title: Identification and expression of a new delta-12 fatty acid desaturase (FAD2-4) gene in upland cotton and its functional expression in yeast and Arabidopsis thaliana plants.
abstract: A cotton (Gossypium hirsutum L.) genomic clone encompassing a 17.9-kb DNA fragment was found to contain a delta-12 fatty acid desaturase gene (designated FAD2-4). The FAD2-4 open reading frame has 1,155bp and is uninterrupted, encoding a conceptual FAD2-4 polypeptide of 384 amino acids that has 98% identity with the cotton FAD2-3 polypeptide. The FAD2-4 gene has a single intron of 2,780 bp in its 5'-untranslated region (5'-UTR). The 3'-flanking regions and 5'-UTR introns in the FAD2-4 and FAD2-3 genes are quite different, indicating that the genes might be paralogs in the cotton genome. Reverse transcriptase (RT)-PCR analysis indicated that the FAD2-4 and FAD2-3 genes were expressed in all tissues examined, including seeds, seedling tissues, young and mature leaves, roots, stems, developing flower buds, and ovule fibers. These constitutive patterns of expression were notably different from that of the FAD2-1 gene, which was restricted to seeds and developing flower buds, or to the expression of a newly-identified FAD2-2 gene isoform, which was barely detectable in roots, hypocotyls, stems, and fibers, but was expressed in all other tissues. The FAD2-4 coding region was expressed in yeast and shown to encode a functional delta-12 desaturase, converting oleic acid (C18:1) to linoleic acid (C18:2) in recombinant yeast cells. In addition, both the FAD2-4 and the FAD2-3 genes were transferred into the Arabidopsis thaliana fad2-1 mutant background where they effectively restored wild type fatty acid composition and growth characteristics. Finally, the cotton FAD2-4 green fluorescent protein (GFP) fusion polypeptide appeared to be localized in the endomembrane system of transgenic Arabidopsis plants in the complemented fad2-1 mutant background, supporting a functional ER location for the cotton FAD2-4 polypeptide in this heterologous plant system. Thus, a new functional member of the FAD2 gene family in cotton has been characterized, indicating a complex regulation of membrane lipid desaturation in this important fiber/oilseed crop.
authors.affiliation: Department of Biological Sciences, Center for Plant Lipid Research, University of North Texas, Denton, TX 76203-5217, USA.
authors.forename: Daiyuan
authors.initials: D
authors.lastname: Zhang
authors.forename: Irma L
authors.initials: IL
authors.lastname: Pirtle
authors.forename: Stacy J
authors.initials: SJ
authors.lastname: Park
authors.forename: Mongkol
authors.initials: M
authors.lastname: Nampaisansuk
authors.forename: Purnima
authors.initials: P
authors.lastname: Neogi
authors.forename: Sylvia W
authors.initials: SW
authors.lastname: Wanjie
authors.forename: Robert M
authors.initials: RM
authors.lastname: Pirtle
authors.forename: Kent D
authors.initials: KD
authors.lastname: Chapman
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D004721:Endoplasmic Reticulum; D044943:Fatty Acid Desaturases / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D017343:Genes, Plant; D003368:Gossypium / Q000201:enzymology / Q000235:genetics*; D019787:Linoleic Acid / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D019301:Oleic Acid / Q000235:genetics / Q000378:metabolism; D010938:Plant Oils / Q000378:metabolism; D018514:Plant Structures / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D014170:Transformation, Genetic
chemical_list: D018744:DNA, Plant; D010938:Plant Oils; D019301:Oleic Acid; D019787:Linoleic Acid; D044943:Fatty Acid Desaturases; C040448:delta-12 fatty acid desaturase