"The first-ever genome project on a seaweed (Ectocarpus siliculosus) presents an unprecedented opportunity to study an algal host-pathogen interaction with state-of-the art molecular approaches. This model has the strength of being both of environmental and fundamental relevance, enabling issues to be addressed ranging from the impact of diseases in marine ecosystems to the evolution of pathogenicity among protists. As a Marie Curie IEF Fellow, I have been setting up a laboratory-controlled pathosystem involving the oomycete pathogen Eurychasma dicksonii and developed robust protocols on this model. My results demonstrate, for the first time in brown algae, the existence of a genetically-determined immunity, most probably mediated by programmed cell death and conserved across the whole phylum. The aim of this proposal is to build on my current work and support the following long term research objectives: 1) Investigating complementary aspects of the defence mechanisms of brown algae: a) programmed cell death as a component of Ectocarpus innate immunity; b) metabolite profiling of algae suceptible or resistant to infection, with the potential of identifying new bioactive (antifungal) compounds 2) Deciphering some infection mechanisms of Eurychasma, through a cDNA-based gene discovery approach. As Eurychasma is the most basal oomycete known so far, this undertaking will give unprecedented insights into the evolution of infection strategies within this lineage, and more generally among protists. 3) Looking for molecular signatures of host-pathogen coevolution in the field, as a contribution to the understanding epidemic impact on algal populations and coastal ecosystems. During the course of this work, a proactive approach will be used towards the identification of bioactive natural compounds or conserved drug targets, potentially resulting in spin-off findings applicable to the development of improved strategies to combat disease in agronomy and medicine."