The H+-sucrose cotransporter NtSUT1 is essential for sugar export from tobacco leaves

In many species translocation of sucrose from the mesophyll to the phloem is carrier mediated. A sucrose/H+-symporter cDNA, NtSUT1, was isolated from tobacco (Nicotiana tabacum) and shown to be highly expressed in mature leaves and at low levels in other tissues, including floral organs. To study the in vivo function of NtSUT1, tobacco plants were transformed with a SUT1 antisense construct under control of the cauliflower mosaic virus 35S promoter. Upon maturation, leaves of transformants expressing reduced amounts of SUT1 mRNA curled downward, and strongly affected plants developed chloroses and necroses that led to death. The leaves exhibited impaired ability to export recently fixed 14CO2 and were unable to export transient starch during extended periods of darkness. As a consequence, soluble carbohydrates accumulated and photosynthesis was reduced. Autoradiographs of leaves show a heterogenous pattern of CO2 fixation even after a 24-h chase. The 14C pattern does not change with time, suggesting that movement of photosynthate between mesophyll cells may also be impaired. The affected lines show a reduction in the development of the root system and delayed or impaired flowering. Taken together, the effects observed in a seed plant (tobacco) demonstrate the importance of SUT1 for sucrose loading into the phloem via an apoplastic route and possibly for intermesophyll transport as well.

[1]  F. Theodoulou,et al.  A Kinetic Model with Ordered Cytoplasmic Dissociation for SUC1, an Arabidopsis H+/Sucrose Cotransporter Expressed in Xenopus Oocytes , 1997, The Journal of Membrane Biology.

[2]  U. Wobus,et al.  A role for sugar transporters during seed development: molecular characterization of a hexose and a sucrose carrier in fava bean seeds. , 1997, The Plant cell.

[3]  W. Frommer,et al.  Macromolecular Trafficking Indicated by Localization and Turnover of Sucrose Transporters in Enucleate Sieve Elements , 1997, Science.

[4]  D. Loo,et al.  Transport Mechanism of the Cloned Potato H+/Sucrose Cotransporter StSUT1* , 1996, The Journal of Biological Chemistry.

[5]  W. Frommer,et al.  Companion cell‐specific inhibition of the potato sucrose transporter SUT1 , 1996 .

[6]  W. Frommer,et al.  Antisense inhibition of the sucrose transporter in potato: effects on amount and activity , 1996 .

[7]  J. Hibberd,et al.  Carbohydrate metabolism in source leaves of barley grown in 700 μmol mol−1 CO2and infected with powdery mildew , 1996 .

[8]  D. Bowles,et al.  Membranes: Specialized Functions in Plants , 1996 .

[9]  W. Frommer,et al.  Systemic Acquired Resistance Mediated by the Ectopic Expression of Invertase: Possible Hexose Sensing in the Secretory Pathway. , 1996, The Plant cell.

[10]  J. Sheen,et al.  Sugar sensing in higher plants. , 1994, The Plant cell.

[11]  N. Sauer,et al.  A phloem-specific sucrose-H+ symporter from Plantago major L. supports the model of apoplastic phloem loading. , 1994, The Plant journal : for cell and molecular biology.

[12]  N. Sauer,et al.  SUC1 and SUC2: two sucrose transporters from Arabidopsis thaliana; expression and characterization in baker's yeast and identification of the histidine-tagged protein. , 1994, The Plant journal : for cell and molecular biology.

[13]  T. Rees.  Plant Physiology: Virtue on both sides , 1994, Current Biology.

[14]  W. Frommer,et al.  Evidence for an essential role of the sucrose transporter in phloem loading and assimilate partitioning. , 1994, The EMBO journal.

[15]  W. Frommer,et al.  Potato sucrose transporter expression in minor veins indicates a role in phloem loading. , 1993, The Plant cell.

[16]  W. Frommer,et al.  Isolation and characterization of a sucrose carrier cDNA from spinach by functional expression in yeast. , 1992, The EMBO journal.

[17]  W. Frommer,et al.  Plasma membrane vesicles from source and sink leaves : changes in solute transport and polypeptide composition. , 1992, Plant physiology.

[18]  M. Stitt,et al.  Expression of a yeast‐derived invertase in the cell wall of tobacco and Arabidopsis plants leads to accumulation of carbohydrate and inhibition of photosynthesis and strongly influences growth and phenotype of transgenic tobacco plants. , 1990, The EMBO journal.

[19]  D. Bush,et al.  Electrogenicity, pH-Dependence, and Stoichiometry of the Proton-Sucrose Symport. , 1990, Plant physiology.

[20]  R. Besford.  The Greenhouse Effect: Acclimation of Tomato Plants Growing in High CO2, Relative Changes in Calvin Cycle Enzymes , 1990 .

[21]  R. Evert,et al.  Minor Veins of the Potato (Solanum tuberosum L.) Leaf: Ultrastructure and Plasmodesmatal Frequency , 1989, Botanical Gazette.

[22]  P. Quick,et al.  Fluoride Leads to an Increase of Inorganic Pyrophosphate and an Inhibition of Photosynthetic Sucrose Synthesis in Spinach Leaves , 1989 .

[23]  W. D. Hitz,et al.  Sucrose transport in plants , 1987 .

[24]  M. Bevan,et al.  Binary Agrobacterium vectors for plant transformation. , 1984, Nucleic acids research.

[25]  K. Zierler,et al.  A critique of compartmental analysis. , 1981, Annual review of biophysics and bioengineering.

[26]  J. Doe.  Sand and Water Culture Methods Used in the Study of Plant Nutrition , 1953, Soil Science Society of America Journal.

[27]  W. Frommer,et al.  Sucrose transport in higher plants. , 1998, International review of cytology.

[28]  R. Furbank,et al.  cDNA cloning and tissue specific expression of a gene for sucrose transporter from rice (Oryza sativa L.). , 1997, Plant & cell physiology.

[29]  N. Sauer,et al.  Expression of the PmSUC1 sucrose carrier gene from Plantago major L. is induced during seed development. , 1996, The Plant journal : for cell and molecular biology.

[30]  E. Komor,et al.  An Active Sucrose Carrier (Scr1) that is Predominantly Expressed in the Seedling of Ricinus communis L. , 1995 .

[31]  T. ap Rees.  Plant physiology. Virtue on both sides. , 1994, Current biology : CB.

[32]  D. Bush.  Proton-Coupled Sugar and Amino Acid Transporters in Plants , 1993 .

[33]  M. Stitt,et al.  Metabolite levels in specific cells and subcellular compartments of plant leaves , 1989 .

[34]  J. Prioul,et al.  Compartmental analysis of assimilate export in a mature maize leaf , 1987 .

[35]  E. Münch,et al.  Die stoffbewegungen in der Pflanze , 1931, Nature.