Department of Evolutionary Ecology, Max Planck Institute for Evolutionary Biology, August-Thienemann-Str. 2, 24306 Plön, Germany.
Current Address: School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, United Kingdom.
Evolution. 2018 Nov;72(11):2478-2490. doi: 10.1111/evo.13591. Epub 2018 Sep 24.
Females choose specific mates in order to produce fitter offspring. However, several factors interfere with females' control over fertilization of their eggs, including sneaker males and phenotypically unpredictable allele segregation during meiosis. Mate choice at the individual level thus provides only a poor approximation for obtaining the best genetic match. Consequently, postcopulatory sperm selection by female oocytes has been proposed as a mechanism to achieve complementary combinations of parental haplotypes. Here, using controlled in vitro fertilization of three-spined stickleback eggs, we find haplotype-specific fertilization bias toward gametes with complementary major histocompatibility complex (MHC) immunogenes. The resulting zygote (and thus offspring) genotypes exhibit an intermediate level of individual MHC diversity that was previously shown to confer highest pathogen resistance. Our finding of haplotype-specific gamete selection thus represents an intriguing mechanism for fine-tuned optimization of the offspring's immune gene composition and an evolutionary advantage in the Red Queen dynamics of host-parasite coevolution.
雌性会选择特定的配偶，以产生更健康的后代。然而，有几个因素会干扰雌性对其卵子受精的控制，包括偷偷交配的雄性和减数分裂过程中表型不可预测的等位基因分离。因此，个体水平的配偶选择只能粗略地获得最佳的遗传匹配。因此，雌性卵母细胞对精子的选择被认为是一种实现父母单倍型互补组合的机制。在这里，我们使用三刺鱼卵的体外受精，发现与具有互补主要组织相容性复合体（MHC）免疫基因的配子有特定的单倍型受精偏倚。由此产生的受精卵（进而产生后代）基因型表现出个体 MHC 多样性的中间水平，先前的研究表明这种多样性水平最高可以赋予病原体抗性。我们发现的单倍型特异性配子选择代表了一种有趣的机制，可以微调优化后代的免疫基因组成，并在宿主-寄生虫共同进化的“红皇后动态”中具有进化优势。
