Physico-chemical characteristics of cell walls from Arabidopsis thaliana microcalli showing different adhesion strengths.

Changes in the composition and structure of cell walls and extracellular polysaccharides (ECP) were studied during the growth of suspension-cultured Arabidopsis thaliana microcalli. Three growth phases, namely the cell division phase, the cell expansion phase, and the stationary phase, were distinguished and associated with a decreasing cell cluster adhesion strength. Degradation of the homogalacturonan pectic backbone and of linear pectic side chains (1,4)-beta-D-galactan were observed concomitantly with the cell expansion and stationary phases and the decrease in cell adhesion. Also, in the stationary phase, branched (1,5)-alpha-L-arabinans were linearized. The AGP content of the culture medium increased while it decreased in the cell wall during cell growth and as cell adhesion decreased. These data suggest that, in addition to homogalacturonan, pectic side chains and AGP are involved in plant cell development and particularly in cell-cell attachment.