共生菌Wolbachia引起宿主细胞质不亲和的研究进展

Research progress in cytoplasmic incompatibility induced by endosymbiont Wolbachia

Wolbachia是一类广泛存在于节肢动物以及线虫体内细胞质中呈母系遗传的共生细菌,能够在宿主中产生细胞质不亲和、孤雌生殖、雌性化及杀雄等多种生殖调控作用,其中细胞质不亲和是指被Wolbachia感染的雄性个体与未感染的雌性个体（单向不亲和）,或者感染不同株系Wolbachia的雌性个体（双向不亲和）交配后不能或很少产生后代,或者后代偏雄性的现象。细胞质不亲和作用使感染的雌性个体在种群中具有很大的生殖优势,凭借这种生殖优势,Wolbachia能够迅速在宿主种群中扩张。细胞质不亲和的机理探索主要集中在细胞学水平上,其中广为接受的精子“修饰”和“拯救”理论认为,精巢中的Wolbachia能够修饰宿主的精细胞,使其不能和卵细胞正常融合,但是当母本感染相同的Wolbachia时,就能够将“修饰”过的精子细胞“拯救”过来,使其恢复与卵细胞的正常融合。而分子机理上的探索也开始在转录组、基因组和miRNA水平上对部分昆虫展开了研究。影响细胞质不亲和的因素有很多,包括宿主遗传背景、Wolbachia株系、Wolbachia基因型、共生菌密度（浓度、滴度）、雄虫年龄、环境因素以及共生菌在宿主生殖组织的分布等。近年来,人类也应用细胞质不亲和控制害虫（主要是蚊虫）和人类疾病,取得了较好的进展。

Wolbachia is a group of maternal-transmitted endosymbionts which are widely spread in arthropods and nematodes. The fungi of this genus cause several reproductive manipulations in hosts such as cytoplasmic incompatibility （CI）, parthenogenesis, feminization and male-killing, among which CI means the crosses between infected males and either uninfected females （unidirectional CI） or females infected by different strains of Wolbachia （bidirectional CI） do not produce offspring or few offspring. The effect of CI makes the infected females have advantage of reproduction. In return, the advantage makes the fast spreading of Wolbachia happen in host populations. Different mechanisms have been proposed to explain the CI and most mechanisms concentrate at the cytological level. Among these mechanisms, the widely-accepted modification-rescue model states that Wolbachia in testis can modify sperm in hosts and make the fusion between paternal and maternal pronuclei abnormal, and that the fusion becomes normal when the females have the same strain of Wolbachia which rescue the modified sperm. The exploration of molecular mechanisms of CI begins in the study of transcriptomes, genomes and miRNA of some insects. Factors influencing CI expression include host background, Wolbachia strain, Wolbachia genotype, density of endosymbionts, male age, environmental parameters and distribution of endosymbionts in reproductive organs of hosts. In recent years, attempts to use CI to control pests （mosquitoes in particular） and human diseases have been made and some promising progresses achieved.