A “futile” cycle of sucrose synthesis and degradation is involved in regulating partitioning between sucrose, starch and respiration in cotyledons of germinating Ricinus communis L. seedlings when phloem transport is inhibited Article Received: 19 December 1990 Accepted: 08 April 1991 DOI:
Cite this article as: Geigenberger, P. & Stitt, M. Planta (1991) 185: 81. doi:10.1007/BF00194518 Abstract
There was a dramatic alteration in the pattern of metabolism of [U
14C]glucose by cotyledons of germinating Ricinus communis L. seedlings when phloem transport was inhibited by removing most of the hypocotyl and root. (i) Incorporation into sucrose was decreased two- to threefold, incorporation into starch was stimulated three- to sixfold, and there was a small increase of respiration, (ii) Pulse-chase experiments using 14C and measurements of the total sucrose content revealed a rapid cycle of sucrose synthesis and degradation. When export is inhibited there is a two- to threefold inhibition of unidirectional sucrose synthesis and a three-fold stimulation of unidirectional sucrose degradation. As a result, the net flux switches from rapid net synthesis to slow net mobilisation of sucrose, (iii) The cotyledons contained adequate activities of sucrose synthase, acid and alkaline invertase and sucrose-phosphate synthase to catalyse the observed rate of sucrose breakdown and synthesis, respectively. The extracted activities of the degradative enzymes did not change after inhibiting phloem transport. The maximum activity of sucrose-phosphate synthase was also unaltered, but the activity measured in the presence of limiting substrates and phosphate was decreased twofold, indicating that sucrose-phosphate synthase has been deactivated by a mechanism analogous to that occurring in spinach leaves. (iv) The switch from sucrose export to starch synthesis when phloem transport was prevented was accompanied by only a small (20–50%) increase of the sucrose concentration in the cotyledons, no change of hexose-phosphates, an increase (16–70%) of fructose-1,6-bisphosphate and triosephosphate, and a small decrease (15–30%) of glycerate-3-phosphate, glycerate-2-phosphate and phosphoenolpyruvate. Fructose-2,6-bisphosphate and pyrophosphate doubled when 10 mM phosphate was included in the medium bathing the cotyledons, but not when phosphate was omitted (v) It is concluded that a futile cycle involving simultaneous synthesis and degradation of sucrose allows sucrose metabolism to respond in an extremely sensitive manner when phloem export is inhibited. There is a dramatic switch of flux through the sucrose pool, even though there are only marginal changes in the concentrations of sucrose and metabolites, or in the rate of respiration. Key words Futile cycle Ricinus Sucrose (metabolism, transport) Abbreviations Fru1,6bisP
This work was supported by the Deutsche Forschungsgemeinschaft (SFB 137) and by Sandoz AG, Basel, Switzerland. We are grateful to E. Komor and G. Orlich (Pfanzenphysiologie, Universität Bayreuth, FRG) for introducing us to Ricinus communis cotyledons and for many helpful discussions, and to Frau U. Küchler for typing the manuscript
ap Rees, T. (1988) Hexose phosphate metabolism by non-photosynthetic tissues of higher plants. In: Biochemistry of plants, vol. 14, pp. 1–33, Preiss, J., ed. Academic Press, New York
Avigad, G. (1982) Sucrose and other dissaccharides. In: Encyclopedia of plant physiology, N.S., vol. 18A, pp. 217–347, Loewus, T.A., Tanner, W., eds. Springer, Heidelberg
Beaudry, R.M., Severson, R.F., Black, C.C., Kays, S.J. (1989) Banana ripening: implications of changes in glycolytic intermediate concentrations, glycolytic and gluconcogenic carbon flux, and fructose-2,6-bisphosphate concentration. Plant Physiol.
Borchert, S., Große, M., Heldt, H.W. (1989) Specific transport of inorganic phosphate, glucose-6-phosphate, dihydroxyacetone phosphate and 3-phosphoglycerate into amyloplasts from pea roots. FEBS Lett.
