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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
Author(s) -
Park SangHyuck,
Mei Chuansheng,
Pauly Markus,
Ong Rebecca Garlock,
Dale Bruce E.,
Sabzikar Robab,
Fotoh Hussien,
Nguyen Thang,
Sticklen Mariam
Publication year - 2012
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2012.04.0253
Subject(s) - lignin , corn stover , genetically modified maize , genetically modified rice , biochemistry , ferulic acid , food science , chemistry , reductase , lignocellulosic biomass , genetically modified crops , cellulose , biology , transgene , enzyme , botany , fermentation , gene
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.