Tian Ran, Yin Daiqing, Liu Yanzhi, Seim Inge, Xu Shixia, Yang Guang
Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China.
Comparative and Endocrine Biology Laboratory, Translational Research Institute-Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology, Brisbane, QLD, Australia.
Front Genet. 2017 Dec 7;8:205. doi: 10.3389/fgene.2017.00205. eCollection 2017.
Animals that are able to sustain life under hypoxic conditions have long captured the imagination of biologists and medical practitioners alike. Although the associated morphological modifications have been extensively described, the mechanisms underlying the evolution of hypoxia tolerance are not well understood. To provide such insights, we investigated genes in four major energy metabolism pathways, and provide evidence of distinct evolutionary paths to mammalian hypoxia-tolerance. Positive selection of genes in the oxidative phosphorylation pathway mainly occurred in terrestrial hypoxia-tolerant species; possible adaptations to chronically hypoxic environments. The strongest candidate for positive selection along cetacean lineages was the citrate cycle signaling pathway, suggestive of enhanced aerobic metabolism during and after a dive. Six genes with cetacean-specific amino acid changes are rate-limiting enzymes involved in the gluconeogenesis pathway, which would be expected to enhance the lactate removal after diving. Intriguingly, 38 parallel amino acid substitutions in 29 genes were observed between hypoxia-tolerant mammals. Of these, 76.3% were radical amino acid changes, suggesting that convergent molecular evolution drives the adaptation to hypoxic stress and similar phenotypic changes. This study provides further insights into life under low oxygen conditions and the evolutionary trajectories of hypoxia-tolerant species.
能够在缺氧条件下维持生命的动物长期以来一直吸引着生物学家和医学从业者的想象力。尽管相关的形态学变化已被广泛描述，但耐缺氧进化的潜在机制仍未得到很好的理解。为了提供这样的见解，我们研究了四个主要能量代谢途径中的基因，并提供了哺乳动物耐缺氧不同进化路径的证据。氧化磷酸化途径中基因的正选择主要发生在陆地耐缺氧物种中；这可能是对长期缺氧环境的适应。沿鲸类谱系进行正选择的最强候选基因是柠檬酸循环信号通路，这表明在潜水期间和之后有氧代谢增强。六个具有鲸类特异性氨基酸变化的基因是参与糖异生途径的限速酶，预计这将增强潜水后乳酸的清除。有趣的是，在耐缺氧哺乳动物之间观察到29个基因中有38个平行氨基酸替换。其中，76.3%是氨基酸的根本性变化，这表明趋同分子进化驱动了对缺氧应激的适应以及相似的表型变化。这项研究进一步深入了解了低氧条件下的生命以及耐缺氧物种的进化轨迹。
