Evidence of multiple sugar uptake across the plasma membrane of laticifer protoplasts from Hevea

In Hevea, rubber synthesis is confined to the cytosol of the highly differe ntiated laticifer cells. Agronomic and biochemical studies showed that this process uses high amounts of sugars that are efficiently imported into the laticifer. A H+-sugar symport system located in the plasma membrane is inv olved in sugar uptake into laticifers. Laticifer protoplasts were prepared and used in electrophysiological and labeling experiments to test the capac ity of this system to transport a variety of sugars such as oligosaccharide s from the raffinose family, trace compounds in rubber. Translocation of su gars known to be transported with different efficiency across the plasma me mbrane of plant cells was also tested. A 1 mM sucrose affinity was found fo r the symport. All the sugars tested, except palatinose induce membrane dep olarization indicating that they were actively absorbed by the laticifer ne twork. This reveals the wide capacity of this peculiar sink for the uptake of sugars. (C) 1999 Elsevier Science S.A. All rights reserved.