UC San Diego

This dissertation is presented in two parts. In the first part, using a broad-scale epidermal enzyme-based wounding protocol that I developed, I uncover evidence that serine protease(s) are required to achieve a localized gradient of wound response transcripts near wounded epidermal cells in late-stage Drosophila embryos. I find that the devised serine protease-mediated wounding protocol is not inducing a massive amplification of the epidermal wound response by merely proteolytically degrading the epidermal paracellular barrier, but instead by mimicking an endogenous serine protease(s) that plays an important role in the activation of a naturally occurring wound response signaling pathway. Microarray analysis of trypsin treated embryos has allowed me to learn more about the transcriptional response to clean wounding on a genome- wide scale, including the conservation of genes induced after epidermal wounding events and the identification of novel wound response genes, eight of which are transcriptionally induced locally in the epidermis around the wound site. In the second part, I present evidence that stems from the data gathered in the first part, in that components of the Toll signaling pathway are activated in epidermal cells in response to clean puncture wounding of Drosophila embryos. Furthermore, I show that Toll-specific genes are responsible for the induction of various epidermal wound response genes after clean puncture wounding. I discovered that spatzle, the Toll signaling ligand, is required for the wound-dependent activation of the ple epidermal wound response gene. These observations point to an interesting connection between the innate immunity and epidermal wound response pathways. Taken together, it seems that after clean puncture wounding, specific serine proteases are utilized to process various innate immunity and barrier repair ligands, leading to a cooperative intersection of these two signaling pathways and the induction of epidermal wound response genes in Drosophila