Two Rhamnogalacturonide Tetrasaccharides Isolated from Semi-Retted Flax Fibers Are Signaling Molecules in Rubus fruticosus L. Cells

Abstract

Abstract Water extraction of semi-retted flax (Linum usitatissimum L.) fiber bundles yielded a mixture of pectic oligosaccharides and two acidic rhamnogalacturonide tetrasaccharides that were separated by size-exclusion chromatography. One- and two-dimensional nuclear magnetic resonance studies and fast atom bombardment-mass spectrometry experiments indicated that the two tetrasaccharides have a common primary structure, i.e. α--D-[delta]GalpA(1[->2)-α--L-Rhap(1->4)-α--D-GalpA-(1 ->2)-L-α-,β-Rha p, with a rhamnopyranose as terminal reducing end, and a 4-deoxy-β-L-threo-hex-4-eno-pyranosiduronic acid at the nonreducing end. However, the two tetrasaccharides differ by an acetyl group located at the O-3 position of the internal galacturonic acid residue. These two tetrasaccharides induce the activation of D-glycohydrolases of Rubus fructicosus L. cells or protoplasts within minutes.