Analysis of KED-mediated wound response to biotic stress and mechanical damage in tomato plants (Solanum lycopersicum)

Lysine-rich KED was previously identified from wounded tobacco (Nicotiana tabacum) leaves before the alignment of protein sequences between NtKED (Nicotiana tabacum KED) and SlKED (Solanum lycopersicum KED) were discovered to display 55.1% identity. Using previously generated SlKED knockout plants by CRISPR/Cas9, we performed biological assays, to investigate the role of KED in wound response to biotic and abiotic stress. Previous studies implied that the KED gene functions as a role in the wound-induced mechanism, as well as suggested that it may also function in the plant defense system against biotic stress and insect herbivory. The results from bioassays using tobacco hornworm (Manduca sexta) have proven inconclusive thus far. Expression of KED is induced not only by mechanical wounding but also by touching such as brushing the leaves, indicating that this gene is sensitive to subtle environmental signal and may be involved in defense response against abiotic stress. To further investigate the KED gene’s role in the plant defense system, biological assays using both specialist and generalist herbivores, transcription analysis using various phytohormone mutant plants, and Evans blue cellular damage assays were performed. Our findings imply that the KED gene does not seem to have a long-term effect on insect herbivory but may have a shortterm anti-feeding effect against insect herbivores. Results from the Evans blue membrane damage assay indicate the KED gene may provide some benefit to mechanically damaged plants in a short-term period post-wounding of leaf tissues. Using the SlKED knockout as genetic tool, we conclude that this gene does not confer resistance to insect herbivores over a long-term but seems to provide a beneficial defense response in the short-term. Our membrane damage assay results also imply that this gene may be involved in membrane stabilization and repair of cellular damage after mechanical wounding.