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This article in CS

  1. Vol. 52 No. 6, p. 2687-2701
     
    Received: Apr 25, 2012
    Published: October 10, 2012


    * Corresponding author(s): stickle1@msu.edu
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doi:10.2135/cropsci2012.04.0253

Downregulation of Maize Cinnamoyl-Coenzyme A Reductase via RNA Interference Technology Causes Brown Midrib and Improves Ammonia Fiber Expansion-Pretreated Conversion into Fermentable Sugars for Biofuels

  1. Sang-Hyuck Parka,
  2. Chuansheng Meib,
  3. Markus Paulyce,
  4. Rebecca Garlock Ongd,
  5. Bruce E. Daled,
  6. Robab Sabzikara,
  7. Hussien Fotoha,
  8. Thang Nguyena and
  9. Mariam Sticklen *a
  1. a Dep. of Crop and Soil Sciences, Michigan State Univ., East Lansing, MI 48824
    b The Institute for Sustainable and Renewable Resources, The Institute for Advanced Learning and Research, Danville, VA 24540
    c Dep. of Biochemistry and Molecular Biology, Michigan State Univ., East Lansing, MI 48824
    e current address: Dep. of Plant and Microbial Biology, Univ. of California-Berkeley, Berkeley, CA 94720
    d Dep. of Chemical Engineering and Materials Science, Michigan State Univ., East Lansing, MI 48824 and Great Lakes Bioenergy Research Center, East Lansing, MI 48824

Abstract

Conversion of lignocellulosic biomass into fermentable sugars for biofuels requires expensive pretreatment processes involving the breakdown of the cell wall structure and/or removal of lignin to increase accessibility of enzymes to the crop structural carbohydrates. Lignin is synthesized from precursors through a complex biosynthesis pathway. One of the important enzymes in this pathway is cinnamoyl-coenzyme A reductase (CCR), which catalyzes the transformation of feruloyl and p-coumaryl thioesters to their respective aldehydes. In an attempt to reduce lignin content and potentially accelerate deconstruction of maize (Zea mays L.) stover structural carbohydrates into fermentable sugars, expression of maize CCR (ZmCCR1; EC 1.2.1.44) was downregulated via ribonucleic acid interference (RNAi). Thirty first generation independent ZmCCR1_RNAi transgenic lines were produced. Among 10 out of 30 randomly tested, six lines showed significantly reduced ZmCCR1 transcription. The second generation of these ZmCCR1 downregulated transgenic plants exhibited brown coloration of midribs, husk, and stems and 7.0 to 8.7% reduction in Klason lignin. Also, crystalline cellulose was slightly increased in the lignin downregulated maize stover and further increased conversion of the ammonia fiber expansion (AFEX)-pretreated maize stover into fermentable sugars. The third generation of CCR downregulated plants showed further reduced CCR transcription as compared to their second generation of transgenic (T1) plants.

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Copyright © 2012. Copyright © by the Crop Science Society of America, Inc.