The Serrate gene encodes an essential ligand for Notch signaling used during development of the adult wing and other systems in Drosophila melanogaster. Animals heterozygous or homozygous for the Ser(D) allele of this gene display characteristic defects in wing margin formation. We have characterized a spontaneously arising intragenic suppressor of Ser(D) named Ser(+r83k). Homozygous double mutant Ser(+r83k), Ser(D) animals are viable, with normal wing margin formation, but display an aberrant outspread wing posture. The two mutations can be separated by meiotic recombination which restores the Ser(D) mutant phenotype and demonstrates that in the absence of Ser(D) the Ser(+r83k) mutation is homozygous lethal. These two mutations therefore display allelic compensation. Molecular analysis reveals a single C-T transition mutation within the 5' (protein encoding region) of the Ser(+r83k) transcript. This mutation is predicted to change Arginine(176) to Cysteine, possibly leading to altered interactions with the Notch receptor.
Copyright 2004 Wiley-Liss, Inc.