Evolutionary Biology, Bielefeld University, Bielefeld, Germany.
J Evol Biol. 2020 Feb;33(2):225-236. doi: 10.1111/jeb.13568. Epub 2019 Nov 21.
Sperm competition commonly occurs whenever females mate multiply, leading to variation in male paternity success. This can be due to variation in the various traits that might affect sperm competitive ability, which itself depends on both genetic and environmental factors, as well as on genotype-by-environment interactions (GEI). Seminal fluid is a major component of the male ejaculate that is often expected to mediate sperm competition, where different genotypes can differ in their seminal fluid expression as a response to different levels of sperm competition (i.e. exhibit GEI). We therefore here focussed on testing for GEI in expression of two recently identified seminal fluid transcripts, suckless-1 and suckless-2, which potentially modulate sperm competitive ability in the simultaneously hermaphroditic flatworm Macrostomum lignano via their effects on manipulating post-mating partner behaviour and ultimately the fate of transferred ejaculates. In addition, we sought to test for GEI in sperm competitive ability in a standardized sperm competition (P and P ) assay, to investigate the relationship between natural variation in the expression of these seminal fluid transcripts generated through GEI and relative paternity success. We found GEI for the expression level of suckless-1 and suckless-2, as well as for sperm competitive ability. Moreover, we found a positive relation between the expression of suckless-1 and relative paternity success (P ). This suggests that natural variation in the expression of this seminal fluid transcript indeed can influence sperm competition outcomes in M. lignano.
当雌性动物多次交配时，通常会发生精子竞争，导致雄性亲代成功的变化。这可能是由于可能影响精子竞争能力的各种特征的变化所致，而精子竞争能力本身取决于遗传和环境因素，以及基因型与环境相互作用（GEI）。精液是雄性精液的主要成分，通常被认为可以介导精子竞争，不同基因型可以通过不同的精液表达来应对不同程度的精子竞争（即表现出 GEI）。因此，我们在这里专注于测试两个最近鉴定的精液转录本 suckless-1 和 suckless-2 的表达中的 GEI，这两个转录本可能通过操纵交配后伴侣的行为，最终影响转移精液的命运，从而调节同时为雌雄同体的扁形虫 Macrostomum lignano 中的精子竞争能力。此外，我们试图在标准化的精子竞争（P 和 P ）测定中测试精子竞争能力中的 GEI，以研究这些通过 GEI 产生的精液转录本的表达水平的自然变异与相对亲代成功之间的关系。我们发现 suckless-1 和 suckless-2 的表达水平以及精子竞争能力存在 GEI。此外，我们发现 suckless-1 的表达与相对亲代成功（P ）之间存在正相关关系。这表明这种精液转录本的表达水平的自然变异确实可以影响 M. lignano 中的精子竞争结果。
