Fucosylation of xyloglucan: localization of the transferase in dictyosomes of pea stem cells.

Microsomal membranes from elongating regions of etiolated Pisum sativum stems were separated by rate-zonal centrifugation on Renografin gradients. The transfer of labeled fucose and xylose from GDP-[(14)C] fucose and UDP-[(14)C]xylose to xyloglucan occurred mainly in dictyosomeenriched fractions. No transferase activity was detected in secretory vesicle fractions. Pulse-chase experiments using pea stem slices incubated with [(3)H]fucose suggest that xyloglucan chains are fucosylated and their structure completed within the dictyosomes, before being transported to the cell wall by secretory vesicles.