PGal4 excision reveals the pleiotropic effects of Voila, a Drosophila locus that affects development and courtship behaviour

In Drosophila melanogaster, the PGal4 transposon inserted at the chromosoma l site 86E(1.2) is associated with the Voila(1) allele that causes multiple phenotypes. Homozygous Voila(1/1) flies rarely reach adulthood and heteroz ygous Voila(11+) adult males display strong homosexual courtship behaviour. Both normal behavioural and developmental phenotypes were rescued by remob ilizing the PGal4 element. Yet, the rescue of heterosexual courtship and of adult viability did not occur in the same strains, indicating that these d efects have different genetic origins. Furthermore, many strains showed a p artial rescue of both characters. Molecular analysis revealed that the PGal 4 transposon is inserted upstream of the 5 ' UTR of the prospero gene. The excision strains with no detectable fragment of the PGal4 transposon remain ing showed a rescued viability for homozygote adults. Moreover, the develop mental period with the highest homozygote lethality was correlated with the size of PGal4 element that remained inserted at the Voila locus. This sugg ests a relationship between developmental viability and the amount of DNA i nserted within the promoter of prospero.