Harrison J Scott, Burton Ronald S
Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, USA.
Mol Biol Evol. 2006 Mar;23(3):559-64. doi: 10.1093/molbev/msj058. Epub 2005 Nov 9.
Deleterious interactions among genes cause reductions in fitness of interpopulation hybrids (hybrid breakdown). Identifying genes involved in hybrid breakdown has proven difficult, and few studies have addressed the molecular basis of this widespread phenomenon. Because proper function of the mitochondrial electron transport system (ETS) requires a coadapted set of nuclear and mitochondrial gene products, ETS genes present an attractive system for studying the evolution of coadapted gene complexes within isolated populations and the loss of fitness in interpopulation hybrids. Here we show the effects of single amino acid substitutions in cytochrome c (CYC) on its functional interaction with another ETS protein, cytochrome c oxidase (COX) in the intertidal copepod Tigriopus californicus. The individual and pairwise consequences of three naturally occurring amino acid substitutions in CYC are examined by site-directed mutagenesis and found to differentially effect the rates of CYC oxidation by COX variants from different source populations. In one case, we show that interpopulation hybrid breakdown in COX activity can be attributed to a single naturally occurring amino acid substitution in CYC.
基因间的有害相互作用会导致种群间杂种的适应性降低（杂种衰败）。事实证明，鉴定参与杂种衰败的基因颇具难度，而且很少有研究探讨这一普遍现象的分子基础。由于线粒体电子传递系统（ETS）的正常功能需要一组相互适应的核基因和线粒体基因产物，ETS基因成为研究隔离种群内相互适应基因复合体的进化以及种群间杂种适应性丧失的一个有吸引力的系统。在此，我们展示了潮间带桡足类动物加州虎斑猛水蚤中细胞色素c（CYC）的单个氨基酸替换对其与另一种ETS蛋白细胞色素c氧化酶（COX）功能相互作用的影响。通过定点诱变研究了CYC中三个自然发生的氨基酸替换的个体和成对效应，发现它们对来自不同来源种群的COX变体氧化CYC的速率有不同影响。在一个案例中，我们表明COX活性的种群间杂种衰败可归因于CYC中单个自然发生的氨基酸替换。
