Overexpression of tobacco ethylene response factor NtERF3 gene and its homologues from tobacco and rice induces hypersensitive response-like cell death in tobacco

Among plant-specific transcription factors, ethylene response factors (ERFs) comprise one of the largest families. ERF s are unique to the plant kingdom and are considered to have crucial roles in plant response to various biotic and abiotic environmental stresses. Here, we report on the functional analysis of a transcriptional repressor, NtERF3, with regard to cell death associated with a hypersensitive response (HR), a plant-specific resistance reaction against pathogens. Expression of NtERF3 was upregulated during HR induction by Tobacco mosaic virus (TMV) infection in tobacco plants harboring the resistance N gene to TMV. Transient overexpression of NtERF3 by Agrobacterium -mediated gene delivery induced HR-like cell death in tobacco, associated with the production of reactive oxygen species and ion leakage. Deletion of the ERF-associated amphiphilic repression (EAR) motif from NtERF3 resulted in no induction of cell death, while the deletion had no effect on nuclear localization of the proteins. After virus-mediated gene delivery, similar results also were observed in tobacco without the N gene. In addition to NtERF3, other EAR motif-containing ERFs from tobacco, Nicotiana benthamiana and rice also induced cell death when overproduced in tobacco plants. The results suggested that many ERF genes encoding EAR motif-containing proteins might have the ability to induce cell death when overexpressed.