昆虫中的母系传递的共生体与生殖寄生作用相关联，通过干扰寄主繁殖来增加感染的雌性比例并在种群中传播。最近鉴定了负责生殖寄生作用的细菌因子的成功案例，以及进一步的组学方法的应用，强调了去泛素酶结构域的普遍出现，尽管对它们的生物学作用，特别是它们与不同的操纵表型之间的联系仍然定义不清楚。Spaid是果蝇的螺旋形运动细菌共生体，具有选择性杀死雄性后代的雄性杀伤毒素Spaid（S. poulsonii androcidin），其编码卵巢肿瘤（OTU）去泛素酶结构域。对果蝇中Spaid的人工表达重现了与杀伤雄性后代相关的病理学现象，包括胚胎发育过程中的异常凋亡和神经缺陷；此外，在剂型补偿的雄性X染色体上大量积累，与在该染色体上特异性诱导的DNA损伤/染色质桥断裂等细胞缺陷相吻合。在这里，展示了OTU的功能缺失导致Spaid通过寄主泛素-蛋白酶体途径多泛素化和降解，从而减弱了先前显示的杀伤雄性活性。此外，发现Spaid利用其OTU结构域以一种分子间方式去泛素化自身。总体上，Spaid的去泛素酶结构域作为一种自我稳定机制，在果蝇中实现杀伤雄性的优化分子策略，从而使共生体能以低能量成本高效操纵寄主。Copyright © 2023 Elsevier Inc. All rights reserved.

A wide variety of maternally transmitted endosymbionts in insects are associated with reproductive parasitism, whereby they interfere with host reproduction to increase the ratio of infected females and spread within populations.1,2 Recent successes in identifying bacterial factors responsible for reproductive parasitism3,4,5,6,7 as well as further omics approaches8,9,10,11,12 have highlighted the common appearance of deubiquitinase domains, although their biological roles-in particular, how they link to distinct manipulative phenotypes-remain poorly defined. Spiroplasma poulsonii is a helical and motile bacterial endosymbiont of Drosophila,13,14 which selectively kills male progeny with a male-killing toxin Spaid (S. poulsonii androcidin), which encodes an ovarian tumor (OTU) deubiquitinase domain.6 Artificial expression of Spaid in flies reproduces male-killing-associated pathologies that include abnormal apoptosis and neural defects during embryogenesis6,15,16,17,18,19; moreover, it highly accumulates on the dosage-compensated male X chromosome,20 congruent with cellular defects such as the DNA damage/chromatin bridge breakage specifically induced upon that chromosome.6,21,22,23 Here, I show that without the function of OTU, Spaid is polyubiquitinated and degraded through the host ubiquitin-proteasome pathway, leading to the attenuation of male-killing activity as shown previously.6 Furthermore, I find that Spaid utilizes its OTU domain to deubiquitinate itself in an intermolecular manner. Collectively, the deubiquitinase domain of Spaid serves as a self-stabilization mechanism to facilitate male killing in flies, optimizing a molecular strategy of endosymbionts that enables the efficient manipulation of the host at a low energetic cost.Copyright © 2023 Elsevier Inc. All rights reserved.