C. elegans responds specifically to different types of infection through the activation of distinct signaling pathways. This can result in the production of multiple effector proteins, including antimicrobial peptides such as NLP-29. Using a reporter specifically induced upon fungal infection, our laboratory already performed a small-scale EMS screen for innate immunity genes. The approach worked well and allowed the identification of genes involved in the regulation of
nlp-29. Indeed, we were able to define a conserved pathway involving the protein kinase C TPA-1 that acts upstream of a
p38 MAPK cascade [1, 2 and 3]. We have now conducted an EMS screen on a much larger scale, and isolated 59 independent alleles that block the induction of an
nlp-29 reporter after infection. In order to characterize them phenotypically and to begin epistatic analysis, we are currently applying a battery of different tests to each mutant. Importantly, our preliminary results indicate that we have isolated mutants affecting the immune response upstream of TPA-1. These mutants potentially represent genes involved in pathogen recognition. In parallel, we are conducting a complementary RNAi screen using the Arhinger and the ORFeome RNAi libraries and an integrated automated platform. This is built around the UBI Biosort, coupled to a TECAN robot, with a dedicated LIMS, meta-data database and statistical tools (see abstract by Montanana et al.). Together, we expect the results of these screens to give a fuller view of the genes and pathways that regulate antifungal peptide gene expression. 1. Pujol, N., Cypowyj, S., Ziegler, K., Millet, A., Astrain, A., Goncharov, A., Jin, Y., Chisholm, A.D., and Ewbank, J.J. (2008). Distinct innate immune responses to infection and wounding in the C. elegans epidermis. Curr Biol 18, 481-489. 2. Ziegler, K., Kurz, C.L., Cypowyj, S., Couillault, C., Pophillat, M., Pujol, N., and Ewbank, J.J. (2009). Antifungal innate immunity in C. elegans: PKCdelta links G protein signaling and a conserved
p38 MAPK cascade. Cell Host Microbe 5, 341-352. 3. Lee, K.Z., Kniazeva, M., Han, M., Pujol, N., and Ewbank, J.J. (in press). The fatty acid synthase
fasn-1 acts upstream of WNK and Ste20/GCK-VI kinases to modulate antimicrobial peptide expression in C. elegans epidermis.