title: Syringyl lignin production in conifers: Proof of concept in a Pine tracheary element system.
abstract: Conifers (softwoods) naturally lack syringyl units in their lignins, rendering lignocellulosic materials from such species more difficult to process than syringyl-rich hardwood species. Using a transformable Pinus radiata tracheary element (TE) system as an experimental platform, we investigated whether metabolic engineering can be used to create syringyl lignin in conifers. Pyrolysis-GC/MS and 2D-NMR analysis of P. radiata TE cultures transformed to express ferulate 5-hydroxylase (F5H) and caffeic acid O-methyltransferase (COMT) from Liquidambar styraciflua confirmed the production and incorporation of sinapyl alcohol into the lignin polymer. Transformation with F5H was sufficient for the production of syringyl lignin in TEs, but cotransformation with COMT improved its formation. In addition, lower levels of the pathway intermediate 5-hydroxyconiferyl alcohol were evidenced in cotransformation experiments, indicating that the introduction of the COMT overcame the inefficiency of the native pine methyltransferases for supporting sinapyl alcohol production.Our results provide the proof of concept that it is possible to generate a lignin polymer that contains syringyl units in softwood species such as P. radiata, suggesting that it might be possible to retain the outstanding fiber properties of softwoods while imbuing them with the lignin characteristics of hardwoods that are more favorable for industrial processing.
authors.affiliation: Biotransformation Department, Scion, 3020, Rotorua 3010, New Zealand;
authors.forename: Armin
authors.initials: A
authors.lastname: Wagner
authors.affiliation: Department of Biochemistry, University of Wisconsin, Madison, WI 53706; and US Department of Energy's Great Lakes Bioenergy Research Center, The Wisconsin Energy Institute, Madison, WI 53726.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tobimatsu
authors.affiliation: Biotransformation Department, Scion, 3020, Rotorua 3010, New Zealand;
authors.forename: Lorelle
authors.initials: L
authors.lastname: Phillips
authors.affiliation: Biotransformation Department, Scion, 3020, Rotorua 3010, New Zealand;
authors.forename: Heather
authors.initials: H
authors.lastname: Flint
authors.affiliation: Biotransformation Department, Scion, 3020, Rotorua 3010, New Zealand;
authors.forename: Barbara
authors.initials: B
authors.lastname: Geddes
authors.affiliation: Department of Biochemistry, University of Wisconsin, Madison, WI 53706; and US Department of Energy's Great Lakes Bioenergy Research Center, The Wisconsin Energy Institute, Madison, WI 53726.
authors.forename: Fachuang
authors.initials: F
authors.lastname: Lu
authors.affiliation: Department of Biochemistry, University of Wisconsin, Madison, WI 53706; and US Department of Energy's Great Lakes Bioenergy Research Center, The Wisconsin Energy Institute, Madison, WI 53726 jralph@wisc.edu.
authors.forename: John
authors.initials: J
authors.lastname: Ralph
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D056804:Biofuels; D018533:Biomass; D002473:Cell Wall / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D018506:Gene Expression Regulation, Plant; D008031:Lignin / Q000096:biosynthesis*; D009682:Magnetic Resonance Spectroscopy; D060847:Metabolic Engineering; D028223:Pinus; D010940:Plant Proteins / Q000378:metabolism; D030821:Plants, Genetically Modified; D011108:Polymers / Q000737:chemistry; D064028:Tracheophyta; D019076:Transgenes
chemical_list: D000438:Alcohols; D056804:Biofuels; D010940:Plant Proteins; D011108:Polymers; D008031:Lignin
keywords: bioenergy; lignification; metabolic engineering; pulping; softwood