Novel fungal MAP kinase signalling in response to a host plant small-molecule signal in the Cochliobolus-maize interaction
Our study aims to investigate the relationship between fungi and their plant hosts during infection, focusing on the maize pathogen C. heterostrophus, which serves as a model for necrotrophic plant pathogens. Analysis of infected leaves at various stages of disease development, using RNA-seq and fluorescence microscopy, uncovered a correlation between fungal hyphal development, necrotrophic gene expression, and plant defense mechanisms. Notably, the host plant upregulates defense-related genes early in infection, particularly those involved in phenolic acid biosynthesis. When germinating spores are exposed to ferulic acid (FA), a phenolic compound abundant in the host plant, the stress-activated MAP kinase Hog1 is, surprisingly, dephosphorylated and sequestered in cytoplasmic foci rather than phosphorylated and accumulated in the nucleus, as expected in stress responses. This unique signalling pathway may play a role in attenuating cell death induced by plant defense compounds like FA. Our findings provide insights into the dynamics of pathogen cell death, survival, and proliferation within lesions, while also shedding light on stress responses mediated by MAP kinases.
