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Unveiling the Complexity of Hybrid Male Sterility: From Identification to Cytological Analyses and Genetic Rescue
Hybrid male sterility (HMS) is a common form of reproductive isolation observed in young species which is a manifestation of genetic incompatibilities between the two genomes. Much work has been accomplished to understand the genetic basis of HMS and the underlying evolutionary forces driving them. The young species triad, D. simulans, D. mauritiana and D. sechellia, has been instrumental in the identification and characterization of these genetic incompatibilities including the first described animal HMS factor, Odysseus. This dissertation continues this progress by first dissecting a 4Mb X-linked D. mauritiana introgression in an otherwise D. simulans genetic background and identifying at least 4 putative HMS regions including the rediscovery of Odysseus. Our results suggest HMS a complex genetic architecture often underlies HMS. Next, we use progressively smaller introgressions (thus harboring fewer putative HMS loci) and describe the spermatogenic defects associated with each introgression using a Protamine transgene fused to GFP to visualize DNA in sperm nuclei. We find that the HMS regions demonstrate a mostly additive relationship with developmental defects as males harboring more HMS regions appear to have earlier breakdowns of spermatogenesis. Finally, Odysseus-mediated sterility is hypothesized to be the consequence of an interaction between the D. mauritiana allele of Odysseus and the D. simulans Y chromosome. We use D. simulans lines with an introgressed D. mauritiana or D. sechellia Y chromosome to test this model and find support as the D. mauritiana Y chromosome rescues fertility.
Evolution and Development|Genetics
Villegas, Rodolfo A, "Unveiling the Complexity of Hybrid Male Sterility: From Identification to Cytological Analyses and Genetic Rescue" (2023). ETD collection for University of Nebraska-Lincoln. AAI30576013.