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

Journal Article · Fri Dec 09 00:00:00 EST 2016 · Plant Physiology (Bethesda)

DOI:https://doi.org/10.1104/pp.16.01108· OSTI ID:1427679

Eloy, Nubia B.  ^[1]; Voorend, Wannes  ^[1]; Lan, Wu  ^[2]; Saleme, Marina de Lyra Soriano  ^[1]; Cesarino, Igor  ^[3]; Vanholme, Ruben  ^[1]; Smith, Rebecca A.  ^[4]; Goeminne, Geert  ^[1]; Pallidis, Andreas  ^[1]; Morreel, Kris  ^[1]; Nicomedes, Jose  ^[1]; Ralph, John  ^[5]; Boerjan, Wout  ^[1]

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1. Center for Plant Systems Biology, VIB (Belgium); Ghent University (Belgium). Department of Plant Biotechnology and Bioinformatics
2. Univ. of Wisconsin, Madison, WI (United States). Department of Energy Great Lakes Bioenergy Research Center, Wisconsin Energy Institute and Department of Biological System Engineering
3. Center for Plant Systems Biology, VIB (Belgium); Ghent University (Belgium). Department of Plant Biotechnology and Bioinformatics; University of Sao Paulo, Butanta, Sao Paulo (Brazil)
4. Univ. of Wisconsin, Madison, WI (United States). Department of Energy Great Lakes Bioenergy Research Center, Wisconsin Energy Institute and Department of Biochemistry
5. Univ. of Wisconsin, Madison, WI (United States). Department of Energy Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, Department of Biological System Engineering and Department of Biochemistry

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 β-β and β-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.

• Research Organization: Univ. of Wisconsin, Madison, WI (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: FC02-07ER64494
• OSTI ID: 1427679
• Journal Information: Plant Physiology (Bethesda), Vol. 173, Issue 2; ISSN 0032-0889
• Publisher: American Society of Plant Biologists
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES