Sugar transport into plasma membrane vesicles of transformed tobacco cells: uptake of sucrose but not of hexoses is stimulated by ΔpH

Abstract

In vitro transport experiments with outside-out plasma membrane vesicles of Agrobacterium tumefaciens-transformed tobacco cells (Nicotiana tabacum cv. Petit Havana SR1-C58) show that despite high cell wall invertase activity transformed cells express not only distinct hexose transporters for 3-O-methyl-D-glucose (OMG) and D-fructose, but also a sucrose transporter. When imposing a ΔpH of 2 units sucrose transport was strongly stimulated indicative of H + /sucrose cotransport whereas transport of both hexoses was almost unaffected. However, imposing a ΔΨ in addition to ΔpH stimulated initial transport rates of hexoses and sucrose. For comparison, electrophysiological experiments were performed