MIRROR, A DROSOPHILA HOMEOBOX GENE IN THE IROQUOIS COMPLEX, IS REQUIRED FOR SENSORY ORGAN AND ALULA FORMATION

The Drosophila notum, the dorsal body wall of the thorax, is subdivide d genetically into longitudinal domains (Calleja, hi., Moreno, E., Pel az, S. and Morata, G. (1996) Science 274, 252-255). Two homeobox genes clustered in the iroquois complex, araucan and caupolican, regulate p roneural genes and are required for development of sensory bristles in the lateral notum (Gomez-Skarmeta, J. L., del Corral, R. D., de la Ca lle-Mustienes, E., Ferres-Marco, D. and Modolell, J. (1996) Cell 85, 9 5-105). An iroquois-related homeobox gene, mirror, was recently isolat ed and is localized close to the iroquois complex region (McNeil, H., Yang, C.-H., Brodsky, ill., Ungos, J. and Simon, M. A. (1997) Genes an d Development 11, 1073-1082; this study). We show that mirror is requi red for the formation of the alula and a subset of sensory bristles in the lateral domain of the notum. Genetic analysis suggests that mirro r and the other iroquois genes interact to form the alula as well as t he sensory organs. Based on similarities between mirror and the iroquo is genes in their genetic map positions, expression, protein structure and function, mirror is considered a new member of the iroquois compl ex and is involved in prepatterning sensory precursor cells in the lat eral notum.