skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: SbCOMT (Bmr12) is involved in the biosynthesis of tricin-lignin in sorghum

Abstract

Lignin in plant biomass represents a target for engineering strategies towards the development of a sustainable bioeconomy. In addition to the conventional lignin monomers, namely p-coumaryl, coniferyl and sinapyl alcohols, tricin has been shown to be part of the native lignin polymer in certain monocot species. Because tricin is considered to initiate the polymerization of lignin chains, elucidating its biosynthesis and mechanism of export to the cell wall constitute novel challenges for the engineering of bioenergy crops. Late steps of tricin biosynthesis require two methylation reactions involving the pathway intermediate selgin. It has recently been demonstrated in rice and maize that caffeate O-methyltransferase (COMT) involved in the synthesis syringyl (S) lignin units derived from sinapyl alcohol also participates in the synthesis of tricin in planta. In this work, we validate in sorghum (Sorghum bicolor L.) that the O-methyltransferase responsible for the production of S lignin units (SbCOMT / Bmr12) is also involved in the synthesis of lignin-linked tricin. In particular, we show that biomass from the sorghum bmr12 mutant contains lower level of tricin incorporated into lignin, and that SbCOMT can methylate the tricin precursors luteolin and selgin. Our genetic and biochemical data point toward a general mechanism whereby COMTmore » is involved in the synthesis of both tricin and S lignin units.« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [6];  [6];  [7];  [8];  [9];  [2];  [6]; ORCiD logo [10];  [11]
  1. Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Environmental Genomics and Systems Biology Division
  2. Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States). Biomass Science and Conversion Technology Dept.
  3. Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States). Biotechnology and Bioengineering Dept.
  4. Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Univ. of Liege (Belgium). Lab. of Biological and Industrial Chemistry
  5. Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Environmental Genomics and Systems Biology Division; Univ. of California, Berkeley, CA (United States). Dept. of Molecular and Cell Biology
  6. Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Biological Systems and Engineering Division
  7. Univ. of Liege (Belgium). Lab. of Biological and Industrial Chemistry
  8. Wheat, Sorghum and Forage Research Univ., Lincoln, NE (United States)
  9. Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Environmental Genomics and Systems Biology Division; USDOE Joint Genome Institute (JGI), Walnut Creek, CA (United States)
  10. Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Environmental Genomics and Systems Biology Division; Univ. of California, Berkeley, CA (United States). Dept. of Plant and Microbial Biology; Univ. of Lyon (France)
  11. Tallinn Univ. of Technology (Estonia)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1361947
Alternate Identifier(s):
OSTI ID: 1379876
Grant/Contract Number:
AC02-05CH11231
Resource Type:
Journal Article: Published Article
Journal Name:
PLoS ONE
Additional Journal Information:
Journal Volume: 12; Journal Issue: 6; Journal ID: ISSN 1932-6203
Publisher:
Public Library of Science
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Eudes, Aymerick, Dutta, Tanmoy, Deng, Kai, Jacquet, Nicolas, Sinha, Anagh, Benites, Veronica T., Baidoo, Edward E. K., Richel, Aurore, Sattler, Scott E., Northen, Trent R., Singh, Seema, Simmons, Blake A., Loqué, Dominique, and Gupta, Vijai. SbCOMT (Bmr12) is involved in the biosynthesis of tricin-lignin in sorghum. United States: N. p., 2017. Web. doi:10.1371/journal.pone.0178160.
Eudes, Aymerick, Dutta, Tanmoy, Deng, Kai, Jacquet, Nicolas, Sinha, Anagh, Benites, Veronica T., Baidoo, Edward E. K., Richel, Aurore, Sattler, Scott E., Northen, Trent R., Singh, Seema, Simmons, Blake A., Loqué, Dominique, & Gupta, Vijai. SbCOMT (Bmr12) is involved in the biosynthesis of tricin-lignin in sorghum. United States. doi:10.1371/journal.pone.0178160.
Eudes, Aymerick, Dutta, Tanmoy, Deng, Kai, Jacquet, Nicolas, Sinha, Anagh, Benites, Veronica T., Baidoo, Edward E. K., Richel, Aurore, Sattler, Scott E., Northen, Trent R., Singh, Seema, Simmons, Blake A., Loqué, Dominique, and Gupta, Vijai. Thu . "SbCOMT (Bmr12) is involved in the biosynthesis of tricin-lignin in sorghum". United States. doi:10.1371/journal.pone.0178160.
@article{osti_1361947,
title = {SbCOMT (Bmr12) is involved in the biosynthesis of tricin-lignin in sorghum},
author = {Eudes, Aymerick and Dutta, Tanmoy and Deng, Kai and Jacquet, Nicolas and Sinha, Anagh and Benites, Veronica T. and Baidoo, Edward E. K. and Richel, Aurore and Sattler, Scott E. and Northen, Trent R. and Singh, Seema and Simmons, Blake A. and Loqué, Dominique and Gupta, Vijai},
abstractNote = {Lignin in plant biomass represents a target for engineering strategies towards the development of a sustainable bioeconomy. In addition to the conventional lignin monomers, namely p-coumaryl, coniferyl and sinapyl alcohols, tricin has been shown to be part of the native lignin polymer in certain monocot species. Because tricin is considered to initiate the polymerization of lignin chains, elucidating its biosynthesis and mechanism of export to the cell wall constitute novel challenges for the engineering of bioenergy crops. Late steps of tricin biosynthesis require two methylation reactions involving the pathway intermediate selgin. It has recently been demonstrated in rice and maize that caffeate O-methyltransferase (COMT) involved in the synthesis syringyl (S) lignin units derived from sinapyl alcohol also participates in the synthesis of tricin in planta. In this work, we validate in sorghum (Sorghum bicolor L.) that the O-methyltransferase responsible for the production of S lignin units (SbCOMT / Bmr12) is also involved in the synthesis of lignin-linked tricin. In particular, we show that biomass from the sorghum bmr12 mutant contains lower level of tricin incorporated into lignin, and that SbCOMT can methylate the tricin precursors luteolin and selgin. Our genetic and biochemical data point toward a general mechanism whereby COMT is involved in the synthesis of both tricin and S lignin units.},
doi = {10.1371/journal.pone.0178160},
journal = {PLoS ONE},
number = 6,
volume = 12,
place = {United States},
year = {Thu Jun 08 00:00:00 EDT 2017},
month = {Thu Jun 08 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1371/journal.pone.0178160

