Functional and Evolutionary Genetics of Seminal Fluid
Evolution, Anthropology
Final Report Abstract
In this project, we sought to investigate the functional and evolutionary genetics of seminal fluid in a promising model organism, the simultaneously hermaphroditic flatworm Macrostomum lignano, employing a wide range of techniques including in situ hybridization, RNA interference, qPCR, transcriptomics, quantitative genetics, and behavioural and fitness assays. We have comprehensively characterised the seminal fluid transcriptome of M. lignano, finding that it comprises a complex mix of transcripts with prostate-limited expression, many of which encode proteins that are putatively secreted. Nevertheless, our expression profiling of these transcripts revealed that they are controlled in a highly coordinated manner, and – somewhat surprisingly – that there are in fact relatively few independent axes of variation in seminal fluid expression. These axes of seminal fluid expression – and the underlying individual transcripts – are affected by different combinations of genetic, environmental and genotype-by-environment effects. Further experiments to characterise the function and evolutionary significance of top seminal fluid candidates confirms that they play important roles mediating sperm competition and sexual conflict; through gene knockdown experiments coupled to appropriate fitness assays, we could demonstrate that three different seminal fluid proteins impact on ‘offensive’ sperm competitiveness, and – using a novel quantitative genetic approach – that two additional seminal fluid proteins mediate sexual conflict over ejaculate fate, by inhibiting the post-copulatory ‘suck’ behaviour of mating partners (and thereby preventing those partners from removing received sperm and other ejaculate components after mating). Finally, comparisons of the transcriptomes of four Macrostomum species suggest that seminal fluid is extremely divergent, supporting the rapid evolution of this important ejaculate component being driven by sexual selection.
Publications
- (2019) Genetic and environmental variation in transcriptional expression of seminal fluid proteins. Heredity 122 (5) 595–611
Patlar, Bahar; Weber, Michael; Ramm, Steven A.
(See online at https://doi.org/10.1038/s41437-018-0160-4) - (2019) Sex allocation plasticity on a transcriptome scale: Socially sensitive gene expression in a simultaneous hermaphrodite. Molecular ecology 28 (9) 2321–2341
Ramm, Steven A.; Lengerer, Birgit; Arbore, Roberto; Pjeta, Robert; Wunderer, Julia; Giannakara, Athina; Berezikov, Eugene; Ladurner, Peter; Schärer, Lukas
(See online at https://doi.org/10.1111/mec.15077) - 2015. Sexual conflict in hermaphrodites. Cold Spring Harbor Perspectives in Biology 7:a017673
Schärer L, Janicke , Ramm SA
(See online at https://doi.org/10.1101/cshperspect.a017673) - 2017. Exploring the sexual diversity of flatworms: ecology, evolution, and the molecular biology of reproduction. Molecular Reproduction & Development 84:120-131
Ramm SA
(See online at https://doi.org/10.1002/mrd.22669) - 2018. A targeted in situ hybridization screen identifies putative seminal fluid proteins in a simultaneously hermaphroditic flatworm. BMC Evolutionary Biology 18:81
Weber M, Wunderer J, Lengerer B, Pjeta R, Rodrigues M, Schärer L, Ladurner P, Ramm SA
(See online at https://doi.org/10.1186/s12862-018-1187-0)
