A TRANS-ACTING MODIFIER CAUSING EXTENSIVE OVEREXPRESSION OF GENES IN DROSOPHILA-MELANOGASTER

A modified P element-induced mutation at cytological position 47A11-12 on chromosome 2 of Drosophila melanogaster inversely alters the expre ssion of several genes examined. In addition, the effect is nearly exp onential in some developmental stages for five of the eleven genes tes ted (white, brown, scarlet, rudimentary and vermilion). Interestingly, the exponential overexpression of the transcripts leads to a sexually dimorphic effect, with female levels being greater. The white allele specificity analysis and the lack of response of an Alcohol dehydrogen ase promoter-white reporter fusion construct suggest that the 5' regul atory sequences of white are required for the response. Because the ca ses of extreme overexpression are more prominent in females than males , the locus is termed Ultra female overexpression (Ufo). Ufo revertant s have no discernible effect on the transcript levels, indicating that the mutation is responsible for the modulation of the tested genes. R egulatory genes such as Ufo may contribute to the wide fluctuations in gene expression between tissues and stages of development.