Plant & Animal Genome IX Conference

Poster: Large Insert Libraries, Gene Isolation, Etc.
P02_54.html

OVEREXPRESSION OF THE TOBACCO TSI1 GENE ENCODING AN EREBP/AP2-TYPE TRANSCRIPTION FACTOR ENHANCES RESISTANCE AGAINST PATHOGEN ATTACK AND OSMOTIC STRESS IN TOBACCO

Graduate School of Biotechnology, Korea University, Seoul, 136-701, Korea

By using mRNA differential display analysis, we isolated a salt-induced transcript that showed a significant sequence homology with an EREBP/AP2 DNA-binding motif from oilseed rape plants. Using this cDNA fragment as probe, a cDNA clone named as Tsi1 (Tobacco stress-induced gene 1) was isolated from a tobacco cDNA library. RNA gel blot analysis indicated that transcripts homologous to Tsi1 were induced not only in NaCl-treated leaves, but also in leaves treated with ethephon or salicylic acid. Transient expression analysis using a Tsi1::smGFP fusion gene in BY-2 cells indicated that the Tsi1 protein was targeted to nucleus. C-terminus of Tsi1 containing 13 amino acids from the carboxyl terminus conferred the transcriptional activation activity of Tsi1 in yeast. Electrophoretic mobility-shift assays revealed that Tsi1 could bind specifically to the GCC and the DRE/CRT sequences, although the binding activity to the former was stronger than that to the latter sequences. Furthermore, Agrobacterium-mediated transient expression and transgenic plants expressing Tsi1 gene demonstrated that overexpression of Tsi1 gene induced expression of several PR genes under normal conditions resulting in an improved tolerance to salt and pathogen. These results suggest that the Tsi1 might be involved as a positive trans-acting factor in two separate signal transduction pathways under abiotic and biotic stress.