| PubMed Abstract |
As defined by dominant and recessive ovo mutations, the ovo gene is required for development of the Drosophila female germ
line, and does not exert any function in males or in somatic tissues. However, reversion of dominant ovo mutations can result
in new phenotypes that are not related to the female germ line: the svb and lzl mutations affect cuticle and eye development,
respectively. We have identified a 7.2 kb genomic fragment that rescues ovo mutations in transgenic Drosophila and thus contains
all sequences necessary for ovo+ function. This fragment has been sequenced almost in its entirety, defining the ovo locus
at the molecular level. Multiple copies of the same fragment also rescue the lzl mutation. They do not rescue svb mutations,
in agreement with genetic evidence that the svb function requires additional, more distal sequences. Nevertheless, a number
of transposable element insertions that induce a svb phenotype interrupt the coding sequence of ovo. Taken together, the genetic
and molecular data indicate the existence of a complex locus, where the ovo and svb functions depend on overlapping coding
sequences but distinct regulatory elements. The data also suggest a model for the lzl phenotype. Expression of ovo at the
RNA level is detectable at stage 8 of oogenesis in nurse cells and persists through the rest of oogenesis and in early embryogenesis.
The ovo transcript encodes a protein of at least 1209 amino acids with four zinc fingers, suggesting that ovo might be a transcription
factor required for female germ line maintenance and gametogenesis.
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