07-P012 Functional analyses of a novel transmembrane protein, Plxdc2, in the developing nervous system of the chick

changes during metamorphosis, a process influenced by hormones, mainly 20-hydroxyecdysone (20E). To understand metamorphosis at the molecular level, we investigated gene expression changes in the honeybee thoracic integument during adult cuticle formation. Using cDNA microarrays constructed from 13,440 oligos, we monitored gene expression during pupal/ pharate-adult transition at three specific time-points (immediately before, during and after apolysis) marked by low, high, and very-low ecdysteroid titers, respectively. We found a higher number of integument genes (IG) differentially expressed after the ecdysteroid pulse. Distinct functional gene ontology classification was attributed for these differentially expressed IG. Among the cuticle protein genes (CPG), 6, 10 and 9 of them were differentially expressed in low/high, high/very-low and low/very-low ecdysteroid titer conditions, respectively. The higher expression of the CPG genes AmelCPR4, AmelCPR6, AmelCPR14 and apd-1 following the ecdysteroid pulse, strongly suggests that they are ecdysone-responsive and involved in the construction of the adult cuticle. In order to explain these differential expression patterns, we searched for motifs at the upstream regions of these genes. The presence of binding sites for Broad-Complex, a zinc finger transcriptional regulator of the ecdysone cascade, is consistent with Ashburner model for ecdysone action during molting and metamorphosis. These findings suggest the inductory activity of 20E on early regulatory genes for a differential regulation of structural late genes in the honeybee integument, via BroadComplex. We also show that distinct CPGs are involved in the construction of the pupal and adult cuticle in the honeybee A. mellifera.