Plastidial phosphorylase is required for normal starch synthesis in Chlamydomonas reinhardtii

• Published in: The Plant journal : for cell and molecular biology 2006-10, Vol.48 (2), p.274-285
• Main Authors: Dauvillée, David, Chochois, Vincent, Steup, Martin, Haebel, Sophie, Eckermann, Nora, Ritte, Gerhard, Ral, Jean-Philippe, Colleoni, Christophe, Hicks, Glenn, Wattebled, Fabrice, Deschamps, Philippe, d'Hulst, Christophe, Liénard, Luc, Cournac, Laurent, Putaux, Jean-Luc, Dupeyre, Danielle, Ball, Steven G
• Format: Article
• Language: English
• Subjects: (glycogen) starch phosphorylase; Algal Proteins - genetics; Algal Proteins - metabolism; Algal Proteins - physiology; Amino acids; amylopectin; Amylopectin - chemistry; Amylopectin - metabolism; Amylose - metabolism; Animals; Biochemistry; Biochemistry, Molecular Biology; Biological and medical sciences; Carbohydrates; Chlamydomonas; Chlamydomonas reinhardtii; Chlamydomonas reinhardtii - enzymology; Chlamydomonas reinhardtii - genetics; Deoxyribonucleic acid; DNA; Enzymes; Flowers & plants; Fundamental and applied biological sciences. Psychology; Genetic Complementation Test; Genomics; Glucose; Isoenzymes - analysis; Isoenzymes - genetics; Isoenzymes - metabolism; Kinetics; Life Sciences; Metabolism; Microscopy, Electron, Scanning; Mutation; Nitrogen - metabolism; Phosphorylases - genetics; Phosphorylases - metabolism; Phosphorylases - physiology; Photosynthesis, respiration. Anabolism, catabolism; Plant physiology and development; starch; Starch - biosynthesis; Starch - ultrastructure
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2006.02870.x

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.