Abstract
Fructan is a fructose-based polymer associated with freezing tolerance in overwintering plants. We have reported an increase in cold tolerance of transgenic rice expressing wheat sucrose:sucrose fructosyltransferase, 1-SST (Kawakami et al. JXB, 2008). To clarify the mechanism of this enhancement of cold tolerance by fructan, we examined the changes in sugar content and the expression levels of OsSUT genes in the source and sink tissues of booting-stage rice exposed to a temperature of 12oC. Remarkable increases in sucrose contents in source leaves and its sheaths and decreases in those in panicles were observed in plants under the low temperature. Those changes recovered after exposure to a temperature of 26oC. In the transgenic rice, fructan increased under the cold treatment condition. Among the OsSUTs, transcript levels of OsSUT1 in the leaf sheath in both fructan-acumulated rice and non-transgenic rice decreased at 12 oC and increased at 26 oC after cold treatment.
