oroshigane, a new segment polarity gene of Drosophila melanogaster, functions in hedgehog signal transduction.

Here we describe a new segment polarity gene of Drosophila melanogaster, oroshigane (oro). Identified as a dominant enhancer of Bar (B), oro is also recessive embryonic lethal, and homozygous oro embryos show variable substitution of naked cuticle with denticles. These patterns are distinctly similar to those of hedgehog (hh) and wingless (wg) embryos, which indicates that oro functions in determining embryonic segment polarity. Evidence that oro function is involved in Hh signal transduction during embryogenesis is provided by its genetic interactions with the segment polarity genes patched (ptc) and fused (fu). Furthermore, ptcIN is a dominant suppressor of the oro embryonic lethal phenotype, suggesting a close and dose-dependent relationship between oro and ptc in Hh signal transduction. oro function is also required in imaginal development. The oroI allele significantly reduces decapentaplegic (dpp), but not hh, expression in the eye imaginal disc. Furthermore, oro enhances the fui wing phenotype in a dominant manner. Based upon the interactions of oro with hh, ptc, and fu, we propose that the oro gene plays important roles in Hh signal transduction.