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BioEnergy Research

, Volume 4, Issue 3, pp 153–164 | Cite as

Downregulation of Cinnamyl Alcohol Dehydrogenase (CAD) Leads to Improved Saccharification Efficiency in Switchgrass

  • Chunxiang Fu
  • Xirong Xiao
  • Yajun Xi
  • Yaxin Ge
  • Fang Chen
  • Joseph Bouton
  • Richard A. Dixon
  • Zeng-Yu WangEmail author
Article

Abstract

The bioconversion of carbohydrates in the herbaceous bioenergy crop, switchgrass (Panicum virgatum L.), is limited by the associated lignins in the biomass. The cinnamyl alcohol dehydrogenase (CAD) gene encodes a key enzyme which catalyzes the last step of lignin monomer biosynthesis. Transgenic switchgrass plants were produced with a CAD RNAi gene construct under the control of the maize ubiquitin promoter. The transgenic lines showed reduced CAD expression levels, reduced enzyme activities, reduced lignin content, and altered lignin composition. The modification of lignin biosynthesis resulted in improved sugar release and forage digestibility. Significant increases of saccharification efficiency were obtained in most of the transgenic lines with or without acid pretreatment. A negative correlation between lignin content and sugar release was found among these transgenic switchgrass lines. The transgenic materials have the potential to allow for improved efficiency of cellulosic ethanol production.

Keywords

Cinnamyl alcohol dehydrogenase Lignin modification Panicum virgatum Saccharification Switchgrass Transgenic plant 

Notes

Acknowledgments

We thank Ko Shimamoto for providing the pANDA vector, Human David for assistance with GC-MS and LC-MS analysis, Stacy Allen and Tui Ray for assistance with real-time RT-PCR analysis, and Dennis Walker for assistance with forage digestibility analysis. The work was supported by the US Department of Agriculture and US Department of Energy Biomass Initiative (project no. 2009-10003-05140), the BioEnergy Science Center and the Samuel Roberts Noble Foundation. The BioEnergy Science Center is supported by the Office of Biological and Environmental Research in the DOE Office of Science.

Supplementary material

12155_2010_9109_MOESM1_ESM.docx (12 kb)
Table S1 Content of cell wall-bound phenolic compounds in internodes of transgenic switchgrass. (DOCX 12 kb)
12155_2010_9109_MOESM2_ESM.docx (12 kb)
Table S2 Cell wall polysaccharides and in vitro true dry matter digestibility (IVTDMD) of transgenic switchgrass plants with downregulated expression of CAD. (DOCX 12 kb)
12155_2010_9109_MOESM3_ESM.docx.pptx
Supplementary Figure (PPTX 146 kb)

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Copyright information

© Springer Science+Business Media, LLC. 2010

Authors and Affiliations

  • Chunxiang Fu
    • 1
  • Xirong Xiao
    • 1
    • 3
  • Yajun Xi
    • 1
  • Yaxin Ge
    • 1
  • Fang Chen
    • 2
    • 3
  • Joseph Bouton
    • 1
  • Richard A. Dixon
    • 2
    • 3
  • Zeng-Yu Wang
    • 1
    • 3
    Email author
  1. 1.Forage Improvement DivisionThe Samuel Roberts Noble FoundationArdmoreUSA
  2. 2.Plant Biology DivisionThe Samuel Roberts Noble FoundationArdmoreUSA
  3. 3.BioEnergy Science CenterOak RidgeUSA

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