Kremer Natacha, Charif Delphine, Henri Hélène, Gavory Frédérick, Wincker Patrick, Mavingui Patrick, Vavre Fabrice
BMC Microbiol. 2012 Jan 18;12 Suppl 1(Suppl 1):S7. doi: 10.1186/1471-2180-12-S1-S7.
Wolbachia are intracellular bacteria known to be facultative reproductive parasites of numerous arthropod hosts. Apart from these reproductive manipulations, recent findings indicate that Wolbachia may also modify the host's physiology, notably its immune function. In the parasitoid wasp, Asobara tabida, Wolbachia is necessary for oogenesis completion, and aposymbiotic females are unable to produce viable offspring. The absence of egg production is also associated with an increase in programmed cell death in the ovaries of aposymbiotic females, suggesting that a mechanism that ensures the maintenance of Wolbachia in the wasp could also be responsible for this dependence. In order to decipher the general mechanisms underlying host-Wolbachia interactions and the origin of the dependence, we developed transcriptomic approaches to compare gene expression in symbiotic and aposymbiotic individuals.
As no genetic data were available on A. tabida, we constructed several Expressed Sequence Tags (EST) libraries, and obtained 12,551 unigenes from this species. Gene expression was compared between symbiotic and aposymbiotic ovaries through in silico analysis and in vitro subtraction (SSH). As pleiotropic functions involved in immunity and development could play a major role in the establishment of dependence, the expression of genes involved in oogenesis, programmed cell death (PCD) and immunity (broad sense) was analyzed by quantitative RT-PCR. We showed that Wolbachia might interfere with these numerous biological processes, in particular some related to oxidative stress regulation. We also showed that Wolbachia may interact with immune gene expression to ensure its persistence within the host.
This study allowed us to constitute the first major dataset of the transcriptome of A. tabida, a species that is a model system for both host/Wolbachia and host/parasitoid interactions. More specifically, our results highlighted that symbiont infection may interfere with numerous pivotal processes at the individual level, suggesting that the impact of Wolbachia should also be investigated beyond reproductive manipulations.
沃尔巴克氏体是细胞内细菌，已知是众多节肢动物宿主的兼性生殖寄生虫。除了这些生殖操纵外，最近的研究结果表明，沃尔巴克氏体还可能改变宿主的生理机能，尤其是其免疫功能。在寄生蜂塔氏阿索斯黄蜂中，沃尔巴克氏体对于卵子发生的完成是必需的，而无共生菌的雌蜂无法产生可存活的后代。卵子生产的缺失还与无共生菌雌蜂卵巢中程序性细胞死亡的增加有关，这表明确保沃尔巴克氏体在黄蜂体内维持的机制也可能是这种依赖性的原因。为了解析宿主 - 沃尔巴克氏体相互作用的一般机制以及这种依赖性的起源，我们开发了转录组学方法来比较共生和无共生个体中的基因表达。
由于没有关于塔氏阿索斯黄蜂的遗传数据，我们构建了几个表达序列标签（EST）文库，并从该物种中获得了12,551个单基因。通过电子分析和体外消减（SSH）比较了共生和无共生卵巢之间的基因表达。由于参与免疫和发育的多效性功能可能在依赖性的建立中起主要作用，通过定量RT-PCR分析了参与卵子发生、程序性细胞死亡（PCD）和免疫（广义）的基因表达。我们表明，沃尔巴克氏体可能会干扰这些众多的生物学过程，特别是一些与氧化应激调节相关的过程。我们还表明，沃尔巴克氏体可能与免疫基因表达相互作用以确保其在宿主体内的持续存在。
这项研究使我们能够构建塔氏阿索斯黄蜂转录组的第一个主要数据集，该物种是宿主/沃尔巴克氏体和宿主/寄生蜂相互作用的模型系统。更具体地说，我们的结果强调共生菌感染可能在个体水平上干扰众多关键过程，这表明沃尔巴克氏体的影响也应在生殖操纵之外进行研究。
