Dorso-ventral asymmetric functions of teashirt in Drosophila eye development depend on spatial cues provided by early DV patterning genes

The teashirt (tsh) gene has dorso-ventral (DV) asymmetric functions in Drosophila eye development: promoting eye development in dorsal and suppressing eye development in ventral by Wingless mediated Homothorax (HTH) induction [Development 129 (2002) 4271]. We looked for DV spatial cues required by tsh for its asymmetric functions. The dorsal Iroquois-Complex (Iro-C) genes and Delta (Dl) are required and sufficient for the tsh dorsal functions. The ventral Serrate (Ser), but not fringe (fng) or Lobe (L), is required and sufficient for the tsh ventral function. We propose that DV asymmetric function of tsh represents a novel tier of DV pattern regulation, which takes place after the spatial expression patterns of early DV patterning genes are established in the eye.