Abstract: Sucrose: sucrose 1-fructosyltransferase catalyses the synthesis of 1-kestose by transferring a fructosyl moiety from one sucrose to another. A full-length cDNA encoding sucrose: sucrose 1-fructosyltransferase from Lactuca sativa was inserted into pCAMBIA1300-als under the control of the CaMV 35S promoter. This plasmid was used for Agrobacteriummediated tobacco leaf disc transformation. Transgenic plants were analyzed by PCR and Southern blotting. 1-SST gene expression was confirmed by RT-PCR. After 6 days without watering, electrolyte leakage and malondialdehyde (MDA) of T₀ transgenic tobacco are obviously lower than those of the wild type. Significant decreases of relative water content (RWC) are detected in wild type tobacco, when compared with transgenic tobacco. According to carbohydrate analysis, the fructan of transgenic tobacco is detected and not in the wild type. Fructan content of transgenic tobacco is significantly increased after drought stress. Seed germination rate of wild type tobacco is 50% of that of transgenic tobacco under 14% PEG treatment. Root development of transgenic tobacco is not affected while that of wild type tobacco is inhibited when they were cultured in 200 mmol/L mannitol. These results indicate that fructan might be related to tobacco's drought tolerance.

Key words: drought tolerance , transgenic tobacco, sucrose: 1-SST, fructan