hiiragi, a gene essential for wing development in Drosophila melanogaster, affects the Notch cascade

A recessive mutation, hiiragi(P1), on the second chromosome of Drosophila was obtained by P element insertion mutagenesis. Flies homozygous for hiiragi(P1) have notched wing margins. Genetic interactions between hiiragi and the genes that encode components of Notch signaling, such as Notch, Hairless, Serrate and deltex, strongly support the involvement of hiiragi in the signal transduction cascade of Notch. It has been reported that Serrate and Delta, other components of Notch signaling, 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 synergistic enhancement of the notched phenotype of wing margins. In contrast, Delta(FX3) had no phenotypic effect on hiiragi(P1) in hiiragi(P1); Delta(FX3)/+ double mutants. Taken together, these results indicate that hiiragi is involved in the Notch signaling cascade induced by Serrate rather than by Delta.