Identification of the Phytophthora PAMP Pep-13 Receptor Using Diploid Potato Inbred Lines

Plants employ cell surface receptors to recognize pathogen-associated molecular patterns (PAMPs) and activate pattern-triggered immunity, a crucial defense mechanism against invading pathogens. Pep-13 is a PAMP derived from a class of conserved cell wall transglutaminases present in Phytophthora species, and its receptor PERU was reported recently. In our parallel study, we observed distinct responses to Pep-13 between two diploid potato inbred lines: E454 recognizes Pep-13, whereas A018 does not. Genetic analysis demonstrated that Pep-13 recognition in E454 is controlled by a single genetic locus, tentatively designated TGER (Transglutaminase elicitor response). Through bulked segregant analysis sequencing, followed by complementation assays, we found that the TGERa gene in E454 is essential for Pep-13 recognition. Sequence alignment revealed that TGERa shares 99.91% amino acid sequence identity with PERU, indicating that TGERa and PERU are allelic variants of the same gene (PERU/TGERa). TGERb, a highly homologous gene of TGERa, was identified in the E454 genome; notably, TGERa, but not TGERb, can recognize Pep-13. We further demonstrated that TGERb exhibits defects in both ligand binding and association with the co-receptor StSERK3A. Additionally, we found that the TGERa allele in A018 is a weak allele with reduced expression levels, presumably resulting from a 3 kb DNA fragment insertion in its first intron. Heterologous introduction of TGERa into Nicotiana benthamiana and tomato significantly enhanced their resistance to Phytophthora infestans. Collectively, our findings confirm that PERU/TGERa functions as the Pep-13 receptor in potato and provide a valuable molecular target for improving Phytophthora resistance in plants.