Bryce, J.H., ap Rees, T. (1985) Effects of sucrose on the rate of respiration of the roots of
. J. Plant Physiol.
Dancer, J.E., Hatzfeld, W.D., Stitt, M. (1990) Cytosolic cycles regulate the accumulation of sucrose in heterotrophic cell-suspension cultures of
Dennis, D.T., Greyson, M. (1987) Fructose-6-phosphate metabolism in plants. Physiol. Plant.
Dietz, K.-J., Foyer, D.H. (1986) The relationship between phosphate status and photosynthesis in leaves. Planta
Hatzfeld, W.-D., Stitt, M. (1990) A study of the rate of recycling of triose phosphates in heterotrophic
cells, potato tubers and maize endosperm. Planta
Hatzfeld, W.D., Stitt, M. (1991) Regulation of glycolysis in heterotrophic cell suspension cultures of
in response to proton fluxes at the plasmalemma. Physiol. Plant
Hatzfeld, W.D., Dancer, J.E., Stitt, M. (1990) Fructose-2,6-bisphosphate, metabolites and ‘coarse’ control of pyrophosphate: fructose-6-phosphate phosphotransferase during triosephosphate cycling in heterotrophic cell-suspension cultures of
Hubbard, H.L., Pharr, D.M., Huber, S.C. (1990) Role of sucrose phosphate synthase in sucrose biosynthesis in ripening bananas and its relationship to the respiratory climacteric. Plant Physiol.
Huber, S.C., Akazawa, H. (1986) A novel sucrose synthase pathway for sucrose degradation in cultured sycamore cells. Plant Physiol.
Huber, J.L.A., Huber, S.C., Nielsen, T.H. (1989) Protein phosphorylation as a mechanism for regulation of spinach leaf sucrose phosphate synthase. Arch. Biochem. Biophys.
Hue, L. (1980) The role of futile cycles in the regulation of carbohydrate metabolism. Adv. Enzymol.
Journet, E.P., Bligny, R., Douce, R. (1986) Biochemical changes during sucrose deprivation in higher plant cells. J. Biol. Chem.
Kallarackal, J., Komor, E. (1989) Transport of hexoses by the phloem of
L. seedlings. Planta
Kallarackal, J., Orlich, G., Schobert, C., Komor, E. (1989) Sucrose transport into the phloem of
L. seedlings as measured by the analysis of sieve-tube sap. Planta
Keeling, P.L., Wood, J.R., Tyson, R.M., Bridges, I.G. (1988) Starch biosynthesis in developing wheat germ. Evidence against the direct involvement of triose-phosphates in the metabolism pathway. Plant Physiol.
Komor, E. (1977) Sucrose uptake by cotyledons of
L. characteristics, mechanism and regulation. Planta
Kriedemann, P., Beevers, H. (1967a) Sugar uptake and translocation in the castor bean seedling I. Characteristics of transfer in intact and excised seedlings. Plant Physiol.
Kriedemann, P., Beevers, H. (1967b) Sugar uptake and translocation in the castor bean seedling II. Sugar transformations during uptake. Plant Physiol.
Kruger, N.J. (1990) Carbohydrate synthesis and degradation. In: Plant physiology, biochemistry and molecular biology, pp. 59–76, Dennis, D.T., Turpin, D.M., eds. Longman, Harlow UK
Kruger, N.J., Beevers, M. (1985) Synthesis and degradation of fructose-2,6-bisphosphate in the endosperm of castor bean seedlings. Plant Physiol.
Lambers, H. (1985) Respiration in intact plants and tissues. In: Encyclopedia of plant physiology, vol. 18, pp. 418–473, Douce, R., Day, D.A., eds. Springer, Berlin
Lunn, J.E., ap Rees, T. (1990) Apparent equilibrium constant and mass-action ratio for sucrose-phosphate synthase in seeds of
. Biochem. J.
