Expression analysis of sucrose phosphate synthase genes (OsSPSs) in fructan-accumulated transgenic rice exposed to cold stress at the booting stage

Abstract

Fructan is a fructose-based polymer associated with freezing tolerance in overwintering plants. We have reported an increase in chilling tolerance of transgenic rice expressing wheat sucrose:sucrose fructosyltransferase (Kawakami et al. JXB, 2008). To clarify the mechanism of this enhancement of chilling tolerance by fructan, we previously examined changes in sugar content and the expression levels of OsSUT and OsSUS, OsINV genes in the source and sink tissues of booting-stage rice exposed to a temperature of 12^oC (PCP supple. 2008-10). The expression levels of OsSPS1-5 were examined in this study. Transcript levels of all of the OsSPSs except for OsSPS1 in source leaves and sheaths in both fructan-acumulated rice and non-transgenic rice decreased at 12^oC, whereas increases in sucrose contents in source leaves and sheaths were observed at 12^oC. The results suggested that expression levels of OsSUT and OsSUS, OsINV, but not that of OsSPS, might be related to changes in sucrose metabolism and partitioning in rice plants under a cold condition. We also discuss the relationship between sucrose metabolism and mechanism of enhancement of chilling tolerance of rice by fructan.