THE EFFECT OF DOMINANT VESTIGIAL ALLELES UPON VESTIGIAL-MEDIATED WINGPATTERNING DURING DEVELOPMENT OF DROSOPHILA-MELANOGASTER

The vestigial gene product is required for the completion of wing deve lopment in Drosophila melanogaster, In the absence of vestigial gene e xpression, cells within the larval wing and haltere imaginal discs fai l to proliferate normally thus producing adults with severely reduced wings. Of a large number of vestigial mutations that have been charact erized, only two are currently known to exist, vestigial(U) and vestig ial(W), which manifest a significant dominant phenotype. Both are asso ciated with chromosomal inversions that fuse the majority of the vesti gial coding regions to other genes; mastermind in vestigial(U) and inv ected in vestigial(W). Examination of vestigial expression in the pres ence of these dominant alleles shows alterations in the disc-specific expression of vestigial during later stages of larval development. The se patterning disruptions are specific to cells of the wing imaginal d isc, as significant suppression of total levels of vestigial expressio n within entire larvae could not be detected, This dominant interferen ce of vestigial patterning appears to be mediated in part by the vesti gial coding sequences that are within the gene fusions. Further eviden ce that the dominant phenotype is the result of disrupted vestigial pa tterning comes from observations that the dominant alleles can be part ially suppressed by mutations within the Drosophila-epidermal growth f actor receptor gene. Mutagenesis of vestigial(U) and vestigial(W) prod uced a series of alleles with partially dominant phenotypes that resto red various amounts of the adult wing. These phenotypes can be correla ted with alterations in specific portions of the vestigial sequences a ssociated with the dominant alleles. In the presence of these partiall y dominant alleles, wing imaginal discs have significantly more cells which express vestigial compared with the number associated with the o riginal dominant phenotype. Additionally, eliminating some of the domi nant effect causes alterations in the patterns of early stage apoptoti c cell death associated with dominant vestigial alleles. Utilizing the se new vestigial alleles, it is possible to correlate the consequence of altered vestigial expression to subsequent changes in patterning of the wing disc. (C) 1997 Elsevier Science Ireland Ltd.