Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1995-11-27
1999-08-17
Hutzell, Paula K.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
536 231, 536 234, 536 236, 435 6, 435 691, 4352523, 4353201, 435410, C07H 2104, C12N 121, C12N 1563, C12Q 168
Patent
active
059395397
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the regulation of plant growth, and more particularly to the molecular cloning and expression of a gibberellin 20-oxidase gene and its use, for example in transgenic plants.
2. Description of the Related Art
Chemical compounds for control of plant growth have been in commercial use for many years. Many of these compounds act by inhibiting various steps in the biosynthesis of gibberellins (GAs). GAs form a large group of diterpenoid natural products, some members of which function as hormones in plants, controlling many aspects of development, including, for example, shoot elongation. Among the groups of compounds which inhibit GA biosynthesis in higher plants are quaternary ammonium and phosphonium compounds, compounds with a nitrogen-containing heterocycle, and acylcyclohexane-diones. However, the use of such chemicals involves several problems. It is, for example, difficult to apply the chemicals to plants in the appropriate quantities, or to select plant organs, without the chemicals spreading to other plants or animal life. There is a risk of persistence which can make it difficult to grow other crops subsequently to treated crops. A problem addressed by the present invention is therefore to avoid the use of such chemicals. This problem can be solved within this application by providing means for plant growth control at the plant gene level.
The later steps of the GA biosynthetic pathway are catalysed by soluble 2-oxoglutarate-dependent dioxygenases, several of which have been proposed as regulatory enzymes in the biosynthesis of the physiologically important C.sub.19 compound, GA.sub.1. For example, the activity of the GA 20-oxidase is enhanced by long days in certain photoperiod-sensitive plants and is down-regulated as a consequence of GA.sub.1 action in several species.
SUMMARY OF THE INVENTION
According to the invention, there is provided a DNA sequence which encodes a polypeptide exhibiting GA 20-oxidase activity. This disclosure is the first example of the molecular cloning of a GA:2-oxoglutarate dioxygenase. The enzyme GA 20-oxidase is also known as a 20-hydroxylase or C-20 oxidase, as it catalyses oxidation reactions at the C-20 carbon atom of the GA structure. It is a dioxygenase, as oxoglutarate is simultaneously oxidised.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As demonstrated in the Examples the DNA sequence of the present invention encodes GA 20-oxidase capable of acting essentially on one or more of the following substrates: GA.sub.12, GA.sub.53, GA.sub.15 (open or closed lactone), GA.sub.44 (open or closed lactone), GA.sub.24, GA.sub.19 and GA.sub.23 among others.
The present invention thus further relates to a DNA sequence encoding a polypeptide exhibiting GA 20-oxidase activity, in which the polypeptide exhibiting GA 20-oxidase activity is capable of acting essentially on one or more of the following substrates: GA.sub.12, GA.sub.53, GA.sub.15 (open or closed lactone), GA.sub.44 (open or closed lactone), GA.sub.24, GA.sub.19 and GA.sub.23.
The DNA sequence of the invention may encode a GA 20-oxidase from, in principle, any plants or fungi, but preferably from monocotyledonous and dicotyledonous plants, and more preferably from dicotyledonous plants. A particularly suitable source is plants of the family Cucurbitaceae, such as C. maxima, of which the immature seeds are a convenient source. A further suitable source is plants of the family Cruciferae, such as Arabidopsis thaliana, of which shoot material is a convenient source.
A preferred embodiment of the invention is therefore a DNA sequence which encodes a GA 20-oxidase obtainable from plants or fungi, preferably from monocotyledonous and dicotyledonous plants respectively, more preferably from dicotyledonous plants and most preferably from plants of the family Cucurbitaceae and Cruciferae respectively, such as C. maxima and Arabidopsis thaliana, or a protein having substantial homology thereto.
As used in the present application, substantial seq
REFERENCES:
patent: 5210189 (1993-05-01), Murata
Gilmour et al., "Partial Purification of Gibberellin Oxidases from Spinach Leaves.sup.1 ", Plant Physiol. vol. 85, pp. 87-90, 1987.
Graebe et al. "The Relationship of Different Gibberellin Biosynthetic Pathways in Cucurbita maxima Endosperm and Embryos and the Purification of a C-20 Oxidase from the Endosperm", Gibberellins; Symposium, Tokyo, Japan, Jul. 20-23, Takahashi et al. (eds), pp. 51-61, 1989.
Kamiya et al., "Conversion of Gibberellin A.sub.20 to Gibberellins A.sub.1 and A.sub.5 in A Cell-Free System from Phaseolus vulgaris", Planta vol. 162, 154-158, 1984.
Lange et al., "The Partial Purification and Characterization of A Gibberellin C-20 hydroxylase from Immature Pisum sativum L. Seeds", Planta vol. 179, pp. 211-221, 1989.
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Graebe Jan E.
Hedden Peter
Lange Theodor
Phillips Andrew
Hutzell Paula K.
Johnson Nancy A.
Long Ashton Research Station
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