title: Sunflower HaGPAT9-1 is the predominant GPAT during seed development.
abstract: In oil crops, triacylglycerol biosynthesis is an important metabolic pathway in which glycerol-3-phosphate acyltransferase (GPAT) performs the first acylation step. Mass spectrometry analysis of developing sunflower (Helianthus annuus) seed membrane fractions identified an abundant GPAT, HaGPAT9 isoform 1, with a N-terminal peptide that possessed two phosphorylated residues with possible regulatory function. HaGPAT9-1 belongs to a broad eukaryotic GPAT family, similar to mammalian GPAT3, and it represents one of the two sunflower GPAT9 isoforms, sharing 90% identity with HaGPAT9-2. Both sunflower genes are expressed during seed development and in vegetative tissues, with HaGPAT9-1 transcripts accumulating at relatively higher levels than those for HaGPAT9-2. Green fluorescent protein tagging of HaGPAT9-1 confirmed its subcellular accumulation in the endoplasmic reticulum. Despite their overall sequence similarities, the two sunflower isoforms displayed significant differences in their enzymatic activities. For instance, HaGPAT9-1 possesses in vivo GPAT activity that rescues the lethal phenotype of the cmy228 yeast strain, while in vitro assays revealed a preference of HaGPAT9-1 for palmitoyl-, oleoyl- and linoleoyl-CoAs of one order of magnitude, with the highest increase in yield for oleoyl- and linoleoyl-CoAs. By contrast, no enzymatic activity could be detected for HaGPAT9-2, even though its over-expression modified the TAG profile of yeast.
authors.affiliation: Department of Biochemistry and Molecular Biology of Plant Products, Instituto de la Grasa (CSIC), Campus Universitario Pablo de Olavide, 41013 Seville, Spain; Department of Entomology & Plant Pathology, University of Tennessee, Knoxville, TN 37996, United States.
authors.forename: Miriam
authors.initials: M
authors.lastname: Payá-Milans
authors.affiliation: Department of Biochemistry and Molecular Biology of Plant Products, Instituto de la Grasa (CSIC), Campus Universitario Pablo de Olavide, 41013 Seville, Spain; Department of Biochemistry & Molecular Biophysics, Kansas State University, Manhattan, KS 66506, United States.
authors.forename: Jose Antonio
authors.initials: JA
authors.lastname: Aznar-Moreno
authors.affiliation: Department of Biochemistry and Interdisciplinary Plant Group, University of Missouri, Columbia, MO 65211, United States; Department of Technology, São Paulo State University, Jaboticabal, São Paulo, Brazil.
authors.forename: Tiago S
authors.initials: TS
authors.lastname: Balbuena
authors.affiliation: Department of Biological Chemistry and Crop Protection, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Haslam
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
authors.forename: Satinder K
authors.initials: SK
authors.lastname: Gidda
authors.affiliation: Department of Biochemistry and Molecular Biology of Plant Products, Instituto de la Grasa (CSIC), Campus Universitario Pablo de Olavide, 41013 Seville, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Pérez-Hormaeche
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Mullen
authors.affiliation: Department of Biochemistry and Interdisciplinary Plant Group, University of Missouri, Columbia, MO 65211, United States.
authors.forename: Jay J
authors.initials: JJ
authors.lastname: Thelen
authors.affiliation: Department of Biological Chemistry and Crop Protection, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom.
authors.forename: Johnathan A
authors.initials: JA
authors.lastname: Napier
authors.affiliation: Department of Biochemistry and Molecular Biology of Plant Products, Instituto de la Grasa (CSIC), Campus Universitario Pablo de Olavide, 41013 Seville, Spain.
authors.forename: Joaquín J
authors.initials: JJ
authors.lastname: Salas
authors.affiliation: Department of Biochemistry and Molecular Biology of Plant Products, Instituto de la Grasa (CSIC), Campus Universitario Pablo de Olavide, 41013 Seville, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Garcés
authors.affiliation: Department of Biochemistry and Molecular Biology of Plant Products, Instituto de la Grasa (CSIC), Campus Universitario Pablo de Olavide, 41013 Seville, Spain.
authors.forename: Enrique
authors.initials: E
authors.lastname: Martínez-Force
authors.affiliation: Department of Biochemistry and Molecular Biology of Plant Products, Instituto de la Grasa (CSIC), Campus Universitario Pablo de Olavide, 41013 Seville, Spain. Electronic address: mvc@ig.csic.es.
authors.forename: Mónica
authors.initials: M
authors.lastname: Venegas-Calerón
mesh_terms: D003001:Cloning, Molecular; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D006368:Helianthus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D013058:Mass Spectrometry; D010802:Phylogeny; D010940:Plant Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D012639:Seeds / Q000201:enzymology / Q000235:genetics / Q000254:growth & development
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger; D005992:Glycerol-3-Phosphate O-Acyltransferase
keywords: Endoplasmic reticulum; Glycerol-3-phosphate acyltransferase; Helianthus annuus; Mass spectrometry; Triacylglycerol; Yeast