Temperature regulates expression of the Drosophila vestigial gene only in mutant wing discs.

All Vestigial mutants in Drosophila melanogaster display a thermosensitive phenotype, with the exception of two which disrupt an intronic wing-specific enhancer element. Here we report a very unusual transcriptional regulation; temperature changes are associated with alterations in the level of vg expression only in the wing disc of thermosensitive mutant flies and not in the brain. No effect is observed in the wild-type strain. The tissue specificity of the temperature effect indicates an involvement of the intronic wing-specific enhancer element in determining the thermosensitivity of mutants.