Locate the Hybrid Male Sterility Related Genes in Two Closely Related Nematodes with an X-Linked Introgression Strain

Speciation is the process of formation and maintenance of species through the evolution of reproductive isolation. Intrinsic postzygotic barriers are built from hybrid defects like sterility or inviability which can result from the conflict between haplotypes. The pair of Caenorhabditis briggsae and C. nigoni are among the most closely related species within the nematode genus Caenorhabditis. Wild-type C. briggsae and C. nigoni can produce fertile F1 hybrid females, but the male progenies are either inviable or sterile.By replacing a small proportion of C. nigoni X chromosome to the syntenic region in C. briggsae, we got a homozygous introgression strain (LRS129) to break the hybridization barrier by rescuing the F1 male fertility. This model gave us an opportunity to monitor the competition of two interspecies haplotypes during long-term hybridization, which will help us understand the mechanism of speciation in diploid animals. In the meantime, another introgression strain, LRS134, which only holds a slightly different introgression region from LRS129, can not rescue the F1 male sterility. The comparison of the two strains gives us a model to study the mechanism of hybrid male sterility. In this study, we propose delineating the hybridization landscape of C. briggsae and C. nigoni using the F1 hybrid from C. briggsae male and X-linked LRS129 female. We will also map and validate the X-linked gene responsible for F1 hybrid male sterility. The findings will provide mechanistic insights into hybrid incompatibility related speciation and genome evolution after hybridization.