Sucrose Metabolism


Sucrose is one of the main products of photosynthesis in plants, and the most common form of carbohydrate transported from source to sink organs. It also functions as a storage reserve, compatible solute and signal metabolite in plants. Sucrose is synthesised via the phosphorylated intermediate sucrose‐6′‐phosphate, by sucrose‐phosphate synthase (SPS) and sucrose‐phosphatase (SPP). In sink organs, sucrose is broken down by invertase or sucrose synthase to provide carbon and energy for growth and accumulation of storage reserves, such as starch, oil and fructans. Sucrose and trehalose are the only common nonreducing disaccharides found in nature, and their metabolism is inextricably linked in plants. Trehalose‐6‐phosphate, the intermediate of trehalose synthesis, is a signal of sucrose availability in plant cells, regulating photoassimilate partitioning in leaves and the utilisation of sucrose in sink organs.

Key Concepts

  • Sucrose is one of the main products of photosynthesis and the most common transport sugar in plants.
  • Sucrose is a nonreducing disaccharide and is synthesised in the cytosol via the phosphorylated intermediate, sucrose‐6′‐phosphate.
  • In leaves, the rate of sucrose synthesis is tightly coordinated with the rates of photosynthetic carbon dioxide fixation and starch synthesis in the chloroplasts.
  • Sucrose is transported from leaves via the phloem, to provide the rest of the plant with carbon and energy for growth and storage product synthesis.
  • Sucrose is unloaded from the phloem in sink organs. It can be hydrolysed by cell wall invertases and imported into the cells as hexose sugars, or taken up intact and metabolised by intracellular invertases or sucrose synthase.
  • Fructans are soluble polymers of fructose found in about 15% of all flowering plants. Dicotyledonous plants generally make inulin‐type fructans, whereas monocotyledonous plants also make levan, inulin neoseries, levan neoseries and mixed levan (graminan)‐type fructans.
  • Fructans are synthesised from sucrose via trisaccharide intermediates – 1‐kestose, 6‐kestose or 6G‐kestose – by various fructosyltransferases in the vacuole.
  • Trehalose is a nonreducing disaccharide found in many bacteria, archaea, invertebrates and fungi, and is often used as a stress protectant, compatible solute, storage reserve or transport sugar.
  • Trehalose metabolism is ubiquitous in plants, and essential for their normal growth and development, but most flowering plants accumulate only trace amounts of trehalose.
  • Trehalose‐6‐phosphate, the intermediate of trehalose synthesis, is a signal of sucrose availability in plants, regulating photoassimilate partitioning in leaves and the utilisation of sucrose in sink organs.

Keywords: fructan; photosynthesis; starch; sucrose; trehalose; trehalose‐6‐phosphate

Figure 1. Sucrose metabolism in plants. (a) Sucrose is synthesised via the phosphorylated intermediate sucrose‐6′‐phosphate (Suc6P), by the sequential activity of sucrose‐phosphate synthase (SPS) and sucrose‐phosphatase (SPP). The crystal structure of the Halothermothrix orenii SPS (top left; PDB accession 2R68) shows Suc6P bound in the active site of the enzyme. The crystal structure of the Synechocystis sp. PCC 6803 SPP (top right; PDB accession 1TJ5) shows hydrolysis of Suc6P to sucrose and Pi and movement of the Mg2+ ion cofactor (green) within the active site. (b) There are two routes of sucrose breakdown in plants, hydrolysis by invertase and cleavage by sucrose synthase.
Figure 2. Domain architecture of sucrose‐phosphate synthase (SPS) and sucrose‐phosphatase (SPP) from bacteria and plants. There are three types of SPS in bacteria. The Halothermothrix orenii SPS (Figure ) belongs to type (I), which contains only the glucosyltransferase domain (blue), whereas the other two types of SPS have an additional SPP‐like domain (red). This domain contains three motifs associated with phosphatase activity (orange) and is catalytically active in type (II), but not in type (III) SPSs. Species with type (I) or type (III) SPSs have a separate SPP enzyme. Plant SPSs have a noncatalytic SPP‐like domain and an N‐terminal extension (black) containing the light/dark regulatory phosphorylation site (P1). Two other phosphorylation sites involved in 14‐3‐3 protein binding (P2) or osmotic stress activation (P3) are present in the A, B and C families, but not the D family. The latter also lacks the highly variable linker region (yellow) between the glucosyltransferase and SPP‐like domains. The plant SPP has a catalytic domain (red) that closely resembles the Synechocystis sp. PCC 6803 SPP (Figure ), with a C‐terminal extension (grey) that might be involved in dimerisation.
Figure 3. Photosynthetic sucrose synthesis. During photosynthesis, carbon dioxide (CO2) is fixed in the chloroplasts via the Calvin–Benson cycle, providing the substrates for starch synthesis in the chloroplasts and sucrose synthesis in the cytosol. Triose‐phosphates are exported from the chloroplast via the triose‐phosphate translocator (TPT), in exchange for Pi. In the cytosol, the triose‐phosphates are equilibrated by triose‐phosphate isomerase (TPI) and then converted in a series of reactions to UDPglucose (UDPGlc) and fructose 6‐phosphate (Fru6P), the substrates for the synthesis of sucrose by sucrose‐phosphate synthase (SPS) and sucrose‐phosphatase (SPP). Most of the sucrose is exported from the leaf via the phloem, but some may be stored in the leaf for metabolism at night. The rate of sucrose synthesis is tightly co‐ordinated with the rates of CO2 fixation and starch synthesis in the chloroplasts by allosteric and posttranslational regulation of the cytosolic fructose‐1,6‐bisphosphatase (FBPase), SPS and ADPglucose pyrophosphorylase (AGPase). Abbreviations: ADPGlc, ADPglucose; Glc1P, glucose 1‐phosphate; Glc6P, glucose 6‐phosphate; PGI, phosphoglucose isomerase; PGM, phosphoglucomutase; RuBP, ribulose‐1,5‐bisphosphate; Suc6P, sucrose‐6′‐phosphate and UGPase, UDPglucose pyrophosphorylase.
Figure 4. Fructan synthesis in plants. Fructans are soluble polymers of fructose that are found in about 15% of all flowering plants. Plants contain five types of fructan, which are all synthesised from sucrose in the vacuole, but vary in conformation, degree of polymerisation and chain branching. One pathway proceeds via synthesis of the trisaccharide 1‐kestose, which contains a fructose residue (shown in green) attached by a β(2,1) glycosidic linkage to the fructosyl moiety of sucrose. Addition of further fructose residues via β(2,1) linkages generates the inulin series of fructans, which are the most common type of fructan in dicotyledonous plants. The trisaccharide, 6G‐kestose, is synthesised from 1‐kestose and contains a fructose residue (shown in red) attached to the glucosyl moiety of sucrose. Addition of fructose residues to 6G‐kestose via β(2,1) or β(2,6) linkages produces the inulin neoseries and levan neoseries of fructans, respectively. The second major pathway of fructan synthesis proceeds via the trisaccharide 6‐kestose, which has the second fructose residue (shown in blue) attached by a β(2,6) linkage to the fructosyl moiety of sucrose. Chain extension via β(2,6) linkages generates the levan series of fructans found in many monocotyledonous plants. The branched, mixed‐levan type of fructan, found in wheat and barley, contains fructose residues attached via β(2,1) and via β(2,6) linkages. The synthesis of this type of fructan is not yet fully resolved, but probably involves 1‐kestose as a precursor. Reactions are catalysed by the following enzymes: (1) 1‐sucrose:sucrose fructosyltransferase (1‐SST); (2) 6‐sucrose:fructan fructosyltransferase (6‐SFT); (3) 6G‐fructan:fructan fructosyltransferase (6G‐FFT) and (4) 1‐fructan:fructan fructosyltransferase (1‐FFT).
Figure 5. Trehalose metabolism in plants. Trehalose and sucrose are the only two common nonreducing disaccharides found in nature. Trehalose is synthesised via the phosphorylated intermediate trehalose‐6‐phosphate (Tre6P), by the sequential activity of trehalose‐phosphate synthase (TPS) and trehalose‐phosphatase (TPP). This pathway closely resembles the synthesis of sucrose (Figure ), and the enzymes, TPS and TPP, have many similarities with SPS and SPP. Trehalose is hydrolysed to glucose by trehalase, in a reaction comparable to the hydrolysis of sucrose by invertase.


Barratt DHP, Barber L, Kruger NJ, et al. (2001) Multiple, distinct isoforms of sucrose synthase in pea. Plant Physiology 127: 655–664.

Barratt DH, Derbyshire P, Findlay K, et al. (2009) Normal growth of Arabidopsis requires cytosolic invertase but not sucrose synthase. Proceedings National Academy of Sciences U S A 106: 13124–13129.

But SY, Khmelenina VN, Reshetnikov AS, et al. (2013) Bifunctional sucrose phosphate synthase/phosphatase is involved in the sucrose biosynthesis by Methylobacillus flagellatus KT. FEMS Microbiology Letters 347: 43–51.

Castleden CK, Aoki N, Gillespie VJ, et al. (2004) Evolution and function of the sucrose‐phosphate synthase gene families in wheat and other grasses. Plant Physiology 135: 1753–1764.

Chen D, Hajirezaei M and Börnke F (2005) Differential expression of sucrose‐phosphate synthase isoenzymes in tobacco reflects their functional specialization during dark‐governed starch mobilization in source leaves. Plant Physiology 139: 1163–1174.

Chourey PS, Taliercio EW, Carlson SJ and Ruan YL (1998) Genetic evidence that the two isozymes of sucrose synthase present in developing maize endosperm are critical, one for cell wall integrity and the other for starch biosynthesis. Molecular and General Genetics 259: 88–96.

Chua TK, Bujnicki JM, Tan T‐C, et al. (2008) The structure of sucrose phosphate synthase from Halothermothrix orenii reveals its mechanism of action and binding mode. The Plant Cell 20: 1059–1072.

Cimini S, Locato V, Vergauwen R, et al. (2015) Fructan biosynthesis and degradation as part of plant metabolism controlling sugar fluxes during durum wheat kernel maturation. Frontiers in Plant Science 6: e89.

Craig J, Barratt P, Tatge H, et al. (1999) Mutations at the rug4 locus alter the carbon and nitrogen metabolism of pea plants through an effect on sucrose synthase. The Plant Journal 17: 353–362.

Delorge I, Figueroa CM, Feil R, Lunn JE and Van Dijck P (2014) Trehalose‐6‐phosphate synthase 1 is not the only active TPS in Arabidopsis thaliana. Biochemical Journal 466: 283–290.

Fedosejevs ET, Ying S, Park J, et al. (2014) Biochemical and molecular characterization of RcSUS1, a cytosolic sucrose synthase phosphorylated in vivo at serine 11 in developing castor oil seeds. Journal of Biological Chemistry 289: 33412–33424.

Fieulaine S, Lunn JE, Borel F and Ferrer J‐L (2005) The structure of a cyanobacterial sucrose‐phosphatase reveals the sugar tongs that release free sucrose in the cell. The Plant Cell 17: 2049–2058.

Figueroa CM, Feil R, Ishihara H, et al. (2016) Trehalose 6‐phosphate coordinates organic and amino acid metabolism with carbon availability. The Plant Journal 85: 410–423.

Gao J, van Kleeff PJ, Oecking C, et al. (2014) Light modulated activity of root alkaline/neutral invertase involves the interaction with 14‐3‐3 proteins. The Plant Journal 80: 785–796.

Gerber L, Zhang B, Roach M, et al. (2014) Deficient sucrose synthase activity in developing wood does not specifically affect cellulose biosynthesis, but causes an overall decrease in cell wall polymers. New Phytologist 204: 1220–1230.

Hardin SC, Winter H and Huber SC (2004) Phosphorylation of the amino terminus of maize sucrose synthase in relation to membrane association and enzyme activity. Plant Physiology 134: 1427–1438.

Huber SC and Huber JL (1996) Role and regulation of sucrose‐phosphate synthase in higher plants. Annual Review of Plant Physiology and Plant Molecular Biology 47: 431–444.

Jia L, Zhang B, Mao C, et al. (2008) OsCYT‐INV1 for alkaline/neutral invertase is involved in root cell development and reproductivity in rice (Oryza sativa L.) Planta 228: 51–59.

Komina O, Zhou Y, Sarath G and Chollet R (2002) In vivo and in vitro phosphorylation of membrane and soluble forms of soybean nodule sucrose synthase. Plant Physiology 129: 1664–1673.

Krasensky J, Broyart C, Rabanal FA and Jonak C (2014) The redox‐sensitive chloroplast trehalose‐6‐phosphate phosphatase AtTPPD regulates salt stress tolerance. Antioxidant Redox Signaling 21: 1289–1304.

Langenkämper G, Fung RWM, Newcomb RD, et al. (2002) Sucrose phosphate synthase genes in plants belong to three different families. Journal of Molecular Evolution 54: 322–332.

Lastdrager J, Hanson J and Smeekens S (2014) Sugar signals and the control of plant growth and development. Journal of Experimental Botany 65: 799–807.

