Monolignol Benzoates Incorporate into the Lignin of Transgenic Populus trichocarpa Depleted in C3H and C4H

Journal Article · Thu Feb 06 04:00:00 EST 2020 · ACS Sustainable Chemistry & Engineering

DOI:https://doi.org/10.1021/acssuschemeng.9b06389· OSTI ID:1601911

Kim, Hoon ^[1]; Li, Quanzi ^[2]; Karlen, Steven D. ^[1]; Smith, Rebecca A. ^[1]; Shi, Rui ^[3]; Liu, Jie ^[4]; Yang, Chenmin ^[4]; Tunlaya-Anukit, Sermsawat ^[4]; Wang, Jack P. ^[4]; Chang, Hou-Min ^[5]; Sederoff, Ronald R. ^[4]; Ralph, John ^[6]; Chiang, Vincent L. ^[7]

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1. Department of Energy Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, Madison, Wisconsin 53726, United States
2. State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China
3. Department of Crop and Soil Science, North Carolina State University, Raleigh, North Carolina 27695, United States
4. Forest Biotechnology Group, Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, North Carolina 27695, United States
5. Department of Forest Biomaterials, North Carolina State University, Raleigh, North Carolina 27695, United States
6. Department of Energy Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, Madison, Wisconsin 53726, United States, Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
7. Forest Biotechnology Group, Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, North Carolina 27695, United States, State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin 150040, China

Lignin, an abundant renewable aromatic biopolymer, is an essential macromolecule in terrestrial vascular plants. Genetic modifications affecting monolignol biosynthesis, which produces lignin monomers, alter the metabolic flux through the pathway and are becoming increasingly explored for improving the lignin and biomass quality and for producing high-value commodity chemical feedstocks. Benzoate (BA) conjugates are important metabolites in plants that have not been adequately characterized as components of the lignin structure. In addition to finding trace levels of BA conjugates in wild-type (WT) Populus trichocarpa, these become significantly augmented in strategic triple transgenics. Genes for three key cytochrome P450 enzymes, two 4-hydroxylases (PtrC4H1 and PtrC4H2), and one 3-hydroxylase (PtrC3H3), were downregulated to produce the transgenic plants in which monolignol benzoate (ML-BA) conjugates were incorporated into their lignin at a level some 16-fold higher than in WT. The co-downregulation of PtrC4H1/PtrC4H2/PtrC3H3 genes may cause a rerouting or modification of the pathway due to the interaction of the benzoate biosynthetic pathway with the conventional pathway for monolignol biosynthesis. The total lignin content in the transgenics was decreased by 50%, and the lignin H-unit level was elevated some 70-fold. The wood from the transgenic trees showed reduced recalcitrance toward enzymatic saccharification, which has value for the conversion of plant biomass to bioenergy.

• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
• Grant/Contract Number: SC0018409
• OSTI ID: 1601911
• Alternate ID(s): OSTI ID: 1603750
• Journal Information: ACS Sustainable Chemistry & Engineering, Journal Name: ACS Sustainable Chemistry & Engineering Journal Issue: 9 Vol. 8; ISSN 2168-0485
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English