"Eukaryotic organisms have the ability to defend themselves against pathogenic microorganisms through the action of pattern recognition receptors (PRRs) perceiving specific pathogen-associated molecular patterns (PAMPs), what activates a range of fast, efficient and multi-layered defense responses leading to PAMP-triggered immunity (PTI), also named basal immunity. To counteract this defense strategy, successful pathogens deploy effectors proteins, the primary function of which is to evade/interfere with PTI.In both plants and animals, extensive attention has been paid over the years to the identification of PRRs, signalling components, pathogens effectors and their host targets, in order to dissect the molecular dialog between hosts and pathogens (including bacteria, fungi and viruses). Strikingly, no information related to basal immunity against plant viruses has been obtained so far, in spite of many converging elements suggesting that basal immunity against viruses also exists in plants.The project IBIS aims at the identification of the cellular processes underlying basal immunity against plant viruses, using the Arabidopsis thaliana - Plum pox virus (PPV) pathosystem as a model for plant-virus interactions.Via holistic and multidisciplinary approaches (combining molecular biology, virology, biochemistry, cellular biology, reverse genetics, transcriptomics and proteomics), I will make use of the knowledge I acquired on both basal immunity signaling and plant virology as entry points to tackle the three project objectives: I will first characterize cellular components involved in basal immunity against PPV through a candidate approach and transcriptomic analyses. In addition, I will identify PPV-encoded proteins acting as viral effectors suppressing basal immunity as well as their cellular targets. Finally, I will address the question of the possible overlap between basal immunity pathways triggered by different classes of plant pathogenic microbes."