Citation Metrics:
Cited by: 2works
Citation information provided by
Web of Science

Save / Share:
  • Lignin in plant biomass represents a target for engineering strategies towards the development of a sustainable bioeconomy. In addition to the conventional lignin monomers, namely p-coumaryl, coniferyl and sinapyl alcohols, tricin has been shown to be part of the native lignin polymer in certain monocot species. Because tricin is considered to initiate the polymerization of lignin chains, elucidating its biosynthesis and mechanism of export to the cell wall constitute novel challenges for the engineering of bioenergy crops. Late steps of tricin biosynthesis require two methylation reactions involving the pathway intermediate selgin. It has recently been demonstrated in rice and maizemore » that caffeate O-methyltransferase (COMT) involved in the synthesis syringyl (S) lignin units derived from sinapyl alcohol also participates in the synthesis of tricin in planta. In this work, we validate in sorghum (Sorghum bicolor L.) that the O-methyltransferase responsible for the production of S lignin units (SbCOMT / Bmr12) is also involved in the synthesis of lignin-linked tricin. In particular, we show that biomass from the sorghum bmr12 mutant contains lower level of tricin incorporated into lignin, and that SbCOMT can methylate the tricin precursors luteolin and selgin. Our genetic and biochemical data point toward a general mechanism whereby COMT is involved in the synthesis of both tricin and S lignin units.« less
  • Cited by 10
  • 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 producesmore » 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.« less
  • The biosynthesis of the tyrosine-derived cyanogenic glucoside dhurrin has been studied with a microsomal preparation obtained from etiolated seedlings of sorghum. The biosynthetic pathway involves tyrosine, N-hydroxytyrosine, and p-hydroxyphenylacetaldehyde oxime as early intermediates. The use of deuterium-labeled tyrosine and mass spectrometric analyses demonstrate that the alpha-hydrogen atom of tyrosine is retained in the conversion of tyrosine to p-hydroxyphenylacetaldehyde oxime. This excludes p-hydroxyphenylpyruvic acid oxime as intermediate in the pathway. A high pressure liquid chromatography method was developed to separate the (E)- and (Z)-isomers of p-hydroxyphenylacetaldehyde oxime. The microsomal enzyme system was found to produce initially the (E)-isomer of p-hydroxyphenylacetaldehyde oxime.more » An isomerase then converts the (E)-isomer to the (Z)-isomer, which is the isomer preferentially utilized by the microsomal enzyme system in the subsequent biosynthetic reactions. The (E)-isomer produced in situ is more efficiently converted to the (Z)-isomer than exogenously added (E)-isomer and may thus be metabolically channeled.« less
  • N-Hydroxytyrosine, (E)- and (Z)-p-hydroxyphenyl-acetaldehyde oxime, p-hydroxyphenylacetonitrile, and p-hydroxymandelonitrile are established intermediates in the biosynthesis of the tyrosine-derived cyanogenic glucoside dhurrin. Simultaneous measurements of oxygen consumption and biosynthetic activity using a microsomal enzyme system isolated from etiolated sorghum seedlings demonstrate a requirement for three oxygen molecules in the conversion of tyrosine to p-hydroxymandelonitrile. Two oxygen molecules are consumed in the conversion of tyrosine to (E)-p-hydroxyphenylacetaldehyde oxime, indicating the existence of a previously undetected hydroxylation step in addition to that resulting in the formation of N-hydroxytyrosine. Radioactively labeled 1-nitro-2-(p-hydroxyphenyl)ethane was chemically synthesized and tested as a possible intermediate. Biosynthetic experiments demonstrate thatmore » the microsomal enzyme system metabolizes the nitro compound to the subsequent intermediates in dhurrin synthesis (Km = 0.05 mM; Vmax = 14 nmol/mg of protein/h). Low amounts of 1-nitro-2-(p-hydroxyphenyl)ethane are produced in the microsomal reaction mixtures when tyrosine is used as substrate. These data support the involvement of 1-nitro-2-(p-hydroxyphenyl)ethane or more likely its aci-nitro tautomer as an intermediate between N-hydroxytyrosine and p-hydroxyphenylacetaldehyde oxime. The conversion of (E)-p-hydroxyphenylacetaldehydeoxime to p-hydroxymandelonitrile requires a single oxygen molecule. The oxygen molecule is utilized for hydroxylation of p-hydroxyphenylacetonitrile into p-hydroxymandelonitrile. This indicates that the conversion of p-hydroxyphenylacetaldehyde oxime into p-hydroxyphenylacetonitrile proceeds by a simple dehydration reaction.« less