Downregulation of Cinnamoyl-Coenzyme A Reductase in Poplar: Multiple-Level Phenotyping Reveals Effects on Cell Wall Polymer Metabolism and Structure

Leplé, Jean‐Charles; Dauwe, Rébecca; Morreel, Kris; Storme, Véronique; Lapierre, Catherine; Pollet, Brigitte; Naumann, Annette; Kang, Kyu Young; Kim, Hoon; Ruel, K.; Lefèbvre, Andrée; Joseleau, J.P.; Grima‐Pettenati, Jacqueline; Rycke, Riet De; Andersson‐Gunnerås, Sara; Erban, Alexander; Fehrle, Ines; Petit‐Conil, Michel; Kopka, Joachim; Polle, Andrea; Messens, Eric; Sundberg, Björn; Mansfield, Shawn D.; Ralph, John; Pilate, Gilles; Boerjan, Wout

doi:10.1105/tpc.107.054148

Cited by 353 publications

(366 citation statements)

References 101 publications

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“…Transgenic poplars (Populus spp.) deficient in different steps of the lignin biosynthetic pathway have been reported to have less lignin and relatively more cellulose in their cell walls (Jouanin et al, 2000;Li et al, 2003a;Leplé et al, 2007). However, such an inverse relation between lignin and cellulose was not observed in a set of Arabidopsis mutants altered in lignin biosynthesis, in which a reduction in lignin content seemed to be compensated for by a relative increase in hemicellulose content (Vanholme et al, 2012;Van Acker et al, 2013).…”

Section: Discussionmentioning

confidence: 96%

Silencing CHALCONE SYNTHASE in Maize Impedes the Incorporation of Tricin into Lignin and Increases Lignin Content

et al. 2016

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Lignin is a phenolic heteropolymer that is deposited in secondary-thickened cell walls, where it provides mechanical strength. A recent structural characterization of cell walls from monocot species showed that the flavone tricin is part of the native lignin polymer, where it is hypothesized to initiate lignin chains. In this study, we investigated the consequences of altered tricin levels on lignin structure and cell wall recalcitrance by phenolic profiling, nuclear magnetic resonance, and saccharification assays of the naturally silenced maize (Zea mays) C2-Idf (inhibitor diffuse) mutant, defective in the CHALCONE SYNTHASE Colorless2 (C2) gene. We show that the C2-Idf mutant produces highly reduced levels of apigenin-and tricin-related flavonoids, resulting in a strongly reduced incorporation of tricin into the lignin polymer. Moreover, the lignin was enriched in b-b and b-5 units, lending support to the contention that tricin acts to initiate lignin chains and that, in the absence of tricin, more monolignol dimerization reactions occur. In addition, the C2-Idf mutation resulted in strikingly higher Klason lignin levels in the leaves. As a consequence, the leaves of C2-Idf mutants had significantly reduced saccharification efficiencies compared with those of control plants. These findings are instructive for lignin engineering strategies to improve biomass processing and biochemical production.

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Section: Discussionmentioning

confidence: 96%

Silencing CHALCONE SYNTHASE in Maize Impedes the Incorporation of Tricin into Lignin and Increases Lignin Content

et al. 2016

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“…1D]) were detected in poplar (Populus spp.) and tobacco (Nicotiana tabacum) xylem with liquid chromatography (LC) coupled to ion trap (IT) MS (Morreel et al, , 2004bDamiani et al, 2005;Dauwe et al, 2007;Leplé et al, 2007). Their structures were resolved using mass spectral information and further authenticated by chemical synthesis.…”

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confidence: 99%

Mass Spectrometry-Based Sequencing of Lignin Oligomers

Morreel

Dima²,

Kim³

et al. 2010

Plant Physiol.

