Department of Biological Sciences, Mississippi State University, Mississippi State, MS, United States.
Department of Mathematics and Statistics, Mississippi State University, Mississippi State, MS, United States.
Evolution. 2023 Sep 1;77(9):1945-1955. doi: 10.1093/evolut/qpad087.
Mother's Curse alleles represent a significant source of potential male fitness defects. The maternal inheritance of mutations with the pattern of sex-specific fitness effects, s♀>0>s♂, allows Mother's Curse alleles to spread through a population even though they reduce male fitness. Although the mitochondrial genomes of animals contain only a handful of protein-coding genes, mutations in many of these genes have been shown to have a direct effect on male fertility. The evolutionary process of nuclear compensation is hypothesized to counteract the male-limited mitochondrial defects that spread via Mother's Curse. Here we use population genetic models to investigate the evolution of compensatory autosomal nuclear mutations that act to restore the loss of fitness caused by mitochondrial mutation pressures. We derive the rate of male fitness deterioration by Mother's Curse and the rate of restoration by nuclear compensatory evolution. We find that the rate of nuclear gene compensation is many times slower than that of its deterioration by cytoplasmic mutation pressure, resulting in a significant lag in the recovery of male fitness. Thus, the numbers of nuclear genes capable of restoring male mitochondrial fitness defects must be large in order to sustain male fitness in the face of mutation pressures.
母亲的诅咒等位基因代表了潜在的男性适合度缺陷的重要来源。具有性别特异性适合度效应模式（s♀>0>s♂）的突变的母系遗传，使得母亲的诅咒等位基因即使降低了男性适合度，也能够在种群中传播。尽管动物的线粒体基因组仅包含少数几个编码蛋白质的基因，但已经证明许多这些基因的突变对雄性生育力有直接影响。核补偿的进化过程被假设可以抵消通过母亲的诅咒传播的雄性受限的线粒体缺陷。在这里，我们使用群体遗传模型来研究恢复由线粒体突变压力引起的适合度丧失的补偿性常染色体核突变的进化。我们推导出由细胞质突变压力导致的雄性适合度恶化的速度和由核补偿进化导致的恢复速度。我们发现，核基因突变的补偿速度比细胞质突变压力导致的恶化速度慢得多，导致雄性适合度的恢复存在显著滞后。因此，为了在面对突变压力时维持雄性的适合度，能够恢复雄性线粒体适合度缺陷的核基因数量必须很大。
