Fructan as a New Carbohydrate Sink in Transgenic Potato Plants.
Abstract
Fructans are polyfructose molecules that function as nonstructural storage carbohydrates in several plant species that are important crops. We have been studying plants for their ability to synthesize and degrade fructans to determine if this ability is advantageous. We have also been analyzing the ability to synthesize fructan in relation to other nonstructural carbohydrate storage forms like starch. To study this, we induced fructan accumulation in normally non-fructan-storing plants and analyzed the metabolic and physiological properties of such plants. The normally non-fructan-storing potato plant was modified by introducing the microbial fructosyltransferase genes so that it could accumulate fructans. Constructs were created so that the fructosyltransferase genes of either Bacillus subtilis (sacB) or Streptococcus mutans (ftf) were fused to the vacuolar targeting sequence of the yeast carboxypeptidase Y (cpy) gene. These constructs were placed under the control of the constitutive cauliflower mosaic virus 35S promoter and introduced into potato tissue. The regenerated potato plants accumulated high molecular mass (>5 [times] 106 D) fructan molecules in which the degree of polymerization of fructose units exceeded 25,000. Fructan accumulation was detected in every plant tissue tested. The fructan content in the transgenic potato plants tested varied between 1 and 30% of dry weight in leaves and 1 and 7% of dry weight in microtubers. Total nonstructural neutral carbohydrate content in leaves of soil-grown plants increased dramatically from 7% in the wild type to 35% in transgenic plants. Our results demonstrated that potato plants can be manipulated to store a foreign carbohydrate by introducing bacterial fructosyltransferase genes. This modification affected photosynthate partitioning in microtubers and leaves and increased nonstructural carbohydrate content in leaves.
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Selected References
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- Bevan M. Binary Agrobacterium vectors for plant transformation. Nucleic Acids Res. 1984 Nov 26;12(22):8711–8721.[PMC free article] [PubMed] [Google Scholar]
- Darwen CW, John P. Localization of the Enzymes of Fructan Metabolism in Vacuoles Isolated by a Mechanical Method from Tubers of Jerusalem Artichoke (Helianthus tuberosus L.). Plant Physiol. 1989 Feb;89(2):658–663.[PMC free article] [PubMed] [Google Scholar]
- Han YW. Microbial levan. Adv Appl Microbiol. 1990;35:171–194. [PubMed] [Google Scholar]
- Müller-Röber B, Sonnewald U, Willmitzer L. Inhibition of the ADP-glucose pyrophosphorylase in transgenic potatoes leads to sugar-storing tubers and influences tuber formation and expression of tuber storage protein genes. EMBO J. 1992 Apr;11(4):1229–1238.[PMC free article] [PubMed] [Google Scholar]
- Shiroza T, Kuramitsu HK. Sequence analysis of the Streptococcus mutans fructosyltransferase gene and flanking regions. J Bacteriol. 1988 Feb;170(2):810–816.[PMC free article] [PubMed] [Google Scholar]
- Sijmons PC, Dekker BM, Schrammeijer B, Verwoerd TC, van den Elzen PJ, Hoekema A. Production of correctly processed human serum albumin in transgenic plants. Biotechnology (N Y) 1990 Mar;8(3):217–221. [PubMed] [Google Scholar]
- Steinmetz M, Le Coq D, Aymerich S, Gonzy-Tréboul G, Gay P. The DNA sequence of the gene for the secreted Bacillus subtilis enzyme levansucrase and its genetic control sites. Mol Gen Genet. 1985;200(2):220–228. [PubMed] [Google Scholar]
- Valls LA, Hunter CP, Rothman JH, Stevens TH. Protein sorting in yeast: the localization determinant of yeast vacuolar carboxypeptidase Y resides in the propeptide. Cell. 1987 Mar 13;48(5):887–897. [PubMed] [Google Scholar]
- van der Steege G, Nieboer M, Swaving J, Tempelaar MJ. Potato granule-bound starch synthase promoter-controlled GUS expression: regulation of expression after transient and stable transformation. Plant Mol Biol. 1992 Oct;20(1):19–30. [PubMed] [Google Scholar]
- Wagner W, Wiemken A. Enzymology of Fructan Synthesis in Grasses: Properties of Sucrose-Sucrose-Fructosyltransferase in Barley Leaves (Hordeum vulgare L. cv Gerbel). Plant Physiol. 1987 Nov;85(3):706–710.[PMC free article] [PubMed] [Google Scholar]
Abstract
Fructans are polyfructose molecules that function as nonstructural storage carbohydrates in several plant species that are important crops. We have been studying plants for their ability to synthesize and degrade fructans to determine if this ability is advantageous. We have also been analyzing the ability to synthesize fructan in relation to other nonstructural carbohydrate storage forms like starch. To study this, we induced fructan accumulation in normally non-fructan-storing plants and analyzed the metabolic and physiological properties of such plants. The normally non-fructan-storing potato plant was modified by introducing the microbial fructosyltransferase genes so that it could accumulate fructans. Constructs were created so that the fructosyltransferase genes of either Bacillus subtilis (sacB) or Streptococcus mutans (ftf) were fused to the vacuolar targeting sequence of the yeast carboxypeptidase Y (cpy) gene. These constructs were placed under the control of the constitutive cauliflower mosaic virus 35S promoter and introduced into potato tissue. The regenerated potato plants accumulated high molecular mass (>5 [times] 106 D) fructan molecules in which the degree of polymerization of fructose units exceeded 25,000. Fructan accumulation was detected in every plant tissue tested. The fructan content in the transgenic potato plants tested varied between 1 and 30% of dry weight in leaves and 1 and 7% of dry weight in microtubers. Total nonstructural neutral carbohydrate content in leaves of soil-grown plants increased dramatically from 7% in the wild type to 35% in transgenic plants. Our results demonstrated that potato plants can be manipulated to store a foreign carbohydrate by introducing bacterial fructosyltransferase genes. This modification affected photosynthate partitioning in microtubers and leaves and increased nonstructural carbohydrate content in leaves.