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Schlagwörter:
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Zusammenfassung:
We are studying the evolution of genetic pathways, using sex determination in nematodes as a model. The hallmark of sex determination is that the final result of the pathway is the same throughout evolution: the production of males and females. Detailed genetic and molecular analysis in Drosophila and C. elegans indicate that this pathway evolves very rapidly, making it an excellent model to study how developmental mechanisms and pathways evolve. Although there is low structural conservation for many sex determination genes in the Rhabditidae familiy, recent studies suggest that the function of some these genes in somatic sex determination is conserved. We are taking a genetic approach to study the sex determination pathway in a nematode of the Diplogasteridae family, Pristionchus pacificus. We would like to know whether in this more distantly related nematode there is conservation in the mode of sex determination. We performed a pilot screen of 1500 gametes and isolated 8 putative transformers. Although the soma is almost completely transformed to a male phenotype (development of spicules, rays and bursa in the tail and an one-armed gonad), using molecular markers we have determined that two of them have a XX genotype. These transformers show no mating behaviour and the germ line may exhibit increased cell death. Both transformers map to P. pacificus linkage group III, which show regions of synteny with C. elegans chromosome III. tra-1, the terminal sex determination gene of C. elegans is located on C. elegans chromosome III. We cloned Ppa-tra-1 and generated a polymorphic marker for this gene. There is strong linkage between the Ppa-tra-1 marker and the two transformers. Further molecular characterization is in progress.
