High-level production of gamma-linolenic acid in Brassica juncea using a delta6 desaturase from Pythium irregulare.
gamma-Linolenic acid (GLA), a nutritionally important fatty acid in mammals, is synthesized by a delta6 desaturase. Here, we report identification of PiD6, a new cDNA from the oleaginous fungus, Pythium irregulare, encoding a 459-amino acid protein that shares sequence similarity to carboxyl-directed desaturases from various species. Expression of PiD6 in yeast (Saccharomyces cerevisiae) revealed that it converts exogenously supplied linoleic acid into GLA, indicating that it encodes a delta6 fatty acid desaturase. Expression of the desaturase in Brassica juncea under the control of the Brassica napus napin promoter resulted in production of three delta6 unsaturated fatty acids (18:2-6, 9; 18:3-6, 9, 12; and 18:4-6, 9, 12, 15) in seeds. Among them, GLA (18:3-6, 9, 12) is the most abundant and accounts for up to 40% of the total seed fatty acids. Lipid class and positional analysis indicated that GLA is almost exclusively incorporated into triacylglycerol (98.5%) with only trace amounts found in the other lipids. Within triacylglycerols, GLA is more abundant at the sn-2 position.
Hong
Haiping
H
National Research Council of Canada, Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, Saskatchewan, Canada S7N 0W9.
Datla
Nagamani
N
Reed
Darwin W
DW
Covello
Patrick S
PS
MacKenzie
Samuel L
SL
Qiu
Xiao
X
D000595:Amino Acid Sequence; D001937:Brassica / Q000235:genetics / Q000378:metabolism*; D002849:Chromatography, Gas; D003001:Cloning, Molecular; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D011775:Pythium / Q000201:enzymology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014280:Triglycerides / Q000378:metabolism; D017965:gamma-Linolenic Acid / Q000096:biosynthesis*
D005227:Fatty Acids; D014280:Triglycerides; D017965:gamma-Linolenic Acid; D044943:Fatty Acid Desaturases