title: Engineering temporal accumulation of a low recalcitrance polysaccharide leads to increased C6 sugar content in plant cell walls.
abstract: Reduced cell wall recalcitrance and increased C6 monosaccharide content are desirable traits for future biofuel crops, as long as these biomass modifications do not significantly alter normal growth and development. Mixed-linkage glucan (MLG), a cell wall polysaccharide only present in grasses and related species among flowering plants, is comprised of glucose monomers linked by both β-1,3 and β-1,4 bonds. Previous data have shown that constitutive production of MLG in barley (Hordeum vulgare) severely compromises growth and development. Here, we used spatio-temporal strategies to engineer Arabidopsis thaliana plants to accumulate significant amounts of MLG in the cell wall by expressing the rice CslF6 MLG synthase using secondary cell wall and senescence-associated promoters. Results using secondary wall promoters were suboptimal. When the rice MLG synthase was expressed under the control of a senescence-associated promoter, we obtained up to four times more glucose in the matrix cell wall fraction and up to a 42% increase in saccharification compared to control lines. Importantly, these plants grew and developed normally. The induction of MLG deposition at senescence correlated with an increase of gluconic acid in cell wall extracts of transgenic plants in contrast to the other approaches presented in this study. MLG produced in Arabidopsis has an altered structure compared to the grass glucan, which likely affects its solubility, while its molecular size is unaffected. The induction of cell wall polysaccharide biosynthesis in senescing tissues offers a novel engineering alternative to enhance cell wall properties of lignocellulosic biofuel crops.
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: Miguel E
authors.identifier: http://orcid.org/0000-0003-0128-2743
authors.initials: ME
authors.lastname: Vega-Sánchez
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: Dominique
authors.initials: D
authors.lastname: Loqué
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: Jeemeng
authors.initials: J
authors.lastname: Lao
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: Michela
authors.initials: M
authors.lastname: Catena
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: Yves
authors.initials: Y
authors.lastname: Verhertbruggen
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Herter
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: Fan
authors.initials: F
authors.lastname: Yang
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Harholt
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.|Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Denmark.
authors.forename: Berit
authors.initials: B
authors.lastname: Ebert
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: Edward E K
authors.initials: EE
authors.lastname: Baidoo
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.|Department of Chemical and Biomolecular Engineering, and Department of Bioengineering, University of California, Berkeley, CA, USA.
authors.forename: Jay D
authors.initials: JD
authors.lastname: Keasling
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.|Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA.
authors.forename: Henrik V
authors.initials: HV
authors.lastname: Scheller
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: Joshua L
authors.initials: JL
authors.lastname: Heazlewood
authors.affiliation: Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.|Department of Plant Pathology and the Genome Center, University of California, Davis, CA, USA.
authors.forename: Pamela C
authors.initials: PC
authors.lastname: Ronald
mesh_terms: D000375:Aging / Q000502:physiology; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism*; D005936:Glucans / Q000378:metabolism*; D059828:Plant Cells / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism*
chemical_list: D005936:Glucans; D011134:Polysaccharides
keywords: CslF6; bioenergy; cell wall engineering; gluconic acid; mixed-linkage glucan; senescence-associated promoter