Multicellular living organisms and unmodified parts thereof and – Plant – seedling – plant seed – or plant part – per se – Higher plant – seedling – plant seed – or plant part
Reexamination Certificate
1998-01-05
2004-12-14
Fox, David T. (Department: 1638)
Multicellular living organisms and unmodified parts thereof and
Plant, seedling, plant seed, or plant part, per se
Higher plant, seedling, plant seed, or plant part
C800S278000, C800S295000, C800S298000, C536S023100, C536S023200, C536S023600
Reexamination Certificate
active
06831217
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a C3 plant which contains a gene for an enzyme involved in a C4 pathway of photosynthesis (hereinafter, referred to as a C4 photosynthesis gene) and expresses the C4 photosynthesis gene at a high level.
2. Description of the Related Art
Plants are classified into C3 plants, C4 plants, and crassulacean acid metabolism (CAM) plants, based on the kind of initial fixed products in photosynthetic fixation of CO
2
. Ninety percent or more of plants on the earth belong to C3 plants, which include, for example, agriculturally important plants such as rice and barley. The photosynthetic pathway of C3 plants is also called the Calvin pathway, and an enzyme involved in photosynthetic fixation of CO
2
in this pathway is ribulose-1,5-bisphosphate carboxylase. This enzyme has a low affinity for CO
2
and has a high affinity for O
2
. Therefore, the efficiency of a photosynthetic reaction as well as photosynthetic fixation of CO
2
is low in the C3 photosynthetic pathway.
The C4 plants are those which have evolved so as to overcome such non-efficient photosynthetic fixation of CO
2
. The C4 plants have a mechanism for concentrating CO
2
and a high photosynthetic capacity. An enzyme involved in photosynthetic fixation of CO
2
in the photosynthetic pathway of the C4 plants is phosphoenolpyruvate carboxylase. This enzyme has a high capacity of photosynthetic fixation of CO
2
without its activity being inhibited by O
2
.
CAM plants have a photosynthetic system suitable for dry environment, and the photosynthetic system is considered to be a sort of evolved form of the C3 photosynthetic system.
It is expected that the photosynthetic capacity and productivity of the agriculturally important C3 plants (e.g., rice) will be remarkably improved by providing a C3 plant with the photosynthetic function of a C4 plant. Some attempts have been made to introduce a C4 photosynthesis gene into a C3 plant.
In order to express a photosynthesis gene of a C4 plant, a chlorophyll a/b binding protein promoter or a Cauliflower mosaic virus (CaMV) 35S promoter linked thereto has been used. For example, there is a report by Kogami et al., Transgenic Research 3: 287-296 (1994): The (CaMV) 35S promoter which can be expressed at a high level in a leaf tissue of a C3 plant was linked to a photosynthesis gene of a C4 plant (the phosphoenolpyruvate carboxylase (PEPC) gene) to produce recombinant DNA, and then the recombinant DNA was introduced into a C3 plant, tobacco; however, the PEPC activity in the C3 plant merely increased by 2 to 3 times at most. There is another report by Matsuoka et al., Plant Physiol. 111: 949-957 (1996): For the purpose of studying the function of a promoter of the C4 photosynthesis gene, a fusion gene of the &bgr;-glucuronidase (GUS) gene from
E. coli
and a 5′-flanking region (promoter region) of the PEPC gene was introduced into tobacco, whereby the GUS gene was expressed at a high level. There is also a report by Hudspeth et al., Plant Physiol. 98:458-464 (1992): As a C4 photosynthesis gene, the PEPC genome gene of maize containing the expression control region (promoter region) was introduced into tobacco; however, the PEPC activity merely increased by 2 to 3 times.
Thus, to the extent that the inventors are aware of, prior to the filing of Japanese Patent application No. 9-56742, on which the present application claims priority, there were no reports on examples where an enzyme involved in photosynthesis was expressed at a high level. Accordingly, there is a demand for techniques of expressing a photosynthesis gene of a C4 plant in a C3 plant at a high level, thereby enhancing the photosynthetic capacity of the C3 plant.
