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Time course field analysis of COMT-downregulated switchgrass: Lignification, recalcitrance, and rust susceptibility

Journal Article · · BioEnergy Research
 [1];  [1];  [2];  [3];  [4];  [4];  [3];  [4];  [2];  [2];  [1]
  1. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Samuel Roberts Noble Foundation, Ardmore, OK (United States)
  3. Univ. of Tennessee, Knoxville, TN (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of North Texas, Denton, TX (United States)
+ Show Author Affiliations
Modifying plant cell walls by manipulating lignin biosynthesis can improve biofuel yields from lignocellulosic crops. For example, transgenic switchgrass lines with downregulated expression of caffeic acid O-methyltransferase, a lignin biosynthetic enzyme, produce up to 38% more ethanol than controls. The aim of the present study was to understand cell wall lignification over the second and third growing seasons of COMT-downregulated field-grown switchgrass. COMT gene expression, lignification, and cell wall recalcitrance were assayed for two independent transgenic lines at monthly intervals. Switchgrass rust (Puccinia emaculata) incidence was also tracked across the seasons. Trends in lignification over time differed between the 2 years. In 2012, sampling was initiated in mid-growing season on reproductive-stage plants and there was little variation in the lignin content of all lines (COMT-downregulated and control) over time. COMT-downregulated lines maintained 11-16% less lignin, 33-40% lower S/G (syringyl-to-guaiacyl) ratios, and 15-42% higher sugar release relative to controls for all time points. In 2013, sampling was initiated earlier in the season on elongation-stage plants and the lignin content of all lines steadily increased over time, while sugar release expectedly decreased. S/G ratios increased in non-transgenic control plants as biomass accumulated over the season, while remaining relatively stable across the season in the COMT-downregulated lines. Differences in cell wall chemistry between transgenic and non-transgenic lines were not apparent until plants transitioned to reproductive growth in mid-season, after which the cell walls of COMT-downregulated plants exhibited phenotypes consistent with what was observed in 2012. There were no differences in rust damage between transgenics and controls at any time point. Finally, these results provide relevant fundamental insights into the process of lignification in a maturing field-grown biofuel feedstock with downregulated lignin biosynthesis.
Research Organization:
NREL (National Renewable Energy Laboratory (NREL), Golden, CO (United States))
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Grant/Contract Number:
AC36-08GO28308
OSTI ID:
1334241
Report Number(s):
NREL/JA--5100-66619
Journal Information:
BioEnergy Research, Journal Name: BioEnergy Research Journal Issue: 4 Vol. 9; ISSN 1939-1234
Publisher:
SpringerCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (6)

Simultaneous Downregulation of MTHFR and COMT in Switchgrass Affects Plant Performance and Induces Lesion-Mimic Cell Death journal June 2017
Effects of field-grown transgenic switchgrass carbon inputs on soil organic carbon cycling journal January 2019
Bioavailability of Carbohydrate Content in Natural and Transgenic Switchgrasses for the Extreme Thermophile Caldicellulosiruptor bescii journal June 2017
Study of traits and recalcitrance reduction of field-grown COMT down-regulated switchgrass journal January 2017
Development and use of a switchgrass (Panicum virgatum L.) transformation pipeline by the BioEnergy Science Center to evaluate plants for reduced cell wall recalcitrance journal December 2017
Low Lignin Mutants and Reduction of Lignin Content in Grasses for Increased Utilisation of Lignocellulose journal May 2019

Figures / Tables (9)

Fig. 1(p. 23)figure Fig. 1
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Table 1(p. 31)table Table 1
Fig. 1(p. 32)figure Fig. 1
Table 1(p. 34)table Table 1
Table 2(p. 35)table Table 2

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Related Subjects

09 BIOMASS FUELS
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
biomass
caffeic acid O-methyltransferase (COMT)
lignin
lignocellulosic biofuel
switchgrass