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

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 f...

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Bibliographic Details
Published in:Crop science 2012-11, Vol.52 (6), p.2687-2701
Main Authors: Park, Sang‐Hyuck, Mei, Chuansheng, Pauly, Markus, Ong, Rebecca Garlock, Dale, Bruce E., Sabzikar, Robab, Fotoh, Hussien, Nguyen, Thang, Sticklen, Mariam
Format: Article
Language:English
Subjects:
Agronomy. Soil science and plant productions
Aldehydes
Ammonia
Biodiesel fuels
Biofuels
Biological and medical sciences
Biomass
Biosynthesis
Carbohydrates
Cellulose
Colleges & universities
Conversion
Corn
Enzymes
Ethanol
Expansion
Fundamental and applied biological sciences. Psychology
Plant growth
Seeds
Stover
Sugar
Transgenic plants
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Summary: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.
ISSN:0011-183X
1435-0653
DOI:10.2135/cropsci2012.04.0253