Age, tissue, genotype and virus infection regulate Wolbachia levels in Drosophila

The bacterial symbiont Wolbachia can protect insects against viral pathogens, and the varying levels of antiviral protection are correlated with the endosymbiont load within the insects. To understand why Wolbachia strains differ in their antiviral effects, we investigated the factors controlling Wolbachia density in five closely related strains in their natural Drosophila hosts. We found that Wolbachia density varied greatly across different tissues and between flies of different ages, and these effects depended on the host-symbiont association. Some endosymbionts maintained largely stable densities as flies aged while others increased, and these effects in turn depended on the tissue being examined. Measuring Wolbachia rRNA levels in response to viral infection, we found that viral infection itself also altered Wolbachia levels, with FHV causing substantial reductions in symbiont loads late in the infection. This effect, however, was virus-specific as DCV had little impact on Wolbachi...细菌共生体沃尔巴克氏体（Wolbachia）可帮助昆虫抵御病毒病原体，其抗病毒保护能力的强弱与昆虫体内的胞内共生菌载量密切相关。为探究为何不同沃尔巴克氏体菌株的抗病毒效果存在差异，我们针对五种近缘沃尔巴克氏体菌株在其自然果蝇（Drosophila）宿主体内调控沃尔巴克氏体密度的相关因子展开了研究。研究发现，沃尔巴克氏体的密度在不同组织间以及不同日龄果蝇之间均存在显著差异，且这种差异依赖于宿主-共生体的配对关系。部分共生体在果蝇衰老过程中基本保持密度稳定，而另一些则出现密度上升，且这类变化同样受所检测组织类型的影响。通过检测病毒感染下的沃尔巴克氏体核糖体RNA（rRNA）水平，我们发现病毒感染本身也会改变沃尔巴克氏体的载量：弗洛克豪斯病毒（FHV）会在感染后期大幅降低共生体的种群负荷。但该效应具有病毒特异性，果蝇C病毒（DCV）对沃尔巴克氏体几乎无影响……