A harpin-induced ethylene-responsive factor regulates plant growth and responses to biotic and abiotic stresses.

Harpin protein induces disease resistance in diverse plant species. Transcriptome study of tomato (Solanum lycopersicum) genome indicated that harpin activated cellular events of transcription regulation, signaling transduction, stress response, membrane transporting, photosynthesis and cell wall biosynthesis. Among the harpin-induced genes, the expression of tomato ethylene-response factor 5 (designated as SlERF5) was induced to the highest level. The amino acid sequence of SlERF5 was closely related to that of CaEREBP-C4, NtERF4 and NsERF4. Overexpression of SlERF5 in Arabidopsis thaliana activated a large number of genes involved in signaling pathways of disease resistance, redox system, abiotic response and protein phosphorylation. Seedlings of transgenic plants exhibited hypersensitive response to exogenous ABA and increased tolerance to salt stress. In summary, the results of this study suggest that SlERF5 is a transcription activator for genes involved in the responses to ABA, biotic and abiotic stress. Thus, harpin may exert its effect on plant growth and defense response through activation of SlERF5 transcription factors.