title: Convergent evolution of polysaccharide debranching defines a common mechanism for starch accumulation in cyanobacteria and plants.
abstract: Starch, unlike hydrosoluble glycogen particles, aggregates into insoluble, semicrystalline granules. In photosynthetic eukaryotes, the transition to starch accumulation occurred after plastid endosymbiosis from a preexisting cytosolic host glycogen metabolism network. This involved the recruitment of a debranching enzyme of chlamydial pathogen origin. The latter is thought to be responsible for removing misplaced branches that would otherwise yield a water-soluble polysaccharide. We now report the implication of starch debranching enzyme in the aggregation of semicrystalline granules of single-cell cyanobacteria that accumulate both glycogen and starch-like polymers. We show that an enzyme of analogous nature to the plant debranching enzyme but of a different bacterial origin was recruited for the same purpose in these organisms. Remarkably, both the plant and cyanobacterial enzymes have evolved through convergent evolution, showing novel yet identical substrate specificities from a preexisting enzyme that originally displayed the much narrower substrate preferences required for glycogen catabolism.
authors.affiliation: Université des Sciences et Technologies de Lille, Unité de Glycobiologie Structurale et Fonctionelle, Unité Mixte de Recherche 8576, Centre National de la Recherche Scientifique, Cité Scientifique, 59655 Villeneuve d'Ascq cedex, France.
authors.forename: Ugo
authors.initials: U
authors.lastname: Cenci
authors.forename: Malika
authors.initials: M
authors.lastname: Chabi
authors.forename: Mathieu
authors.initials: M
authors.lastname: Ducatez
authors.forename: Catherine
authors.initials: C
authors.lastname: Tirtiaux
authors.forename: Jennifer
authors.initials: J
authors.lastname: Nirmal-Raj
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Utsumi
authors.forename: Daiki
authors.initials: D
authors.lastname: Kobayashi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sasaki
authors.forename: Eiji
authors.initials: E
authors.lastname: Suzuki
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Putaux
authors.forename: Xavier
authors.initials: X
authors.lastname: Roussel
authors.forename: Amandine
authors.initials: A
authors.lastname: Durand-Terrasson
authors.forename: Debashish
authors.initials: D
authors.lastname: Bhattacharya
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Vercoutter-Edouart
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Maes
authors.forename: Maria Cecilia
authors.initials: MC
authors.lastname: Arias
authors.forename: Monica
authors.initials: M
authors.lastname: Palcic
authors.forename: Lyann
authors.initials: L
authors.lastname: Sim
authors.forename: Steven G
authors.initials: SG
authors.lastname: Ball
authors.forename: Christophe
authors.initials: C
authors.lastname: Colleoni
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005075:Biological Evolution; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000201:enzymology* / Q000235:genetics; D006003:Glycogen / Q000378:metabolism*; D006004:Glycogen Debranching Enzyme System / Q000235:genetics* / Q000378:metabolism; D016296:Mutagenesis; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D013213:Starch / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D006004:Glycogen Debranching Enzyme System; D010940:Plant Proteins; D013213:Starch; D006003:Glycogen