Differential patterns of arabinosylation by membranes of suspension-cultured cells of Phaseolus vulgaris (French bean) after subculture or elicitation.

Suspension-cultured cells of Phaseolus vulgaris (French bean) incorporated [1-3H] arabinose in vivo into high-Mr polymers that could be separated into glycoprotein and polysaccharide. Microsomal membranes from suspension-cultured cells of beans incorporated arabinose from UDP-beta-L-arabinose in vitro into both polysaccharide and glycoprotein. The enzyme involved in arabinan synthesis, arabinan synthase, appeared to be immunologically distinct from the protein:arabinosyltransferase system. Both these activities are inducible, but behave differently with either plant-growth-regulator or fungal-elicitor treatments. After subculture of cells entering the stationary growth phase the arabinan synthase activity reaches much higher values than does that of the protein transferase system during the initial period of cell division and growth, whereas after elicitation at the same growth stage, all the increased incorporation of arabinose occurs into glycoprotein of Mr higher than 200 000 and to a greater extent into a specific glycoprotein of Mr 42 500. Preliminary characterization of these glycoproteins prepared under non-reducing conditions and after acid and alkaline hydrolysis suggests that the high-Mr glycoprotein material is similar to arabinogalactan protein, whereas the lower-Mr material may be a hydroxyproline-rich protein existing as a dimer and that specifically increases during the hypersensitive response of the cells to the fungal elicitor from Colletotrichum lindemuthianum.