Research on Fructan in Wheat and Temperate Forage Grasses in Japan

Abstract

In autumn, winter wheat and temperate forage grasses, such as orchardgrass, timothy, and perennial ryegrass, accumulate fructan, which is a kind of fructose-based oligo-and polysaccharide. The fructan content in their crown tissue reaches more than 30% of their dry weight before snow cover, and this increase in fructan content is associated with both the freezing tolerance and the snow mold resistance of winter crops in the northern region of Japan. These crops mainly accumulate the β(2,6)-linked levan type of fructan, and their structure and composition vary among wheat and grasses. We cloned several kinds of genes encoding fructosyltransferase and fructan exohydrolase from these plants, and analysis of the expression of fructosyltransferase revealed varietal differences in wheat under field conditions and low-temperature responses in grasses. Further investigation of the control of fructan metabolism through molecular biology and genetics should lead to the development of methods for improving the over-wintering ability of these crops.

Comparative ecophysiological study of the seasonally dependent non-structural carbohydrate pool of the fructan-accumulating Helianthus tuberosus, Cichorium intybus and Dactylis glomerata

“…In the case of D. glomerata, based on only the analysis of the the above-ground organs (stem end leaves), the amount of fructans peaked in the fall in order for the plant to survive winter frosts. We could draw the same conclusions as Yoshida and Tamura (2011). During the physiological process that is called 'hardening', carbohydrates are accumulated in their tissues, therefore plants can acclimate to cold months by increasing their tolerance to freezing.…”

Effects of Potassium Fertilizer on Water-Soluble Carbohydrate Content of Timothy (<i>Phleum pratense</i> L.), Silage Fermentation, Nutritive Values, and Nutrient Intake

“…The most plausible explanation lies in the grasses with different sugar compositions. Timothy mainly contains long-chain fructosan, while perennial ryegrass mainly contains short-chain fructosan [32] [33]. Excessive K supply inhibits long-chain carbohydrate synthesis, increasing low-molecular-weight carbohydrates.…”

Key molecular and metabolic processes used for genetic engineering to improve freezing tolerance in cereals.

“…Wheat also uses fructan as a temporal photoassimilate instead of starch in plastids. Temperate grasses accumulate a levan type of fructan, which is composed primarily of β(2→1)-and β(2→1)-linked fructosyl units, which are biosynthesized by sucrose:sucrose 1-fructosyltransferase (1-SST wft2, AB029888), sucrose:fructan 6-fructosyltransferase (6-SFT wft1, AB029887; Kawakami and Yoshida, 2002) and fructan:-fructan 1-fructosyltransferase enzymes, while it is degraded by fructan exohydrolase (FEH) (Gallagher et al, 2007;Yoshida and Tamura, 2011).…”

“…Wheat also uses fructan as a temporal photoassimilate instead of starch in plastids. Temperate grasses accumulate a levan type of fructan, which is composed primarily of β(2→1)-and β(2→1)-linked fructosyl units, which are biosynthesized by sucrose:sucrose 1-fructosyltransferase (1-SST wft2, AB029888), sucrose:fructan 6-fructosyltransferase (6-SFT wft1, AB029887; Kawakami and Yoshida, 2002) and fructan:-fructan 1-fructosyltransferase enzymes, while it is degraded by fructan exohydrolase (FEH) (Gallagher et al, 2007;Yoshida and Tamura, 2011).Transgenic approaches proved to be very useful in verifying the role of key enzymes in fructan metabolism, and also in monitoring the changes in physiology-related traits. Transgenic perennial ryegrass (Lolium perenne) that overexpressed wheat 1-SST and 6-SFT genes under the control of the constitutive CaMV 35S promoter accumulated an increased level of fructan.…”