Kruppel homolog (Kr h) is a dosage-dependent modifier of gene expression in Drosophila

A lethal mutation in the Kruppel homolog (Kr h) was isolated in screens of P-element insertion mutations for modifiers of white gene expression. The m utation occurs in the 5' untranslated region of the Kr h gene and causes a lightening of the eye colour for several alleles of white due to a decrease in white steady-state mRNA levels at pupal stages. Two related genes, scar let and brown, were significantly affected as well in early pupae. Genetic analysis of different white alleles suggests that enhancer sequences are ne cessary for interaction with KR H. Thus, the Kr h gene is a member of the d osage-dependent hierarchy effective upon white.