Illumina Sequencing of different Wolbachia strains wPip infecting the Culex pipiens mosquitoes complex

Maternally inherited Wolbachia are commonly found in arthropods and known to manipulate host reproduction to enhance their vertical spread in the host population. The most common strategy used by Wolbachia is called cytoplasmic incompatibility (CI) which cause a drastic reduction in the hatching rate of eggs. CI occurs when infected male mates with uninfected female or female infected with incompatible Wolbachia strains. In the Culex pipiens mosquitoes complex all the individuals are infected with Wolbachia wPip strain. Multi Locus Sequence Typing usually used to classify Wolbachia strains revealed no genetic diversity within wPip strain harbouring different CI patterns. To genetically differentiate these strains hyper variables markers such as repetitive element were needed. These markers revealed that wPip in a monophyletic group divided in five group : wPip_I to wPip_V. This highlight the genetic proximity of all wPip strains.Many crossing experiment between mosquitoes infected with Wolbachia from these five groups have revealed the highest diversity of CI patterns observed among all the arthropods in which Wolbachia induced CI. Even if CI was discovered decades ago, little is known about its genetic basis. Culex pipiens infected by Wolbachia genetically very close but habouring different CI patterns offers a perfect system for a comparative genomic study to find the genetic basis of CI. We thus sequenced Wolbachia strains harbouring different CI patterns to find variable genes between these strains.母系遗传的沃尔巴克氏体（Wolbachia）广泛分布于节肢动物体内，已知其可通过调控宿主生殖过程以提升自身在宿主种群中的垂直传播效率。沃尔巴克氏体最常见的策略为细胞质不相容（cytoplasmic incompatibility, CI），该现象会显著降低虫卵的孵化率。当感染沃尔巴克氏体的雄虫与未感染雌虫，或感染不相容沃尔巴克氏体菌株的雌虫交配时，即会发生细胞质不相容。在尖音库蚊（Culex pipiens）复合群中，所有个体均感染沃尔巴克氏体wPip菌株。通常用于分型沃尔巴克氏体菌株的多位点序列分型（Multi Locus Sequence Typing, MLST）技术，未在携带不同细胞质不相容模式的wPip菌株中检测到遗传多样性。若要对这些菌株进行遗传区分，需借助重复序列等高变分子标记。此类标记研究显示，wPip菌株属于单系群，可划分为wPip_I至wPip_V共5个类群，这一结果凸显了所有wPip菌株间的遗传亲缘关系。针对上述5个类群的感染沃尔巴克氏体的库蚊开展的大量杂交实验，揭示了目前已知节肢动物中由沃尔巴克氏体诱导的最丰富的细胞质不相容模式多样性。尽管细胞质不相容现象在数十年前就已被发现，但学界对其遗传基础仍知之甚少。遗传上高度相似但携带不同细胞质不相容模式的感染沃尔巴克氏体的尖音库蚊，为开展比较基因组学研究以解析细胞质不相容的遗传基础提供了理想模型。因此，本研究对携带不同细胞质不相容模式的沃尔巴克氏体菌株进行了测序，以筛选这些菌株间的差异基因。