Le Roy K, Lammens W, Verhaest M, et al. (2007) Unraveling the difference between invertases and fructan exohydrolases: a single amino acid (Asp‐239) substitution transforms Arabidopsis cell wall invertase1 into a fructan 1‐exohydrolase. Plant Physiology 145: 616–625.

Lee HS and Sturm A (1996) Purification and characterization of neutral and alkaline invertase from carrot. Plant Physiology 112: 1513–1522.

Liu J, Han L, Huai B, et al. (2015) Down‐regulation of a wheat alkaline/neutral invertase correlates with reduced host susceptibility to wheat stripe rust caused by Puccinia striiformis. Journal of Experimental Botany pii: erv428.

Lunn JE and ap Rees T (1990) Apparent equilibrium constant and mass‐action ratio for sucrose‐phosphate synthase from seeds of Pisum sativum. Biochemical Journal 267: 739–743.

Lunn JE, Ashton AR, Hatch MD and Heldt HW (2000) Purification, molecular cloning, and sequence analysis of sucrose‐6 F‐phosphate phosphohydrolase from plants. Proceedings of the National Academy of Sciences of the USA 97: 12914–12919.

Lunn JE (2002) Evolution of sucrose synthesis. Plant Physiology 128: 1490–1500.

Lunn JE, Feil R, Hendriks JHM, et al. (2006) Sugar‐induced increases in trehalose 6‐phosphate are correlated with redox activation of ADPglucose pyrophosphorylase and higher rates of starch synthesis in Arabidopsis thaliana. Biochemical Journal 397: 139–148.

Lunn JE, Delorge I, Figueroa CM, Van Dijck P and Stitt M (2014) Trehalose metabolism in plants. The Plant Journal 79: 544–567.

Maloney VJ, Park JY, Unda F and Mansfield SD (2015) Sucrose phosphate synthase and sucrose phosphate phosphatase interact in planta and promote plant growth and biomass accumulation. Journal of Experimental Botany 66: 4383–4394.

Martins MCM, Hejazi M, Fettke J, et al. (2013) Feedback inhibition of starch degradation in Arabidopsis leaves mediated by trehalose 6‐phosphate. Plant Physiology 163: 1142–1163.

Mason MG, Ross JJ, Babst BA, Wienclaw BN and Beveridge CA (2014) Sugar demand, not auxin, is the initial regulator of apical dominance. Proceedings National Academy of Sciences U S A 111: 6092–6097.

Mugford ST, Fernandez O, Brinton J, et al. (2014) Regulatory properties of ADP glucose pyrophosphorylase are required for adjustment of leaf starch synthesis in different photoperiods. Plant Physiology 166: 1733–1747.

Murayama S and Handa H (2007) Genes for alkaline/neutral invertase in rice: alkaline/neutral invertases are located in plant mitochondria and also in plastids. Planta 225: 1193–1203.

Proels RK and Hückelhoven R (2014) Cell‐wall invertases, key enzymes in the modulation of plant metabolism during defence responses. Molecular Plant Pathology 15: 858–864.

Ritsema T and Smeekens S (2003) Fructans: beneficial for plants and humans. Current Opinion in Plant Biology 6: 223–230.

Salerno G and Curatti L (2003) Origin of sucrose metabolism in higher plants: when, how and why? Trends in Plant Science 8: 63–69.

Schluepmann H, Pellny T, van Dijken A, Smeekens S and Paul M (2003) Trehalose 6‐phosphate is indispensable for carbohydrate utilization and growth in Arabidopsis thaliana. Proceedings of the National Academy of Sciences of the USA 100: 6849–6854.

Schroeven L, Lammens W, Van Laere A and Van den Ende W (2008) Transforming wheat vacuolar invertase into a high affinity sucrose:sucrose 1‐fructosyltransferase. New Phytologist 180: 822–831.

Sergeeva LI, Keurentjes JJ, Bentsink L, et al. (2006) Vacuolar invertase regulates elongation of Arabidopsis thaliana roots as revealed by QTL and mutant analysis. Proceedings National Academy of Sciences U S A 103: 2994–2999.

Singh V, Louis J, Ayre BG, et al. (2011) TREHALOSE PHOSPHATE SYNTHASE11‐dependent trehalose metabolism promotes Arabidopsis thaliana defense against the phloem‐feeding insect Myzus persicae. The Plant Journal 67: 94–104.

Stitt M, Lunn J and Usadel B (2010) Arabidopsis and primary photosynthetic metabolism ‐ more than the icing on the cake. The Plant Journal 61: 1067–1091.

