Abstract
Plants are often facing several stresses simultaneously. Understanding how they reactand the way pathogens adapt to such combinational stresses is poorly documented.Here, we developed an experimental system mimicking field intermittent drought onrice followed by inoculation by the pathogenic fungus Magnaporthe oryzae. Thisexperimental system triggers an enhancement of susceptibility that could be correlatedwith the dampening of several aspects of plant immunity, namely the oxidative burst andthe transcription of several pathogenesis-related genes. Quite strikingly, the analysisof fungal transcription by RNASeq analysis under drought reveals that the fungus isgreatly modifying its virulence program: genes coding for small secreted proteins weremassively repressed in droughted plants compared to unstressed ones whereas genescoding for enzymes involved in degradation of cell-wall were induced. We also showthat drought can lead to the partial breakdown of several major resistance genes byaffecting R plant gene and/or pathogen effector expression.We propose a model wherea yet unknown plant signal can trigger a change in the virulence program of the pathogento adapt to a plant host that was affected by drought prior to infection.