Method for changing nitrogen utilization efficiency in plants

Abstract

The present invention provides a method for changing nitrogen utilization efficiency in a plant comprises regulating the expression of Arabidopsis NRT 1.7 or an orthologue thereof so that the nitrate remobilization from older leaves to young leaves in the plant is regulated, thereby the nitrogen utilization efficiency is changed. The present invention also provides a transgenic plant obtainable by transforming a plant with an expression construct with a high or low level of expression of NRT 1.7. On the other hand, the present invention yet provides a chimera nitrate transporter, a DNA molecule coding for this chimera transporter and an expression vector thereof.

1 . A method for changing nitrogen utilization efficiency in a plant comprises regulating the expression of  Arabidopsis  NRT1.7 or an orthologue thereof so that the nitrate remobilization from older leaves to young leaves in the plant is regulated, thereby the nitrogen utilization efficiency is changed. 
     
     
         2 . The method of  claim 1 , which comprises transforming a plant with an expression construct with a high level of expression of  Arabidopsis  NRT1.7 or an orthologue thereof to enhance the nitrogen utilization efficiency. 
     
     
         3 . The method of  claim 1 , which comprises transforming a plant with an expression construct with a low level of expression of  Arabidopsis  NRT1.7 or an orthologue thereof to decrease the nitrogen utilization efficiency. 
     
     
         4 . The method of  claim 2 , wherein the expression of NRT1.7 or an orthologue thereof is enhanced by an enhancer. 
     
     
         5 . The method of  claim 2 , wherein NRT1.7 is overexpressed in a plant by transforming an expression construct comprising a nucleic acid sequence of NRT1.7 and an enhance into the plant to produce a transgenic plant. 
     
     
         6 . The method of  claim 4 , wherein the enhancer is 35S enhancer. 
     
     
         7 . The method of  claim 5 , wherein the 35S enhancer has a nucleotide sequence of SEQ ID NO: 4. 
     
     
         8 . The method of  claim 3 , wherein the quantity or activity of NRT1.7 is decreased or the expression of NRT1.7 is inhibited to causes a defect in remobilizing nitrogen from older leaves to younger leaves so as to retard growth in the plant. 
     
     
         9 . The method of  claim 3 , wherein the expression of NRT1.7 mRNA is inhibited to decrease quantity or availability of functional NRT1.7. 
     
     
         10 . A transgenic plant, which is transformed with an expression construct causing overexpression of NRT1.7 or enhancement of NRT1.7 function within the transgenic plant, whereby the transgenic plant enhances the nitrogen remobilization from older leaves to young leaves in the plant, and the nitrogen use efficiency is improved. 
     
     
         11 . The transgenic plant of  claim 10 , wherein the growth of the transgenic plant is enhanced. 
     
     
         12 . A transgenic plant, which is transformed with an construct that has a defect in the gene of NRT1.7, wherein the defect results in inhibiting the expression of NRT 1.7 or NRT1.7 mRNA to decrease quantity or availability of functional NRT1.7, whereby the nitrogen remobilization from older leaves to younger leaves in the transgenic plant is defective. 
     
     
         13 . The transgenic plant of  claim 12 , wherein the growth of the transgenic plant is retarded. 
     
     
         14 . A chimera nitrate transporter protein having the amino acid sequence of SEQ ID NO:  11 . 
     
     
         15 . An isolated DNA molecule encoding the chimera nitrate transporter protein having the amino acid sequence of SEQ ID NO: 11 of  claim 14 . 
     
     
         16 . The DNA molecule of  claim 15  comprising the nucleotide sequence of SEQ ID NO:10. 
     
     
         17 . An expression vector comprising the DNA molecule having the nucleotide sequence coding for NRT1.7 operatively liked to a promoter. 
     
     
         18 . The expression vector of  claim 17 , wherein the promoter is a NRT1.7 promoter. 
     
     
         19 . The expression vector of  claim 17 , which further comprises an enhancer. 
     
     
         20 . The expression vector of  claim 19 , wherein the enhancer is 35S enhancer. 
     
     
         21 . A transgenic plant, which is transformed with an expression construct comprising a DNA molecule encoding the chimera nitrate transporter protein having the amino acid sequence of SEQ ID NO:11, whereby the nitrogen utilization efficiency in the transgenic plant is improved. 
     
     
         22 . The transgenic plant of  claim 21 , wherein the DNA molecule is driven by a NRT 1.7 promoter.