title: Downregulation of RWA genes in hybrid aspen affects xylan acetylation and wood saccharification.
abstract: High acetylation of angiosperm wood hinders its conversion to sugars by glycoside hydrolases, subsequent ethanol fermentation and (hence) its use for biofuel production. We studied the REDUCED WALL ACETYLATION (RWA) gene family of the hardwood model Populus to evaluate its potential for improving saccharification. The family has two clades, AB and CD, containing two genes each. All four genes are expressed in developing wood but only RWA-A and -B are activated by master switches of the secondary cell wall PtNST1 and PtMYB21. Histochemical analysis of promoter::GUS lines in hybrid aspen (Populus tremula × tremuloides) showed activation of RWA-A and -B promoters in the secondary wall formation zone, while RWA-C and -D promoter activity was diffuse. Ectopic downregulation of either clade reduced wood xylan and xyloglucan acetylation. Suppressing both clades simultaneously using the wood-specific promoter reduced wood acetylation by 25% and decreased acetylation at position 2 of Xylp in the dimethyl sulfoxide-extracted xylan. This did not affect plant growth but decreased xylose and increased glucose contents in the noncellulosic monosaccharide fraction, and increased glucose and xylose yields of wood enzymatic hydrolysis without pretreatment. Both RWA clades regulate wood xylan acetylation in aspen and are promising targets to improve wood saccharification.
authors.affiliation: Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, S-901 83, Sweden.
authors.forename: Prashant Mohan-Anupama
authors.initials: PM
authors.lastname: Pawar
authors.affiliation: Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, S-901 83, Sweden.
authors.forename: Christine
authors.initials: C
authors.lastname: Ratke
authors.affiliation: Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, S-901 83, Sweden.
authors.forename: Vimal K
authors.initials: VK
authors.lastname: Balasubramanian
authors.affiliation: Department of Food and Environmental Sciences, University of Helsinki, PO Box 27, FI-Helsinki, 00014, Finland.
authors.forename: Sun-Li
authors.initials: SL
authors.lastname: Chong
authors.affiliation: Department of Chemistry, Umeå University, Umeå, S-901 87, Sweden.
authors.forename: Madhavi Latha
authors.initials: ML
authors.lastname: Gandla
authors.affiliation: School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Centre, SE-106 91, Stockholm, Sweden.
authors.forename: Mathilda
authors.initials: M
authors.lastname: Adriasola
authors.affiliation: Department of Chemistry, Umeå University, Umeå, S-901 87, Sweden.
authors.forename: Tobias
authors.initials: T
authors.lastname: Sparrman
authors.affiliation: Department of Chemistry, Umeå University, Umeå, S-901 87, Sweden.
authors.forename: Mattias
authors.initials: M
authors.lastname: Hedenström
authors.affiliation: Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, S-901 83, Sweden.
authors.forename: Klaudia
authors.initials: K
authors.lastname: Szwaj
authors.affiliation: Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, S-901 83, Sweden.
authors.forename: Marta
authors.initials: M
authors.lastname: Derba-Maceluch
authors.affiliation: Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech, ERL3559 CNRS, Saclay Plant Sciences, INRA, Versailles, 78026, France.
authors.forename: Cyril
authors.initials: C
authors.lastname: Gaertner
authors.affiliation: Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech, ERL3559 CNRS, Saclay Plant Sciences, INRA, Versailles, 78026, France.
authors.forename: Gregory
authors.initials: G
authors.lastname: Mouille
authors.affiliation: School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Centre, SE-106 91, Stockholm, Sweden.
authors.forename: Ines
authors.initials: I
authors.lastname: Ezcurra
authors.affiliation: Department of Food and Environmental Sciences, University of Helsinki, PO Box 27, FI-Helsinki, 00014, Finland.
authors.forename: Maija
authors.initials: M
authors.lastname: Tenkanen
authors.affiliation: Department of Chemistry, Umeå University, Umeå, S-901 87, Sweden.
authors.forename: Leif J
authors.initials: LJ
authors.lastname: Jönsson
authors.affiliation: Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, S-901 83, Sweden.
authors.forename: Ewa J
authors.identifier: http://orcid.org/0000-0001-6817-1031
authors.initials: EJ
authors.lastname: Mellerowicz
mesh_terms: D000107:Acetylation; D002473:Cell Wall / Q000737:chemistry / Q000235:genetics; D002678:Chimera; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D005936:Glucans / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D005810:Multigene Family; D030821:Plants, Genetically Modified; D032107:Populus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014026:Nicotiana / Q000235:genetics; D014934:Wood / Q000235:genetics / Q000378:metabolism*; D014990:Xylans / Q000235:genetics / Q000378:metabolism*; D052584:Xylem / Q000378:metabolism
chemical_list: D005936:Glucans; D014990:Xylans; C029353:xyloglucan
keywords: 
  Populus
  ; 
  REDUCED CELL WALL ACETYLATION
  ; Cas1p; saccharification; wood acetylation; xylan; xylan acetylation; xylem