This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Hedrich, R. Articles by Stitt, M. Search for Related Content PubMed PubMed Citation Articles by Hedrich, R. Articles by Stitt, M. Agricola Articles by Hedrich, R. Articles by Stitt, M.

Articles

A Role for Fructose 2,6-Bisphosphate in Regulating Carbohydrate Metabolism in Guard Cells ¹

Pflanzenphysiologisches Institut und Botanischer Garten, Universität Göttingen, Untere Karspüle 2, 3400 Göttingen, Federal Republic of Germany, Institut für Biochemie der Pflanze, Universität Göttingen, Untere Karspüle 2, 3400 Göttingen, Federal Republic of Germany

Fructose 2,6-bisphosphate (Fru2,6P₂) appears to function as a regulator metabolite in glycolysis and gluconeogenesis in animal tissues, yeast, and the photosynthetic cells of leaves. We have investigated the role of Fru2,6P₂ in guard-cell protoplasts from Vicia faba L. and Pisum sativum L. (Argenteum mutant), and in epidermal strips purified by sonication from all cells except for the guard cells. Guard-cell protoplasts were separated into fractions enriched in cytosol and in chloroplasts by passing them through a nylon net, followed by silicone oil centrifugation. The cytosol contained a pyrophosphate: fructose 6-phosphate phosphotransferase (involved in glycolysis) which was strongly stimulated by Fru2,6P₂. A cytosolic fructose 1,6-bisphosphatase (a catalyst of gluconeogenesis) was inhibited by Fru2,6P₂. There was virtually no fructose 1,6-bisphosphatase activity in guard-cell chloroplasts of V. faba. It is therefore unlikely that the starch formed in these chloroplasts originates from imported triose phosphates or phosphoglycerate.

The level of Fru2,6P₂ in guard-cell protoplasts and epidermal strips was about 0.1 to 1 attomole per guard cell in the dark (corresponding to 0.05 to 0.5 nanomole per milligram chlorophyll) and increased three- to tenfold within 15 minutes in the light. Within the same time span, hexose phosphate levels in guard-cell protoplasts declined to approximately one-half, indicating that acceleration of glycolysis involved stimulation of reactions using hexose phosphates. The level of Fru2,6P₂ in guard cells appears to determine the direction in which carbohydrate metabolism proceeds.

This article has been cited by other articles:

				P. Niewiadomski, S. Knappe, S. Geimer, K. Fischer, B. Schulz, U. S. Unte, M. G. Rosso, P. Ache, U.-I. Flugge, and A. Schneider The Arabidopsis Plastidic Glucose 6-Phosphate/Phosphate Translocator GPT1 Is Essential for Pollen Maturation and Embryo Sac Development PLANT CELL, March 1, 2005; 17(3): 760 - 775. [Abstract] [Full Text] [PDF]

				C. G. Bowsher and A. K. Tobin Compartmentation of metabolism within mitochondria and plastids J. Exp. Bot., April 1, 2001; 52(356): 513 - 527. [Abstract] [Full Text] [PDF]

				B. Kammerer, K. Fischer, B. Hilpert, S. Schubert, M. Gutensohn, A. Weber, and U.-I. Flügge Molecular Characterization of a Carbon Transporter in Plastids from Heterotrophic Tissues: The Glucose 6-Phosphate/Phosphate Antiporter PLANT CELL, January 1, 1998; 10(1): 105 - 118. [Abstract] [Full Text]