Functional characterization of the switchgrass (Panicum virgatum) R2R3-MYB transcription factor PvMYB4 for improvement of lignocellulosic feedstocks

Authors

  • Hui Shen,

    1. Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA
    2. BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN37831, USA
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  • Xianzhi He,

    1. Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA
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  • Charleson R. Poovaiah,

    1. Department of Plant Sciences, University of Tennessee at Knoxville, 2431 Joe Johnson Dr, Knoxville, TN 37996, USA
    2. BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN37831, USA
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  • Wegi A. Wuddineh,

    1. Department of Plant Sciences, University of Tennessee at Knoxville, 2431 Joe Johnson Dr, Knoxville, TN 37996, USA
    2. BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN37831, USA
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  • Junying Ma,

    1. Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA
    2. BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN37831, USA
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  • David G. J. Mann,

    1. Department of Plant Sciences, University of Tennessee at Knoxville, 2431 Joe Johnson Dr, Knoxville, TN 37996, USA
    2. BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN37831, USA
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  • Huanzhong Wang,

    1. Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA
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  • Lisa Jackson,

    1. Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA
    2. BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN37831, USA
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  • Yuhong Tang,

    1. Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA
    2. BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN37831, USA
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  • C. Neal Stewart Jr,

    1. Department of Plant Sciences, University of Tennessee at Knoxville, 2431 Joe Johnson Dr, Knoxville, TN 37996, USA
    2. BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN37831, USA
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  • Fang Chen,

    1. Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA
    2. BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN37831, USA
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  • Richard A. Dixon

    1. Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA
    2. BioEnergy Science Center (BESC), Oak Ridge National Laboratory, Oak Ridge, TN37831, USA
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Author for correspondence:
Richard A. Dixon
Tel: +1 580 224 6601
Email: radixon@noble.org

Summary

  • The major obstacle for bioenergy production from switchgrass biomass is the low saccharification efficiency caused by cell wall recalcitrance. Saccharification efficiency is negatively correlated with both lignin content and cell wall ester-linked p-coumarate: ferulate (p-CA : FA) ratio. In this study, we cloned and functionally characterized an R2R3-MYB transcription factor from switchgrass and evaluated its potential for developing lignocellulosic feedstocks.
  • The switchgrass PvMYB4 cDNAs were cloned and expressed in Escherichia coli, yeast, tobacco and switchgrass for functional characterization. Analyses included determination of phylogenetic relations, in situ hybridization, electrophoretic mobility shift assays to determine binding sites in target promoters, and protoplast transactivation assays to demonstrate domains active on target promoters.
  • PvMYB4 binds to the AC-I, AC-II and AC-III elements of monolignol pathway genes and down-regulates these genes in vivo. Ectopic overexpression of PvMYB4 in transgenic switchgrass resulted in reduced lignin content and ester-linked p-CA : FA ratio, reduced plant stature, increased tillering and an approx. threefold increase in sugar release efficiency from cell wall residues.
  • We describe an alternative strategy for reducing recalcitrance in switchgrass by manipulating the expression of a key transcription factor instead of a lignin biosynthetic gene. PvMYB4-OX transgenic switchgrass lines can be used as potential germplasm for improvement of lignocellulosic feedstocks and provide a platform for further understanding gene regulatory networks underlying switchgrass cell wall recalcitrance.

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