Combining loss of function of FOLYLPOLYGLUTAMATE SYNTHETASE1 and CAFFEOYL-COA 3-O-METHYLTRANSFERASE1 for lignin reduction and improved saccharification efficiency in Arabidopsis thaliana

Hongli Xie, Nancy L. Engle, Sivasankari Venketachalam, Chang Geun Yoo, Jaime Barros, Mitch Lecoultre, Nikki Howard, Guifen Li, Liang Sun, Avinash C. Srivastava, Sivakumar Pattathil, Yunqiao Pu, Michael G. Hahn, Arthur J. Ragauskas, Richard S. Nelson, Richard A. Dixon, Timothy J. Tschaplinski, Elison B. Blancaflor, Yuhong Tang

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Abstract

Background: Downregulation of genes involved in lignin biosynthesis and related biochemical pathways has been used as a strategy to improve biofuel production. Plant C1 metabolism provides the methyl units used for the methylation reactions carried out by two methyltransferases in the lignin biosynthetic pathway: caffeic acid 3-O-methyltransferase (COMT) and caffeoyl-CoA 3-O-methyltransferase (CCoAOMT). Mutations in these genes resulted in lower lignin levels and altered lignin compositions. Reduced lignin levels can also be achieved by mutations in the C1 pathway gene, folylpolyglutamate synthetase1 (FPGS1), in both monocotyledons and dicotyledons, indicating a link between the C1 and lignin biosynthetic pathways. To test if lignin content can be further reduced by combining genetic mutations in C1 metabolism and the lignin biosynthetic pathway, fpgs1ccoaomt1 double mutants were generated and functionally characterized. Results: Double fpgs1ccoaomt1 mutants had lower thioacidolysis lignin monomer yield and acetyl bromide lignin content than the ccoaomt1 or fpgs1 mutants and the plants themselves displayed no obvious long-term negative growth phenotypes. Moreover, extracts from the double mutants had dramatically improved enzymatic polysaccharide hydrolysis efficiencies than the single mutants: 15.1% and 20.7% higher than ccoaomt1 and fpgs1, respectively. The reduced lignin and improved sugar release of fpgs1ccoaomt1 was coupled with changes in cell-wall composition, metabolite profiles, and changes in expression of genes involved in cell-wall and lignin biosynthesis. Conclusion: Our observations demonstrate that additional reduction in lignin content and improved sugar release can be achieved by simultaneous downregulation of a gene in the C1 (FPGS1) and lignin biosynthetic (CCOAOMT) pathways. These improvements in sugar accessibility were achieved without introducing unwanted long-term plant growth and developmental defects.

Original languageEnglish
Article number108
JournalBiotechnology for Biofuels
Volume12
Issue number1
DOIs
StatePublished - May 3 2019

Funding

The authors thank Stacy Allen at the Genomics Core of the Noble Research Institute for microarray data generation and Dr. Sanja Roje at Washington State University for critical reading of the manuscript. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government and the publisher, by accepting the article for publication, acknowledges that the US government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/ doe-public-access-plan). The generation of the CCRC series of plant cell-wall glycan-directed monoclonal antibodies used in this work was supported by the National Science Foundation Plant Genome Research Program (DBI-0421683 and IOS-0923992). This work was funded by Noble Research Institute as well as the BioEnergy Science Center (BESC) and The Center for Bioenergy Innovation (CBI), US Department of Energy (DOE) Bioenergy Research Centers supported by the Office of Biological and Environmental Research in the DOE Office of Science. Oak Ridge National Laboratory is managed by UT-Battelle, LLC under Contract DE-AC05-00OR22725 with the US DOE. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights.

FundersFunder number
BioEnergy Science Center
DOE Office of Science
National Science Foundation Plant Genome Research ProgramIOS-0923992, DBI-0421683
Office of Biological and Environmental Research
US Department of Energy
UT-BattelleDE-AC05-00OR22725
U.S. Department of Energy
Directorate for Biological Sciences0421683, 0923992
Oak Ridge National Laboratory
Noble Research Institute
Center for Bioenergy Innovation

    Keywords

    • Glycome profiling
    • Lignin
    • Metabolite profiling
    • Phenylpropanoid pathway
    • caffeoyl-CoA 3-O-methyltransferase1
    • ccoaomt1
    • folylpolyglutamate synthetase1
    • fpgs1

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