Division of Biological Sciences, University of Montana, Missoula, MT.
Department of Biology, McMaster University, Hamilton, ON, Canada.
Mol Biol Evol. 2020 Aug 1;37(8):2309-2321. doi: 10.1093/molbev/msaa086.
Aerobic performance is tied to fitness as it influences an animal's ability to find food, escape predators, or survive extreme conditions. At high altitude, where low O2 availability and persistent cold prevail, maximum metabolic heat production (thermogenesis) is an aerobic performance trait that is closely linked to survival. Understanding how thermogenesis evolves to enhance survival at high altitude will yield insight into the links between physiology, performance, and fitness. Recent work in deer mice (Peromyscus maniculatus) has shown that adult mice native to high altitude have higher thermogenic capacities under hypoxia compared with lowland conspecifics, but that developing high-altitude pups delay the onset of thermogenesis. This finding suggests that natural selection on thermogenic capacity varies across life stages. To determine the mechanistic cause of this ontogenetic delay, we analyzed the transcriptomes of thermoeffector organs-brown adipose tissue and skeletal muscle-in developing deer mice native to low and high altitude. We demonstrate that the developmental delay in thermogenesis is associated with adaptive shifts in the expression of genes involved in nervous system development, fuel/O2 supply, and oxidative metabolism pathways. Our results demonstrate that selection has modified the developmental trajectory of the thermoregulatory system at high altitude and has done so by acting on the regulatory systems that control the maturation of thermoeffector tissues. We suggest that the cold and hypoxic conditions of high altitude force a resource allocation tradeoff, whereby limited energy is allocated to developmental processes such as growth, versus active thermogenesis, during early development.
有氧表现与健康状况有关，因为它影响动物寻找食物、逃避捕食者或在极端条件下生存的能力。在高海拔地区，氧气供应不足且持续寒冷，最大代谢产热（生热作用）是一种与生存密切相关的有氧表现特征。了解生热作用如何进化以提高在高海拔地区的生存能力，将深入了解生理学、表现和健康之间的联系。最近在鹿鼠（Peromyscus maniculatus）中的研究表明，与低地同种动物相比，原产于高海拔地区的成年老鼠在低氧环境下具有更高的生热能力，但高海拔地区的幼鼠会延迟生热作用的发生。这一发现表明，生热能力的自然选择在不同的生命阶段有所不同。为了确定这种发育延迟的机制原因，我们分析了原产于低海拔和高海拔地区的发育中的鹿鼠的热效应器官（棕色脂肪组织和骨骼肌）的转录组。我们证明，生热作用的发育延迟与涉及神经系统发育、燃料/O2 供应和氧化代谢途径的基因表达的适应性变化有关。我们的结果表明，选择已经改变了高海拔地区体温调节系统的发育轨迹，其通过作用于控制热效应组织成熟的调节系统来实现这一点。我们认为，高海拔地区的寒冷和低氧条件迫使资源分配产生权衡，即在早期发育过程中，有限的能量被分配给生长等发育过程，而不是主动生热作用。