Stitt M and Zeeman SC (2012) Starch turnover: pathways, regulation and role in growth. Current Opinion in Plant Biology 15: 282–292.

Subbaiah CC, Palaniappan A, Duncan K, et al. (2006) Mitochondrial localization and putative signalling function of sucrose synthase in maize. Journal of Biological Chemistry 281: 15625–15635.

Sun J, Zhang J, Larue CT and Huber SC (2011) Decrease in leaf sucrose synthesis leads to increased leaf starch turnover and decreased RuBP regeneration‐limited photosynthesis but not Rubisco‐limited photosynthesis in Arabidopsis null mutants of SPSA1. Plant, Cell and Environment 34: 592–604.

Suzuki N, Bajad S, Shuman J, Shulaev V and Mittler R (2008) The transcriptional co‐activator MBF1c is a key regulator of thermotolerance in Arabidopsis thaliana. Journal of Biological Chemistry 283: 9269–9275.

Van den Ende W, De Coninck B, Clerens S, Vergauwen R and Van Laere A (2003) Unexpected presence of fructan 6‐exohydrolases (6‐FEHs) in non‐fructan plants: characterization, cloning, mass mapping and functional analysis of a novel “cell‐wall invertase‐like” specific 6FEH from sugar beet (Beta vulgaris L.) The Plant Journal 36: 697–710.

Vandesteene L, Ramon M, Le Roy K, Van Dijck P and Rolland F (2010) A single active trehalose‐6‐P synthase (TPS) and a family of putative regulatory TPS‐like proteins in Arabidopsis. Molecular Plant 3: 406–419.

Vargas WA, Pontis HG and Salerno GL (2008) New insights on sucrose metabolism: evidence for an active A/N‐Inv in chloroplasts uncovers a novel component of the intracellular carbon trafficking. Planta 227: 795–807.

Volkert K, Debast S, Voll LM, et al. (2014) Loss of the two major leaf isoforms of sucrose‐phosphate synthase in Arabidopsis thaliana limits sucrose synthesis and nocturnal starch degradation but does not alter carbon partitioning during photosynthesis. Journal of Experimental Botany 65: 5217–5229.

Welham T, Pike J, Horst I, et al. (2009) A cytosolic invertase is required for normal growth and cell development in the model legume, Lotus japonicus. Journal of Experimental Botany 60: 3353–3365.

Weschke W, Panitz R, Gubatz S, et al. (2003) The role of invertases and hexose transporters in controlling sugar ratios in maternal and filial tissues of barley caryopses during early development. The Plant Journal 33: 395–411.

Winter H and Huber SC (2000) Regulation of sucrose metabolism in higher plants: localization and regulation of activity of key enzymes. Critical Review in Biochemistry and Molecular Biology 35: 253–289.

Yadav UP, Ivakov A, Feil R, et al. (2014) The sucrose‐trehalose 6‐phosphate (Tre6P) nexus: specificity and mechanisms of sucrose signalling by Tre6P. Journal of Experimental Botany 65: 1051–1068.

Zhang Y, Primavesi LF, Jhurreea D, et al. (2009) Inhibition of SNF1‐related protein kinase1 activity and regulation of metabolic pathways by trehalose‐6‐phosphate. Plant Physiology 149: 1860–1871.

Zheng Y, Anderson S, Zhang Y and Garavito RM (2011) The structure of sucrose synthase‐1 from Arabidopsis thaliana and its functional implications. Journal of Biological Chemistry 286: 36108–36118.

Zrenner R, Salanoubat M, Willmitzer L and Sonnewald U (1995) Evidence of the crucial role of sucrose synthase for sink strength using transgenic potato plants (Solanum tuberosum L.) The Plant Journal 7: 97–107.

Further Reading

Heldt HW and Heldt F (2005) Polysaccharides, Plant Biochemistry, 3rd edn, pp. 243–273. Burlington, CA: Elsevier Academic Press.

Kandler O and Hopf H (1980) Occurrence, metabolism, and function of oligosaccharides. In: Preiss J (ed) The Biochemistry of Plants – A Comprehensive Treatise. Vol. 3 Carbohydrates – Structure and Function, pp. 221–270. New York: Academic Press.

Taiz L and Zeiger E (2010) Translocation in the Phloem, Plant Physiology, 5th edn, pp. 271–303. Sunderland, MA: Sinauer Associates Inc.

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Lunn, John E(Apr 2016) Sucrose Metabolism. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0021259.pub2]