the virus longer, and exhibited nearly double the transmission efficiency compared to an uninfected B. tabaci strain with the same genetic background. Temporal and spatial antagonistic relationships were discovered between Rickettsia and TYLCV within the whitefly. In different time course experiments, the levels of virus and Rickettsia within the insect were inversely correlated. Fluorescence in situ hybridization analysis of Rickettsia-infected midguts provided evidence for niche exclusion between Rickettsia and TYLCV. In particular, high levels of the bacterium in the midgut resulted in higher virus concentrations in the filter chamber, a favored site for virus translocation along the transmission pathway, whereas low levels of Rickettsia in the midgut resulted in an even distribution of the virus. Taken together, these results indicate that Rickettsia, by infecting the midgut, increases TYLCV transmission efficacy, adding further insights into the complex association between persistent plant viruses, their insect vectors, and microorganism tenants that reside within these insects.
Interest in bacterial endosymbionts in arthropods and many aspects of their host biology in agricultural and human health systems has been increasing. A recent and relevant studied example is the influence of Wolbachia on dengue virus transmission by mosquitoes. In parallel with our recently studied whitefly-Rickettsia-TYLCV system, other studies have shown that dengue virus levels in the mosquito vector are inversely correlated with bacterial load. Our work here presents evidence of unifying principles between vectors of plant and animal viruses in a role for endosymbionts in manipulating vector biology and pathogen transmission. Our results demonstrate the influence of an interesting and prominent bacterial endosymbiont in Bemisia tabaci in TYLCV transmission, a worldwide disease infecting tomatoes. Besides its agricultural importance, this system provides interesting insights into Bemisia interaction with these newly discovered endosymbionts.
许多动物和植物病毒通过节肢动物载体以持久的循环方式传播。番茄黄曲叶病毒（TYLCV）由甘薯粉虱烟粉虱传播。我们在这里报告说，白蝇体内的共生体立克次体的感染改变了 TYLCV-B. tabaci 的相互作用。感染立克次体的烟粉虱从感染植物中获得了更多的 TYLCV，保留病毒的时间更长，与具有相同遗传背景的未感染烟粉虱相比，其传播效率几乎提高了一倍。在粉虱体内发现了立克次体和 TYLCV 之间的时间和空间拮抗关系。在不同的时间过程实验中，昆虫体内的病毒和立克次体水平呈负相关。对立克次体感染的中肠进行荧光原位杂交分析提供了立克次体和 TYLCV 之间小生境排斥的证据。特别是，中肠中高水平的细菌导致滤室中病毒浓度更高，这是病毒沿传播途径易位的首选部位，而中肠中低水平的立克次体导致病毒均匀分布。总的来说，这些结果表明，立克次体通过感染中肠，增加了 TYLCV 的传播效率，进一步深入了解了持久的植物病毒、它们的昆虫载体以及栖息在这些昆虫体内的微生物租户之间的复杂关系。
人们对立克次体等节肢动物内共生体及其在农业和人类健康系统中对宿主生物学的许多方面的兴趣一直在增加。最近一个相关的研究例子是沃尔巴克氏体对蚊子传播登革热病毒的影响。与我们最近研究的粉虱-立克次体-TYLCV 系统并行，其他研究表明，蚊子载体中的登革热病毒水平与细菌负荷呈负相关。我们在这里的工作提供了植物和动物病毒载体之间统一原则的证据，证明了内共生体在操纵载体生物学和病原体传播方面的作用。我们的研究结果表明，一种有趣的突出细菌内共生体在番茄黄曲叶病毒传播中的作用，这是一种感染番茄的世界性疾病。除了其农业重要性外，该系统还为粉虱与这些新发现的内共生体的相互作用提供了有趣的见解。
