title: Toward production of jet fuel functionality in oilseeds: identification of FatB acyl-acyl carrier protein thioesterases and evaluation of combinatorial expression strategies in Camelina seeds.
abstract: Seeds of members of the genus Cuphea accumulate medium-chain fatty acids (MCFAs; 8:0-14:0). MCFA- and palmitic acid- (16:0) rich vegetable oils have received attention for jet fuel production, given their similarity in chain length to Jet A fuel hydrocarbons. Studies were conducted to test genes, including those from Cuphea, for their ability to confer jet fuel-type fatty acid accumulation in seed oil of the emerging biofuel crop Camelina sativa. Transcriptomes from Cuphea viscosissima and Cuphea pulcherrima developing seeds that accumulate >90% of C8 and C10 fatty acids revealed three FatB cDNAs (CpuFatB3, CvFatB1, and CpuFatB4) expressed predominantly in seeds and structurally divergent from typical FatB thioesterases that release 16:0 from acyl carrier protein (ACP). Expression of CpuFatB3 and CvFatB1 resulted in Camelina oil with capric acid (10:0), and CpuFatB4 expression conferred myristic acid (14:0) production and increased 16:0. Co-expression of combinations of previously characterized Cuphea and California bay FatBs produced Camelina oils with mixtures of C8-C16 fatty acids, but amounts of each fatty acid were less than obtained by expression of individual FatB cDNAs. Increases in lauric acid (12:0) and 14:0, but not 10:0, in Camelina oil and at the sn-2 position of triacylglycerols resulted from inclusion of a coconut lysophosphatidic acid acyltransferase specialized for MCFAs. RNA interference (RNAi) suppression of Camelina β-ketoacyl-ACP synthase II, however, reduced 12:0 in seeds expressing a 12:0-ACP-specific FatB. Camelina lines presented here provide platforms for additional metabolic engineering targeting fatty acid synthase and specialized acyltransferases for achieving oils with high levels of jet fuel-type fatty acids.
authors.affiliation: Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
authors.forename: Hae Jin
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
authors.forename: Jillian E
authors.initials: JE
authors.lastname: Silva
authors.affiliation: Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
authors.forename: Hieu Sy
authors.initials: HS
authors.lastname: Vu
authors.affiliation: Department of Biology, and Center for Genomics and Bioinformatics, Indiana University, Bloomington, IN 47405, USA.
authors.forename: Keithanne
authors.initials: K
authors.lastname: Mockaitis
authors.affiliation: Donald Danforth Plant Science Center, Saint Louis, MO 63132, USA.
authors.forename: Jeong-Won
authors.initials: JW
authors.lastname: Nam
authors.affiliation: Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE 68588, USA ecahoon2@unl.edu.
authors.forename: Edgar B
authors.initials: EB
authors.lastname: Cahoon
mesh_terms: D000595:Amino Acid Sequence; D031562:Cuphea / Q000196:embryology / Q000201:enzymology / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D008969:Molecular Sequence Data; D010170:Palmitoyl-CoA Hydrolase / Q000737:chemistry / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D012639:Seeds / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D005227:Fatty Acids; D010170:Palmitoyl-CoA Hydrolase
keywords: Camelina; Cuphea; FatB acyl-ACP thioesterase; jet fuel oilseed; medium-chain fatty acid.