Expression of a novel NAC domain-containing transcription factor (CaNAC1) is preferentially associated with incompatible interactions between chili pepper and pathogens

We aim to isolate genes in chili pepper that are regulated during the hypersensitive response to infection by nonhost pathogens, with a view to elucidating the defense responses against pathogen attack. Among the 90 transcription factors initially characterized by reverse RNA gel blot analysis, a cDNA clone, CaNAC1 (Capsicum annuum NAC1) containing the plant-specific NAC domain motif was further characterized. Expression of the CaNAC1 gene was rapidly and specifically induced during incompatible interactions between pepper and bacterial or viral pathogens. Additionally, this gene was strongly induced by exogenously applied salicylic acid and ethephon, whereas methyl jasmonate only had a transient effect. A CaNAC1-smGFP (soluble modified green fluorescent protein) fusion protein localized to the nucleus following transfection into the epidermis of onion. Using the yeast system, we further disclose that the transcription activation domain of CaNAC1 is located in the C-terminal half of the protein. Our results collectively suggest that the plant-specific NAC domain protein, CaNAC1, may play a role in the regulation of defense responses in plants.