Healy Timothy M, Burton Ronald S
Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive #0202, La Jolla, CA, USA.
Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive #0202, La Jolla, CA, USA.
Comp Biochem Physiol B Biochem Mol Biol. 2023 Jun-Jul;266:110836. doi: 10.1016/j.cbpb.2023.110836. Epub 2023 Feb 16.
Environmental temperatures have pervasive effects on the performance and tolerance of ectothermic organisms, and thermal tolerance limits likely play key roles underlying biogeographic ranges and responses to environmental change. Mitochondria are central to metabolic processes in eukaryotic cells, and these metabolic functions are thermally sensitive; however, potential relationships between mitochondrial function, thermal tolerance limits and local thermal adaptation in general remain unresolved. Loss of ATP synthesis capacity at high temperatures has recently been suggested as a mechanistic link between mitochondrial function and upper thermal tolerance limits. Here we use a common-garden experiment with seven locally adapted populations of intertidal copepods (Tigriopus californicus), spanning approximately 21.5° latitude, to assess genetically based variation in the thermal performance curves of maximal ATP synthesis rates in isolated mitochondria. These thermal performance curves displayed substantial variation among populations with higher ATP synthesis rates at lower temperatures (20-25 °C) in northern populations than in southern populations. In contrast, mitochondria from southern populations maintained ATP synthesis rates at higher temperatures than the temperatures that caused loss of ATP synthesis capacity in mitochondria from northern populations. Additionally, there was a tight correlation between the thermal limits of ATP synthesis and previously determined variation in upper thermal tolerance limits among populations. This suggests that mitochondria may play an important role in latitudinal thermal adaptation in T. californicus, and supports the hypothesis that loss of mitochondrial performance at high temperatures is linked to whole-organism thermal tolerance limits in this ectotherm.
环境温度对外温性生物的表现和耐受性具有广泛影响，热耐受极限可能是生物地理分布范围以及对环境变化响应的关键基础。线粒体在真核细胞的代谢过程中起着核心作用，且这些代谢功能对温度敏感；然而，线粒体功能、热耐受极限与局部热适应性之间的潜在关系总体上仍未得到解决。最近有人提出，高温下ATP合成能力的丧失是线粒体功能与热耐受上限之间的一种机制联系。在此，我们采用了一项共同花园实验，研究了潮间带桡足类动物（加州虎斑猛水蚤）的七个本地适应种群，这些种群跨越了约21.5°的纬度，以评估分离线粒体中最大ATP合成速率的热性能曲线的基于遗传的变异。这些热性能曲线在种群间表现出显著差异，北方种群在较低温度（20 - 25°C）下的ATP合成速率高于南方种群。相比之下，南方种群的线粒体在比导致北方种群线粒体ATP合成能力丧失的温度更高的温度下仍能维持ATP合成速率。此外，ATP合成的热极限与先前确定的种群间热耐受上限的变异之间存在紧密的相关性。这表明线粒体可能在加州虎斑猛水蚤的纬度热适应中发挥重要作用，并支持了高温下线粒体性能丧失与这种外温动物的整体热耐受极限相关的假说。
