Method of producing transgenic plants having improved amino acid composition and improved yielding

Abstract

The object of the present invention is to provide transgenic plants which accumulate free amino acids, particularly at least one amino acid selected from among glutamic acid, asparagine, aspartic acid, serine, threonine, alanine and histidine accumulated in a large amount, in the edible parts thereof, and a method of producing them are provided. The other object of the present invention is to provide a method of increasing the yielding of potato and to provide a transgenic potato of which yielding can be increased. In the present invention, a sequence encoding glutamate dehydrogenase (GDH) gene is introduced into a plant together with a suitable regulatory sequence to express it in a plant cell, and thereby the GDH gene is excessively expressed.

What is claimed is:  
     
         1 . A method of producing a transgenic plant containing one or more free amino acids in edible parts in an amount larger than that contained in a untransformed plant of the same species cultured under the same conditions, which comprises the step of transforming a plant with a genetic construct causing excessive expression of a glutamate dehydrogenase (GDH) gene, selecting or identifying the transformed plant based on a characteristics imparted by a marker gene connected to the genetic construct, screening the transformed plant in which one or more amino acids are accumulated in a larger amount and selecting the transformed plant in which one or more free amino acids are accumulated in a larger amount.  
     
     
         2 . The method according to  claim 1 , wherein the genetic construct contains a gene encoding GDH functionally connected to a powerful constitutive promoter or fruit-specific promoter.  
     
     
         3 . The method according to  claim 2 , wherein the constitutive promoter is CaMV35S promoter and the fruit-specific promoter is 2A11 promoter.  
     
     
         4 . The method according to  claim 1 , wherein the genetic construct is selected from the group consisting of pAN-gdh-17, pCt-AN-gdh, pCt-dAN-gdh, pMt-dAN-gdh, p2ACt-dAN-gdh and p2AMt-dAN-gdh, each of said genetic construct containing NADP-GDH gene derived  Aspergillus nidulans.    
     
     
         5 . The method according to  claim 1 , wherein the genetic construct is pT-gdh-4 or ptd-gdh containing tomato NAD-GDH gene.  
     
     
         6 . The method according to  claim 1 , wherein the free amino acid is selected from the group consisting of asparagine, aspartic acid, serine, threonine, alanine, histidine and glutamic acid.  
     
     
         7 . The method according to  claim 6 , wherein one of the free amino acids is free glutamic acid.  
     
     
         8 . The method according to  claim 1 , wherein the transgenic plant is a transgenic tomato.  
     
     
         9 . The method according to  claim 1 , wherein the transgenic plant is a transgenic potato.  
     
     
         10 . A transgenic plants produced by the method according to  claim 1  or a progeny plant thereof, which contains the genetic construct excessively express glutamate dehydrogenase.  
     
     
         11 . A transgenic plant produced by the method according to  claim 1 , which has a glutamic acid content of an edible part thereof of at least twice as high as a corresponding untransformed plant, or a progeny plant thereof which has a glutamic acid content of the edible parts thereof of at least twice as high.  
     
     
         12 . A transgenic plant produced by the method according to  claim 1 , wherein the total free amino acid content of an edible parts thereof is at least twice as high as a corresponding natural plant, or a progeny thereof wherein the total free amino acid content of an edible parts thereof is increased to at least twice as high.  
     
     
         13 . A seed of the transgenic plant according to  claim 10  or a seed of the progeny thereof, which contains a genetic construct which excessively expresses glutamate dehydrogenase.  
     
     
         14 . A transgenic potato, wherein said potato contains a genetic construct being able to express a GDH gene, and the total weight of tuber parts of the potato exhibits statistically significant increase compared to a untransformed potato cultured under the same conditions.  
     
     
         15 . The transgenic potato according to  claim 14 , wherein said potato contains a genetic construct being able to express a GDH gene, and the total weight of tuber parts of the potato exhibits 1.5-fold or more increase compared to a untransformed potato cultured under the same conditions.  
     
     
         16 . The transgenic potato according to  claim 14 , wherein the genetic construct contains a gene encoding GDH functionally connected to a powerful constitutive promoter.  
     
     
         17 . The transgenic potato according to  claim 16 , wherein the constitutive promoter is CaMV35S promoter.  
     
     
         18 . The transgenic potato according to  claim 14 , wherein the genetic construct contains  Aspergillus nidulans  NADP-GDH gene.  
     
     
         19 . The transgenic potato according to  claim 14 , wherein GDH contains a transit peptide for mitochondria.  
     
     
         20 . A method of producing a transgenic potato increased in the total weight of the tuber parts compared to a untransformed potato cultured under the same conditions, which comprises the step of transforming a plant with a genetic construct causing excessive expression of a glutamate dehydrogenase (GDH) gene, and selecting or identifying the transformed plant based on a character imparted by a marker gene connected to the genetic construct, screening the transformed plant in which the total weight of the tuber parts is increased and selecting the transformed plant in which the total weight of the tuber parts is increased.  
     
     
         21 . The method according to  claim 20 , wherein the total weight of the tuber parts of the potato exhibits 1.5-fold or more increase compared to a untransformed potato cultured under the same conditions.  
     
     
         22 . The method according to  claim 20 , wherein the genetic construct contains a gene encoding GDH functionally connected to a powerful constitutive promoter.  
     
     
         23 . The method according to  claim 20 , wherein the constitutive promoter is CaMV35S promoter.  
     
     
         24 . The method according to  claim 20 , wherein the genetic construct contains  Aspergillus nidulans  NADP-GDH gene.  
     
     
         25 . The method according to  claim 20 , wherein GDH contains a transit peptide for mitochondria.