title: Expression of Escherichia coli glycogen branching enzyme in an Arabidopsis mutant devoid of endogenous starch branching enzymes induces the synthesis of starch-like polyglucans.
abstract: Starch synthesis requires several enzymatic activities including branching enzymes (BEs) responsible for the formation of α(1 → 6) linkages. Distribution and number of these linkages are further controlled by debranching enzymes that cleave some of them, rendering the polyglucan water-insoluble and semi-crystalline. Although the activity of BEs and debranching enzymes is mandatory to sustain normal starch synthesis, the relative importance of each in the establishment of the plant storage polyglucan (i.e. water insolubility, crystallinity and presence of amylose) is still debated. Here, we have substituted the activity of BEs in Arabidopsis with that of the Escherichia coli glycogen BE (GlgB). The latter is the BE counterpart in the metabolism of glycogen, a highly branched water-soluble and amorphous storage polyglucan. GlgB was expressed in the be2 be3 double mutant of Arabidopsis, which is devoid of BE activity and consequently free of starch. The synthesis of a water-insoluble, partly crystalline, amylose-containing starch-like polyglucan was restored in GlgB-expressing plants, suggesting that BEs' origin only has a limited impact on establishing essential characteristics of starch. Moreover, the balance between branching and debranching is crucial for the synthesis of starch, as an excess of branching activity results in the formation of highly branched, water-soluble, poorly crystalline polyglucan.
authors.affiliation: Univ. Lille, CNRS, UMR 8576 - UGSF  - Unité de Glycobiologie Structurale et Fonctionnelle, F-59000, Lille, France.
authors.forename: Laura
authors.initials: L
authors.lastname: Boyer
authors.affiliation: Univ. Lille, CNRS, UMR 8576 - UGSF  - Unité de Glycobiologie Structurale et Fonctionnelle, F-59000, Lille, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: Roussel
authors.affiliation: Univ. Lille, CNRS, UMR 8576 - UGSF  - Unité de Glycobiologie Structurale et Fonctionnelle, F-59000, Lille, France.
authors.forename: Adeline
authors.initials: A
authors.lastname: Courseaux
authors.affiliation: Université Grenoble Alpes, Centre de Recherches sur les Macromolécules Végétales (CERMAV), F-38000, Grenoble, France.|CNRS, CERMAV, F-38000, Grenoble, France.
authors.forename: Ofilia M
authors.initials: OM
authors.lastname: Ndjindji
authors.affiliation: Université Grenoble Alpes, Centre de Recherches sur les Macromolécules Végétales (CERMAV), F-38000, Grenoble, France.|CNRS, CERMAV, F-38000, Grenoble, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Lancelon-Pin
authors.affiliation: Université Grenoble Alpes, Centre de Recherches sur les Macromolécules Végétales (CERMAV), F-38000, Grenoble, France.|CNRS, CERMAV, F-38000, Grenoble, France.
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Putaux
authors.affiliation: Department of Molecular and Cellular Biology, Science Complex, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Tetlow
authors.affiliation: Department of Molecular and Cellular Biology, Science Complex, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Emes
authors.affiliation: UR1268 BIA, INRA, F-44300, Nantes, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Pontoire
authors.affiliation: Univ. Lille, CNRS, UMR 8576 - UGSF  - Unité de Glycobiologie Structurale et Fonctionnelle, F-59000, Lille, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: D' Hulst
authors.affiliation: Univ. Lille, CNRS, UMR 8576 - UGSF  - Unité de Glycobiologie Structurale et Fonctionnelle, F-59000, Lille, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Wattebled
mesh_terms: D015061:1,4-alpha-Glucan Branching Enzyme / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D002736:Chloroplasts / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005936:Glucans / Q000096:biosynthesis* / Q000648:ultrastructure; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*
chemical_list: D005936:Glucans; D015061:1,4-alpha-Glucan Branching Enzyme
keywords: Arabidopsis thaliana; GlgB; branching enzyme; debranching enzyme; α-glucan