Department of Biological Sciences, University of Idaho, Moscow, Idaho, 83844.
Department of Biology, Reed College, Portland, Oregon, 97202.
Evolution. 2022 Sep;76(9):2162-2180. doi: 10.1111/evo.14579. Epub 2022 Aug 1.
In many animals, sperm competition and sexual conflict are thought to drive the rapid evolution of male-specific genes, especially those expressed in the testes. A potential exception occurs in the male pregnant pipefishes, where females transfer eggs to the males, eliminating testes from participating in these processes. Here, we show that testis-related genes differ dramatically in their rates of molecular evolution and expression patterns in pipefishes and seahorses (Syngnathidae) compared to other fish. Genes involved in testis or sperm function within syngnathids experience weaker selection in comparison to their orthologs in spawning and livebearing fishes. An assessment of gene turnover and expression in the testis transcriptome suggests that syngnathids have lost (or significantly reduced expression of) important classes of genes from their testis transcriptomes compared to other fish. Our results indicate that more than 50 million years of male pregnancy have removed syngnathid testes from the molecular arms race that drives the rapid evolution of male reproductive genes in other taxa.
在许多动物中，精子竞争和性冲突被认为是推动雄性特异性基因快速进化的原因，尤其是那些在睾丸中表达的基因。一个潜在的例外发生在雄性怀孕的海龙鱼中，雌性将卵子转移到雄性体内，使睾丸无法参与这些过程。在这里，我们发现与其他鱼类相比，海龙鱼和海马（海龙目）的睾丸相关基因在分子进化率和表达模式上存在显著差异。与产卵和胎生鱼类的同源基因相比，海龙目鱼类中与睾丸或精子功能相关的基因受到的选择压力较弱。对睾丸转录组中基因转换和表达的评估表明，与其他鱼类相比，海龙目鱼类的睾丸转录组中丢失了（或显著降低了表达）重要的基因类别。我们的研究结果表明，5000 多万年的雄性怀孕使海龙目鱼类的睾丸脱离了驱动其他分类群雄性生殖基因快速进化的分子军备竞赛。
