Botrytis cinerea is a nectrotrophic plant pathogen that leads to important economic losses in many crops. B. cinerea has a large arsenal of virulence, including the production of cell wall degrading enzymes, reactive oxygen species and toxins. B. cinerea has a wide host range and plant resistance to this pathogen is quantitative. Nitrogen (N) is a major limiting factor of plant growth and soils frequently lack sufficient N. Large quantities of N fertilizers are used worldwide and have an impact on crop disease. However, the variety of effects observed indicate that there is a complex relationship linking N availability to plant disease. We showed previously that high N supply increases the susceptibility of A. thaliana to B. cinerea (Fagard et al., 2014, J. Exp Bot 65: 5643-5656). A transcriptomic approach of B. cinerea-infected A. thaliana plants grown in low or high N has enabled us to identify both fungal and plant genes for which expression is affected by the plant’s N status. Characterization of corresponding fungal knock-out mutants led to the identification of novel B. cinerea virulence genes, including a GST. On the plant side, we identified the jasmonate signaling pathway as a key player in the modulation of A. thaliana susceptibility by N supply. Our current working model is that N availability for plants primarily affects the outcome of plant-pathogen interactions through its effect on plant defense and pathogen virulence gene expression.