Fad4, fad5, fad5-2, and fad6, novel fatty acid desaturase family members and uses thereof

Abstract

The invention provides isolated nucleic acid molecules which encode novel fatty acid desaturase family members. The invention also provides recombinant expression vectors containing desaturase nucleic acid molecules, host cells into which the expression vectors have been introduced, and methods for large-scale production of long chain polyunsaturated fatty acids (LCPUFAs), e.g., DHA.

1 . (canceled) 
     
     
         2 . A method for producing high levels of gamma-linolenic acid (GLA) in a plant, comprising:
 a) selecting a first plant line having high content of linoleic acid (LA) relative to a second plant line of the same plant species; and   b) providing at least one Δ6 desaturase in said first plant line,   wherein the level of GLA produced in said first plant line is higher than the level of GLA produced in the second plant line expressing the Δ6 desaturase.   
     
     
         3 . The method of  claim 2 , wherein said at least one Δ6 desaturase comprises a cytochrome b5-like domain 
     
     
         4 . The method of  claim 3 , wherein said at least one Δ6 desaturase further comprises at least two histidine motifs. 
     
     
         5 . The method of  claim 3 , wherein said at least one Δ6 desaturase comprises three histidine motifs. 
     
     
         6 . The method of  claim 2 , wherein said at least one Δ6 desaturase has at least 70% sequence identity to the amino acid sequence of SEQ ID NO: 8. 
     
     
         7 . The method of  claim 2 , wherein said at least one Δ6 desaturase comprises:
 a) the amino acid sequence of SEQ ID NO: 8; or 
 b) an amino acid sequence encoded by the nucleotide sequence of SEQ ID NO: 7. 
 
     
     
         8 . The method of  claim 2 , wherein the plant species is a  Brassica  species. 
     
     
         9 . The method of  claim 2 , wherein the plant species is a  Brassica  species, and wherein the first plant line produces GLA at a level of 30% to 38% of the total fatty acids in seeds. 
     
     
         10 . The method of  claim 9 , wherein the first plant line further produces stearidonic acid (SDA) at a level of 3% to 10% of the total fatty acids in seeds. 
     
     
         11 . The method of  claim 2 , wherein the plant species is a  Brassica  species, and wherein the level of LA in the first plant line is reduced to less than 10%. 
     
     
         12 . The method of  claim 2 , wherein the plant species is a  Brassica  species, and wherein the level of linolenic acid in the first plant line is reduced to 5%. 
     
     
         13 . The method of  claim 2 , wherein the plant species is a  Brassica  species, and wherein the level of LA in the first plant line is reduced to less than 10% and the level of linolenic acid in the first plant line is reduced to 5%. 
     
     
         14 . A method for the production of unsaturated fatty acids, comprising:
 a) producing high levels of GLA in a plant according to the method of  claim 2 ; and   b) isolating unsaturated fatty acids from said plant.   
     
     
         15 . The method of  claim 14 , wherein said unsaturated fatty acids are isolated from seeds of said plant. 
     
     
         16 . The method of  claim 14 , wherein said unsaturated fatty acids are isolated in form of lipids. 
     
     
         17 . A composition comprising the unsaturated fatty acids produced in  claim 14 . 
     
     
         18 . A dietary supplement, animal feed, a neutraceutical, or a pharmaceutical composition comprising the unsaturated fatty acids produced in  claim 14 .