Animals interact with microbes that affect their performance and fitness, including endosymbionts that reside inside their cells. Maternally transmitted Wolbachia bacteria are the most common known endosymbionts, in large part because of their manipulation of host reproduction. For example, many Wolbachia cause cytoplasmic incompatibility (CI) that reduces host embryonic viability when Wolbachia-modified sperm fertilize uninfected eggs. Operons termed cifs control CI, and a single factor (cifA) rescues it, providing Wolbachia-infected females a fitness advantage. Despite CI’s prevalence in nature, theory indicates that natural selection does not act to maintain CI, which varies widely in strength. Here, we investigate the genetic and functional basis of CI-strength variation observed among sister Wolbachia that infect Drosophila melanogaster subgroup hosts. We cloned, Sanger sequenced, and expressed cif repertoires from weak CI–causing wYak in Drosophila yakuba, revealing mutations suspected to weaken CI relative to model wMel in D. melanogaster. A single valine-to-leucine mutation within the deubiquitylating (DUB) domain of the wYak cifB homolog (cidB) ablates a CI-like phenotype in yeast. The same mutation reduces both DUB efficiency in vitro and transgenic CI strength in the fly, each by about twofold. Our results map hypomorphic transgenic CI to reduced DUB activity and indicate that deubiquitylation is central to CI induction in cid systems. We also characterize effects of other genetic variation distinguishing wMel-like cifs. Importantly, CI strength determines Wolbachia prevalence in natural systems and directly influences the efficacy of Wolbachia biocontrol strategies in transinfected mosquito systems. These approaches rely on strong CI to reduce human disease.

动物与影响其表现和健康的微生物相互作用，包括驻留在其细胞内的内共生体。母体传播的沃尔巴克氏体细菌是最常见的已知内共生体，很大程度上是因为它们对宿主繁殖的操纵。例如，许多沃尔巴克氏体会导致细胞质不相容（CI），当沃尔巴克氏体修饰的精子与未感染的卵子受精时，细胞质不相容性会降低宿主胚胎的活力。操纵子被称为cifs控制 CI，并且单因子 ( cifA ) 可以拯救它，为感染沃尔巴克氏体的雌性提供健康优势。尽管 CI 在自然界中普遍存在，但理论表明，自然选择并不能维持 CI，因为 CI 的强度差异很大。在这里，我们研究了在感染果蝇亚群宿主的姐妹沃尔巴克氏体中观察到的 CI 强度变异的遗传和功能基础。我们克隆、Sanger 测序并表达了果蝇 yakuba中弱 CI 引起的w Yak 的cif库，揭示了相对于黑腹果蝇中模型w Mel 疑似削弱 CI 的突变。 w Yak cifB同源物 ( cidB ) 的去泛素化 (DUB) 结构域内的单个缬氨酸到亮氨酸突变消除了酵母中的 CI 样表型。相同的突变降低了体外 DUB 效率和果蝇转基因 CI 强度，各降低约两倍。我们的结果将低效转基因 CI 映射到 DUB 活性降低，并表明去泛素化是cid系统中 CI 诱导的核心。 我们还描述了其他遗传变异的影响，以区分梅尔样cif 。重要的是，CI 强度决定了自然系统中沃尔巴克氏体的流行程度，并直接影响转染蚊子系统中沃尔巴克氏体生物防治策略的功效。这些方法依靠强大的 CI 来减少人类疾病。