| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
|
First published online June 9, 2006; 10.1104/pp.106.080804 Plant Physiology 141:1563-1577 (2006) © 2006 American Society of Plant Biologists Pathways of Glucose Regulation of Monosaccharide Transport in Grape Cells1Departamento de Biologia, Universidade do Minho, Campus de Gualtar, 4710–057 Braga, Portugal (C.C., A.A., R.T., H.G.); Unité Mixte de Recherche, Centre National de la Recherche Scientifique 6161, Transport des Assimilats, Laboratoire de Physiologie, Biochimie, et Biologie Moléculaire Végétales, Bâtiment Botanique, Unité Fondamentale de Recherche Sciences, 86022 Poitiers cédex, France (D.G., S.D.)
Grape (Vitis vinifera) heterotrophic suspension-cultured cells were used as a model system to study glucose (Glc) transport and its regulation. Cells transported D-[14C]Glc according to simple Michaelis-Menten kinetics superimposed on first-order kinetics. The saturating component is a high-affinity, broad-specificity H+-dependent transport system (Km = 0.05 mM). Glc concentration in the medium tightly regulated the transcription of VvHT1 (Vitis vinifera hexose transporter 1), a monosaccharide transporter previously characterized in grape berry, as well as VvHT1 protein amount and monosaccharide transport activity. All the remaining putative monosaccharide transporters identified so far in grape were poorly expressed and responded weakly to Glc. VvHT1 transcription was strongly repressed by Glc and 2-deoxy-D-Glc, but not by 3-O-methyl-D-Glc or Glc plus mannoheptulose, indicating the involvement of a hexokinase-dependent repression. 3-O-Methyl-D-Glc, which cannot be phosphorylated, and Glc plus mannoheptulose induced a decrease of transport activity caused by the reduction of VvHT1 protein in the plasma membrane without affecting VvHT1 transcript levels. This demonstrates hexokinase-independent posttranscriptional regulation. High Glc down-regulated VvHT1 transcription and Glc uptake, whereas low Glc increased those parameters. Present data provide an example showing control of plant sugar transporters by their own substrate both at transcriptional and posttranscriptional levels. VvHT1 protein has an important role in the massive import of monosaccharides into mesocarp cells of young grape berries because it was localized in plasma membranes of the early developing fruit. Protein amount decreased abruptly throughout fruit development as sugar content increases, consistent with the regulating role of Glc on VvHT1 expression found in suspension-cultured cells.
1 This work was supported in part by the Pessoa Program (GRICES/EGIDE), the Conférence des Présidents d'Université, the Conselho de Reitores das Universidades Portuguesas, the Fundação para a Ciência e a Tecnologia (research project no. POCI/AGR/56378/2004; grant no. SFRH/BD/10689/2002 to C.C. and grant no. SFRH/PBD/17166/2004 to A.A.), and the Conseil Régional Poitou-Charentes (to D.G.). 2 These authors contributed equally to the paper. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Hernâni Gerós (geros{at}bio.uminho.pt). Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.106.080804. * Corresponding author; e-mail geros{at}bio.uminho.pt; fax 351–253678980. Received March 22, 2006; returned for revision May 30, 2006; accepted May 30, 2006. This article has been cited by other articles:
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ASPB Publications | PLANT PHYSIOLOGY® | THE PLANT CELL | |
|---|---|---|---|
