In-vivo formation of xyloglucan nonasaccharide: A possible biologically active cell-wall fragment

The in-vivo formation of a specific nonasaccharide of xyloglucan was investigated. This nonasaccharide has been reported to have biological activity, inhibiting auxin-induced growth in pea stem segments. Cell-suspension cultures of spinach were grown in the presence of [³H]arabinose and [³H]fucose, and the culture-filtrates were examined for oligosaccharides by gelpermeation chromatography and by paper chromatography. Sixteen [³H]pentose-containing oligosaccharides were found, including twelve that contained the sequence [³H]xylosyl-(16)-glucose, which is diagnostic of xyloglucan. In addition, [³H]fucose-containing oligosaccharides of at least three sizes were found. Radiochemical evidence is presented that one of these oligosaccharides was labelled with both [³H]fucose and with [³H]pentose, and was identical with the major xyloglucan-derived nonasaccharide associated with anti-auxin activity. It was largely present in the form of acylated (possibly acetylated) derivatives. It accumulated extracellularly to a steady-state concentration of about 4.3·10^-7M. This is the first report of the production of a biologically-active oligosaccharide by living plant cells.Abbreviations BAB butanone/acetic acid/H₃BO₃-saturated water (9:1:1) - BAW butan-1-ol/acetic acid/water (12:3:5) - BPW butan-1-ol/pyridine/water/(4:3:4) - DP degree of polymerisation - FAW ethyl acetate/acetic acid/water (10:5:6) - EPW ethyl acetate/pyridine/water (8:2:1) - k _av elution volume relative to Blue Dextran (k _av.=0.0) and glucose (k _av.=1.0) - XG7 XG9 minus the fucose and galactose residues - XG9 the particular xyloglucan nonasaccharide illustrated in Fig. 1 - W water-saturated phenol