Multicellular living organisms and unmodified parts thereof and – Method of introducing a polynucleotide molecule into or... – The polynucleotide alters carbohydrate production in the plant
Reexamination Certificate
1999-09-02
2002-07-23
Fox, David T. (Department: 1638)
Multicellular living organisms and unmodified parts thereof and
Method of introducing a polynucleotide molecule into or...
The polynucleotide alters carbohydrate production in the plant
C800S286000, C800S305000, C800S306000, C800S312000, C800S314000, C800S315000, C800S317100, C800S317200, C800S317400, C800S320000, C800S320100, C800S320200, C800S320300, C800S322000, C435S069100, C435S320100, C435S419000, C536S023600, C536S024500, C536S023200
Reexamination Certificate
active
06423886
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to plant molecular biology. More specifically, it relates to nucleic acids and methods for modulating their expression in plants.
BACKGROUND OF THE INVENTION
Starches are polymers of glucose molecules produced and stored only in the chloroplasts and amyloplasts of plants. Most of the starch produced in the world is used as food, but about one-third of the total production is employed for a variety of industrial purposes that take advantage of starch's unique properties. These properties (e.g. viscosity, gelatinization temperature) vary greatly with the plant source and affect the usefulness of the starch for food and nonfood products. (Sivak and Preiss,
Advances in Food and Nutrition Research,
Vol. 41. Academic Press, 1998, p. 163.) The properties of a starch are determined by the structure of its constituent granules and the polymers from which the granules are formed. Molecular structure is, in turn, dependent largely upon the presence and activity of specific isozymes of starch synthase. Genes encoding the starch synthase enzymes are therefore of interest.
The presence or absence of specific starch synthase isozymes in tissues can have profound effects upon the nature of starch polymers and granules produced in plants, although the exact role of different synthase isozymes in defining the specificity of amylose, amylopectin and granule properties is still unclear. Recent research suggests that the contribution of a starch synthase isozyme is determined not only by intrinsic properties of the enzyme but also by interactions among various synthases, branching enzymes, and/or debranching enzymes. Thus, the genetic, environmental, and developmental backgrounds in which a particular starch synthase isozyme is expressed affect the role of that isozyme in dictating distinct features of starch. This implies that almost any manipulation of combinations of starch synthesizing enzymes may have surprising and potentially useful results. (Smith, A. M.
Current Opinion in Plant Biology
2:223-229 (1999))
When a mutation affecting a particular starch biosynthetic enzyme results in changes in the appearance of a seed, the resulting changes in starch structure may be subtle: for example, a slight decrease in the average chain length of amylopectin or a small increase in the proportion of amylose to amylopectin. (Sivak and Preiss, supra, p. 29.) However, even small changes in the molecular structure of a starch may have significant effects on its industrial utility. Identification of enzymatic changes and of the consequent modification of starch will result in enhanced diversity of starch functionalities for industrial purposes.
Certain genes encoding starch synthases have been identified and cloned, and modifications of starch content using these genes have been attempted or accomplished. See, for example, U.S. Pat. No. 5,824,798; WO Publication No. 96/15248; WO Publication No. 97/45545; WO Publication No. 97/26362; and WO Publication No. 97/20936.
Starch synthase enzymes utilize ADPglucose and/or UDPglucose in a polymerization reaction. The glycosyl portion of the substrate is transferred to, in most cases, preexisting maltooligosaccharides or polymers of &agr;-(1,4) or mixed &agr;-(1,4) and &agr;-(1,6) linkages. In other words, these enzymes are involved in the biosynthesis of amylose [&agr;-(1,4) polymer] and amylopectin [polymer of &agr;-(1,4) branched with &agr;-(1-4,6) linkages], the primary types of molecules occurring in starch granules.
Starch composition varies with species and tissue. Maize starch stored in the endosperm is typically composed of 28% amylose and 72% amylopectin. Amylose of maize starch has an average degree of polymerization (number-average; DP
n
) of 960 and an average chain length (CL) of 305. Maize amylopectin, on the other hand, has a DP
n
of 10.2×10
3
and a CL of 22. (Morrison et al., “Starch” in Dey & Harborne,
Methods in Plant Biochemistry
(London, Academic Press, 1990), pp. 323-352).
The different structures of amylose and amylopectin confer distinctive properties to these polysaccharides. For example, the amylose fraction of starch will precipitate from an aqueous solution over time as the linear amylose molecules align themselves parallel to each other and become held together by hydrogen bonds. This precipitation is known as retrogradation. Amylopectin, on the other hand, does not readily form intermolecular complexes and is more stable in aqueous solutions. However, the crystalline nature of starch is due to the presence of amylopectin and not to amylose. This is contrary to the general principle that branching in a molecule is detrimental to crystallization. (Sivak and Preiss, supra, pp. 20-22) Indeed, the chain length of amylopectin is a basic factor in the determination of the crystalline type of the starch. (Hizukuri, S.,
Carbohydrate Research
141, pp. 295-306 (1985))
The ease of isolation of starch granules for food and industrial purposes is affected by starch composition. In each bushel of maize processed, roughly 2.2 to 3.4 pounds of starch are unrecoverable. This represents a 6% to 8% loss of potential starch yield. Thus, a need exists for improved yield of starch from maize grain; alteration of granule size and/or density could improve this processing yield.
Starches with unusual, desirable functional properties may be currently available only in small quantities, or in plants or plant parts not commonly processed. Therefore, a need exists to develop plants, especially cereals, potato, or cassava, capable of synthesizing unusual starch for use in specific food and non-food industrial applications.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide nucleic acids and polypeptides relating to the biosynthesis of starch.
It is another object of the present invention to provide nucleic acids and polypeptides that can be used to identify proteins involved in starch biosynthesis.
It is another object of the present invention to provide antigenic fragments of the polypeptides of the present invention.
It is another object of the present invention to provide transgenic plants comprising the nucleic acids of the present invention.
It is another object of the present invention to provide methods for modulating, in a transgenic plant, the expression of the nucleic acids of the present invention.
It is another object of the present invention to provide a method for modulating the type and level of starch synthase in a plant.
It is another object of the present invention to provide a method for modulating the type and level of starch in a plant.
It is another object of the present invention to improve the industrial processing yield of starch from maize grain by altering starch granule size and/or density.
It is another object of the present invention to provide plants, especially maize, wheat, sorghum, barley, millet, rice, potato, or cassava plants, capable of synthesizing unusual starch with desirable functional properties for use in specific food and non-food industrial applications.
It is another object of the present invention to provide plants capable of synthesizing starch with altered granule sizes.
It is another object of the present invention to provide plants capable of synthesizing starch with altered degrees of crystallinity.
It is another object of the present invention to provide plants capable of synthesizing starch with altered densities.
It is another object of the present invention to provide plants capable of synthesizing starch with altered digestibilities.
It is another object of the present invention to provide plants capable of synthesizing starch with altered levels of covalently bound phosphate.
It is another object of the present invention to provide plants capable of synthesizing starch with altered patterns of branching and/or average chain lengths.
It is another object of the present invention to provide plants capable of synthesizing starch with altered temperatures of gelatinization.
It is another object
Singletary George W.
Zhou Lan
Fox David T.
Pioneer Hi-Bred International , Inc.
Pioneer Hi-Bred International Inc.
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