Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden.
Department of Biological Sciences, University of the Pacific, Stockton, CA, USA.
Mol Biol Evol. 2024 Apr 2;41(4). doi: 10.1093/molbev/msae075.
The molecular evolution of the mammalian heater protein UCP1 is a powerful biomarker to understand thermoregulatory strategies during species radiation into extreme climates, such as aquatic life with high thermal conductivity. While fully aquatic mammals lost UCP1, most semiaquatic seals display intact UCP1 genes, apart from large elephant seals. Here, we show that UCP1 thermogenic activity of the small-bodied harbor seal is equally potent compared to terrestrial orthologs, emphasizing its importance for neonatal survival on land. In contrast, elephant seal UCP1 does not display thermogenic activity, not even when translating a repaired or a recently highlighted truncated version. Thus, the thermogenic benefits for neonatal survival during terrestrial birth in semiaquatic pinnipeds maintained evolutionary selection pressure on UCP1 function and were only outweighed by extreme body sizes among elephant seals, fully eliminating UCP1-dependent thermogenesis.
哺乳动物解偶联蛋白 UCP1 的分子进化是一个强大的生物标志物，可用于了解物种辐射到极端气候（如具有高热导性的水生生物）时的体温调节策略。虽然完全水生的哺乳动物失去了 UCP1，但大多数半水生海豹除了大型象海豹外，都显示出完整的 UCP1 基因。在这里，我们表明，与陆地同源物相比，小体型的港湾海豹的 UCP1 产热活性同样强大，这强调了其对陆地新生幼崽存活的重要性。相比之下，即使在翻译修复或最近突出显示的截短版本时，象海豹的 UCP1 也没有表现出产热活性。因此，在半水生鳍足类动物的陆地产仔过程中，新生儿存活的产热益处对 UCP1 功能保持了进化选择压力，只有在象海豹极端的体型下才超过了 UCP1 依赖的产热，完全消除了 UCP1 依赖的产热。
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