Influence of a specific xyloglucan-nonasaccharide derived from cell walls of suspension-cultured cells of Daucus carota L. on regenerating carrot protoplasts

A xyloglucan oligosaccharide was isolated from cell walls of Daucus carota L. suspension-cultured cells. From analytical data (gel-permeation chromatography, thin-layer chromatography, monosaccharide analysis, methylation analysis) it can be concluded that this oligosaccharide preparation consists mainly of a nonasaccharide known as XG9 (Glc₄Xyl₃GalFuc). This nonasaccharide showed excellent “anti-auxin” properties in the pea-stem bioassay, with 80% inhibition of 2,4-dichlorophenoxyacetic acid (2,4-D)-induced longitudinal growth of etiolated pea stem segments at concentrations of 1-0.1 nM. Applied in nanomolar concentrations to protoplasts regenerating in a medium containing 4.52 μM 2,4-D, the nonasaccharide influenced the viability of the protoplasts and the activities of glycan synthases in vitro. The effects were similar to those achieved by the omission of 2,4-D from the regeneration medium. The composition of the regenerated cell wall was not changed significantly by the use of 2,4-D-depleted medium or the addition of XG9 to 2,4-D-containing medium.