Journal Article

Sucrose-inducible Endocytosis as a Mechanism for Nutrient Uptake in Heterotrophic Plant Cells

Ed Etxeberria, Edurne Baroja-Fernandez, Francisco José Muñoz and Javier Pozueta-Romero

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 3, pages 474-481
Published in print March 2005 | ISSN: 0032-0781
Published online March 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci044
Sucrose-inducible Endocytosis as a Mechanism for Nutrient Uptake in Heterotrophic Plant Cells

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The capacity of plant heterotrophic organs to transport and accumulate incoming nutrients (mostly in the form of sucrose) directly impacts their final size, crop productivity and nutritional value. Endocytosis as a mechanism for nutrient uptake in heterotrophic cells was investigated using suspension culture cells of sycamore (Acer pseudoplatanus L.) and the endocytic inhibitors wortmannin and LY294002. 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. Walled cells were assessed for their capacity to incorporate the fluorescent endocytosis marker lucifer yellow-CH (LY) in the presence or absence of sucrose. Rates of sucrose and LY accumulation were virtually identical, as was their response to wortmannin. 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. Microscopic observations revealed the formation of vesicles containing LY and its eventual accumulation on the vacuole when sucrose was present in the incubation medium. These results demonstrate the existence of a sucrose-inducible endocytic process as a viable mechanism for solute transport into the vacuole of storage cells.

Keywords: Acer pseudoplatanus; Endocytosis; Metabolite uptake; Photoassimilate transport; Sucrose uptake; Vacuole.; ADH, alcohol dehydrogenase; dTR, dextran–Texas red; LY, lucifer yellow-CH; LY294002, 2-(4-morpholynyl-)-8-phenyl-4H-1 benzopyran-4-one.

Journal Article.  5428 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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