Genetic Factors Influencing Sperm Competition

Abstract

Females of many different species often mate with multiple males, creating opportunities for competition among their sperm. Although originally unappreciated, sperm competition is now considered a central form of post-copulatory male–male competition that biases fertilization. Assays of differences in sperm competitive ability between males, and interactions between females and males, have made it possible to infer some of the main mechanisms of sperm competition. Nevertheless, classical genetic approaches have encountered difficulties in identifying loci influencing sperm competitiveness while functional and comparative genomic methodologies, as well as genetic variant association studies, have uncovered some interesting candidate genes. We highlight how the systematic implementation of approaches that incorporate gene perturbation assays in experimental competitive settings, together with the monitoring of progeny output or sperm features and behavior, has allowed the identification of genes unambiguously linked to sperm competitiveness. The emerging portrait from 45 genes (33 from fruit flies, 8 from rodents, 2 from nematodes, and 2 from ants) is their remarkable breadth of biological roles exerted through males and females, the non-preponderance of sperm genes, and their overall pleiotropic nature.

Understanding the Early Evolutionary Stages of a Tandem Drosophilamelanogaster-Specific Gene Family: A Structural and Functional Population Study

“…First, we focused on a panel of 15 strains (eight from the Americas; two from Africa; and five from Eurasia and the Middle East; supplementary tables S1 and S2 , Supplementary Material online) for which female-derived reference-quality assemblies have been generated ( Chakraborty et al. 2018 , 2019 ). These assemblies offer the opportunity to parse patterns of additional structural variation, including inversions and TE insertions, in addition to calibrate two other approaches to estimate CNV: qPCR and read-depth analysis.…”

“…A form of sexual selection, sperm competition, biases fertilization at the postcopulatory level in numerous species groups ( Parker 1970 ; Birkhead 1998 ). Among the few genetic factors known to affect sperm competition ( Civetta and Ranz 2019 ), there is one that resides within a complex region of the Drosophila melanogaster euchromatin: the tandem multigene family Sdic. Sdic is absent in the rest of the genus Drosophila , having originated at some point in the D. melanogaster lineage after diverging from the simulans clade ∼1.4 Ma ( Nurminsky et al.…”

TheDrosophilaseminal proteome and its role in postcopulatory sexual selection

“…This can be explained by SP's function in facilitating the release of sperm from storage: mates of SP 0 males lay and fertilize fewer eggs, and more sperm are retained than normal [64]. Having more sperm present in the female's storage organs should, all else being equal, give the first male a competitive boost in defence against incoming rival sperm [13]. However, the reduced egg laying of their mates lowers SP 0 male reproductive success prior to female remating.…”

“…Although females have a sexual refractory period after mating, they are polyandrous and typically remate before they completely deplete their sperm stores. This results in the mixing of sperm from rival males and the potential for PCSS [12,13]. Drosophila melanogaster therefore represents an ideal system for dissecting the role of seminal fluid molecules in PCSS [7,14].…”

Interactions between the microbiome and mating influence the female’s transcriptional profile inDrosophila melanogaster

“…These transcriptome changes 26 typically reach their highest magnitude at around six hours after mating [5, 10], and 27often include genes that encode proteolytic/metabolic enzymes and immune response 28 genes [5,[9][10][11]. Furthermore, these female post-mating responses are influenced by an 29 1/28 interplay between the genotypes of the female and her mate [12][13][14][15][16], and are induced in 30 part by male ejaculate components that are transferred to the female during 31 mating [1, 4-6, 17, 18]. The post-mating changes in metabolism and food uptake are 32 thought to be required to meet the high energetic demands of oocyte production [19,20], 33 and can be potentially be influenced by transient factors such as the host microbiome.…”