Role of transglycosylation in the integration of xyloglucan into the growing plant cell wall in vivo

Xyloglucan endotransglycosylase (XET) activity is widespread in plant cell walls, but its action on xyloglucan in vivo has been difficult to prove because the reaction products are not expected to differ chemically from the reactants. By feeding of cultured Rosa cells with [13C]glucose and [3H]arabinose followed by [12-C]glucose, and isopyenic centrifugation of the extracted xyloglucan in caesium trifluoroacetate, we have obtained evidence for the annealing of segments of newly-secreted xyloglucan to xyloglucan chains that were already present in the cell wall. This is the first evidence for interpolymeric transglycosylation of xyloglucan in vivo.