title: The O-methyltransferase PMT2 mediates methylation of pinosylvin in Scots pine.
abstract: Heartwood extractives are important determinants of the natural durability of pine heartwood. The most important phenolic compounds affecting durability are the stilbenes pinosylvin and its monomethylether, which in addition have important functions as phytoalexins in active defense. A substantial portion of the synthesized pinosylvin is 3-methoxylated but the O-methyltransferase responsible for this modification has not been correctly identified. We studied the expression of the stilbene pathway during heartwood development as well as in response to wounding of xylem and UV-C treatment of needles. We isolated and enzymatically characterized a novel O-methyltransferase, PMT2. The methylated product was verified as pinosylvin monomethylether using ultra performance liquid chromatography-tandem mass spectrometry and high performance liquid chromatography analyses. The PMT2 enzyme was highly specific for stilbenes as substrate, in contrast to caffeoyl-CoA O-methyltransferase (CCoAOMT) and PMT1 that were multifunctional. Expression profile and multifunctional activity of CCoAOMT suggest that it might have additional roles outside lignin biosynthesis. PMT1 is not involved in the stilbene pathway and its biological function remains an open question. We isolated a new specific O-methyltransferase responsible for 3-methoxylation of pinosylvin. Expression of PMT2 closely follows stilbene biosynthesis during developmental and stress induction. We propose that PMT2 is responsible for pinosylvin methylation in Scots pine (Pinus sylvestris), instead of the previously characterized methyltransferase, PMT1.
authors.affiliation: Department of Agricultural Sciences, Viikki Plant Science Centre, University of Helsinki, PO Box 27, Helsinki, 00014, Finland.
authors.forename: Tanja
authors.initials: T
authors.lastname: Paasela
authors.affiliation: Department of Agricultural Sciences, Viikki Plant Science Centre, University of Helsinki, PO Box 27, Helsinki, 00014, Finland.
authors.forename: Kean-Jin
authors.initials: KJ
authors.lastname: Lim
authors.affiliation: Department of Agricultural Sciences, Viikki Plant Science Centre, University of Helsinki, PO Box 27, Helsinki, 00014, Finland.
authors.forename: Milla
authors.initials: M
authors.lastname: Pietiäinen
authors.affiliation: Department of Agricultural Sciences, Viikki Plant Science Centre, University of Helsinki, PO Box 27, Helsinki, 00014, Finland.
authors.forename: Teemu H
authors.initials: TH
authors.lastname: Teeri
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D041605:Pinus sylvestris / Q000378:metabolism* / Q000528:radiation effects; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D013267:Stilbenes / Q000378:metabolism*; D013379:Substrate Specificity; D053719:Tandem Mass Spectrometry; D014466:Ultraviolet Rays; D052584:Xylem / Q000378:metabolism; D000094162:Phytoalexins
chemical_list: D008780:Methyltransferases; D010940:Plant Proteins; D013267:Stilbenes; C049032:pinosylvin; D000094162:Phytoalexins; C059825:caffeoyl-CoA O-methyltransferase
keywords: O-methyltransferase; Scots pine (Pinus sylvestris); caffeoyl-CoA O-methyltransferase; hydroxycinnamic acids/hydroxycinnamoyl CoA esters OMT; pinosylvin; pinosylvin O-methyltransferase; stilbene