SUMMARY OF THE INVENTION
The present invention intends to overcome the above-mentioned problems, and its objective is to express a photosynthesis gene of a C4 plant in a C3 plant at a high level.
As described above, there is an example in which attempts have been made to introduce a PEPC genome gene involved in a photosynthetic pathway of a C4 plant, maize (poaceae) into a C3 plant, tobacco (solanaceae), resulting in low expression efficiency. The inventors of the present invention found that by introducing a gene containing (a) an expression control region of an enzyme involved in photosynthetic pathway of a C4 plant which is phylogenetically related to a C3 plant and (b) a structural gene for an enzyme involved in a photosynthetic pathway of a C4 plant which is phylogenetically related to a C3 plant, into the C3 plant, the expression efficiency of the enzyme involved in the C4 pathway of photosynthesis is remarkably enhanced, thereby achieving the present invention.
A C3 plant expressing a gene of a phylogenetically related C4 plant according to the present invention includes DNA containing (a) an expression control region of a gene for an enzyme involved in a photosynthetic pathway of a phylogenetically related C4 plant and (b) a structural gene for an enzyme involved in a photosynthetic pathway of the C4 plant, wherein the C3 plant expresses the enzyme encoded by the structural gene at a high level.
A method for producing a C3 plant which expresses a gene of a phylogenetically related C4 plant according to the present invention includes the steps of: transforming cells of the C3 plant with DNA containing (a) an expression control region of a gene for an enzyme involved in a photosynthetic pathway of a phylogenetically related C4 plant and (b) a structural gene for an enzyme involved in a photosynthetic pathway of the C4 plant; and regenerating the transformed cells of the C3 plant into the C3 plant; wherein the regenerated C3 plant expresses the enzyme encoded by the structural gene at a high level.
In one embodiment of the present invention, the C4 plant is a monocotyledonous plant, and the C3 plant is a monocotyledonous plant.
In another embodiment of the present invention, the C4 plant is a dicotyledonous plant, and the C3 plant is a dicotyledonous plant.
In another embodiment of the present invention, the DNA is a genome gene of the C4 plant.
In another embodiment of the present invention, the genome gene of the C4 plant is a genome gene of a C4 poaceous plant, and the C3 plant is a C3 poaceous plant.
In another embodiment of the present invention, the genome gene of the C4 poaceous plant is a genome gene for phosphoenolpyruvate carboxylase from maize, and the C3 poaceous plant is rice.
The present invention also relates to a C3 plant obtainable by a method according to the present invention, and a portion of the C3 plant.
In one embodiment of the present invention, the portion of a C3 plant according to the present invention is a vegetable.
In another embodiment of the present invention, the portion of a C3 plant according to the present invention is a fruit.
In another embodiment of the present invention, the portion of a C3 plant according to the present invention is a flower.
In another embodiment of the present invention, the portion of a C3 plant according to the present invention is a seed.
A C3 plant tissue expressing a gene of a phylogenetically related C4 plant according to the present invention includes DNA containing (a) an expression control region of a gene for an enzyme involved in a photosynthetic pathway of a phylogenetically related C4 plant and (b) a structural gene for an enzyme involved in a photosynthetic pathway of the C4 plant, wherein the C3 plant tissue expresses the enzyme encoded by the structural gene at a high level.
A method for producing a C3 plant tissue which expresses a gene of a phylogenetically related C4 plant according to the present invention includes the steps of: transforming cells of the C3 plant with DNA containing (a) an expression control region of a gene for an enzyme involved in a photosynthetic pathway of a phylogenetically related C4 plant and (b) a structural gene for an enzyme involved in a photosynthetic pathway of the C4 plant; and regenerating the transformed cells of the C3 plant into the C3 plant tissue; wherein t
Matsuoka Makoto
Sun-Ben Ku Maurice
Toki Seiichi
Tokutomi Mitsue
Fox David T.
Kallis Russell
National Institute of Agrobiological Sciences
Townsend and Townsend / and Crew LLP
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