Gene Discovery and Molecular Dissection of Fructan Metabolism in Perennial Ryegrass (Lolium Perenne)

Fructans are the main soluble carbohydrate stored in up to a third of the vegetation of the earth, including the economically important temperate grasses. Fructans are polymers of fructose attached to a sucrose precursor. Perennial ryegrass (L. perenne L.) accumulates fructans of the inulin series, inulin neoseries and levan neoseries. Four enzymes are required to produce fructans of this profile: 1-SST (sucrose:sucrose 1- fructosyltransferase), 1-FFT (fructan:fructan 1-fructosyltransferase), 6G-FFT (6-glucose fructosyltransferase) and 6-FFT (fructan:fructan 6-fructosyltransferase) or 6-SFT (sucrose:fructan 6-fructosyltransferase) (Figure 1). Fructan biosynthetic enzymes have evolved from invertases and thus it is argued that fructan metabolism is an extension of sucrose metabolism. A high fructan content is a valuable resource in perennial ryegrass as it can be readily mobilised to sustain regrowth immediately after defoliation as well as adding to the nutritive value of the feed. However, the physiological role of fructans in grasses is not fully understood