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Although the primary structure of proteins, nucleic acids, and carbohydrates can be readily determined, no sequencing method has been described yet for the second most abundant biopolymer on earth (i.e. lignin). Within secondary-thickened plant cell walls, lignin forms an aromatic mesh arising from the combinatorial radical-radical coupling of monolignols and many other less abundant monomers. This polymerization process leads to a plethora of units and linkage types that affect the physicochemical characteristics of the cell wall. Current methods to analyze the lignin structure focus only on the frequency of the major monomeric units and interunit linkage types but do not provide information on the presence of less abundant unknown units and linkage types, nor on how linkages affect the formation of neighboring linkages. Such information can only be obtained using a sequencing approach. Here, we describe, to our knowledge for the first time, a sequencing strategy for lignin oligomers using mass spectrometry. This strategy was then evaluated on the oligomers extracted from wild-type poplar (Populus tremula 3 Populus tremuloides) xylem. In total, 134 lignin trimers to hexamers were observed, of which 36 could be completely sequenced. Interestingly, based on molecular mass data of the unknown monomeric and dimeric substructures, at least 10 unknown monomeric units or interunit linkage types were observed, one of which was identified as an arylglycerol end unit.Lignin is an aromatic heteropolymer that is mainly present in secondary-thickened plant cell walls, allowing the transport of water and nutrients and providing the necessary strength for the plant to grow upwardly Vanholme et al., 2008Vanholme et al., , 2010. In angiosperms, lignin is predominantly composed of guaiacyl (G) and syringyl (S) units that are derived from combinatorial radical-radical coupling of the monolignols coniferyl and sinapyl alcohol, respectively Fig. 1A). Following oxidation of the monolignols by peroxidase and/or laccase, the resulting electron-delocalized radical has unpaired electron density at its 1-, 3-, O-4-, 5-, and 8-positions (Fig. 1B); note that much of the lignin literature uses Greek letters for the side chain, a, b, and g for the 7-, 8-, and 9-positions. As radical coupling at the 8-position is favored, coupling with another monolignol radical affords, after rearomatization, a mixture of dehydrodimers with 8-8-, 8-5-, and 8-O-4-linkages (Fig. 1C). Following dimerization, polymerization will continue by the coupling of the 8-position of an incoming monolignol radical to the O-4-position of the dimer's phenolic end. In the case of a G dimer, coupling can also occur, albeit at a lower frequency, to the 5-position. Thus, chain elongation creates 8-5-and 8-O-4-linkages (Adler, 1977). Besides the monolignols and other monomers that are present in minor amounts , the plasticity of lignin polymerization permits the incorporation of any phenolic that enters the lignification site, subject to its chemical cross-coupling propensit...

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“…CCR-downregulated poplars are characterized by an orange to wine-red coloration of the xylem that often appears in patches along the stem. This pronounced coloration is associated with a reduction in lignin amount and the incorporation of low levels of ferulic acid into the polymer (13,14).…”

mentioning

confidence: 99%

“…Cinnamoyl-CoA reductase (CCR) catalyzes the first step of the monolignol-specific pathway. It converts the hydroxycinnamoylCoA esters to their corresponding hydroxycinnamaldehydes (mainly feruloyl-CoA to coniferaldehyde), and down-regulation of CCR typically results in reduced lignin content (8)(9)(10)(11)(12)(13). CCR-downregulated poplars are characterized by an orange to wine-red coloration of the xylem that often appears in patches along the stem.…”

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confidence: 99%

Improved saccharification and ethanol yield from field-grown transgenic poplar deficient in cinnamoyl-CoA reductase

Acker

Leplé²,

Aerts

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Lignin is one of the main factors determining recalcitrance to enzymatic processing of lignocellulosic biomass. Poplars (Populus tremula x Populus alba) down-regulated for cinnamoyl-CoA reductase (CCR), the enzyme catalyzing the first step in the monolignolspecific branch of the lignin biosynthetic pathway, were grown in field trials in Belgium and France under short-rotation coppice culture. Wood samples were classified according to the intensity of the red xylem coloration typically associated with CCR downregulation. Saccharification assays under different pretreatment conditions (none, two alkaline, and one acid pretreatment) and simultaneous saccharification and fermentation assays showed that wood from the most affected transgenic trees had up to 161% increased ethanol yield. Fermentations of combined material from the complete set of 20-mo-old CCR-down-regulated trees, including bark and less efficiently down-regulated trees, still yielded ∼20% more ethanol on a weight basis. However, strong down-regulation of CCR also affected biomass yield. We conclude that CCR down-regulation may become a successful strategy to improve biomass processing if the variability in down-regulation and the yield penalty can be overcome.bioethanol | GM | second-generation bioenergy

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Downregulation of Cinnamoyl-Coenzyme A Reductase in Poplar: Multiple-Level Phenotyping Reveals Effects on Cell Wall Polymer Metabolism and Structure

Cited by 353 publications

References 101 publications

Silencing CHALCONE SYNTHASE in Maize Impedes the Incorporation of Tricin into Lignin and Increases Lignin Content

Silencing CHALCONE SYNTHASE in Maize Impedes the Incorporation of Tricin into Lignin and Increases Lignin Content

Mass Spectrometry-Based Sequencing of Lignin Oligomers

Improved saccharification and ethanol yield from field-grown transgenic poplar deficient in cinnamoyl-CoA reductase

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