Components of different signalling pathways regulated by a new orthologue of A t PROPEP 1 in tomato following infection by pathogens

Plants express different defence mechanisms in response to pathogens. Understanding the recognition of pathogen‐associated molecular patterns ( PAMP s) by specific receptors, and the role of endogenous signals such as A t P ep1 that regulate expression of genes in A rabidopsis thaliana , has aided the understanding of the defence mechanisms in different species. The aim of this study was to identify possible orthologous sequences of At PROPEP s in tomato ( S olanum lycopersicum ) and characterize its role in resistance to necrotrophic pathogens. The presence of an orthologue of the A . thaliana At PROPEP 1 gene in S . lycopersicum , Sl PROPEP , by in silico analysis, is reported here. This has 96% identity with the C ‐terminal region of a previously described potato peptide, another possible orthologue of At P ep1. A virus‐induced gene silencing ( VIGS ) system was employed to investigate the role of the SlPROPEP . Silencing of SlPROPEP in tomato made plants more susceptible to P ythium dissotocum ; approximately 30% of SlPROPEP ‐silenced plants showed stem constriction compared with 4% in control plants. Furthermore, quantification of P . dissotocum by qPCR revealed that the increase in symptom severity in SlPROPEP ‐silenced plants was associated with a 15 times increase in growth of the pathogen compared to control plants. Silencing of SlPROPEP also resulted in decreased expression of genes involved in plant defence against pathogens, such as PR‐1 , PR ‐5 , ERF 1 , LOX ‐ D and DEF 2 . These results suggest that SlPROPEP is involved in tomato resistance to P . dissotocum and probably acts as a pathogen‐associated molecular pattern through signalling pathways mediated by jasmonic acid/ethylene ( JA/ET ).