title: Identification of Arabidopsis GPAT9 (At5g60620) as an Essential Gene Involved in Triacylglycerol Biosynthesis.
abstract: The first step in the biosynthesis of nearly all plant membrane phospholipids and storage triacylglycerols is catalyzed by a glycerol-3-phosphate acyltransferase (GPAT). The requirement for an endoplasmic reticulum (ER)-localized GPAT for both of these critical metabolic pathways was recognized more than 60 years ago. However, identification of the gene(s) encoding this GPAT activity has remained elusive. Here, we present the results of a series of in vivo, in vitro, and in silico experiments in Arabidopsis (Arabidopsis thaliana) designed to assign this essential function to AtGPAT9. This gene has been highly conserved throughout evolution and is largely present as a single copy in most plants, features consistent with essential housekeeping functions. A knockout mutant of AtGPAT9 demonstrates both male and female gametophytic lethality phenotypes, consistent with the role in essential membrane lipid synthesis. Significant expression of developing seed AtGPAT9 is required for wild-type levels of triacylglycerol accumulation, and the transcript level is directly correlated to the level of microsomal GPAT enzymatic activity in seeds. Finally, the AtGPAT9 protein interacts with other enzymes involved in ER glycerolipid biosynthesis, suggesting the possibility of ER-localized lipid biosynthetic complexes. Together, these results suggest that GPAT9 is the ER-localized GPAT enzyme responsible for plant membrane lipid and oil biosynthesis.
authors.affiliation: U.S. Department of Agriculture-Agricultural Research Service, Southern Regional Research Center, New Orleans, Louisiana 70124 (J.S.);Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, Mississippi 39406 (A.R., P.D.B.); andInstitute of Biological Chemistry, Washington State University, Pullman, Washington 99163 (K.C., N.A., J.B.).
authors.forename: Jay
authors.identifier: http://orcid.org/0000-0002-5057-5457
authors.initials: J
authors.lastname: Shockey
authors.affiliation: U.S. Department of Agriculture-Agricultural Research Service, Southern Regional Research Center, New Orleans, Louisiana 70124 (J.S.);Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, Mississippi 39406 (A.R., P.D.B.); andInstitute of Biological Chemistry, Washington State University, Pullman, Washington 99163 (K.C., N.A., J.B.).
authors.forename: Anushobha
authors.identifier: http://orcid.org/0000-0003-1819-6147
authors.initials: A
authors.lastname: Regmi
authors.affiliation: U.S. Department of Agriculture-Agricultural Research Service, Southern Regional Research Center, New Orleans, Louisiana 70124 (J.S.);Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, Mississippi 39406 (A.R., P.D.B.); andInstitute of Biological Chemistry, Washington State University, Pullman, Washington 99163 (K.C., N.A., J.B.).
authors.forename: Kimberly
authors.identifier: http://orcid.org/0000-0003-0972-7671
authors.initials: K
authors.lastname: Cotton
authors.affiliation: U.S. Department of Agriculture-Agricultural Research Service, Southern Regional Research Center, New Orleans, Louisiana 70124 (J.S.);Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, Mississippi 39406 (A.R., P.D.B.); andInstitute of Biological Chemistry, Washington State University, Pullman, Washington 99163 (K.C., N.A., J.B.).
authors.forename: Neil
authors.identifier: http://orcid.org/0000-0002-2935-1870
authors.initials: N
authors.lastname: Adhikari
authors.affiliation: U.S. Department of Agriculture-Agricultural Research Service, Southern Regional Research Center, New Orleans, Louisiana 70124 (J.S.);Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, Mississippi 39406 (A.R., P.D.B.); andInstitute of Biological Chemistry, Washington State University, Pullman, Washington 99163 (K.C., N.A., J.B.).
authors.forename: John
authors.initials: J
authors.lastname: Browse
authors.affiliation: U.S. Department of Agriculture-Agricultural Research Service, Southern Regional Research Center, New Orleans, Louisiana 70124 (J.S.);Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, Mississippi 39406 (A.R., P.D.B.); andInstitute of Biological Chemistry, Washington State University, Pullman, Washington 99163 (K.C., N.A., J.B.) philip.bates@usm.edu.
authors.forename: Philip D
authors.identifier: http://orcid.org/0000-0002-1291-3363
authors.initials: PD
authors.lastname: Bates
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D017124:Conserved Sequence; D004721:Endoplasmic Reticulum / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D020043:Genes, Essential; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000235:genetics* / Q000378:metabolism; D006720:Homozygote; D008563:Membrane Lipids / Q000096:biosynthesis; D009154:Mutation; D030821:Plants, Genetically Modified; D011058:Pollen / Q000235:genetics; D012639:Seeds / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014280:Triglycerides / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D008563:Membrane Lipids; D014280:Triglycerides; C000610951:GPAT9 protein, Arabidopsis; D005992:Glycerol-3-Phosphate O-Acyltransferase