Understanding the role of selection at the gametic level in adaptation to changing environments

在一个瞬息万变的世界里，迅速适应变化的环境条件的能力是生存的关键。因此，了解生物体如何应对和适应环境变化是一个紧迫的问题。我们的大部分注意力都集中在了解生物体在幼年和成年时是如何适应的，而对配子(精子和卵子)阶段的关注很少，这是令人惊讶的，因为在单倍体(基因组的一个副本)配子阶段的适应选择被预测要比作用于二倍体(两个基因组的副本)生物体在任何其他生命阶段的选择更有效和更便宜。这在雄配子(精子)中尤其如此，它产生大量的精子，但只有极少数受精于一个卵子，这表明了强大的选择压力。此外，精液中的精子在遗传和非遗传含量上存在差异，这种差异与精子表型有关。最后，在体外肥料中，精子暴露在与产生的后代相似的环境条件下，因此精子中受青睐的特征也可能对后代有利。我们实验室的研究提供了强有力的证据，证明斑马鱼个体的精子性能与后代的存活和晚年的繁殖之间存在直接联系。我们还将精子表型与其遗传含量联系起来，从而推翻了长期以来的观点，即精子特征完全取决于男性基因型，而不是其自身的单倍体遗传含量。在这里，我们探索配子选择对于适应不断变化的环境条件，特别是不同的温度的重要性。气温发生了前所未有的变化。热环境可能对冷血外温类和体外受精物种特别重要，在这些物种中，配子暴露在不同的环境条件下。我们将使用体外受精的斑马鱼来测试温度的变化如何影响受精过程中单个雄性精子的选择，以及这些影响与二倍体胚胎或成鱼阶段的影响如何比较。斑马鱼是理想的，因为它是一种体外受精的外胚层，这使得在不同热力条件下使用体外受精进行强有力的平衡实验比较，以及它们如何转化为不同热力条件下的后代表现。此外，斑马鱼有一个测序的基因组，所以它也提供了正确的遗传工具来更深入地研究基因组、表观基因组或表达系统中的潜在机制。在我们的项目结束时，我们的目标是：a)通过配子水平来衡量选择对后代适应的影响，b)记录单倍体基因组内的遗传变异的来源或通过表观遗传机制，以及c)解释单倍体精子生命阶段的表型和遗传变异的选择是否可以加快适应快速环境变化的速度。我们最近的发现表明，在动物的配子水平上进行选择，在快速响应环境变化方面发挥关键作用的潜力。在这里，我们将结合精心设计的体外受精鱼类系统实验和尖端测序技术，为配子选择在适应中的作用提供新的见解。我们的项目不仅将对生态学和进化论领域产生影响，还将对家畜饲养、保护计划和人类健康等应用领域产生影响。

In a rapidly changing world, the ability to swiftly adapt to varying environmental conditions is key for survival. Understanding how organisms cope and adapt to environmental changes is therefore a burning question. Much of our focus has been directed towards understanding how organisms adapt as juveniles and adults, whereas little to no attention is being paid to the gametic (sperm and egg) stages This is surprising because selection for adaptation during the haploid (one copy of the genome) gametic stages is predicted to be much more efficient and cheaper than selection acting on diploid (two copies of the genome) organisms at any other life stage. This is particularly true in male gametes (sperm), which are produced in vast numbers while only very few fertilise an egg, suggesting strong selective pressure. In addition, sperm within an ejaculate vary in their genetic and non-genetic content and this variation is linked to the sperm phenotype. Finally, in external fertilisers, sperm are exposed to similar environmental conditions as the resulting offspring and hence traits favoured in sperm may also benefit the offspring. Research from our lab provides strong evidence for a direct link between individual sperm performance and offspring survival and reproduction later in life in the zebrafish. We also linked sperm phenotype to its genetic content and by that overthrew a long-standing believe that sperm traits are exclusively dependent on the male genotype, but not its own haploid genetic contentHere we explore the importance of gametic selection for adaptation to changing environmental conditions and to varying temperature in particular. Temperature has seen unprecedented rates of change. The thermal environment may be of particular importance for cold-blooded ectotherms and in externally fertilising species, where gametes are exposed to varying environmental conditions. We will use the externally-fertilising zebrafish to test how variation in temperature affects selection among sperm produced by a single male during fertilisation, and how these effects compare to effects experienced during the diploid embryos or adult fish stages. The zebrafish is ideal because it is an ectotherm with external fertilisation, which allows for powerfully balanced experimental comparisons using in vitro fertilisation under different thermal regimes, and how they translate into offspring performance under different thermal regimes. In addition, the zebrafish has a sequenced genome so it also provides the right genetic tools to look deeper at the underlying mechanism within the genome, epigenome, or expression systems. At the conclusion of our project, we aim to: a) have measured the impact of selection through the gamete level for offspring fitness, b) have documented the source of genetic variation within the haploid genome or through epigenetic mechanisms, and c) explained whether selection on phenotypic and genetic variation within the haploid sperm stage of life can speed adaptation under rapid environmental change. Our recent discoveries indicate the potential for selection at the gametic level in animals to play a crucial role in rapid response to environmental change. Here, we will combine carefully-designed experiments in an externally fertilising fish system with cutting-edge sequencing technologies, to provide novel insights into the role of gametic selection in adaptation. Our project will have implications not only for the fields of ecology and evolution, but also for applied areas such as livestock breeding, conservation programs, and human health.