Macqueen Daniel J, Garcia de la Serrana Daniel, Johnston Ian A
Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK Scottish Oceans Institute, University of St Andrews, St Andrews, Fife KY16 8LB, UK
Scottish Oceans Institute, University of St Andrews, St Andrews, Fife KY16 8LB, UK.
Biol Lett. 2014 Jun;10(6). doi: 10.1098/rsbl.2014.0225.
Myoglobin (Mb) is the classic vertebrate oxygen-binding protein present in aerobic striated muscles. It functions principally in oxygen delivery and provides muscle with its characteristic red colour. Members of the Antarctic icefish family (Channichthyidae) are widely thought to be extraordinary for lacking cardiac Mb expression, a fact that has been attributed to their low metabolic rate and unusual evolutionary history. Here, we report that cardiac Mb deficit, associated with pale heart colour, has evolved repeatedly during teleost evolution. This trait affects both gill- and air-breathing species from temperate to tropical habitats across a full range of salinities. Cardiac Mb deficit results from total pseudogenization in three-spined stickleback and is associated with a massive reduction in mRNA level in two species that evidently retain functional Mb. The results suggest that near or complete absence of Mb-assisted oxygen delivery to heart muscle is a common facet of teleost biodiversity, even affecting lineages with notable oxygen demands. We suggest that Mb deficit may affect how different teleost species deal with increased tissue oxygen demands arising under climate change.
肌红蛋白（Mb）是存在于有氧横纹肌中的经典脊椎动物氧结合蛋白。它主要在氧气输送中发挥作用，并赋予肌肉特有的红色。南极冰鱼科（Channichthyidae）的成员普遍被认为非同寻常，因为它们缺乏心脏肌红蛋白表达，这一事实被归因于它们的低代谢率和独特的进化历史。在此，我们报告称，与心脏颜色苍白相关的心脏肌红蛋白缺失在硬骨鱼进化过程中反复出现。这一特征影响了从温带至热带栖息地、涵盖各种盐度的鳃呼吸和空气呼吸物种。三刺鱼的心脏肌红蛋白缺失是由于完全假基因化导致的，并且在另外两个明显保留功能性肌红蛋白的物种中，其与mRNA水平的大幅降低有关。结果表明，心肌几乎或完全缺乏肌红蛋白辅助的氧气输送是硬骨鱼生物多样性的一个常见特征，甚至影响到对氧气需求显著的谱系。我们认为，肌红蛋白缺失可能会影响不同硬骨鱼物种应对气候变化下组织氧气需求增加的方式。
