Figure 3.

Priming, plant–microbe interactions and innate immunity. Physical barriers (waxes, suberin, callose, lignin) and innate immunity defences (MTI, MAMP-triggered immunity, and ETI, effector-triggered immunity, indicated by vertical red lines) may affect priming by biotic inducers. Interactions can either be disease-related due to biotrophic or necrotrophic pathogenic microorganisms, or beneficial due to plant growth-promoting rhizo microorganisms (PGPR) interactions with plant roots. The red crosses indicate the inability of the interacting microbe to overcome the line of defence.