title: RNAi trigger fragment truncation attenuates soybean FAD2-1 transcript suppression and yields intermediate oil phenotypes.
abstract: Suppression of the microsomal ω6 oleate desaturase during the seed development of soybean (Glycine max) with the 420-bp soybean FAD2-1A intron as RNAi trigger shifts the conventional fatty acid composition of soybean oil from 20% oleic and 60% polyunsaturates to one containing greater than 80% oleic acid and less than 10% polyunsaturates. To determine whether RNAi could be attenuated by reducing the trigger fragment length, transgenic plants were generated to express successively shorter 5' or 3' deletion derivatives of the FAD2-1A intron. We observed a gradual reduction in transcript suppression with shorter trigger fragments. Fatty acid composition was less affected with shorter triggers, and triggers less than 60 bp had no phenotypic effect. No trigger sequences conferring significantly higher or lower suppression efficiencies were found, and the primary determinant of suppression effect was sequence length. The observed relationship of transcript suppression with the induced fatty acid phenotype indicates that RNAi is a saturation process and not a step change between suppressed and nonsuppressed states and intermediate suppression states can be achieved.
authors.affiliation: Monsanto Company, Calgene Campus, Davis, CA, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Wagner
authors.forename: Andrew
authors.initials: A
authors.lastname: Mroczka
authors.forename: Peter D
authors.initials: PD
authors.lastname: Roberts
authors.forename: William
authors.initials: W
authors.lastname: Schreckengost
authors.forename: Toni
authors.initials: T
authors.lastname: Voelker
mesh_terms: D044943:Fatty Acid Desaturases / Q000235:genetics* / Q000378:metabolism; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000032:analysis / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D007438:Introns / Q000235:genetics; D019301:Oleic Acid / Q000032:analysis / Q000378:metabolism; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D034622:RNA Interference; D018749:RNA, Plant / Q000235:genetics; D012639:Seeds / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D013024:Soybean Oil / Q000737:chemistry*; D013025:Glycine max / Q000737:chemistry / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D010940:Plant Proteins; D018749:RNA, Plant; D019301:Oleic Acid; D013024:Soybean Oil; D044943:Fatty Acid Desaturases; C040448:delta-12 fatty acid desaturase