Signalling cascades involved in induced resistance

Abstract

Plant innate immunity is based on a surprisingly complex response that is highly flexible in its capacity to recognize and counteract different invaders. To effectively combat invasion by microbial pathogens and herbivorous insects, plants make use of pre-existing physical and chemical barriers, as well as inducible defence mechanisms that become activated upon attack. Apart from reacting locally, plants can mount a systemic response, establishing an enhanced defensive capacity in parts distant from the site of primary attack. This systemically induced response protects the plant against subsequent invaders. Several biologically induced, systemic defence responses have been characterized in detail, such as systemic acquired resistance (SAR), which is triggered by pathogens causing limited infection, such as hypersensitive necrosis, rhizobacteria induced systemic resistance (ISR), which is activated upon colonization of roots by selected strains of non-pathogenic rhizobacteria, and wound induced defence, which is typically elicited upon tissue damage, such as caused by insect feeding.