Functional Analysis Of ERF Transcription Factor TSRF1

Adverse environmental conditions such as drought, high salt, extreme temperatures and pathogen attack greatly impair crop productivity. To survive these different biotic and abiotic stresses, plants have developed an elaborate signaling network that perceives these signals and modulates the expression of specific resistance genes. In these pathways, transcription factors play important roles in controlling the expression of specific stress-related genes. Ethylene responsive factors (ERFs) were first identified in tobacco as downstream component of ethylene signaling pathway to modulate the expression of many pathogenesis-related (PR) genes through interaction with GCC box present in their promoters. Recently, ERFs have been evidenced to regulate different plant signaling pathways, indicating their roles in mediating the interaction of different plant signaling pathways. However, the regulation mechanism of ERFs in regulating the interaction between different plant signaling pathways is not well understood.To better understand the regulationg mechanism of ERFs in plant, we isolated an ERF protein TSRF1 (Tomato Stress Responsive Factor 1) from tomato with yeast-one-hybrid system. Our experiments showed that TSRF1 was localized in the nuclear, and TSRF1 could interact with both GCC box and the CE1 element to activate the expression of GCC box or CE1 controlled reporter gene. The expression of TSRF1 was induced by pathogen infection, ethylene, salicylic acid, ABA, NaCl or mannitol treatment etc. These results indicated the involvement of TSRF1 in both plant biotic and abiotic stress responses. Using transgenic tobacco that overexpressing TSRF1, we find that TSRF1 can constitutively activate the expression of downstream PR genes to enhance the plant resistance to pathogens. Expression of TSRF1 can also induce the expression of CE1 element regulated genes and also some ABA related genes and cause enhanced osmotic stress and ABA sensitivity in germination, seedling developoment and root growth. Furthermore, the TSRF1 expressing tobacco possess elevated ethylene and ABA production and the presence of exogenous ABA can further enhance the ethylene production and influence the regulation of TSRF1. However, expressing TSRF1 decreased the osmotic stress resistance of tobaccos, suggesting TSRF1 is a negative regulator for plant osmotic stress resistance. These results indicate TSRF1 integrates both plant ethylene and ABA responses, providing some clues to understand our understanding of ERFs in regulating the interaction between ehtyelne and ABA signaligng pathways.