Gonad formation and development requires the abd-A domain of the bithorax complex in Drosophila melanogaster.
The abdominal-A (abd-A) gene, a member of the bithorax complex, is required for the correct identity of parasegments (PS) 7 through 13. Mutations in iab-4, one of the cis-regulatory regions of abd-A, transform epidermal structures of PS 9 and also cause loss of gonads in adult flies. Here, we describe a developmental and molecular analysis of the role of iab-4 functions in gonadal development. In flies homozygous for a strong iab-4 allele, gonadogenesis is not initiated in the embryo because the mesodermal cells fail to encapsulate the pole cells. Flies homozygous for weaker iab-4 mutations sometimes form ovaries. The ovary-oviduct junctions are abnormal, however, and egg transfer from the ovary to the uterus is blocked in the adult. To localize the sites that require iab-4 function, we have analyzed animals chimeric for the mutant and wild-type cells. These chimeras were generated by three kinds of transplantation experiments: pole cells, embryonic somatic nuclei or larval ovaries. Our results suggest that iab-4 is required in the somatic cells of the gonadal primordia, but not the germ line. In addition, the formation of functional ovary-oviduct junctions and egg transfer also requires iab-4 functions in the somatic cells of the ovary and in at least one additional somatic tissue.
Howard Hughes Medical Institute, Department of Human Genetics, University of Utah, Salt Lake City 84112.
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Cumberledge
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Szabad
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Sakonju
D000818:Animals; D002678:Chimera / Q000235:genetics; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000196:embryology* / Q000235:genetics; D005260:Female; D015870:Gene Expression / Q000235:genetics; D005801:Genes, Homeobox / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D008648:Mesoderm / Q000502:physiology; D009154:Mutation / Q000235:genetics; D053652:Nuclear Transfer Techniques; D010053:Ovary / Q000033:anatomy & histology / Q000196:embryology* / Q000637:transplantation; D013737:Testis / Q000033:anatomy & histology / Q000196:embryology*