Plant Nitrogen Supply Affects Thebotrytis Cinereainfection Process And Modulates Known And Novel Virulence Factors

Plant nitrogen (N) fertilization is known to affect disease; however, the underlying mechanisms remain mostly unknown. We investigated the impact of N supply on theArabidopsis thaliana-Botrytis cinereainteraction.A. thalianaplants grown in low nitrate were more tolerant to all wild-typeB. cinereastrains tested. We determined leaf nitrate concentrations and showed that they had a limited impact onB. cinereagrowth in vitro. For the first time, we performed a dual RNA-Seq of infected leaves of plants grown with different nitrate concentrations. Transcriptome analysis showed that plant and fungal transcriptomes were marginally affected by plant nitrate supply. Indeed, only a limited set of plant (182) and fungal (22) genes displayed expression profiles altered by nitrate supply. The expression of selected genes was confirmed by quantitative reverse transcription PCR at 6 hr postinfection (hpi) and analysed at a later time point (24 hpi). We selected three of the 22B. cinereagenes identified for further analysis.B. cinereamutants affected in these genes were less aggressive than the wild-type strain. We also showed that plants grown in ammonium were more tolerant toB. cinerea. Furthermore, expression of the selectedB. cinereagenes in planta was altered when plants were grown with ammonium instead of nitrate, demonstrating an impact of the nature of N supplied to plants on the interaction. Identification ofB. cinereagenes expressed differentially in planta according to plant N supply unveils two novel virulence functions required for full virulence inA. thaliana: a secondary metabolite (SM) and an acidic protease (AP).