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K-State Today

November 10, 2022

Manfred Schartl to present Division of Biology Seminar

Submitted by Division of Biology

Manfred Schartl, professor, University of Würzburg, will present "Sex Determination Diversity and Sex Chromosome Evolution in Fish" as part of the Division of Biology Seminar Series at 3:30 p.m. Monday, Nov. 14, in 221 Ackert Hall.

Fish show the greatest plasticity of sex determination mechanisms amongst vertebrates. In the case of genetic sex determination, this is linked to similarly high variability of sex chromosome differentiation. While in a handful of species with genetic sex determination, the master sex determination genes have been identified, their molecular function in directing the development of the bipotential gonad primordium toward the testis or ovary is unclear in many cases, or incompletely known in others. To obtain a deeper understanding of this diversity we need a better knowledge of the molecular basis of sex determination mechanisms and the structure and genetic organization of sex chromosomes across a broad diversity of fish. To identify sex chromosomes and primary sex determination genes, we use high throughput RAD-tag marker mapping, transcriptomics, Pool-Seq and whole genome sequencing to identify sex-specific chromosomal regions and candidate sex determination genes in sharks, sturgeons and teleosts, with a special focus on livebearing fishes of the family Poeciliidae. This led to the identification of sex-specific markers, allowing delineation to the extent of recombination suppression, which turned out to be highly variable between species. We identified several species with clear-cut XX/XY or ZZ/ZW monofactorial systems but also species with more complex sex-determination systems including species with a mix of genetic sex determination and environmental sex determination and species with potential polygenic systems. In species with available genomic resources, sex-specific markers could be used to assign scaffolds to regions that are supposed to contain the primary sex-determination gene. We identified candidate genes in several species and find that most of them belong to already known factors of the primary sex determination regulatory network including candidate genes that have not been found so far as being sex determination genes. We also find that many species harbor very poorly differentiated sex chromosomes. The sex determination variety does not follow a phylogenetic pattern and turnovers of the genetic sex-determination system from male to female heterogamety and vice versa are frequent in some groups, making the evolutionary instability of sex determination a unique trait whose biological meaning is not yet understood.

If you would like to visit with Schartl, please contact Michi Tobler at tobler@k-state.edu