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Drosophila melanogaster Male Somatic Cells Feminized Solely by TraF Can Collaborate With Female Germ Cells to Make Functional Eggs

2006; Oxford University Press; Volume: 175; Issue: 2 Linguagem: Inglês

10.1534/genetics.106.066332

1943-2631

Daniel S. Evans, Thomas W. Cline,

Developmental Biology and Gene Regulation

Abstract Female differentiation of Drosophila germ cells is induced by cell-nonautonomous signals generated in the gonadal soma that work with germ-cell-autonomous signals determined by germ-cell X chromosome dose. Generation of the nonautonomous feminizing signals was known to involve female-specific protein encoded by the master sex-determination gene Sex-lethal (Sxl) acting on its switch-gene target transformer (tra) to produce TraF protein. However, it was not known whether Sxl's action on tra alone would suffice to trigger a fully feminizing nonautonomous signal. We developed a constitutively feminizing tra transgene that allowed us to answer this question. In gynanders (XX//XO mosaics) feminized by this TraF transgene, functionally Sxl− haplo-X (chromosomally male) somatic cells collaborated successfully with diplo-X (chromosomally female) germ cells to make functional eggs. The fertility of such gynanders shows not only that TraF is sufficient to elicit a fully feminizing nonautonomous signal, but also that haplo-X somatic cells can execute all other somatic functions required for oogenesis, despite the fact that their genome is not expected to be dosage compensated for such diplo-X-specific functions. The unexpected observation that some TraF-feminized gynanders failed to lay their eggs showed there to be diplo-X cells outside the gonad for which TraF-feminized haplo-X cells cannot substitute.