Polyunsaturated fatty acids in plants

Abstract

The present invention relates to compositions and methods for preparing polyunsaturated long chain fatty acids in plants, plant parts and plant cells, such as leaves, roots, fruits and seeds. Nucleic acid sequences and constructs encoding fatty acid desaturases, including Δ5-desaturases, Δ6-desaturases and Δ12-desaturases, are used to generate transgenic plants, plant parts and cells which contain and express one or more transgenes encoding one or more desaturases. Expression of the desaturases with different substrate specificities in the plant system permit the large scale production of polyunsaturated long chain fatty acids such as docosahexaenoic acid, eicosapentaenoic acid, α-linolenic acid, gamma-linolenic acid, arachidonic acid and the like for modification of the fatty acid profile of plants, plant parts and tissues. Manipulation of the fatty acid profiles allows for the production of commercial quantities of novel plant oils and products.

1. A method for producing stearidonic acid in a plant seed, said method comprising:
 growing a plant having integrated into its genome:  
 a first DNA construct comprising, in the 5′ to 3′ direction of transcription, a promoter functional in a plant seed cell, a DNA sequence encoding a delta-six desaturase from the genus Mortierella, and a transcription termination region functional in a plant cell,  
 a second DNA construct comprising, in the  5 ′ to  3 ′ direction of transcription, a promoter function in a plant seed cell, and a DNA sequence encoding a delta  15  desaturase, and a transcription termination region functional in a plant cell, and  
   a third DNA construct comprising, in the  5 ′ to  3 ′ direction of transcription, a promoter functional in a plant seed cell, and a DNA sequence encoding a delta  12  desaturase, and a transcription termination region functional in a plant cell,   
 and growing said plant under conditions whereby said delta-six desaturase, delta  15  desaturase and delta  12  desaturase is  are expressed.  
 
     
     
       2. The method according to  claim 1  wherein said plant has a second construct integrated into its genome, wherein said second construct has in the 5′ to 3′ direction of transcription, a promoter functional in a plant seed cell, and a DNA sequence encoding a delta 12 desaturase. 
     
     
       3. The method according to  claim 1  wherein said plant has a second construct integrated into its genome, wherein said second construct has in the 5′ to 3′ direction of transcription, a promoter functional in a plant seed cell,and a DNA sequence encoding a delta 15 desaturase. 
     
     
       4. The method of  claim 1  wherein said desaturase encoding sequence is from the genus Mortierella. 
     
     
       5. The method according to  claim 1 , wherein said promoter for the first DNA construct is a napin promoter. 
     
     
       6. The method according to  claim 1 , wherein said promoter for the first DNA construct is from the soybean β-conglycinin 7S subunit transcription initiation region. 
     
     
       7. The method according to  claim 1 , wherein said method further comprises extracting oil from said plant seed. 
     
     
       8. The method of  claim 7 , wherein said oil comprises about 5 weight percent or greater stearidonic acid. 
     
     
       9. The method of  claim 7 , wherein said oil comprises about 10 weight percent or greater stearidonic acid. 
     
     
       10. The method of  claim 7 , wherein said oil comprises about 15 weight percent or greater stearidonic acid. 
     
     
       11. The method of  claim 7 , wherein said oil comprises about 20 weight percent or greater stearidonic acid. 
     
     
       12. The method of  claim 7 , wherein said oil comprises about 25 weight percent or greater stearidonic acid. 
     
     
       13. A method for producing stearidonic acid in a plant seed, said method comprising:
   growing a plant having integrated into its genome;        a first DNA construct comprising, in the  5 ′ to  3 ′ direction of transcription, a promoter functional in a plant seed cell, a DNA sequence encoding a delta - six desaturase, and a transcription termination region functional in a plant cell,        a second DNA construct comprising, in the  5 ′ to  3 ′ direction of transcription, a promoter functional in a plant seed cell, and a DNA sequence encoding a delta  15  desaturase, and a transcription termination region functional in a plant cell, and        a third DNA construct comprising, in the  5 ′ to  3 ′ direction of transcription, a promoter functional in a plant seed cell, and a DNA sequence encoding a delta  12  desaturase, and a transcription termination region functional in a plant cell, and        growing said plant under conditions whereby said delta - six desaturase, delta  15  desaturase, and delta -   12  desaturase are expressed.     
     
     
       14. The method according to  claim 13 , wherein said promoter for the first DNA construct is a napin promoter. 
     
     
       15. The method according to  claim 13 , wherein said promoter for the first DNA construct is from the soybean β- conglycinin  7 S subunit transcription initiation region.   
     
     
       16. The method according to  claim 13 , wherein said method further comprises extracting oil from said plant seed. 
     
     
       17. The method of  claim 16 , wherein said oil comprises about  5  weight percent or greater stearidonic acid. 
     
     
       18. The method of  claim 16 , wherein said oil comprises about  10  weight percent or greater stearidonic acid. 
     
     
       19. The method of  claim 16 , wherein said oil comprises about  15  weight percent or greater stearidonic acid. 
     
     
       20. The method of  claim 16 , wherein said oil comprises about  20  weight percent or greater stearidonic acid. 
     
     
       21. The method of  claim 16 , wherein said oil comprises about  25  weight percent or greater stearidonic acid.