Fructans and fructan‐metabolizing enzymes in leaves of Lolium perenne

Abstract

Summary• Longitudinal variability is reported in internal carbon partitioning as is the activity of enzymes involved in fructan synthesis during leaf development of Lolium perenne cv. Bravo.• Sink activity was reduced in L. perenne plants by cooling the roots while continuous illumination enhanced source activity, resulting in preferential accumulation of fructans at the leaf base. Fructan contents and enzymatic activity of two trisaccharides (SST (sucrose : sucrose fructosyltransferase) and 6G-FT (fructan : fructan 6G-fructosyltransferase) ) were measured in segments of elongating leaves, both mature leaf blades and sheaths.• The complement of fructans accumulated was similar in both elongating leaves and mature leaf sheaths. 6G-FT activity was found in L. perenne and characterized in a crude extract; this activity was greatest in the basal segment of elongating leaves and mature leaf sheaths. Throughout the leaf blade, however, SST and 6G-FT activities remained low and constant, and did not increase under conditions of sucrose accumulation.• Differences are shown in fructan accumulation between leaf tissues; the significance of these findings and the putative pathway of fructan synthesis in L. perenne are discussed.

Partitioning of water soluble carbohydrates in vegetative tissues of Lolium multiflorum Lam. ssp. italicum cv. Lema

“…Carbohydrates with a degree of polymerization higher than three were observed mainly in the roots, while monosaccharides and sucrose predominated throughout the other parts of the plants but in lower proportions in the elongating and in the expanded leaf blades. Similarly, Pavis et al (2001a) found the highest level of low molecular weight fructans in the roots of L. perenne, when compared to other parts of the plant.…”

“…Carbohydrates with a degree of polymerization higher than three were observed mainly in the roots, while monosaccharides and sucrose predominated throughout the other parts of the plants but in lower proportions in the elongating and in the expanded leaf blades. Similarly, Pavis et al (2001a) found the highest level of low molecular weight fructans in the roots of L. perenne, when compared to other parts of the plant.Considerable variations have been reported in the proportion of individual chain size fructans between fructanstoring grass species (Chatterton et al, 1990), but variations can also exist among different tissues of the same plant. The outer leaf sheath of tall fescue, for example, contained significantly more DP > 6 fructans and less DP 3-6 fructans than the expanding leaves (Housley and Volenec, 1988).…”

“…Fructans based on 1-kestotriose and 6G-kestotriose are accumulated in these species. The enzymatic activities responsible for the synthesis of both trisaccharides were found to be distributed longitudinally in expanding leaves of Lolium perenne (Pavis et al, 2001a), with low temperature and continuous illumination underlying the main differences found in different tissues (Bonnett et al, 1994). The partition of fructans within the plant is well known in Lolium perenne (Guerrand et al, 1996;Morvan-Bertrand et al, 2001; Pavis et al, 2001a,b), but not in the Italian ryegrass (Lolium multiflorum).…”

Fructan 1-Exohydrolases. β-(2,1)-Trimmers during Graminan Biosynthesis in Stems of Wheat? Purification, Characterization, Mass Mapping, and Cloning of Two Fructan 1-Exohydrolase Isoforms,

“…For a long time, it has been a matter of debate whether the 6-kestose necessary for levan-type fructan biosynthesis in cereals originates from the direct action of a specific 6-SST (Penson and Cairns, 1994;Chatterton and Harrison, 1997) rather than by the ␤-(2,1)-hydrolysis of bifurcose (Bancal et al, 1992), the main product of 6-SFT (Sprenger et al, 1995). To explain the biosynthesis of the levan neoseries in ryegrass (Lolium perenne; Pavis et al, 2001a) and the authentic levan series in Poa secunda (Wei et al, 2002), these authors suggest the existence of 6-SST or 6-FT-like enzymes that might prefer fructans other than 1-kestose (e.g. neokestose or 6-kestose) as acceptor substrates.…”

Biossíntese e degradação de frutanos em diferentes regiões do rizóforo de Vernonia herbacea (Vell.) Rusby (Asteraceae)

“…A variação na estrutura e no grau de polimerização das cadeias de frutanos das diferentes espécies e nos diferentes tecidos pode ser atribuída principalmente a diferenças nas frutosiltransferases (Hellwege et al, 2000;Pavis et al, 2001;Vergauwen et al, 2003).…”