Plants are surrounded by a complex, ever changing environment. The MAPK signaling cascade is central to conveying the perceived signals of pathogen presence to downstream substrates through phosphorylation events. These modifications lead to modulation of various defence related responses. A small number of these MAPK substrates have been identified to date. Three proteins, Proline Rich Protein (PRP), PRP Homolog 1 (PH1) and PRP Homolog 2 (PH2), are in vitro kinase substrates of MPK3 and MPK6. Targeted mutagenesis revealed that the PRP-like proteins posses a MAPK docking domain that is required for the interaction with MAPKs and revealed that MPK3 and MPK6 target a conserved phospho in all three proteins. Both PRP and PH1 are transcriptionally activated by the MAMPs flg22 and elf18. Co-expression of the PRP-like proteins augment the promoter activities of the defense related genes, FRK1 and NHL10. Finally, transgenic lines over-expressing PRP displayed an increased resistance to Pseudomonas syringae. This study identified the PRP-like proteins as a novel class of MAPK substrates that may have a role in defence related responses in Arabidopsis.