• damping off;
  • disease resistance;
  • gene silencing;

Plants express different defence mechanisms in response to pathogens. Understanding the recognition of pathogen-associated molecular patterns (PAMPs) by specific receptors, and the role of endogenous signals such as AtPep1 that regulate expression of genes in Arabidopsis thaliana, has aided the understanding of the defence mechanisms in different species. The aim of this study was to identify possible orthologous sequences of AtPROPEPs in tomato (Solanum lycopersicum) and characterize its role in resistance to necrotrophic pathogens. The presence of an orthologue of the A. thaliana AtPROPEP1 gene in S. lycopersicum, SlPROPEP, 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 AtPep1. 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 Pythium 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, ERF1, LOX-D and DEF2. 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).