Peptides as Danger Signals: MAMPs and DAMPs
In plants, active defense against pathogens and parasites relies substantially on the perception of danger. It has been well established that plants recognize invading microbes through the perception of microbe-associated molecular patterns(MAMPs), i.e., structures characteristic for whole classes of microbes. Among the MAMPs are highly conserved epitopes of important microbial proteins, such as bacterial flagellin or EF-Tu. These MAMPs are perceived by pattern recognition receptors (PRRs) on the plant cell surface. In Arabidopsis, the PRRs FLS2 and EFR, perceiving flagellin and EF-Tu, respectively, are leucine-rich repeat receptor-like kinases (LRR-RLKs). They bind their cognate ligands at the outside of the cell and relay the signal to the cytoplasm, inducing a potent defense response. In addition, alarm may also be caused by endogenous danger signals arising simply from cellular damage. In Arabidopsis thaliana, the small peptides AtPep1 to AtPep7 appear to act as such damage-associated molecular patterns (DAMPs), since they were found to induce various defense responses. AtPeps are perceived by two receptors, PEPR1 and PEPR2, which are surprisingly similar to FLS2 and EFR. The AtPep/PEPR system is suggested to act as an amplifier of resistance, possibly during infections by pathogens as well as during responses to herbivore attack and other wounding events.
KeywordsDefense Response Danger Signal Cold Shock Protein Defense Gene Expression Induce Defense Response
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