Soluble starch synthase I: a major determinant for the synthesis of amylopectin in Arabidopsis thaliana leaves

• Published in: The Plant journal : for cell and molecular biology 2005-08, Vol.43 (3), p.398-412
• Main Authors: Delvalle, D, Dumez, S, Wattebled, F, Roldan, I, Planchot, V, Berbezy, P, Colonna, P, Vyas, D, Chatterjee, M, Ball, S
• Format: Article
• Language: English
• Subjects: amylopectin; Amylopectin - biosynthesis; amylopectin structure; Arabidopsis; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis thaliana; Biochemistry; Biochemistry, Molecular Biology; Biological and medical sciences; biosynthesis; Botany; Chromatography, Gel; Chromosome Mapping; Enzymes; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; gene expression regulation; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Kinetics; Life Sciences; Metabolism; Metabolism. Physicochemical requirements; Microscopy, Electron, Transmission; mutants; Mutation; Phenotype; phenotypic variation; Plant Leaves - enzymology; Plant Leaves - metabolism; Plant Leaves - ultrastructure; Plant physiology and development; plant proteins; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; solubility; starch; starch synthase; Starch Synthase - metabolism; α‐glucan
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313x.2005.02462.x

A minimum of four soluble starch synthase families have been documented in all starch-storing green plants. These activities are involved in amylopectin synthesis and are extremely well conserved throughout the plant kingdom. Mutants or transgenic plants defective for SSII and SSIII isoforms have been previously shown to have a large and specific impact on the synthesis of amylopectin while the function of the SSI type of enzymes has remained elusive. We report here that Arabidopsis mutants, lacking a plastidial starch synthase isoform belonging to the SSI family, display a major and novel type of structural alteration within their amylopectin. Comparative analysis of beta-limit dextrins for both wild type and mutant amylopectins suggests a specific and crucial function of SSI during the synthesis of transient starch in Arabidopsis leaves. Considering our own characterization of SSI activity and the previously described kinetic properties of maize SSI, our results suggest that the function of SSI is mainly involved in the synthesis of small outer chains during amylopectin cluster synthesis.