title: Transgenic switchgrass (Panicum virgatum L.) targeted for reduced recalcitrance to bioconversion: a 2-year comparative analysis of field-grown lines modified for target gene or genetic element expression.
abstract: Transgenic Panicum virgatum L. silencing (KD) or overexpressing (OE) specific genes or a small RNA (GAUT4-KD, miRNA156-OE, MYB4-OE, COMT-KD and FPGS-KD) was grown in the field and aerial tissue analysed for biofuel production traits. Clones representing independent transgenic lines were established and senesced tissue was sampled after year 1 and 2 growth cycles. Biomass was analysed for wall sugars, recalcitrance to enzymatic digestibility and biofuel production using separate hydrolysis and fermentation. No correlation was found between plant carbohydrate content and biofuel production pointing to overriding structural and compositional elements that influence recalcitrance. Biomass yields were greater for all lines in the second year as plants establish in the field and standard amounts of biomass analysed from each line had more glucan, xylan and less ethanol (g/g basis) in the second- versus the first-year samples, pointing to a broad increase in tissue recalcitrance after regrowth from the perennial root. However, biomass from second-year growth of transgenics targeted for wall modification, GAUT4-KD, MYB4-OE, COMT-KD and FPGS-KD, had increased carbohydrate and ethanol yields (up to 12% and 21%, respectively) compared with control samples. The parental plant lines were found to have a significant impact on recalcitrance which can be exploited in future strategies. This summarizes progress towards generating next-generation bio-feedstocks with improved properties for microbial and enzymatic deconstruction, while providing a comprehensive quantitative analysis for the bioconversion of multiple plant lines in five transgenic strategies.
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: Alexandru
authors.initials: A
authors.lastname: Dumitrache
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: Jace
authors.initials: J
authors.lastname: Natzke
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: Miguel
authors.initials: M
authors.lastname: Rodriguez
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: Kelsey L
authors.initials: KL
authors.lastname: Yee
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: Olivia A
authors.initials: OA
authors.lastname: Thompson
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA.
authors.forename: Charleson R
authors.initials: CR
authors.lastname: Poovaiah
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|BioDiscovery Institute and Department of Biological Sciences, University of North Texas, Denton, TX, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Shen
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA.
authors.forename: Mitra
authors.initials: M
authors.lastname: Mazarei
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA.
authors.forename: Holly L
authors.initials: HL
authors.lastname: Baxter
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK, USA.
authors.forename: Chunxiang
authors.initials: C
authors.lastname: Fu
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK, USA.
authors.forename: Zeng-Yu
authors.initials: ZY
authors.lastname: Wang
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Complex Carbohydrate Research Center and Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA.
authors.forename: Ajaya K
authors.initials: AK
authors.lastname: Biswal
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Forage Improvement Division, The Samuel Roberts Noble Foundation, Ardmore, OK, USA.
authors.forename: Guifen
authors.initials: G
authors.lastname: Li
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK, USA.
authors.forename: Avinash C
authors.initials: AC
authors.lastname: Srivastava
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK, USA.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Tang
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA.
authors.forename: Charles Neal
authors.initials: CN
authors.lastname: Stewart
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|BioDiscovery Institute and Department of Biological Sciences, University of North Texas, Denton, TX, USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Dixon
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK, USA.
authors.forename: Richard S
authors.initials: RS
authors.lastname: Nelson
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Complex Carbohydrate Research Center and Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA.
authors.forename: Debra
authors.initials: D
authors.lastname: Mohnen
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Mielenz
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: Steven D
authors.initials: SD
authors.lastname: Brown
authors.affiliation: BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: Brian H
authors.identifier: http://orcid.org/0000-0002-7408-3609
authors.initials: BH
authors.lastname: Davison
mesh_terms: D056804:Biofuels; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D008897:Panicum / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*
chemical_list: D056804:Biofuels; D010940:Plant Proteins
keywords: bioconversion; bioenergy; comparison; recalcitrance; switchgrass; transgenic