title: Loss of function of folylpolyglutamate synthetase 1 reduces lignin content and improves cell wall digestibility in Arabidopsis.
abstract: BACKGROUND
  One-carbon (C1) metabolism is important for synthesizing a range of biologically important compounds that are essential for life. In plants, the C1 pathway is crucial for the synthesis of a large number of secondary metabolites, including lignin. Tetrahydrofolate and its derivatives, collectively referred to as folates, are crucial co-factors for C1 metabolic pathway enzymes. Given the link between the C1 and phenylpropanoid pathways, we evaluated whether folylpolyglutamate synthetase (FPGS), an enzyme that catalyzes the addition of a glutamate tail to folates to form folylpolyglutamates, can be a viable target for reducing cell wall recalcitrance in plants.
  
  
  RESULTS
  Consistent with its role in lignocellulosic formation, FPGS1 was preferentially expressed in vascular tissues. Total lignin was low in fpgs1 plants leading to higher saccharification efficiency of the mutant. The decrease in total lignin in fpgs1 was mainly due to lower guaiacyl (G) lignin levels. Glycome profiling revealed subtle alterations in the cell walls of fpgs1. Further analyses of hemicellulosic polysaccharides by NMR showed that the degree of methylation of 4-O-methyl glucuronoxylan was reduced in the fpgs1 mutant. Microarray analysis and real-time qRT-PCR revealed that transcripts of a number of genes in the C1 and lignin pathways had altered expression in fpgs1 mutants. Consistent with the transcript changes of C1-related genes, a significant reduction in S-adenosyl-l-methionine content was detected in the fpgs1 mutant. The modified expression of the various methyltransferases and lignin-related genes indicate possible feedback regulation of C1 pathway-mediated lignin biosynthesis.
  
  
  CONCLUSIONS
  Our observations provide genetic and biochemical support for the importance of folylpolyglutamates in the lignocellulosic pathway and reinforces previous observations that targeting a single FPGS isoform for down-regulation leads to reduced lignin in plants. Because fpgs1 mutants had no dramatic defects in above ground biomass, selective down-regulation of individual components of C1 metabolism is an approach that should be explored further for the improvement of lignocellulosic feedstocks.
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401 USA ; BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA.
authors.forename: Avinash C
authors.initials: AC
authors.lastname: Srivastava
authors.affiliation: BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA ; Department of Biological Sciences, University of North Texas, Denton, TX 76203 USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Chen
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401 USA.
authors.forename: Tui
authors.initials: T
authors.lastname: Ray
authors.affiliation: BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA ; Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602 USA ; Department of Plant Biology, University of Georgia, Athens, GA 30602 USA.
authors.forename: Sivakumar
authors.initials: S
authors.lastname: Pattathil
authors.affiliation: BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA ; Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602 USA.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Peña
authors.affiliation: BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA ; Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602 USA ; Department of Plant Biology, University of Georgia, Athens, GA 30602 USA.
authors.forename: Utku
authors.initials: U
authors.lastname: Avci
authors.affiliation: BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA ; Center for Environmental Research and Technology (CE-CERT), Bourns College of Engineering, University of California, Riverside, CA 92507 USA.
authors.forename: Hongjia
authors.initials: H
authors.lastname: Li
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401 USA.
authors.forename: David V
authors.initials: DV
authors.lastname: Huhman
authors.affiliation: BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA ; Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602 USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Backe
authors.affiliation: BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA ; Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602 USA.
authors.forename: Breeanna
authors.initials: B
authors.lastname: Urbanowicz
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602 USA.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Miller
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401 USA.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Bedair
authors.affiliation: BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA ; Center for Environmental Research and Technology (CE-CERT), Bourns College of Engineering, University of California, Riverside, CA 92507 USA.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Wyman
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401 USA.
authors.forename: Lloyd W
authors.initials: LW
authors.lastname: Sumner
authors.affiliation: BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA ; Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602 USA ; Department of Plant Biology, University of Georgia, Athens, GA 30602 USA.
authors.forename: William S
authors.initials: WS
authors.lastname: York
authors.affiliation: BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA ; Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602 USA ; Department of Plant Biology, University of Georgia, Athens, GA 30602 USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hahn
authors.affiliation: BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA ; Department of Biological Sciences, University of North Texas, Denton, TX 76203 USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Dixon
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401 USA ; BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA.
authors.forename: Elison B
authors.initials: EB
authors.lastname: Blancaflor
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73401 USA ; BioEnergy Science Center, United States Department of Energy, Oak Ridge, TN 37831 USA.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Tang
keywords: Arabidopsis; Bioenergy; C1 metabolism; Cell-wall recalcitrance; FPGS1; Folylpolyglutamate synthetase; Lignin