Abstract
Fructan, fructose-based polymers, is accumulated in many C3 plants. Fructan is considered to play important roles not only as a reserve carbohydrate but also as a biologically regulatory substance of cytoplasm against osmotic stress caused by freezing and drought in plants. Therefore, an understanding of the metabolism of fructan is important to clarify the mechanisms of plant cold tolerance.
Six genes, prft1-prft6 encoding fructosyltransferases, were isolated from the cDNA library that was derived from crown tissues of cold-acclimated perennial ryegrass plants. Functional characterization of these genes indicated that the prft3 and prft5 encode 6G-FFT (fructan:fructan 6G-fructosyltransferase) and the prft4 encodes 1-SST (sucrose:sucrose 1-fructosyltransferase). Real-time RT-PCR showed that the mRNA levels of these genes increased, in different pattern, in both leaf and crown tissues during cold acclimation. These results indicated that changes in the mRNA level of these genes coincided with those in the fructan contents of perennial ryegrass plants.
