Transport of amino acids (L-valine, L-lysine, L-glutamic acid) and sucrose into plasma membrane vesicles isolated from cotyledons of developing pea seeds.
Transport of the amino acids L-valine, L-lysine, and L-glutamic acid and of sucrose was studied in plasma membrane vesicles isolated from developing cotyledons of pea (Pisum sativum L. cv. Marzia). The vesicles were obtained by aqueous polymer two-phase partitioning of a microsomal fraction and the uptake was determined after the imposition of a H(+)-gradient (DeltapH, inside alkaline) and/or an electrical gradient (Deltapsi, inside negative) across the vesicle membrane. In the absence of gradients, a distinct, time-dependent uptake of L-valine was measured, which could be enhanced about 2-fold by the imposition of DeltapH. The imposition of Deltapsi stimulated the influx of valine by 20%, both in the absence and in the presence of DeltapH. Uptake of L-lysine was more strongly stimulated by Deltapsi than by DeltapH, and its DeltapH-dependent uptake was enhanced about 6-fold by the simultaneous imposition of Deltapsi. In the absence of gradients the uptake of L-glutamic acid was about 2-fold higher than that of L-valine, but it was not detectably affected by DeltapH or Deltapsi. Although the transport of sucrose was very low, a stimulating effect of DeltapH could be clearly demonstrated. The results lend further support to the contention that during seed development cotyledonary cells employ H(+)-symporters for the active uptake of sucrose and amino acids.
de Jong
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A
Transport Physiology Research Group, Department of Plant Ecology and Evolutionary Biology, Utrecht University, Sorbonnelaan 16, NL-3584 CA Utrecht, The Netherlands.
Borstlap
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AC
D000596:Amino Acids / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D018532:Pisum sativum / Q000196:embryology / Q000378:metabolism*; D012639:Seeds / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*
D000596:Amino Acids; D013395:Sucrose