Sucrose inducible endocytosis as a mechanism for nutrient uptake in heterotrophic plant cells

Abstract

Endocytosis as a mechanism for nutrient uptake in heterotrophic cells was investigated using suspension culture cells of Acer pseudoplatanus L, the endocytic inhibitors wortmannin and LY294002 and the fluorescent endocytosis marker Lucifer Yellow-CH (LY). Time-course analysis of sucrose uptake in intact walled cells revealed a two-phase process involving an initial 90 min wortmannin- and LY294002-insensitive sucrose uptake period, followed by a prolonged phase of rapid sucrose accumulation which was greatly inhibited by the two endocytic inhibitors. Rates of sucrose and LY accumulation were virtually identical. In addition, LY incorporation increased as a function of external sucrose concentration. When sucrose was substituted by other sugars or amino acids, uptake of LY greatly diminished, indicating that sucrose itself is the primary signal of endocytosis. These results demonstrate the existence of a sucrose inducible endocytic process as a viable mechanism for solute transport into the vacuole of storage cells.