PCK-type C4 cycle

Abstract

The present invention relates a method for transforming a C3 plant to provide it with a C4 photoshynthetic pathway by way of the introduction of some genes participating in a C4 photosynthetic pathway. To this end, the method of the invention comprises introducing a phosphoenolpyruvate carboxylase (PEPC) and a gene coding for a phosphoenolpyruvate carboxykinase (PCK) which has been connected with a DNA fragment coding for a transit peptide into a C3 plant.

1 . A method for transforming a C3 plant to provide the plant with a photosynthetic pathway formed in a single cell to mimic the C4 photosynthetic pathway which comprises introducing 
 a gene coding for a phosphoenolpyruvate carboxylase (PEPC), wherein the PEPC gene is operably linked to a promoter; and    a gene coding for a phosphoenolpyruvate carboxykinase (PKC), wherein the PCK gene is operably linked to a promoter and a gene coding for chloroplast transit peptide.    
     
     
         2 . The method according to  claim 1  which further comprises introducing a gene coding for a carbonic anhydrase (CA) into the C3 plant, wherein the CA gene is operably linked to a promoter.  
     
     
         3 . The method according to  claim 1  which further comprises introducing a gene coding for a pyruvate, orthophoshate dikinase (PPDK) into the C3 plant, wherein the PPDK gene is operably linked to a promoter.  
     
     
         4 . The method according to any of claims  1 - 3  or  12  wherein the promoter operably linked to each of the genes is a photosynthetic tissue specific promoter.  
     
     
         5 . The method according to  claim 4  wherein at least two of said genes are carried on a single gene construct.  
     
     
         6 . A chimeric gene comprising a gene coding for a phospoenolpyruvate carboxylase (PEPC), and a gene coding for a phosphoenolpyruvate carboxykinase (PCK) which has been operably linked to a DNA fragment coding for a transit peptide.  
     
     
         7 . A transformed C3 plant comprising a gene coding for a phospoenolpyruvate carboxylase (PEPC), and a gene coding for a phosphoenolpyruvate carboxykinase (PCK), wherein the PEPC gene is operably linked to a promoter, and the PCK gene is operably linked to a promoter and a gene coding for a chloroplast transit peptide.  
     
     
         8 . The transformed C3 plant as claimed in  claim 7  wherein the PEPC and PCK enzymes form a photosynthetic pathway in a single cell to mimic the photosynthetic pathway of a C4 plant, in concert with a gene coding for a carbonic anhydrase (CA) and a gene coding for a pyruvate, orthophosphate dikinase (PPDK).  
     
     
         9 . The transformed C3 plant according to  claim 8  wherein each of the PEPC gene and the PCK gene is operably linked to a promoter specific to a photosynthetic tissue.  
     
     
         10 . The transformed C3 plant according to  claim 8  or  9  wherein one or both of the CA gene and the PPDK gene are endogenous to the C3 plant.  
     
     
         11 . The transformed C3 plant according to  claim 8  or  9  wherein one or both of the CA gene and the PPDK gene are isolated from another plant and operably linked to a promoter specific to a photosynthetic tissue.  
     
     
         12 . The method according to  claim 2  which further comprises introducing a gene coding for a pyruvate, orthophosphate dikinase (PPDK) into the rice plant, wherein the PPDK gene is operably linked to a promoter.  
     
     
         13 . The method according to  claim 1  wherein said C3 plant is monocotyledon.  
     
     
         14 . The method according to  claim 13 , wherein said monocotyledon is selected from the group consisting of rice, wheat and barley.  
     
     
         15 . The transformed C3 plant as claimed in  claim 7  or  8 , wherein said C3 plant is monocotyledon.  
     
     
         16 . The transformed C3 plant as claimed in  claim 15 , wherein said monocotyledon is selected from the group consisting of rice, wheat or barley.