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OVO transcription factors function antagonistically in the Drosophila female germline
J Andrews1, D Garcia-Estefania, I Delon
1Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda MD, USA.
Abstract:
OVO controls germline and epidermis differentiation in flies and mice. In the Drosophila germline, alternative OVO-B and OVO-A isoforms have a common DNA-binding domain, but different N-termini. We show that these isoforms are transcription factors with opposite regulatory activities. Using yeast one-hybrid assays, we identified a strong activation domain within a common region and a counteracting repression domain within the OVO-A-specific region. In flies, OVO-B positively regulated the ovarian tumor promoter, while OVO-A was a negative regulator of the ovarian tumor and ovo promoters. OVO-B isoforms supplied ovo(+) function in the female germline and epidermis, while OVO-A isoforms had dominant-negative activity in both tissues. Moreover, elevated expression of OVO-A resulted in maternal-effect lethality while the absence of OVO-A resulted in maternal-effect sterility. Our data indicate that tight regulation of antagonistic OVO-B and OVO-A isoforms is critical for germline formation and differentiation.
Insights
The OVO protein isoforms, OVO-B and OVO-A, act as transcription factors with opposing roles in fruit fly development. Precise control of these OVO isoforms is essential for germline formation and differentiation.
Area of Science:
- Developmental Biology
- Genetics
- Molecular Biology
Background:
- The OVO gene product is crucial for germline and epidermis differentiation in both flies and mice.
- Alternative OVO-B and OVO-A isoforms in Drosophila share a DNA-binding domain but differ in their N-termini.
Purpose of the Study:
- To investigate the distinct regulatory activities of OVO-B and OVO-A isoforms.
- To elucidate the critical role of OVO isoform regulation in germline development.
Main Methods:
- Yeast one-hybrid assays were employed to identify functional domains.
- In vivo studies in Drosophila assessed the regulatory functions of OVO isoforms on specific promoters.
- Analysis of OVO isoform expression effects on maternal-effect lethality and sterility.
Main Results:
- OVO isoforms exhibit antagonistic transcriptional activities: OVO-B acts as a positive regulator, while OVO-A functions as a negative regulator.
- OVO-B isoforms restore normal function in the female germline and epidermis, whereas OVO-A isoforms display dominant-negative effects.
- Aberrant OVO-A expression leads to maternal-effect lethality, and its absence causes maternal-effect sterility.
Conclusions:
- The opposing regulatory functions of OVO-B and OVO-A isoforms are critical for proper germline formation and differentiation.
- Precise stoichiometric control of OVO isoforms is essential for reproductive success in Drosophila.