Mobilization of the gypsy and copia retrotransposons in Drosophila melanogaster induces reversion of the ovo ^D dominant female-sterile mutations: molecular analysis of revertant alleles

Abstract

The ovo locus is required for the maintenance of the female germ line in Drosophila melanogaster. In the absence of an ovo+ gene, males are completely normal but females have no germ‐line stem cells. Three dominant mutations at the ovo locus, called ovoD, were observed to revert towards recessive alleles at high frequency when ovoD males were crossed to females of the strain y v f mal. We have found that this strain contains an inordinately high number of gypsy transposable elements, and crossing it with the ovoD strains results in the mobilization of both gypsy and copia, with high‐frequency insertions into the ovo locus: of 16 revertants examined 12 have gypsy and four have copia inserted at 4E, the ovo cytological site. Using gypsy DNA as a tag we have cloned 32 kb of wild‐type DNA sequences surrounding a gypsy insertion and characterized molecular rearrangements in several independent revertants: in 10 of them gypsy appears to be inserted into the same site. The orientation of gypsy is strictly correlated with whether the neighbouring lozenge‐like mutation appears in the revertants. A distal limit of the ovo locus was molecularly determined from the breakpoint of a deletion affecting closely flanking regions.

Multiple products from the shavenbaby-ovo gene region of Drosophila melanogaster: relationship to genetic complexity.

“…Certain fragments of the svb-ovo gene region contain repeated DNA sequences (13,22). In particular, probe A (0.65-kb EcoRI-HindlIl fragment; Fig.…”

“…Recessive, apparently null, alleles cause female-specific sterility due to the loss of germ cells in the embryo (27 ovo alleles to suppress partially P-M hybrid dysgenesisinduced female germ line cell death (39). Thus, ovo appears to play a prominent role in the early female-specific establishment of the germ line as well as in subsequent oocyte development and differentiation.Genomic DNA sequences required for ovo function are genetically overlapping and interdigitated with the genomic DNA sequences required for the shavenbaby (svb) function (13,22). svb is known to affect epidermal locomotor and sensory structures in a sex-independent fashion (42).…”

“…Three classes of mutation affect ovo and svb functions: svb-ovo+ mutations, svb+ ovo-mutations, and svb-ovo-mutations (27). Single DNA insertions are associated with examples of the latter two classes of mutations, suggesting that there are ovo-specific and svb-ovo-common regions (13,22).A 5.0-kb ovarian poly(A)+ mRNA ovo candidate transcript that is female specific and germ line dependent in adult flies has been identified (13, 23). Mevel-Ninio et al (23) isolated and sequenced cDNAs from an 8-to 12-h embryonic cDNA library and a 6.7-kb genomic DNA segment.…”

“…Genomic DNA sequences required for ovo function are genetically overlapping and interdigitated with the genomic DNA sequences required for the shavenbaby (svb) function (13,22). svb is known to affect epidermal locomotor and sensory structures in a sex-independent fashion (42).…”

“…Three classes of mutation affect ovo and svb functions: svb-ovo+ mutations, svb+ ovo-mutations, and svb-ovo-mutations (27). Single DNA insertions are associated with examples of the latter two classes of mutations, suggesting that there are ovo-specific and svb-ovo-common regions (13,22).…”