Analysis of the Inverse Effect in Drosophila

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The overall objective of the proposed research is to characterize a class of trans-acting regulatory genes that produce an inverse dosage response on the white eye color locus. A saturation mutagenesis involving hybrid dysgenesis, ethyl methanesulfonate and X-rays will be conducted to recover transposon insertions, point mutants and chromosomal rearrangements in inverse regulators effective upon white. Secondly, the autosomes will be screened for segmental trisomics that alter the expression of white. A previously isolated mutant in an inverse regulator of white will be used to determine the tissues in which the recessive recombination. Other genes expressed in the eye will be tested to determine whether these are affected by the inverse regulator that works on white. A refined set of white promoter fusions will be constructed and transformed into the Drosophila germline. These will be tested with the inverse regulator to determine the sequences of the white gene required to respond. Selected examples of inverse regulators that are P element insertion mutants affecting white will be cloned and used to analyze the gene products via DNA sequencing and protein fusion productions. Finally, the involvement of the inverse effect in X chromosomal dosage compensation will be examined by determining whether white locus regulatory mutants exhibit dosage compensation in metafemales and by conducting a reversion analysis on white- ivory, a non-compensating allele that does not respond to inverse regulators, to establish whether compensation and response to inverse regulators is correlated. An understanding of how gene expression is regulated is central to insight into genetic mechanisms and development. This proposal contains innovative experiments which should result in increased knowledge relating to mechanisms involved in gene dosage compensation and trans-acting regulatory loci in Drosophila.