title: Structural Redesigning Arabidopsis Lignins into Alkali-Soluble Lignins through the Expression of p-Coumaroyl-CoA:Monolignol Transferase PMT.
abstract: Grass lignins can contain up to 10% to 15% by weight of p-coumaric esters. This acylation is performed on monolignols under the catalysis of p-coumaroyl-coenzyme A monolignol transferase (PMT). To study the impact of p-coumaroylation on lignification, we first introduced the Brachypodium distachyon Bradi2g36910 (BdPMT1) gene into Arabidopsis (Arabidopsis thaliana) under the control of the constitutive maize (Zea mays) ubiquitin promoter. The resulting p-coumaroylation was far lower than that of lignins from mature grass stems and had no impact on stem lignin content. By contrast, introducing either the BdPMT1 or the Bradi1g36980 (BdPMT2) gene into Arabidopsis under the control of the Arabidopsis cinnamate-4-hydroxylase promoter boosted the p-coumaroylation of mature stems up to the grass lignin level (8% to 9% by weight), without any impact on plant development. The analysis of purified lignin fractions and the identification of diagnostic products confirmed that p-coumaric acid was associated with lignins. BdPMT1-driven p-coumaroylation was also obtained in the fah1 (deficient for ferulate 5-hydroxylase) and ccr1g (deficient for cinnamoyl-coenzyme A reductase) lines, albeit to a lower extent. Lignins from BdPMT1-expressing ccr1g lines were also found to be feruloylated. In Arabidopsis mature stems, substantial p-coumaroylation of lignins was achieved at the expense of lignin content and induced lignin structural alterations, with an unexpected increase of lignin units with free phenolic groups. This higher frequency of free phenolic groups in Arabidopsis lignins doubled their solubility in alkali at room temperature. These findings suggest that the formation of alkali-leachable lignin domains rich in free phenolic groups is favored when p-coumaroylated monolignols participate in lignification in a grass in a similar manner.
authors.affiliation: Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, Université Paris-Saclay, 78000 Versailles, France (R.S., P.L.B., F.L., L.C., C.L.);Institute of Plant Molecular Biology, Centre National de la Recherche Scientifique-University of Strasbourg, 67084 Strasbourg, France (H.R.); andFreiburg Institute for Advanced Studies, University of Freiburg, 79104 Freiburg, Germany (H.R.).
authors.forename: Richard
authors.initials: R
authors.lastname: Sibout
authors.affiliation: Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, Université Paris-Saclay, 78000 Versailles, France (R.S., P.L.B., F.L., L.C., C.L.);Institute of Plant Molecular Biology, Centre National de la Recherche Scientifique-University of Strasbourg, 67084 Strasbourg, France (H.R.); andFreiburg Institute for Advanced Studies, University of Freiburg, 79104 Freiburg, Germany (H.R.).
authors.forename: Philippe
authors.initials: P
authors.lastname: Le Bris
authors.affiliation: Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, Université Paris-Saclay, 78000 Versailles, France (R.S., P.L.B., F.L., L.C., C.L.);Institute of Plant Molecular Biology, Centre National de la Recherche Scientifique-University of Strasbourg, 67084 Strasbourg, France (H.R.); andFreiburg Institute for Advanced Studies, University of Freiburg, 79104 Freiburg, Germany (H.R.).
authors.forename: Frédéric
authors.identifier: http://orcid.org/0000-0003-2818-9186
authors.initials: F
authors.lastname: Legée
authors.affiliation: Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, Université Paris-Saclay, 78000 Versailles, France (R.S., P.L.B., F.L., L.C., C.L.);Institute of Plant Molecular Biology, Centre National de la Recherche Scientifique-University of Strasbourg, 67084 Strasbourg, France (H.R.); andFreiburg Institute for Advanced Studies, University of Freiburg, 79104 Freiburg, Germany (H.R.).
authors.forename: Laurent
authors.initials: L
authors.lastname: Cézard
authors.affiliation: Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, Université Paris-Saclay, 78000 Versailles, France (R.S., P.L.B., F.L., L.C., C.L.);Institute of Plant Molecular Biology, Centre National de la Recherche Scientifique-University of Strasbourg, 67084 Strasbourg, France (H.R.); andFreiburg Institute for Advanced Studies, University of Freiburg, 79104 Freiburg, Germany (H.R.).
authors.forename: Hugues
authors.identifier: http://orcid.org/0000-0002-0871-9912
authors.initials: H
authors.lastname: Renault
authors.affiliation: Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, Université Paris-Saclay, 78000 Versailles, France (R.S., P.L.B., F.L., L.C., C.L.);Institute of Plant Molecular Biology, Centre National de la Recherche Scientifique-University of Strasbourg, 67084 Strasbourg, France (H.R.); andFreiburg Institute for Advanced Studies, University of Freiburg, 79104 Freiburg, Germany (H.R.) catherine.lapierre@versailles.inra.fr.
authors.forename: Catherine
authors.identifier: http://orcid.org/0000-0002-6757-1524
authors.initials: C
authors.lastname: Lapierre
mesh_terms: D000468:Alkalies; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics; D056804:Biofuels; D058431:Brachypodium / Q000201:enzymology* / Q000235:genetics; D000431:Ethanol / Q000378:metabolism; D008031:Lignin / Q000737:chemistry / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D012995:Solubility; D050564:Trans-Cinnamate 4-Monooxygenase / Q000235:genetics; D003313:Zea mays / Q000235:genetics
chemical_list: D000468:Alkalies; D029681:Arabidopsis Proteins; D056804:Biofuels; D010940:Plant Proteins; C036909:lignocellulose; D000431:Ethanol; D008031:Lignin; D050564:Trans-Cinnamate 4-Monooxygenase
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