title: Plastidial phosphorylase is required for normal starch synthesis in Chlamydomonas reinhardtii.
abstract: Among the three distinct starch phosphorylase activities detected in Chlamydomonas reinhardtii, two distinct plastidial enzymes (PhoA and PhoB) are documented while a single extraplastidial form (PhoC) displays a higher affinity for glycogen as in vascular plants. The two plastidial phosphorylases are shown to function as homodimers containing two 91-kDa (PhoA) subunits and two 110-kDa (PhoB) subunits. Both lack the typical 80-amino-acid insertion found in the higher plant plastidial forms. PhoB is exquisitely sensitive to inhibition by ADP-glucose and has a low affinity for malto-oligosaccharides. PhoA is more similar to the higher plant plastidial phosphorylases: it is moderately sensitive to ADP-glucose inhibition and has a high affinity for unbranched malto-oligosaccharides. Molecular analysis establishes that STA4 encodes PhoB. Chlamydomonas reinhardtii strains carrying mutations at the STA4 locus display a significant decrease in amounts of starch during storage that correlates with the accumulation of abnormally shaped granules containing a modified amylopectin structure and a high amylose content. The wild-type phenotype could be rescued by reintroduction of the cloned wild-type genomic DNA, thereby demonstrating the involvement of phosphorylase in storage starch synthesis.
authors.affiliation: Unité de Glycobiologie Structurale et Fonctionnelle, UMR8576 CNRS/USTL, IFR 118, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq, Cedex, France.
authors.forename: David
authors.initials: D
authors.lastname: Dauvillée
authors.forename: Vincent
authors.initials: V
authors.lastname: Chochois
authors.forename: Martin
authors.initials: M
authors.lastname: Steup
authors.forename: Sophie
authors.initials: S
authors.lastname: Haebel
authors.forename: Nora
authors.initials: N
authors.lastname: Eckermann
authors.forename: Gerhard
authors.initials: G
authors.lastname: Ritte
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Ral
authors.forename: Christophe
authors.initials: C
authors.lastname: Colleoni
authors.forename: Glenn
authors.initials: G
authors.lastname: Hicks
authors.forename: Fabrice
authors.initials: F
authors.lastname: Wattebled
authors.forename: Philippe
authors.initials: P
authors.lastname: Deschamps
authors.forename: Christophe
authors.initials: C
authors.lastname: d'Hulst
authors.forename: Luc
authors.initials: L
authors.lastname: Liénard
authors.forename: Laurent
authors.initials: L
authors.lastname: Cournac
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Putaux
authors.forename: Danielle
authors.initials: D
authors.lastname: Dupeyre
authors.forename: Steven G
authors.initials: SG
authors.lastname: Ball
mesh_terms: D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000687:Amylopectin / Q000737:chemistry / Q000378:metabolism; D000688:Amylose / Q000378:metabolism; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000201:enzymology* / Q000235:genetics; D005816:Genetic Complementation Test; D007527:Isoenzymes / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism; D006005:Phosphorylases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013213:Starch / Q000096:biosynthesis* / Q000648:ultrastructure
chemical_list: D020418:Algal Proteins; D007527:Isoenzymes; D013213:Starch; D000688:Amylose; D000687:Amylopectin; D006005:Phosphorylases; D009584:Nitrogen