title: A land-plant-specific glycerol-3-phosphate acyltransferase family in Arabidopsis: substrate specificity, sn-2 preference, and evolution.
abstract: Arabidopsis (Arabidopsis thaliana) has eight glycerol-3-phosphate acyltransferase (GPAT) genes that are members of a plant-specific family with three distinct clades. Several of these GPATs are required for the synthesis of cutin or suberin. Unlike GPATs with sn-1 regiospecificity involved in membrane or storage lipid synthesis, GPAT4 and -6 are unique bifunctional enzymes with both sn-2 acyltransferase and phosphatase activity resulting in 2-monoacylglycerol products. We present enzymology, pathway organization, and evolutionary analysis of this GPAT family. Within the cutin-associated clade, GPAT8 is demonstrated as a bifunctional sn-2 acyltransferase/phosphatase. GPAT4, -6, and -8 strongly prefer C16:0 and C18:1 ω-oxidized acyl-coenzyme As (CoAs) over unmodified or longer acyl chain substrates. In contrast, suberin-associated GPAT5 can accommodate a broad chain length range of ω-oxidized and unsubstituted acyl-CoAs. These substrate specificities (1) strongly support polyester biosynthetic pathways in which acyl transfer to glycerol occurs after oxidation of the acyl group, (2) implicate GPAT specificities as one major determinant of cutin and suberin composition, and (3) argue against a role of sn-2-GPATs (Enzyme Commission 2.3.1.198) in membrane/storage lipid synthesis. Evidence is presented that GPAT7 is induced by wounding, produces suberin-like monomers when overexpressed, and likely functions in suberin biosynthesis. Within the third clade, we demonstrate that GPAT1 possesses sn-2 acyltransferase but not phosphatase activity and can utilize dicarboxylic acyl-CoA substrates. Thus, sn-2 acyltransferase activity extends to all subbranches of the Arabidopsis GPAT family. Phylogenetic analyses of this family indicate that GPAT4/6/8 arose early in land-plant evolution (bryophytes), whereas the phosphatase-minus GPAT1 to -3 and GPAT5/7 clades diverged later with the appearance of tracheophytes.
authors.affiliation: Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Weili
authors.initials: W
authors.lastname: Yang
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Simpson
authors.forename: Yonghua
authors.initials: Y
authors.lastname: Li-Beisson
authors.forename: Fred
authors.initials: F
authors.lastname: Beisson
authors.forename: Mike
authors.initials: M
authors.lastname: Pollard
authors.forename: John B
authors.initials: JB
authors.lastname: Ohlrogge
mesh_terms: D051103:1-Acylglycerol-3-Phosphate O-Acyltransferase / Q000737:chemistry* / Q000145:classification / Q000235:genetics; D000214:Acyl Coenzyme A / Q000737:chemistry; D000215:Acylation; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000145:classification / Q000235:genetics; D002462:Cell Membrane / Q000737:chemistry; D003001:Cloning, Molecular; D004789:Enzyme Activation; D057075:Enzyme Assays; D019143:Evolution, Molecular; D035264:Flowers / Q000201:enzymology / Q000235:genetics; D005990:Glycerol / Q000737:chemistry; D008055:Lipids / Q000096:biosynthesis / Q000737:chemistry; D008246:Lysophospholipids / Q000737:chemistry*; D008563:Membrane Lipids / Q000096:biosynthesis / Q000737:chemistry; D050178:Monoglycerides / Q000737:chemistry; D005810:Multigene Family; D010084:Oxidation-Reduction; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry; D010802:Phylogeny; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics; D013379:Substrate Specificity
chemical_list: D000214:Acyl Coenzyme A; D029681:Arabidopsis Proteins; D008055:Lipids; D008246:Lysophospholipids; D008563:Membrane Lipids; D050178:Monoglycerides; D011994:Recombinant Proteins; C000521:cutin; C065875:suberin; D051103:1-Acylglycerol-3-Phosphate O-Acyltransferase; C519879:GPAT5 protein, Arabidopsis; D010744:Phosphoric Monoester Hydrolases; D005990:Glycerol; C032881:lysophosphatidic acid