PDF(Pubmed)
Abstract：
Sirenians of the superorder Afrotheria were the first mammals to transition from land to water and are the only herbivorous marine mammals. Here, we generated a chromosome-level dugong (Dugong dugon) genome. A comparison of our assembly with other afrotherian genomes reveals possible molecular adaptations to aquatic life by sirenians, including a shift in daily activity patterns (circadian clock) and tolerance to a high-iodine plant diet mediated through changes in the iodide transporter NIS (SLC5A5) and its co-transporters. Functional in vitro assays confirm that sirenian amino acid substitutions alter the properties of the circadian clock protein PER2 and NIS. Sirenians show evidence of convergent regression of integumentary system (skin and its appendages) genes with cetaceans. Our analysis also uncovers gene losses that may be maladaptive in a modern environment, including a candidate gene (KCNK18) for sirenian cold stress syndrome likely lost during their evolutionary shift in daily activity patterns. Genomes from nine Australian locations and the functionally extinct Okinawan population confirm and date a genetic break ~10.7 thousand years ago on the Australian east coast and provide evidence of an associated ecotype, and highlight the need for whole-genome resequencing data from dugong populations worldwide for conservation and genetic management.
摘要：
超级Afrotheria的Sirenians是第一批从陆地过渡到水的哺乳动物，并且是唯一的食草海洋哺乳动物。这里,我们产生了一个染色体水平的儒艮（Dugongdugon）基因组。将我们的组装与其他非洲基因组进行比较，揭示了Sirenians可能对水生生物进行分子适应，包括日常活动模式（昼夜节律）的变化以及通过碘化物转运蛋白NIS（SLC5A5）及其共同转运蛋白的变化介导的对高碘植物饮食的耐受性。功能性体外测定证实西伦氨基酸取代改变昼夜节律时钟蛋白PER2和NIS的性质。Sirenians显示了鲸类动物的外皮系统（皮肤及其附属物）基因的趋同回归的证据。我们的分析还发现了在现代环境中可能适应不良的基因丢失，包括Sirenian冷应激综合征的候选基因（KCNK18），可能在日常活动模式的进化转变过程中丢失。来自9个澳大利亚地点和功能上已灭绝的冲绳人口的基因组确认并确定了约10.7万年前在澳大利亚东海岸发生的遗传断裂，并提供了相关生态型的证据。并强调需要对全世界儒艮种群的全基因组重新测序数据进行保护和基因管理。
