LETHAL P-LACZ INSERTION LINES EXPRESSED DURING PATTERN RESPECIFICATION IN THE IMAGINAL DISCS OF DROSOPHILA

The imaginal discs of Drosophila are a useful experimental system in w hich we can study the origin and genetic determination of spatial patt erns in development. This involves the separation of the disc-cell pop ulation into distinct lineage compartments, based on clonally transmit ted expression states of a number of known selector genes. However, th ese commitments can be abrogated and the compartment boundaries redepl oyed, when repatterning occurs in cultured disc fragments. This has so far only been explained using the idea of positional information. The genetic basis of this property of the imaginal disc system and its re lationship to compartments have not been identified. Here we have scre ened over 470 recessive lethal P-lacZ enhancer-trap insertions from th e Berkeley Drosophila Genome Project for expression after cell death, which initiates pattern respecification in the imaginal discs. The pos itive lines obtained identify essential genes that may be important fo r pattern formation. Most show patterned imaginal disc expression, and many have maternal or zygotic effects on embryonic development. One i s an allele of schnurri, a gene that encodes a component of the decape ntaplegic (dpp) signal transduction pathway used for positional signal ling in the embryo and in imaginal discs.