RNA-seq analysis of Drosophila melanogaster embryos infected and uninfected with male-killing Spiroplasma. Drosophila melanogaster

Spiroplasma (Mollicutes) is one of the heritable bacterial endosymbionts of Drosophila species. Several strains like S. poulsonii manipulate host reproduction in a selfish manner. When females of D. melanogaster are infected with natural S. poulsonii strain MSRO (melanogaster sex ratio organism), only male offspring are killed during embryogenesis, and this phenomenon is called male-killing. To understand the molecular mechanism of male-killing, we compared gene expression profiles between MSRO-infected and uninfected embryos of D. melanogaster by using RNA-sequencing (RNA-seq). For embryonic sexing, we employed a transgenic reporter strain Sex-lethal (Sxl)-Pe-EGFP, which expresses GFP only in females. We collected female and male embryos at stage 10-11, when abnormal apoptosis associated with male-killing starts to occur in male progenies. For each sample, we analyzed three biological replicates.

螺原体属（Spiroplasma，柔膜菌纲Mollicutes）是果蝇属（Drosophila）物种的可遗传细菌内共生体之一。部分菌株，例如普氏螺原体（S. poulsonii），会以自私的方式操控宿主生殖行为。当黑腹果蝇（D. melanogaster）雌性个体感染天然普氏螺原体菌株MSRO（黑腹果蝇性比有机体，melanogaster sex ratio organism）后，仅雄性后代会在胚胎发育阶段死亡，该现象被称为杀雄现象（male-killing）。为阐明杀雄现象的分子机制，本研究通过RNA测序（RNA-seq）对比了感染与未感染MSRO的黑腹果蝇胚胎的基因表达谱。在胚胎性别鉴定方面，本研究采用了转基因报告菌株性别致死（Sex-lethal, Sxl）-Pe-EGFP，该菌株仅在雌性个体中表达绿色荧光蛋白（GFP）。我们在与杀雄现象相关的异常细胞凋亡开始在雄性后代中出现的胚胎发育10-11期，收集雌雄胚胎。每个样本设置三次生物学重复。