The Wolbachia protein TomO interacts with a host RNA to induce polarization defects in Drosophila oocytes

Wolbachia is an endosymbiont prevalent in arthropods. To maximize its transmission thorough the female germline, Wolbachia induces in infected hosts male‐to‐female transformation, male killing, parthenogenesis, and cytoplasmic incompatibility, depending on the host species and Wolbachia strain involved. However, the molecular mechanisms underlying these host manipulations by Wolbachia remain largely unknown. The Wolbachia strain wMel, an inhabitant of Drosophila melanogaster, impairs host oogenesis only when transplanted into a heterologous host, for example, Drosophila simulans. We found that egg polarity defects induced by wMel infection in D. simulans can be recapitulated in the natural host D. melanogaster by transgenic overexpression of a variant of the Wolbachia protein Toxic manipulator of oogenesis (TomO), TomO_wMel^?HS, in the female germline. RNA immunoprecipitation assays demonstrated that TomO physically associates with orb mRNA, which, as a result, fails to interact with the translation repressor Cup. This leads to precocious translation of Orb, a posterior determinant, and thereby to the misspecification of oocytes and accompanying polarity defects. We propose that the ability of TomO to bind to orb mRNA might provide a means for Wolbachia to enter the oocyte located at the posterior end of the egg chamber, thereby accomplishing secure maternal transmission thorough the female germline.     

霍氏肠杆菌对黑腹果蝇生长和发育的影响

【背景】共生菌群可以影响宿主的生理、代谢以及神经行为,黑腹果蝇是研究宿主与共生菌作用机制的优秀遗传模型。【目的】分离和鉴定黑腹果蝇体内的共生菌,并研究其对果蝇生长和发育的影响。【方法】利用YG固体培养基分离果蝇肠道菌;革兰氏染色、生化鉴定和16S rRNA基因比对鉴定菌种;体内定殖和世代传递实验验证细菌与果蝇的共生关系;建立无菌和悉菌模型,通过发育历期和生长速率来验证其促生长作用;RT-PCR检测促生长分子基因表达;免疫荧光染色检测果蝇肠道细胞的增殖;葡萄糖氧化酶法检测葡萄糖浓度。【结果】分离到一株能够明显促进果蝇生长发育的细菌,经鉴定为霍氏肠杆菌(Enterobacter hormaechei),该菌可以稳定定殖于黑腹果蝇肠道以及培养基内,而且可以世代垂直传递。该菌可明显地促进果蝇的生长,并通过加速促胸腺激素的分泌来发挥促生长作用,同时可以促进果蝇肠道细胞的增殖。霍氏肠杆菌相较于无菌果蝇可以降低体内葡萄糖水平。【结论】霍氏肠杆菌是黑腹果蝇的有益共生菌,实验证实其可以促进果蝇的生长和发育。