A SEX-INFLUENCED MODIFIER IN DROSOPHILA THAT AFFECTS A BROAD-SPECTRUMOF TARGET LOCI INCLUDED THE HISTONE REPEATS

A second chromosomal trans-acting modifier, Lightener of white (Low), modulates the phenotypic expression of various alleles of the white ey e color gene. This modifier has an unusually broad spectrum of affecte d genes including white, brown, scarlet and the eye developmental gene s, Bar and Lobe. In addition, Low weakly suppresses position effect va riegation. Northern blot hybridization with different X and autosomal probes reveals that Low modulates genes of independent expression patt erns. Interestingly, many of the modulations of gene expression are de velopmentally restricted and differ in intensity between the sexes. Lo w also elevates the expression of the histone tandem repeats in three distinct developmental stages. A deficiency encompassing the histone c luster reduces their transcript levels and significantly alters the ex pression of some of the tested genes. Thus, Low is a modifier that pla ys a role in modulating the expression of genes governing various proc esses including pigment deposition, eye development, chromosomal prote ins and position effect variegation.