Polyamines: double agents in disease and plant immunity.

Polyamines (PAs) are ubiquitous amine molecules found in all living organisms. In plants, beside their role in signaling and protection against abiotic stresses, there is increasing evidence that PAs have a major role in the interaction between plants and pathogens. Plant PAs are involved in immunity against pathogens, notably by amplifying pattern-triggered immunity (PTI) responses through the production of reactive oxygen species (ROS). In response, pathogens use phytotoxins and effectors to manipulate the levels of PAs in the plant, most likely to their own benefit. It also appears that pathogenic microorganisms produce PAs during infection, sometimes in large quantities. This may reflect different infectious strategies based on the selective exploitation of these molecules and the functions they perform in the cell.