A ROLE FOR ULTRASPIRACLE, THE DROSOPHILA RXR, IN MORPHOGENETIC FURROWMOVEMENT AND PHOTORECEPTOR CLUSTER FORMATION

Many of the same genes needed for proper eye and limb development in v ertebrates, such as hairy, hedgehog, patched and cyclic AMP-dependent protein kinase A, are responsible for patterning Drosophila imaginal d iscs, the tissues that will give rise to the adult cuticle structures. This is well demonstrated in the control of morphogenetic furrow move ment and differentiation in the eye imaginal disc. We report that ultr aspiracle, the gene encoding the Drosophila cognate of the Retinoid X Receptor, is required for normal morphogenetic furrow movement and omm atidial cluster formation. Examination of the expression of genes invo lved in regulating the furrow suggests that ultraspiracle defines a no vel regulatory pathway in eye differentiation.