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The O ‐methyltransferase PMT 2 mediates methylation of pinosylvin in Scots pine
Author(s) -
Paasela Tanja,
Lim KeanJin,
Pietiäinen Milla,
Teeri Teemu H.
Publication year - 2017
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.14480
Subject(s) - o methyltransferase , scots pine , chemistry , methyltransferase , biosynthesis , methylation , biochemistry , xylem , enzyme , botany , pinus <genus> , biology , gene
Summary 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, PMT 2. The methylated product was verified as pinosylvin monomethylether using ultra performance liquid chromatography–tandem mass spectrometry and high performance liquid chromatography analyses. The PMT 2 enzyme was highly specific for stilbenes as substrate, in contrast to caffeoyl‐CoA O ‐methyltransferase (CCoAOMT) and PMT 1 that were multifunctional. Expression profile and multifunctional activity of CC o AOMT suggest that it might have additional roles outside lignin biosynthesis. PMT 1 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 PMT 2 closely follows stilbene biosynthesis during developmental and stress induction. We propose that PMT 2 is responsible for pinosylvin methylation in Scots pine ( Pinus sylvestris ), instead of the previously characterized methyltransferase, PMT 1.