Expression of EPL1 from Trichoderma atroviride in Arabidopsis Confers Resistance to Bacterial and Fungal Pathogens

During plant interaction with beneficial microorganisms, fungi secrete a battery of elicitors that trigger plant defenses against pathogenic microorganisms. Among the elicitor molecules secreted by Trichoderma are cerato-platanin proteins, such as EPL1, from Trichoderma atroviride. In this study, Arabidopsis thaliana plants that express the TaEPL1 gene were challenged with phytopathogens to evaluate whether expression of EPL1 confers increased resistance to the bacterial pathogen Pseudomonas syringae and the necrotrophic fungus Botrytis cinerea. Infection assays showed that Arabidopsis EPL1-2, EPL1-3, EPL1-4 expressing lines were more resistant to both pathogens in comparison to WT plants. After Pseudomonas syringae infection, there were reduced disease symptoms (e.g., small chlorotic spots) and low bacterial titers in the three 35S::TaEPL1 expression lines. Similarly; 35S::TaEPL1 expression lines were more resistant to Botrytis cinerea infection, showing smaller lesion size in comparison to WT. Interestingly, an increase in ROS levels was detected in 35S::TaEPL1 expression lines when compared to WT. A higher expression of SA- and JA-response genes occurred in the 35S::TaEPL1 lines, which could explain the resistance of these EPL1 expression lines to both pathogens. We propose that EPL1 is an excellent elicitor, which can be used to generate crops with improved resistance to broad-spectrum diseases.