The phenotype of soluble starch synthase IV defective mutants of Arabidopsis thaliana suggests a novel function of elongation enzymes in the control of starch granule formation

• Published in: The Plant journal : for cell and molecular biology 2007-02, Vol.49 (3), p.492-504
• Main Authors: Roldán, Isaac, Wattebled, Fabrice, Mercedes Lucas, M., Delvallé, David, Planchot, Veronique, Jiménez, Sebastian, Pérez, Ricardo, Ball, Steven, D'Hulst, Christophe, Mérida, Ángel
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Alleles; amylopectin; Arabidopsis; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - growth & development; Biochemistry; Biochemistry, Molecular Biology; Biological and medical sciences; Botany; Carbohydrates; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Genotype & phenotype; knock‐out mutant; Life Sciences; Metabolism; Mutation; Net assimilation, photosynthesis, carbon metabolism. Photorespiration, respiration, fermentation (anoxia, hypoxia); Nutrition. Photosynthesis. Respiration. Metabolism; Phenotype; Photosynthesis, respiration. Anabolism, catabolism; Plant physiology and development; Plastids - metabolism; RNA, Messenger - metabolism; Starch - biosynthesis; starch granule; starch granule initiation; starch synthase; Starch Synthase - physiology
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2006.02968.x

Summary All plants and green algae synthesize starch through the action of the same five classes of elongation enzymes: the starch synthases. Arabidopsis mutants defective for the synthesis of the soluble starch synthase IV (SSIV) type of elongation enzyme have now been characterized. The mutant plants displayed a severe growth defect but nonetheless accumulated near to normal levels of polysaccharide storage. Detailed structural analysis has failed to yield any change in starch granule structure. However, the number of granules per plastid has dramatically decreased leading to a large increase in their size. These results, which distinguish the SSIV mutants from all other mutants reported to date, suggest a specific function of this enzyme class in the control of granule numbers. We speculate therefore that SSIV could be selectively involved in the priming of starch granule formation.