Toxin-antidote elements (TAs) are selfish genetic dyads that spread in populations by selectively killing non-carriers. TAs are common in prokaryotes, but very few examples are known in animals. Here, we report the discovery of maternal-effect TAs in both C. tropicalis and C. briggsae, two distant relatives of C. elegans. In C. tropicalis, multiple TAs combine to cause a striking degree of intraspecific incompatibility: five elements reduce the fitness of >70% of the F₂ hybrid progeny of two Caribbean isolates. We identified the genes underlying one of the novel TAs, slow-1/grow-1, and found that its toxin, slow-1, is homologous to nuclear hormone receptors. Remarkably, although previously known TAs act during embryonic development, maternal loading of slow-1 in oocytes specifically slows down larval development, delaying the onset of reproduction by several days. Finally, we found that balancing selection acting on linked, conflicting TAs hampers their ability to spread in populations, leading to more stable genetic incompatibilities. Our findings indicate that TAs are widespread in Caenorhabditis species and target a wide range of developmental processes and that antagonism between them may cause lasting incompatibilities in natural populations. We expect that similar phenomena exist in other animal species.

毒素-解毒剂元素 (TA) 是自私的遗传二元组，通过选择性杀死非携带者在人群中传播。TA 在原核生物中很常见，但在动物中很少见。在这里，我们报告了在C.tropicalis和C. briggsae这两个秀丽隐杆线虫的远亲中发现了母体效应 TA 。在热带梭状芽孢杆菌中，多种 TA 结合导致种内不相容的程度惊人：五种元素降低了两个加勒比分离株的 F ₂杂种后代的 70% 以上的适应度。我们确定了一种新型 TAs，slow-1/grow-1的基因，并发现它的毒素，slow-1，与核激素受体同源。值得注意的是，尽管先前已知的 TA 在胚胎发育过程中起作用，但母体在卵母细胞中的slow-1负载会特别减慢幼虫的发育，从而将繁殖的开始延迟数天。最后，我们发现平衡选择作用于相关的、相互冲突的 TA 会阻碍它们在人群中传播的能力，从而导致更稳定的遗传不相容性。我们的研究结果表明，TAs 在Caenorhabditis物种中广泛存在并针对广泛的发育过程，并且它们之间的对抗可能导致自然种群中的持久不相容性。我们预计其他动物物种中也存在类似现象。