Males and females often differ in their fitness optima for shared traits that have a shared genetic basis, leading to sexual conflict. Morphologically differentiated sex chromosomes can resolve this conflict and protect sexually antagonistic variation, but they accumulate deleterious mutations. However, how sexual conflict is resolved in species that lack differentiated sex chromosomes is largely unknown. Here we present a chromosome-anchored genome assembly for rainbow trout (Oncorhynchus mykiss) and characterize a 55-Mb double-inversion supergene that mediates sex-specific migratory tendency through sex-dependent dominance reversal, an alternative mechanism for resolving sexual conflict. The double inversion contains key photosensory, circadian rhythm, adiposity and sex-related genes and displays a latitudinal frequency cline, indicating environmentally dependent selection. Our results show sex-dependent dominance reversal across a large autosomal supergene, a mechanism for sexual conflict resolution capable of protecting sexually antagonistic variation while avoiding the homozygous lethality and deleterious mutations associated with typical heteromorphic sex chromosomes.

中文翻译：

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性别依赖性优势维持虹鳟的迁移表生。

男性和女性在拥有共同遗传基础的共同性状的适应性最佳方面常常会有所不同，从而导致性冲突。形态上不同的性染色体可以解决这种冲突并保护性拮抗变异，但它们会累积有害的突变。然而，在缺乏分化性染色体的物种中如何解决性冲突仍然是未知的。在这里，我们介绍了虹鳟鱼（Oncorhynchus mykiss）的染色体锚定基因组装配体，并描述了一个55 Mb的双反转超基因，该基因通过通过性别依赖性的优势逆转来解决特定性的迁徙趋势，这是解决性冲突的另一种机制。双重反转包含关键的光感，昼夜节律，肥胖和与性相关的基因，并显示纬度频率谱线，表示对环境的依赖选择。我们的结果表明，跨过大型常染色体超基因的性别依赖性优势逆转，一种解决性冲突的机制，能够保护性拮抗变异，同时避免与典型异型性染色体相关的纯合子致死率和有害突变。