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 [(3)H]arabinose and [(3)H]fucose, and the culture-filtrates were examined for oligosaccharides by gelpermeation chromatography and by paper chromatography. Sixteen [(3)H]pentose-containing oligosaccharides were found, including twelve that contained the sequence [(3)H]xylosyl-α(1→6)-glucose, which is diagnostic of xyloglucan. In addition, [(3)H]fucose-containing oligosaccharides of at least three sizes were found. Radiochemical evidence is presented that one of these oligosaccharides was labelled with both [(3)H]fucose and with [(3)H]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(-7)M. This is the first report of the production of a biologically-active oligosaccharide by living plant cells.