title: Transition from glycogen to starch metabolism in Archaeplastida.
abstract: In this opinion article we propose a scenario detailing how two crucial components have evolved simultaneously to ensure the transition of glycogen to starch in the cytosol of the Archaeplastida last common ancestor: (i) the recruitment of an enzyme from intracellular Chlamydiae pathogens to facilitate crystallization of α-glucan chains; and (ii) the evolution of novel types of polysaccharide (de)phosphorylating enzymes from preexisting glycogen (de)phosphorylation host pathways to allow the turnover of such crystals. We speculate that the transition to starch benefitted Archaeplastida in three ways: more carbon could be packed into osmotically inert material; the host could resume control of carbon assimilation from the chlamydial pathogen that triggered plastid endosymbiosis; and cyanobacterial photosynthate export could be integrated in the emerging Archaeplastida.
authors.affiliation: Laboratoire de Chimie Biologique, Université des Sciences et Technologies de Lille, CNRS, UMR8576, Cité Scientifique, 59655 Villeneuve d'Ascq, France.
authors.forename: Ugo
authors.initials: U
authors.lastname: Cenci
authors.affiliation: Institute of Biochemistry and Biology and Plant Physiology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Nitschke
authors.affiliation: Institute of Biochemistry and Biology and Plant Physiology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Steup
authors.affiliation: Division of Neurology, Department of Pediatrics, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada; Institute of Medical Sciences, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada.
authors.forename: Berge A
authors.initials: BA
authors.lastname: Minassian
authors.affiliation: Laboratoire de Chimie Biologique, Université des Sciences et Technologies de Lille, CNRS, UMR8576, Cité Scientifique, 59655 Villeneuve d'Ascq, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Colleoni
authors.affiliation: Laboratoire de Chimie Biologique, Université des Sciences et Technologies de Lille, CNRS, UMR8576, Cité Scientifique, 59655 Villeneuve d'Ascq, France. Electronic address: steven.ball@univ-lille1.fr.
authors.forename: Steven G
authors.initials: SG
authors.lastname: Ball
mesh_terms: D005075:Biological Evolution; D002689:Chlamydia / Q000201:enzymology; D006003:Glycogen / Q000378:metabolism*; D010766:Phosphorylation; D010802:Phylogeny; D010940:Plant Proteins / Q000378:metabolism; D010944:Plants / Q000201:enzymology / Q000378:metabolism*; D018087:Plastids / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism; D013213:Starch / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D011134:Polysaccharides; D013213:Starch; D006003:Glycogen
keywords: Chlamydia-like bacteria; Lafora disease; evolution of plastids; polyglucan debranching reactions; starch and glycogen (de)phosphorylation; starch and glycogen metabolism