BioEnergy Research

, 1:180 | Cite as

Improving Saccharification Efficiency of Alfalfa Stems Through Modification of the Terminal Stages of Monolignol Biosynthesis

  • Lisa A. Jackson
  • Gail L. Shadle
  • Rui Zhou
  • Jin Nakashima
  • Fang Chen
  • Richard A. Dixon
Article

Abstract

A series of transgenic lines of alfalfa (Medicago sativa) were generated in which either one of the two potentially terminal enzymes of the monolignol pathway, cinnamoyl CoA reductase (CCR) or cinnamyl alcohol dehydrogenase (CAD) was down-regulated by expression of antisense transgenes. Levels of CCR enzymatic activity were reduced to between 10% to 65% of the control level, and levels of CAD activity were similarly reduced to between 5% to 40% of the control. Biomass yields were reduced in the most strongly down-regulated lines for both transgenes, but many of the lines exhibited reduced lignin levels but normal biomass and flowering time. In vitro dry matter digestibility was increased for most transgenic lines compared to controls. Saccharification efficiency was determined by measuring the release of sugars from cell walls directly, or after sulfuric acid pre-treatment and subsequent digestion with a mixture of cellulase and cellobiase. Several CCR down-regulated lines had significantly enhanced saccharification efficiency with both pre-treated and untreated tissues, whereas CAD down-regulation had less impact on sugar release when compared to that from CCR lines with similar lignin contents. One CCR line with a 50–60% improvement in saccharification efficiency exhibited normal biomass production, indicating the potential for producing high yielding, improved feedstocks for bioethanol production through genetic modification of the monolignol pathway.

Keywords

Alfalfa Genetic modification Lignin pathway Saccharification Transgenic plants 

Abbreviations

CAD

cinnamyl alcohol dehydrogenase

CCR

cinnamoyl coenzyme A reductase

G

guaiacyl

HCT

hydroxycinnamoyl transferase

S

syringyl

Supplementary material

12155_2008_9020_MOESM1_ESM.doc (410 kb)
ESM 1Improving saccharification efficiency of alfalfa stems through modification of the terminal stages of monolignol biosynthesis. (DOC 410 KB)

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Copyright information

© Springer Science+Business Media, LLC. 2008

Authors and Affiliations

  • Lisa A. Jackson
    • 1
  • Gail L. Shadle
    • 1
  • Rui Zhou
    • 1
  • Jin Nakashima
    • 1
  • Fang Chen
    • 1
  • Richard A. Dixon
    • 1
  1. 1.Plant Biology Division, Samuel Roberts Noble FoundationArdmoreUSA

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