Institute of Life Science, College of Medicine, Swansea University, Swansea SA28PP, Wales UK;
Mol Cell Proteomics. 2013 Nov;12(11):3068-80. doi: 10.1074/mcp.M113.031401. Epub 2013 Jul 18.
Many bivalves have an unusual mechanism of mitochondrial DNA (mtDNA) inheritance called doubly uniparental inheritance (DUI) in which distinctly different genomes are inherited through the female (F genome) and male (M genome) lineages. In fertilized eggs that will develop into male embryos, the sperm mitochondria remain in an aggregation, which is believed to be delivered to the primordial germ cells and passed to the next generation through the sperm. In fertilized eggs that will develop into female embryos, the sperm mitochondria are dispersed throughout the developing embryo and make little if any contribution to the next generation. The frequency of embryos with the aggregated or dispersed mitochondrial type varies among females. Previous models of DUI have predicted that maternal nuclear factors cause molecular differences among unfertilized eggs from females producing embryos with predominantly dispersed or aggregated mitochondria. We test this hypothesis using females of each of the two types from a natural population. We have found small, yet detectable, differences of the predicted type at the proteome level. We also provide evidence that eggs of females giving the dispersed pattern have consistently lower expression for different proteasome subunits than eggs of females giving the aggregated pattern. These results, combined with those of an earlier study in which we used hatchery lines of Mytilus, and with a transcriptomic study in a clam that has the DUI system of mtDNA transmission, reinforce the hypothesis that the ubiquitin-proteasome system plays a key role in the mechanism of DUI and sex determination in bivalves. We also report that eggs of females giving the dispersed pattern have higher expression for arginine kinase and enolase, enzymes involved in energy production, whereas ferritin, which is involved in iron homeostasis, has lower expression. We discuss these results in the context of genetic models for DUI and suggest experimental methods for further understanding the role of these proteins in DUI.
许多双壳类动物具有一种不寻常的线粒体 DNA（mtDNA）遗传机制，称为双重单亲遗传（DUI），其中截然不同的基因组通过雌性（F 基因组）和雄性（M 基因组）谱系遗传。在将发育成雄性胚胎的受精卵中，精子线粒体保持聚集状态，据信这些线粒体被输送到原始生殖细胞，并通过精子传递给下一代。在将发育成雌性胚胎的受精卵中，精子线粒体分散在整个发育胚胎中，对下一代的贡献很小或没有。具有聚集或分散的线粒体类型的胚胎的频率在雌性之间有所不同。以前的 DUI 模型预测，母体核因子导致产生主要分散或聚集线粒体的胚胎的未受精卵之间存在分子差异。我们使用来自产生主要分散或聚集线粒体的胚胎的自然种群中的每一种雌性的两种类型来测试这一假设。我们在蛋白质组水平上发现了小而可检测的预测类型的差异。我们还提供了证据表明，具有分散模式的雌性的卵子的不同蛋白酶体亚基的表达始终低于具有聚集模式的雌性的卵子。这些结果与我们之前在贻贝中使用孵化场系的研究以及在具有 DUI 系统的 mtDNA 传递的蛤中进行的转录组学研究相结合，强化了泛素-蛋白酶体系统在 DUI 和贝类性别决定机制中起关键作用的假设。我们还报告说，具有分散模式的雌性的卵子的精氨酸激酶和烯醇酶表达更高，这些酶参与能量产生，而铁蛋白的表达较低，铁蛋白参与铁稳态。我们在 DUI 的遗传模型的背景下讨论这些结果，并提出了进一步了解这些蛋白质在 DUI 中的作用的实验方法。
