Department of Biology, University of Southern Denmark, Odense, Denmark.
Paleontology & Geobiology, Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, Munich, Germany.
Elife. 2018 Feb 6;7:e31176. doi: 10.7554/eLife.31176.
Animals have a carefully orchestrated relationship with oxygen. When exposed to low environmental oxygen concentrations, and during periods of increased energy expenditure, animals maintain cellular oxygen homeostasis by enhancing internal oxygen delivery, and by enabling the anaerobic production of ATP. These low-oxygen responses are thought to be controlled universally across animals by the hypoxia-inducible factor (HIF). We find, however, that sponge and ctenophore genomes lack key components of the HIF pathway. Since sponges and ctenophores are likely sister to all remaining animal phyla, the last common ancestor of extant animals likely lacked the HIF pathway as well. Laboratory experiments show that the marine sponge maintains normal transcription under oxygen levels down to 0.25% of modern atmospheric saturation, the lowest levels we investigated, consistent with the predicted absence of HIF or any other HIF-like pathway. Thus, the last common ancestor of all living animals could have metabolized aerobically under very low environmental oxygen concentrations.
动物与氧气有着精心协调的关系。当暴露在低环境氧气浓度下，以及在能量消耗增加的时期，动物通过增强内部氧气输送，并通过使 ATP 进行无氧生产，来维持细胞内氧气的平衡。人们认为，这些低氧反应是通过缺氧诱导因子 (HIF) 在动物中普遍控制的。然而，我们发现，海绵和栉水母的基因组缺乏 HIF 通路的关键组成部分。由于海绵和栉水母可能与所有其他现存动物门是姐妹关系，现存动物的最后共同祖先可能也缺乏 HIF 通路。实验室实验表明，海洋海绵在氧气水平下降到现代大气饱和度的 0.25%以下时，仍能维持正常的转录，这是我们研究的最低水平，这与预测的没有 HIF 或任何其他 HIF 样通路是一致的。因此，所有现存动物的最后共同祖先可能在非常低的环境氧气浓度下就能进行有氧代谢。
