HIIRAGI, A GENE ESSENTIAL FOR WING DEVELOPMENT IN DROSOPHILA-MELANOGASTER, AFFECTS THE NOTCH CASCADE

A recessive mutation, hiiragi(P1), on the second chromosome of Drosoph ila was obtained by P element insertion mutagenesis. Flies homozygous for hiiragi(P1) have notched wing margins. Genetic interactions betwee n hiiragi and the genes that encode components of Notch signaling, suc h as Notch, Hairless, Serrate and deltex, strongly support the involve ment of hiiragi in the signal transduction cascade of Notch. It has be en reported that Serrate and Delta, other components of Notch signalin g, share EGF-like repeats and a second conserved cysteine-rich motif, and that these components interact physically with the same region of Notch. In hiiragi(P1); Serrate(D)/+ double mutants, we observed synerg istic enhancement of the notched phenotype of wing margins. In contras t, Delta(FX3) had no phenotypic effect on hiiragi(P1) in hiiragi(P1); Delta(FX3)/+ double mutants. Taken together, these results indicate th at hiiragi is involved in the Notch signaling cascade induced by Serra te rather than by Delta.