"RNA interference (RNAi) induces gene silencing and is involved in host responses to pathogens. Faced with the bacterium Serratia (S.) marcescens, Caenorhabditis (C.) elegans responds with a behavioural response (""lawn avoidance""). Since mutation of the RNAi gene rde-4 impairs lawn avoidance, RNAi seems to be involved. S. marcescens infection leads to upregulation of antimicrobial peptide genes in C. elegans. Our hypothesis is that RNAi is involved in controlling this transcriptional response. This project aims to characterise the role of RDE-4 and other RNAi pathway components in the avoidance behaviour and the transcriptional response of C. elegans. This will be achieved by identifying putative RNA-protein-complexes formed with RDE-4 upon S. marcescens infection. Concerning the role of RNAi in controlling defence gene expression, it will be investigated if two antimicrobial peptide genes, nlp-29 and cnc-2, are regulated by microRNAs (miRNA). miRNA arrays will be used to investigate which of the annotated miRNAs are regulated by S. marcescens infection. Candidate miRNA genes and their targets will be characterised. The multidisciplinary project “MicroDetect” will support competence diversification and career development of the fellow. Its research training objectives are scientific and technical. The fellow wishes to extend her knowledge in molecular biology and learn techniques required to use C. elegans as model system to study host-pathogen interactions. This will be achieved by training through research. The fellow will extend her complementary skills in project management, presentation, manuscript preparation and collaboration building through implementation of the project and mentoring by the supervising scientist. By offering scientific and complementary training this project will support the fellow in attaining a leading position. The Community will benefit from the strengthening of the research field by gaining a highly qualified independent researcher."