Abstract
A 23-amino acid peptide, AtPep1, and its homologues are endogenous amplifiers of innate immunity of Arabidopsis. AtPep peptides bind to AtPEPR1, a plasma membrane leucine-rich repeat (LRR) receptor kinase. Here we identify a plasma membrane LRR receptor kinase with 76 % amino acid similarity to AtPEPR1, designated AtPEPR2, and characterize its role in the perception of AtPep peptides and defense responses. Both AtPEPR1 and AtPEPR2 were transcriptionally induced by wounding, treatment with methyl jasmonate, AtPep peptides and PAMPs. The effects of AtPep1 application on defense-related gene induction and enhancement of resistance to Pseudomonas syringae pv. tomato DC3000 were partially reduced in single mutants of AtPEPR1 and AtPEPR2, and abolished completely in double mutants. Photoaffinity labeling and binding assays using transgenic tobacco cells expressing AtPEPR1 and AtPEPR2 clearly demonstrated that AtPEPR1 is a receptor for AtPep1-6, and that AtPEPR2 is a receptor for AtPep1 and AtPep2.
