Plant haemoglobin

Abstract

The invention relates generally to a method for improving growth of plants, under normal and under stress conditions, more particularly under osmotic stress and/or temperature extremes, comprising modifying plant haemoglobin gene expression and/or by modifying plant haemoglobin protein levels in a plant. The invention furthermore relates to a method for increasing yield of a plant, comprising modifying plant gene expression and/or by modifying plant haemoglobin levels in a plant. The invention also relates to a nucleic acid encoding a haemoglobin conferring this altered growth and stress tolerance.

1 . An isolated nucleic acid encoding a plant class-2 non-symbiotic haemoglobin selected from:
 (i) a nucleic acid sequence comprising a sequence according to SEQ ID NO:1 or the complement thereof;   (ii) a nucleic acid sequence encoding a protein with an amino acid sequence which is at least, in increasing order of preference, 79%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identical to the amino acid sequence as given in SEQ ID NO:2;   (iii) a nucleic acid sequence encoding a protein comprising the amino acid sequence as given in SEQ ID NO:2;   (iv) a nucleic acid sequence according to any of (i) to (iii) which is degenerate as a result of the genetic code;   (v) a nucleic acid sequence which is a splice variant of a nucleic acid according to any of (i) to (iv);   (vi) a nucleic acid sequence which is divergent due to differences between alleles encoding a protein as given in SEQ ID NO:2, or as defined in (i) to (v);   (vii) a nucleic acid sequence encoding an immunologically active and/or functional fragment of a protein encoded by a DNA sequence according to any of (i) to (vi); and,   (viii) a nucleic acid sequence which hybridises under stringent conditions to any one of the sequences defined in (i) to (vii),   
       with the proviso that none of (i) to (viii) include the sequence as given in GenBank acc no BE590299 or BQ586966. 
     
     
         2 . A nucleic acid construct comprising:
 (i) isolated nucleic acid sequence according to  claim 1 ;   (ii) one or more control sequences controlling expression of the nucleic acid sequence of (i); and optionally,   (iii) a transcription terminator sequence.   
     
     
         3 . Construct of  claim 2  wherein said isolated nucleic acid sequence is as represented by SEQ ID NO:1. 
     
     
         4 . A host cell comprising a nucleic acid according to  claim 1  or a construct comprising (a) said nucleic acid sequence; (b) one or more control sequences controlling expression of the nucleic acid sequences of (a); and optionally, (c) transcription terminator sequence, wherein said host cell is a bacterial, yeast, fungal, plant or animal cell. 
     
     
         5 . Method for producing a transgenic plant having altered growth characteristics comprising the steps of:
 (i) introducing into a plant or plant cell a nucleic acid sequence according to  claim 1 ;   (ii) cultivating said plant or plant cell under conditions promoting regeneration and/or mature plant growth.   
     
     
         6 . Plant cell, plant part or plant having increased tolerance to high temperature stress, said plant cell, plant part or plant having increased expression of a nucleic acid sequence encoding a plant haemoglobin protein. 
     
     
         7 . A method of increasing abiotic stress tolerance of a plant comprising expressing a nucleic acid sequence encoding a plant class-2 non-symbiotic haemoglobin in said plant. 
     
     
         8 . The method of  claim 7 , wherein said abiotic stress is osmotic stress. 
     
     
         9 . The method of  claim 8 , wherein said nucleic acid sequence encoding a plant class-2 non-symbiotic haemoglobin is isolated from a dicotyledonous plant, preferably from Brassicaceae, more preferably from Beta vulgaris, most preferably the isolated nucleic acid is as represented by SEQ ID NO:1. 
     
     
         10 . A method of increasing high temperature tolerance of a plant comprising expressing a nucleic acid sequence encoding a plant haemoglobin in said plant, preferably said plant haemoglobin is a non-symbiotic haemoglobin, more preferably a class-2 non-symbiotic haemoglobin. 
     
     
         11 . The method of  claim 10 , wherein said nucleic acid sequence encoding plant class-2 non-symbiotic haemoglobin is isolated from a dicotyledonous plant, preferably from Brassicaceae, more preferably from  Beta vulgaris,  most preferably the isolated nucleic acid is as represented by SEQ ID NO:1.