Biosynthesis in vitro of high‐molecular mass fructan by cell‐free extracts from tuberous roots of Viguiera discolor (Asteraceae)

Abstract

SUMMARYTuberous roots of Viguiera discolor accumulate up to 80% of their dry mass as fructans. The distribution pattern of oligomers suggests the predominance of anabolic reactions at the beginning of dormancy, when a continuous series of fructans between sucrose and higher polymers is present. This paper describes the synthesis in vitro of fructans of high molecular mass by enzyme extracts prepared from growing tuberous roots of V. discolor at the beginning of dormancy. Sucrose: sucrose fructosyl transferase activity was characterized by the synthesis of 1-kestose from sucrose and fructan: fructan fructosyl transferase activity by the production of nystose from 1-kestose. The optimal temperature for both activities was 30 °C and the optimal pH range was between 5-5 and 6-0. The apparent K^ for sucrose with respect to 1-kestose synthesis was 173 mol m^^, whereas the K^.^ for nystose synthesis from 1-kestose was much higher (592 mol m"^^). Long incubation periods (up to 264 h) with sucrose, 1-kestose or nystose produced fructans of high molecular mass in vitro that resembled those found in vivo. Our data show that the higher the molecular mass of the substrate, the higher the average molecular mass of the product that u'as formed.

The resilience of perennial grasses under two climate scenarios is correlated with carbohydrate metabolism in meristems

“…The higher degree of polymerization of fructans in D. glomerata (up to DP65) could contribute to its greater survival compared with H. lanatus , which accumulated smaller fructans (up to DP45). Similar differences have been observed among the Asteraceae family, in which drought-resistant species ( Echinops ritro and Vigueira discolor ) accumulate fructans of higher DP (30–100) (Itaya et al , 1997; Vergauwen et al , 2003) than species with lower drought resistance ( Cichorium intybus , Helianthus tuberosus ; Van den Ende et al , 1996; Marx et al , 1997). It has been observed in vitro that highly polymerized fructans (from bacteria) had a greater protective effect against water stress than lower DP fructans (from Cichorium ) (Demel et al , 1998), and that positive synergistic effects on membrane stabilization were obtained with a mixture of DP<7 and DP>7 fructans (from oat or rye) compared with either DP<7 or DP>7 fructans alone (Hincha et al , 2007).…”

Hydrolase and fructosyltransferase activities implicated in the accumulation of different chain size fructans in three Asteraceae species

“…However, the presence of higher DP fructans (up to DP 25) in the incubation products was confirmed by HPAEC-PAD analysis using another gradient mixture appropriate to resolve higher DP fructans (data not shown). Previous work by Itaya et al [20,23] showed that longer term incubation (up to 12 days) with 400 mM sucrose and 200 mM nystose led to the production of fructans with higher chain length (DP ca. 56 and 70, respectively).…”

Propagation, growth, and carbohydrates of Dendrobium Second Love (Orchidaceae) in vitro as affected by sucrose, light, and dark

“…Neutral sugars were eluted with ten volumes of deionized water, lyophilized until dryness, and then resuspended in 1 ml of deionized water. The concentrated samples were again quantified by the phenol-sulfuric method, filtered (0.45 mm), and analyzed by highperformance anion exchange chromatography coupled to a pulsed amperometric detector (HPAEC-PAD) in a Dionex DX-300 (Dionex Corporation, Sunnyvale, CA), using a 4× 250-mm CarboPac PA-10 anion exchange column with a linear gradient of 25-500 molm −3 sodium acetate in 150 molm −3 sodium hydroxide with a flux of 1 cm 3 min −1 (Itaya et al 1997). To quantify individual sugars by HPAEC-PAD, the following elution system was used: 0-2 min, 12 mM NaOH; 2-5 min, 24 mM NaOH; 5-9 min, 44 mM NaOH; 9-13 min, 54 mM NaOH; 13-16 min, 62 mM NaOH; 16-18 min, 66 mM NaOH; 18-25 min, 96 mM NaOH; 25-30 min, 120 mM NaOH; 30-40 min, 140 mM NaOH; 41 min, 12 mM NaOH, with a flux of 0.4 cm 3 min −1 .…”