Down-regulation of the Caffeic acid O-methyltransferase Gene in Switchgrass Reveals a Novel Monolignol Analog

Journal Article · Sun Jan 01 00:00:00 EST 2012 · Biotechnology for Biofuels

DOI:https://doi.org/10.1186/1754-6834-5-71· OSTI ID:1052242

Tschaplinski, Timothy J ^[1]; Standaert, Robert F ^[1]; Engle, Nancy L ^[1]; Martin, Madhavi Z ^[1]; Sangha, Amandeep K ^[1]; Parks, Jerry M ^[1]; Smith, Jeremy C ^[1]; Samuel, Reichel ^[1]; Pu, Yunqiao ^[1]; Ragauskas, A J ^[2]; Hamilton, Choo Yieng ^[1]; Fu, Chunxiang ^[3]; Wang, Zeng-Yu ^[3]; Davison, Brian H ^[1]; Dixon, Richard A ^[3]; Mielenz, Jonathan R ^[1]

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1. ORNL
2. Georgia Institute of Technology
3. Noble Foundation

Down-regulation of the caffeic acid 3-O-methyltransferase (COMT) gene in the lignin biosynthetic pathway of switchgrass (Panicum virgatum) resulted in cell walls of transgenic plants releasing more constituent sugars after pretreatment by dilute acid and treatment with glycosyl hydrolases from an added enzyme preparation and from Clostridium thermocellum. Fermentation of both wild-type and transgenic switchgrass after milder hot water pretreatment with no water washing showed that only the transgenic switchgrass inhibited C. thermocellum. Gas chromatography-mass spectrometry-based metabolomics were undertaken on cell wall aqueous extracts to determine the nature of the microbial inhibitors, confirming the increased concentration of a number of phenolic acids and aldehydes that are known inhibitors of fermentation. Metabolomic analyses of the transgenic biomass additionally revealed the presence of a novel monolignol-like metabolite, identified as trans-3, 4-dimethoxy-5-hydroxycinnamyl alcohol (iso-sinapyl alcohol) in both non-pretreated, as well as hot water pretreated samples. Although there was no indication that iso-sinapyl alcohol was integrated into the cell wall, diversion of substrates from sinapyl alcohol to free iso-sinapyl alcohol, its glucoside, and associated upstream lignin pathway changes, including increased phenolic aldehydes and acids, are associated with more facile cell wall deconstruction, and to the observed inhibitory effect on microbial growth.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1052242
• Journal Information: Biotechnology for Biofuels, Vol. 5, Issue 0; ISSN 1754--6834
• Country of Publication: United States
• Language: English