DNA sequences which lead to the formation of levans plasmids con

Details DNA sequences which lead to the formation of levans plasmids con DNA sequences which lead to the formation of levans plasmids con

1995-02-09

1998-08-11

Fox, David T.

Multicellular living organisms and unmodified parts thereof and

Method of introducing a polynucleotide molecule into or...

The polynucleotide alters fat, fatty oil, ester-type wax, or...

800DIG42, 800DIG43, 800DIG55, 800DIG56, 800DIG57, 800DIG58, 435 691, 435101, 435103, 4351723, 435200, 435210, 435211, 4353201, 435419, 536 237, A01H 500, C12N 1531, C12N 1556, C12N 1582, C12P 1904

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057929238

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BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to DNA sequences which lead to the formation of polyfructans (levans), as well as a process for preparing transgenic plants using plasmids on which these DNA sequences are located.
High molecular weight, water soluble, linear polymers, for example those based on polyacrylates or polymethacrylates, are products of mineral oils and have many important uses. In particular their properties in increasing the viscosity of aqueous systems, in suspending or sedimentation acceleration and complexing are especially valuable from the technical viewpoint. These products are also used in exceptionally large amounts in super absorbers for water binding and in water dilutable lacquers. In spite of the outstanding positive properties, because such products are difficult to dispose of, their use is increasingly coming under criticism because they are not biodegradable.
Alternatives based on recyclable raw materials, especially starches and cellulose, because of the macromolecular structure of these polysaccharides, have been shown to have limited value. As a replacement for non-biodegradable chemically derived polymers, a number of derivatised high polymeric polysaccharides have been considered. Until now, such polysaccharides could only be obtained biotechnologically via suitable fermentation and transglycosidation processes. The products obtained in this way, such as dextrans and polyfructans (levans) are not competitive as raw materials for mass production.
Polyfructans are found in a number of monocotyledonous and dicotyledonous higher plants, in green algae as well as in a number of gram positive and gram negative bacteria (Meier and Reid, (1982) Encyclopedia of Plant Physiology, New Series, 13A. 418-471). The role of fructans for the plant development and plant growth is not fully understood. Functions of the fructans that have been proposed are as a protectant against freezing at low temperatures, as alternative carbohydrate stores which limit starch biosynthesis, as well as applied intermediary stores for photoassimilates, which are situated in the stems of grasses shortly before their transfer into the seeds.
All fructans contain, as starter molecule for the polymerisation reaction, a molecule of sucrose (glucose-fructose) to which fructose polymers are added.
Depending on the coupling of the fructose molecule, fructans of plant origin can be classified into four classes (Meier and Reid (1982), Encyclopedia of Plant Physiology, New Series, 13A, 418-471): a-c, are added completely from fructose residues of polymerisation both from glucose and also from fructose residues from polyfructose residues (neokestose type).
Fructans of bacterial origin correspond either to the levan or to the inulin type (Carlsson (1970) Caries Research 4, 97-113) and Dedonder (1966) Methods Enzymology 8, 500-505).
Experiments on the biosynthesis of fructans in plants and bacteria lead one to conclude that the biosynthesis proceeds by various routes. Bacterial and plant fructans are further distinguished, not particularly in their primary structure but mainly in their molecular weight. Thus, fructans isolated from plants have been shown to have molecular weights of between 5000 and 50,000 d (Pollock and Chatterton (1988) in: The Biochemistry of Plants 14, 109-140), while fructans isolated from bacteria, molecular weights of up to 2,000,000 d have been described (Clarke et al (1991) in: Carbohydrates as Organic Raw Materials, VCH Weinheim, 169-182).
Various microorganisms from the group of Bacillus spp as well as Streptococcus spp produce polyfructoses in which both fructans of the levan type and fructans of the inulin type have been described (Carlsson (1970) Caries Research 4, 97-113 and Dedonder (1966) Methods Enzymology 8, 500-505).
Experiments on biosynthesis pathways have made it clear that, in comparison to biosynthesis pathways in higher plants, there is a more simple pattern and a sharing of only one enzyme. This enzyme with the trivial name levan sucrase is a transfructosylase (

REFERENCES:
Geier, G., et al., "Levansucrase as a Virulence Factor in Fireblight Development", Mitteilungen Aus Der Biologischen Bundesanstalt Fuer Land-Und Forstwirtschaft Berlin-Dahlem, (Communications from the Federal Biological Institute for Agriculture and Forestry Berlin-Dahlem), Symposium on Fireblight, Landenburg, Germany, Jun. 13-14, 1991, vol. 282, 1992, pp. 78-81.
Cote, G.L., et al., "Purification and Properties of an Extracellular Levansucrase from Erwinia Herbicola NRRL B-1678", Carbohydrate Research, vol. 190, 1989, pp. 299-307.
Tang et al. 1990 Gene 96(1):89-93.
Shiroza et al. 1988, J. Bacteriol. 170(2):810-816.
Geier et al. 1993, Physiol. Mol. Plant Pathol. 42(6):387-404.
Rober et al. 1996, Planta 199:528-536.
Stryer, L. 1988. Biochemistry, pp. 796-797, Third Edition, W.H. Freeman and Co.: New York.
Sonnewald et al. 1991, Plant J. 1:95-106.

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