Arabidopsis GPAT9 contributes to synthesis of intracellular glycerolipids but not surface lipids.
GLYCEROL-3-PHOSPHATE ACYLTRANSFERASE (GPAT) genes encode enzymes involved in glycerolipid biosynthesis in plants. Ten GPAT homologues have been identified in Arabidopsis. GPATs 4-8 have been shown to be involved in the production of extracellular lipid barrier polyesters. Recently, GPAT9 was reported to be essential for triacylglycerol (TAG) biosynthesis in developing Arabidopsis seeds. The enzymatic properties and possible functions of GPAT9 in surface lipid, polar lipid and TAG biosynthesis in non-seed organs, however, have not been investigated. Here we show that Arabidopsis GPAT9 exhibits sn-1 acyltransferase activity with high specificity for acyl-coenzyme A, thus providing further evidence that this GPAT is involved in storage lipid biosynthesis. We also confirm a role for GPAT9 in seed oil biosynthesis and further demonstrate that GPAT9 contributes to the biosynthesis of both polar lipids and TAG in developing leaves, as well as lipid droplet production in developing pollen grains. Conversely, alteration of constitutive GPAT9 expression had no obvious effects on surface lipid biosynthesis. Taken together, these studies expand our understanding of GPAT9 function to include modulation of several different intracellular glycerolipid pools in plant cells.
Agricultural Lipid Biotechnology Program, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.
Stacy D
SD
Singer
Agricultural Lipid Biotechnology Program, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.
Guanqun
G
Chen
Agricultural Lipid Biotechnology Program, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.
Elzbieta
E
Mietkiewska
USDA-ARS, US Arid-Land Agricultural Research Center, 21881 North Cardon Lane, Maricopa, AZ 85138, USA.
Pernell
P
Tomasi
Agricultural Lipid Biotechnology Program, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.
Kethmi
K
Jayawardhane
USDA-ARS, US Arid-Land Agricultural Research Center, 21881 North Cardon Lane, Maricopa, AZ 85138, USA.
John M
JM
Dyer
Agricultural Lipid Biotechnology Program, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada randall.weselake@ualberta.ca.
Randall J
RJ
Weselake
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000502:physiology*; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000502:physiology*; D006017:Glycolipids / Q000378:metabolism*; D050356:Lipid Metabolism / Q000502:physiology; D008563:Membrane Lipids / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D030821:Plants, Genetically Modified; D060888:Real-Time Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000378:metabolism
D029681:Arabidopsis Proteins; D006017:Glycolipids; D008563:Membrane Lipids; C000521:cutin; C000610951:GPAT9 protein, Arabidopsis; D005992:Glycerol-3-Phosphate O-Acyltransferase
Acyl-CoA specificity; GPAT; acyl lipid biosynthesis; cutin; lipid droplet; pollen grain; regio-specificity; surface wax.