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Developmental analysis of the ovarian tumor gene during Drosophila oogenesis
C Rodesch1, P K Geyer, J S Patton
1Department of Biological Sciences, University of Iowa, Iowa City 52242, USA.
Abstract:
Severe alleles of the ovarian tumor (otu) and ovo genes result in female sterility in Drosophila melanogaster, producing adult ovaries that completely lack egg chambers. We examined the developmental stage in which the agametic phenotype first becomes apparent. Germ cell development in embryos was studied using a strategy that allowed simultaneous labeling of pole cells with the determination of embryonic genotype. We found that ovo- or otu- XX embryonic germ cells were indistinguishable in number and morphology from those present in wild-type siblings. The effects of the mutations were not consistently manifested in the female germline until pupariation, and there was no evidence that either gene was required for germ cell viability at earlier stages of development. The requirement for otu function in the pupal and adult ovary is supported by temperature-shift experiments using a heat-inducible otu gene construct. We demonstrate that otu activity limited to prepupal stages was not sufficient to support oogenesis, while induction during the pupal and adult periods caused suppression of the otu mutant phenotype.
Insights
Severe mutations in ovarian tumor (otu) and ovo genes cause female sterility in fruit flies. These genes are crucial for egg chamber development during pupal and adult stages, not earlier embryonic development.
Area of Science:
- Developmental Biology
- Genetics
- Reproductive Biology
Background:
- Severe alleles of ovarian tumor (otu) and ovo genes induce female sterility in Drosophila melanogaster.
- Mutations result in adult ovaries lacking egg chambers, indicating a critical role in oogenesis.
Purpose of the Study:
- To determine the specific developmental stage at which the agametic phenotype manifests in ovo and otu mutant fruit flies.
- To investigate the requirement of ovo and otu genes for germ cell viability during early embryonic development.
Main Methods:
- Studied germ cell development in embryos using simultaneous labeling of pole cells and genotype determination.
- Utilized temperature-shift experiments with a heat-inducible otu gene construct.
- Analyzed the effects of restricted otu gene activity during specific developmental periods.
Main Results:
- ovo- and otu- XX embryonic germ cells were morphologically and numerically similar to wild-type siblings.
- The agametic phenotype was primarily observed after pupariation, not during embryonic stages.
- otu activity during pupal and adult stages, but not prepupal stages, suppressed the mutant phenotype.
Conclusions:
- ovo and otu genes are not required for early embryonic germ cell viability in Drosophila.
- Ovarian tumor (otu) gene function is essential during the pupal and adult stages for successful oogenesis.
- The timing of otu gene activity is critical for its role in supporting oogenesis.