489:	Tsi1, a gene encoding an AP2/EREBP-type transcription factor in tobacco, is induced by NaCl, abscisic acid, and salicylic acid.

Authors:	Park, Jeong-Mee(A)Lee, Suk-Bae(A)Ham, Byung-Kook(A)Paek, Kyung-Hee(A)
Affiliations:	(A): Graduate School of Biotechnology, Korea University
Presenter:	Paek, Kyung-Hee , khpaek95@kuccnx.korea.ac.kr

To investigate salt-induced gene expression mechanism in plants, we treated rapeseed (Brassica napus) plants with 200 mM NaCl. RNA was isolated from these plants and used in mRNA differential display analysis. Several transcripts showed specific expression under salt stress, one of which encoded a putative polypeptide exhibiting significant homology with a domain of an AP2/EREBP-type transcription factor. Using this cDNA fragment as probe, we screened a tobacco cDNA library and isolated a homologous gene, Tsi1 (Tobacco salt-induced gene 1). This full-length cDNA clone shares substantial sequence similarity with tomato Pti6. Its deduced amino acid sequence has a potential nuclear localization sequence, a possible acidic activation domain, and an AP2/EREBP DNA binding motif that is found in EREBP of the ethylene responsive pathway and in APETALATA2 that functions in floral morphogenesis. To monitor the expression pattern of Tsi1 gene, RNA gel blot analysis was carried out using total RNA isolated from tobacco cell suspension cultures challenged with various exogenous stimuli. Strikingly, transcripts homologous to Tsi1 were induced not only in NaCl-treated cells but also in cells treated with abscisic acid or salicylic acid. To determine subcellular localization of the putative Tsi1 gene product, we constructed a Tsi1:smGFP fusion gene and introduced it into tobacco BY-2 cells by polyethylene glycol-mediated transformation. Transient expression analysis revealed that the Tsi1 protein was targeted to nucleus. A likely role of Tsi1 in regulating gene expression during response to environmental changes or in plant defense to pathogens is presented. Supported by an AST research grant from the Korean Ministry of Agriculture and Forestry.