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.
Cumberledge
S
S
Howard Hughes Medical Institute, Department of Human Genetics, University of Utah, Salt Lake City 84112.
Szabad
J
J
Sakonju
S
S
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*