Structure of fructan oligomers in cheatgrass (Bromus tectorum L.) ^*

Abstract

SUMMARYLeaves of field-grown cheatgrass {Bromus tectorum L.) plants were sampled during early spring when day-and night-time temperatures were relatively cool. Eructan oligomers with a degree of polymerization (DP) 3-6 were extracted and purified using gel and anion-exchange chromatography. The structures of 13 cheatgrass fructans were established. They included two trisaccharides [1-kestotriose (1-kestose) and 6-kestotriose (6-kestose)], four tetrasaccharides [(l,l)-kestotetraose (nystose), (l&6)-kestotetraose (bifurcose), (6,l)-kestotetraose and (6,6)-kestotetraose], three pentasaccharides [(l,l&6)-kestopentaose, (l&6,6)-kestopentaose and (6; l&6)-kestopentaose] plus four hexasaccharides [(1,1 ,l&6)-kestohexaose (l&6,6,6)-kestohexaose, (6; l&6,6)-kestohexaose and (6; 1,6&6)-kestohexaose]. All fructans larger then DP 4 contained a branch point. Each member of the dominant series(l&6)-kestotetraose, (l&6,6)-kestopentaose and (l&6,6,6)-kestohexaose, is a branched fructan in which two fructose moieties are linked to the fructose subunit of each sucrose molecule. 7^hus the dominant series is built upon (l&6)-kestotetraose. Eructans larger than DP 3 with exclusively 2->l-or 2 >6-linkages were absent except for a very small amount of (6,6)-kestotetraose. The unique fructan structures synthesized in cheatgrass, wheat and oats illustrate diversity in the enzymology of fructan biosynthesis among grass species.

Purification and characterization of fructans with β‐2, 1‐ and β‐2, 6‐glycosidic linkages suitable for enzyme studies

“….^n underestimate of the DP might occur if fructose residues were degraded after hydrolysis (Chatterton et al, 1993) whereas an overestimate can occur if all of the glucose is not released from the sucrose portion of each fructan molecule. In this experiment, unhydrolyzed sucrose was accounted for when glucose and fructose were measured hy HPLC, as sucrose was resolved as a separate peak.…”

Fructan metabolism in two species of Bromus subjected to chilling and water stress

“…It is unclear how fructan metabolism might be involved in osmotic adjustment during water deficit, and it has also been argued whether there is a relationship between fructan accumulation and the tolerance of plants to low temperatures (Pollock & Cairns, 1991). Species of Bromus growing in North America accumulate fructan (Chatterton et al, 1989(Chatterton et al, , 1993 and therefore it was thought that the use of Bromus species growing in southern latitudes and under very different climatic conditions might constitute a very good system for evaluating changes in sucrose and fructan metabolism under stress conditions. This paper reports the comparison of enzyme activities related to sucrose and fructan synthesis, the amounts of fructose-containing sugars, and the microscopic observations of drought injury, in B.…”

Variation and Correlations among European and North American Orchardgrass Germplasm for Herbage Yield and Nutritive Value

“…In addition to their role in abiotic stress tolerance, increased WSC in leaf and stem tissue can result in improved protein digestion, decreased nitrogen waste through feces and urine, and increased meat and milk productivity in feeding animals [23]. In orchardgrass, the overwhelming majority of all WSC are fructans [14,24], which bridge the gap between resource availability and demands [17]. Increasing WSC (i.e., fructans) is a tangible method of increasing both abiotic stress tolerance and forage quality in orchardgrass.…”