Morell, S., ap Rees, T. (1986) Sugar metabolism in developing tubers of
Neuhaus, H.E., Siegl, G., Quick, W.P., Stitt, M. (1990) Control of photosynthate partitioning in spinach leaves. Planta
Penning de Vries, F.W.T., Witlage, J. M., Kremer, D. (1979) Rates of respiration and increase in structural dry matter in young wheat, ryegrass and maize plants in relation to temperature, to water stress and to their water content. Ann. Bot.
Rebeille, F., Bligny, R., Douce, R. (1982) Regulation of P
cells. Arch. Biochem. Biophys.
Rebeille, F., Bligny, R., Martin, J.-B., Douce, R. (1985) Effect of sucrose starvation on sycamore (
cell carbohydrate and P
status. Arch. Biochem. Biophys
Saglio, P.M., Pradet, A. (1990) Soluble sugars, respiration and energy charge during aging of excised maize root tips. Plant Physiol.
Sicher, R.C., Kremer, D.F. (1984) Changes of sucrose phosphate synthase activity in barley primary leaves during light/dark transistions. Plant Physiol.
Siegl, G., MacKintosh, C., Stitt, M. (1990) Sucrose-phosphate synthase is dephosphorylated by protein phosphatase 2A in spinach leaves: evidence from the effects of okadic acid and microcystin. FEBS Lett
Stitt, M. (1990) Fructose-2,6-bisphosphate as a regulatory molecule in plants. Annu. Rev. Plant Physiol. Plant Mol. Biol.
Stitt, M., Schreiber, U. (1988) Interaction between sucrose synthesis and CO
fixation III. Response of biphasic induction kinetics and oscillations to manipulation of the relation between electron transport, calvin cycle and sucrose synthesis. J. Plant Physiol.
Stitt, M., Quick, W.P. (1989) Photosynthetic carbon partitioning: its regulation and possibilities for manipulation. Physiol. Plant.
Stitt, M., Mieskes, G., Söling, H.-D., Heldt, H.W. (1982) On a possible role of fructose-2,6-bisphosphate in regulating photosynthetic metabolism in leaves. FEBS Lett.
Stitt, M., Wirtz, W., Gerhardt, R., Heldt, H.W., Spencer, C., Walker D.A., Foyer, C.H. (1985) A comparative study of metabolite levels in plant leaf material in the dark. Planta
Stitt, M., Huber, S.C., Kerr, P. (1987) Control of photosynthetic sucrose formation. In: Biochemistry of plants, vol. 8, pp. 327–409, Hatch M.D., Boardman, N.K., eds. Academic Press, New York
Stitt, M., Wilke, I., Feil, R., Heldt, H.W. (1988) Coarse control of sucrose phosphate synthase in leaves: alterations of the kinetic properties in response to the rate of photosynthesis and the accumulation of sucrose. Planta
Stitt, M., Lilley, R.McC., Gerhardt, R., Heldt, H.W. (1989) Metabolite levels in specific cells and subcellular compartments of plant leaves. Methods Enzymol.
Stitt, M., Von Schaewen, A., Sonnewald, U., Willmitzer, U. (1991) Sink regulation of photosynthetic metabolism in transgenic tobacco expressing yeast invertase in their cell wall involves a decreasing of the Calvin cycle enzymes and an increase of glycolytic enzymes. Planta
Weiner, H., Heldt, H.W., Stitt, M. (1987) Subcellular compartmentation of pyrophosphate and pyrophosphatase in leaves. Biochim. Biophys. Acta
Wendler, R., Veith, R., Dancer, J. Stitt, M. Komor, E. (1991) Sucrose storage in cell suspension cultures of
(sugar cane) is regulated by a cycle of synthesis and degradation. Planta
Williams, J.H.H., Farrar, J.F. (1990) Control of barley root respiration. Physiol. Plant.