Cloning and Characterization of a Gene Encoding the Major Surface Protein of the Bacterial Endosymbiont Wolbachia pipientis

The maternally inherited intracellular symbiont Wolbachia pipientis is well known for inducing a variety of reproductive abnormalities in the diverse arthropod hosts it infects. It has been implicated in causing cytoplasmic incompatibility, parthenogenesis, and the feminization of genetic males in different hosts. The molecular mechanisms by which this fastidious intracellular bacterium causes these reproductive and developmental abnormalities have not yet been determined. In this paper, we report on (i) the purification of one of the most abundantly expressed Wolbachia proteins from infected Drosophila eggs and (ii) the subsequent cloning and characterization of the gene (wsp) that encodes it. The functionality of the wsp promoter region was also successfully tested in Escherichia coli. Comparison of sequences of this gene from different strains of Wolbachia revealed a high level of variability. This sequence variation correlated with the ability of certain Wolbachia strains to induce or rescue the cytoplasmic incompatibility phenotype in infected insects. As such, this gene will be a very useful tool for Wolbachia strain typing and phylogenetic analysis, as well as understanding the molecular basis of the interaction of Wolbachia with its host.

母系遗传的胞内共生菌沃尔巴克氏体（Wolbachia pipientis）以其在感染的多样节肢动物宿主中诱导多种生殖异常而广受关注。该菌已被证实可在不同宿主中引发细胞质不相容性、孤雌生殖以及遗传雄性的雌性化。目前，这种难以体外培养的胞内细菌引发上述生殖与发育异常的分子机制仍未阐明。本文报道了两项研究内容：（i）从感染的果蝇卵中纯化得到一种沃尔巴克氏体高丰度表达蛋白；（ii）对编码该蛋白的基因（wsp）进行克隆与功能表征。此外，本研究还在大肠杆菌（Escherichia coli）中成功验证了wsp启动子区域的功能。对不同沃尔巴克氏体菌株的该基因序列进行比对后发现，其存在高度的序列变异。这种序列变异与特定沃尔巴克氏体菌株诱导或挽救感染昆虫细胞质不相容性表型的能力显著相关。因此，该基因将成为沃尔巴克氏体菌株分型、系统发育分析，以及解析沃尔巴克氏体与宿主互作分子基础的极具应用价值的工具。