Abstract
BackgroundJerusalem artichoke (Helianthus tuberosus) is a fructan-accumulating plant, and an industrial source of raw material for fructan production, but the crucial enzymes involved in fructan biosynthesis remain poorly understood in this plant.ResultsIn this study, a fructan: fructan 1-fructosyl-transferase (1-FFT) gene, Ht1-FFT, was isolated from Jerusalem artichoke. The coding sequence of Ht1-FFT was 2025 bp in length, encoding 641 amino acids. Ht1-FFT had the type domain of the 1-FFT protein family, to which it belonged, according to phylogenetic tree analysis, which implied that Ht1-FFT had the function of catalyzing the formation and extension of beta-(2,1)-linked fructans. Overexpression of Ht1-FFT in the leaves of transgenic tobacco increased fructan concentration. Moreover, the soluble sugar and proline concentrations increased, and the malondialdehyde (MDA) concentration was reduced in the transgenic lines. The changes in these parameters were associated with increased stress tolerance exhibited by the transgenic tobacco plants. A PEG-simulated drought stress experiment confirmed that the transgenic lines exhibited increased PEG-simulated drought stress tolerance.ConclusionsThe 1-FFT gene from Helianthus tuberosus was a functional fructan: fructan 1-fructosyl-transferase and played a positive role in PEG-simulated drought stress tolerance. This transgene could be used to increase fructan concentration and PEG-simulated drought stress tolerance in plants by genetic transformation.
Highlights
Jerusalem artichoke (Helianthus tuberosus) is a fructan-accumulating plant, and an industrial source of raw material for fructan production, but the crucial enzymes involved in fructan biosynthesis remain poorly understood in this plant
Ht1-FFT contained the intact active site, the substrate-binding site and the beta-sandwich domain interface, which was important for the fructosidase domain-containing protein to carry out its catalytic activity (Fig. 1a)
These results indicate that Ht1-FFT belongs to glycoside hydrolase family 32 (Fig. 1a)
Summary
Jerusalem artichoke (Helianthus tuberosus) is a fructan-accumulating plant, and an industrial source of raw material for fructan production, but the crucial enzymes involved in fructan biosynthesis remain poorly understood in this plant. Fructans are the third most-common storage carbohydrate in higher plants, currently found in about 15% of flowering plants [1, 2]. In addition to being an important storage carbohydrate for plants, fructans are important for plants to tolerate environmental stresses [3, 4]. Fructans participate in plant abiotic stress tolerance mainly through osmotic regulation and the maintenance of membrane stability [7]. The hexose produced by fructan hydrolysis can reduce the freezing point of liquid water in cells and allow the sustained growth of leaves under drought conditions, as well as reducing the phase transition temperature of membranes and stabilizing the phospholipid bilayer [8,9,10,11]
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