High-stearic and High-oleic cottonseed oils produced by hairpin RNA-mediated post-transcriptional gene silencing.
We have genetically modified the fatty acid composition of cottonseed oil using the recently developed technique of hairpin RNA-mediated gene silencing to down-regulate the seed expression of two key fatty acid desaturase genes, ghSAD-1-encoding stearoyl-acyl-carrier protein Delta 9-desaturase and ghFAD2-1-encoding oleoyl-phosphatidylcholine omega 6-desaturase. Hairpin RNA-encoding gene constructs (HP) targeted against either ghSAD-1 or ghFAD2-1 were transformed into cotton (Gossypium hirsutum cv Coker 315). The resulting down-regulation of the ghSAD-1 gene substantially increased stearic acid from the normal levels of 2% to 3% up to as high as 40%, and silencing of the ghFAD2-1 gene resulted in greatly elevated oleic acid content, up to 77% compared with about 15% in seeds of untransformed plants. In addition, palmitic acid was significantly lowered in both high-stearic and high-oleic lines. Similar fatty acid composition phenotypes were also achieved by transformation with conventional antisense constructs targeted against the same genes, but at much lower frequencies than were achieved with the HP constructs. By intercrossing the high-stearic and high-oleic genotypes, it was possible to simultaneously down-regulate both ghSAD-1 and ghFAD2-1 to the same degree as observed in the individually silenced parental lines, demonstrating for the first time, to our knowledge, that duplex RNA-induced posttranslational gene silencing in independent genes can be stacked without any diminution in the degree of silencing. The silencing of ghSAD-1 and/or ghFAD2-1 to various degrees enables the development of cottonseed oils having novel combinations of palmitic, stearic, oleic, and linoleic contents that can be used in margarines and deep frying without hydrogenation and also potentially in high-value confectionery applications.
Liu
Qing
Q
Commonwealth Scientific and Industrial Research Organization Plant Industry, P.O. Box 1600, Canberra, Australian Capitol Territory 2601, Australia.
Singh
Surinder P
SP
Green
Allan G
AG
D003433:Crosses, Genetic; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D003368:Gossypium / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019301:Oleic Acid / Q000096:biosynthesis; D019308:Palmitic Acid / Q000378:metabolism; D010938:Plant Oils / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D012323:RNA Processing, Post-Transcriptional; D016337:RNA, Catalytic / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012639:Seeds / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013229:Stearic Acids / Q000378:metabolism; D013230:Stearoyl-CoA Desaturase
D005227:Fatty Acids; D010938:Plant Oils; D010940:Plant Proteins; D016337:RNA, Catalytic; D012333:RNA, Messenger; D013229:Stearic Acids; C418481:hairpin ribozyme; D019301:Oleic Acid; D019308:Palmitic Acid; C031183:stearic acid; D044943:Fatty Acid Desaturases; D013230:Stearoyl-CoA Desaturase; C040448:delta-12 fatty acid desaturase; C029627:delta-9 fatty acid desaturase