Organisms that live in deserts offer the opportunity to investigate how species adapt to environmental conditions that are lethal to most plants and animals. In the hot deserts of North America, high temperatures and lack of water are conspicuous challenges for organisms living there. The cactus mouse (Peromyscus eremicus) displays several adaptations to these conditions, including low metabolic rate, heat tolerance, and the ability to maintain homeostasis under extreme dehydration. To investigate the genomic basis of desert adaptation in cactus mice, we built a chromosome-level genome assembly and resequenced 26 additional cactus mouse genomes from two locations in southern California (USA). Using these data, we integrated comparative, population, and functional genomic approaches. We identified 16 gene families exhibiting significant contractions or expansions in the cactus mouse compared to 17 other Myodontine rodent genomes, and found 232 sites across the genome associated with selective sweeps. Functional annotations of candidate gene families and selective sweeps revealed a pervasive signature of selection at genes involved in the synthesis and degradation of proteins, consistent with the evolution of cellular mechanisms to cope with protein denaturation caused by thermal and hyperosmotic stress. Other strong candidate genes included receptors for bitter taste, suggesting a dietary shift towards chemically defended desert plants and insects, and a growth factor involved in lipid metabolism, potentially involved in prevention of dehydration. Understanding how species adapted to deserts will provide an important foundation for predicting future evolutionary responses to increasing temperatures, droughts and desertification in the cactus mouse and other species.

中文翻译：

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比较和种群基因组学方法揭示了在小型啮齿动物中适应沙漠的基础。

生活在沙漠中的生物提供了机会来研究物种如何适应对大多数动植物有害的环境条件。在北美炎热的沙漠中，高温和缺水对居住在那里的生物构成了明显的挑战。仙人掌小鼠（Peromyscus eremicus）对这些疾病表现出多种适应性，包括低代谢率，耐热性以及在极端脱水下保持体内平衡的能力。为了研究仙人掌小鼠沙漠适应的基因组基础，我们建立了染色体水平的基因组装配体，并从美国加利福尼亚州南部的两个位置对26个其他的仙人掌小鼠基因组进行了重新测序。利用这些数据，我们整合了比较，种群和功能基因组方法。与其他17个Myodontine啮齿类动物基因组相比，我们确定了16个基因家族在仙人掌小鼠中表现出明显的收缩或扩增，并在整个基因组中发现了与选择性清除相关的232个位点。候选基因家族的功能注释和选择性扫描揭示了参与蛋白质合成和降解的基因普遍存在的选择标记，与细胞机制的演变相一致，以应对由热和高渗胁迫引起的蛋白质变性。其他强大的候选基因包括苦味受体，这表明饮食向化学防御的沙漠植物和昆虫转变，以及涉及脂质代谢的生长因子，可能与预防脱水有关。