摘要
Sexually reproducing eukaryotes are typically going through a biphasic life cycle with a diploid and a haploid phase. Unlike in plants where selection on haploid pollen genotypes is well established, the possibility of selection occurring in animal sperm is currently not known. One of the main reasons for this lack of knowledge is the general assumption that due to the shortness and the apparent absence of gene expression in haploid sperm, selection during that phase is unlikely to occur. The aim of this thesis was to fill this gap and address some of the main fundamental questions. I investigated the interaction between sperm phenotype and offspring phenotype with a focus on the trans-generational effects of (i) selection on the haploid sperm genotype, (ii) sperm ageing and (iii) sperm-mediated epigenetic effects. For one, we performed several experimental studies to investigate how selection on the sperm phenotype affects offspring performance in two externally fertilizing fishes, Atlantic salmon and zebrafish. We found that in Atlantic salmon, sperm of intermediate post-activation longevity sire offspring that hatch earlier. In zebrafish, longer living sperm sire more viable offspring with a higher fitness than their short-lived sibling sperm. We explored the mechanisms of these trans-generational effects and found that neither intrinsic post-ejaculation sperm ageing (Atlantic salmon and zebrafish) nor pre-ejaculation sperm ageing (zebrafish) affect offspring performance. However, we identified genetic differences between sperm pools that were obtained by selecting different phenotypes within ejaculates of zebrafish males. These results suggest a genetic basis for intra-ejaculate sperm phenotype variation and show that there is potential for haploid selection in sperm. In a separate experiment, we explored the role of sexual selection in shaping sperm-mediated epigenetic effects, and found that short-time changes in male-male competition affect offspring hatching time and survival. In conclusion, this thesis provides evidence that sperm phenotype affects offspring phenotype, and that sperm phenotype is affected by both epigenetic changes influenced by the male environment and differences in the haploid genome of sperm.
摘要译文
有性繁殖的真核生物通常经历具有二倍体和单倍体相的双相生命周期。与在植物中已经很好地确定单倍体花粉基因型的植物不同，目前尚不知道在动物精子中发生选择的可能性。缺乏知识的主要原因之一是普遍的假设，即由于单倍体精子中基因表达的不足和缺乏，在该阶段的选择不太可能发生。本文的目的是填补这一空白，并解决一些主要的基本问题。我研究了精子表型与后代表型之间的相互作用，重点研究了（i）选择对单倍体精子基因型，（ii）精子衰老和（iii）精子介导的表观遗传效应的跨代效应。其中一项是，我们进行了几项实验研究，以研究精子表型的选择如何影响两种外部受精鱼类大西洋鲑和斑马鱼的后代表现。我们发现，在大西洋鲑鱼中，激活后寿命长寿的精子的后代较早孵化。在斑马鱼中，寿命更长的精子比寿命短的同胞精子具有更强的适应性和更高的后代活力。我们探索了这些跨代效应的机制，发现内在射精后的精子衰老（大西洋鲑鱼和斑马鱼）和内射精子前的衰老（斑马鱼）都没有影响后代的表现。但是，我们确定了通过选择斑马鱼男性射精中不同表型而获得的精子库之间的遗传差异。这些结果表明了射精内精子表型变异的遗传基础，并表明在精子中有选择单倍体的潜力。在一个单独的实验中，我们探索了性选择在塑造精子介导的表观遗传效应中的作用，并发现雄性雄性竞争中的短期变化会影响后代的孵化时间和生存。总之，本论文提供了证据，即精子表型影响后代表型，并且精子表型既受雄性环境影响的表观遗传变化又受精子单倍体基因组差异的影响。
Hermans Née Hotzy, Cosima . Selection in sperm and its consequences: Exploring haploid selection, ageing and epigenetic effects in sperm[D]. SE: Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Educational Sciences, Department of Education, 2017