Abstract
In the present study, the feeding of stem-flag leaf-ear explants of wheat, triticale and barley with d-chiro-inositol and d-pinitol was used for modification of the composition of soluble carbohydrates in grains without genetic transformation of plants. Maturing grains indicated ability to uptake exogenously applied cyclitols, not occurring naturally in cereal plants, and synthesized their a-d-galactosides. The pattern of changes in soluble carbohydrates during grain maturation and germination was not disturbed by the uptake and accumulation of cyclitols. Both, d-chiro-inositol and d-pinitol as well as their a-d-galactosides can be an additional pool of soluble carbohydrates accumulated by maturing grains, without decreasing seeds viability. This is the first report indicating the possibility of introduction of cyclitols with potentially human health benefits properties into cereal grains.
Highlights
Soluble carbohydrates like monosaccharides and sucrose are primary products of photosynthesis and play an essential role in metabolism, development and maturation of sink organs
The remaining soluble carbohydrates were: fructose, glucose, myo-inositol, galactinol and maltose. Their concentration was below 1 mg g-1 of dry weight (DW), except maltose in barley grains (3.8 mg g-1 DW, Fig. 1C)
The accumulation of raffinose during natural drying of seeds is well documented, little is known about accumulation of 1-kestose in maturing cereal grains. 1-Kestose can be an initial oligomer from which biosynthesis of different linear or branched fructans with higher degree of polymerization starts (Valluru and Van den Ende 2008)
Summary
Soluble carbohydrates like monosaccharides and sucrose are primary products of photosynthesis and play an essential role in metabolism, development and maturation of sink organs. By acting as signal molecules soluble carbohydrates can regulate embryo development. At the late stages of maturation, beside sucrose seeds accumulate oligosaccharides α-D-galactosides of sucrose raffinose family oligosaccharides (RFOs) or different fructosyl derivatives of sucrose (fructan series, in cereal grains). RFOs are ubiquitous in legumes seeds (Obendorf 1997), but in cereal grains raffinose dominates among RFOs, whereas stachyose is present at a very low level (Henry and Saini 1989). Rye grains contain greater concentrations of high molecular weight fructan whereas wheat and barley accumulate higher concentrations of fructan tri- and tetrasaccharides (Henry and Saini 1989). RFOs may function as compatible solute alleviating the effects of water deficit by osmotic adjustment, act as osmoprotectants which stabilize membranes and proteins against osmotic alternations and participate in establish-
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