title: 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.
abstract: 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.
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis. CSIC-US. Avda Américo Vespucio 49. Isla de la Cartuja, 41092-Sevilla, Spain.
authors.forename: Isaac
authors.initials: I
authors.lastname: Roldán
authors.forename: Fabrice
authors.initials: F
authors.lastname: Wattebled
authors.forename: M
authors.initials: M
authors.lastname: Mercedes Lucas
authors.forename: David
authors.initials: D
authors.lastname: Delvallé
authors.forename: Veronique
authors.initials: V
authors.lastname: Planchot
authors.forename: Sebastian
authors.initials: S
authors.lastname: Jiménez
authors.forename: Ricardo
authors.initials: R
authors.lastname: Pérez
authors.forename: Steven
authors.initials: S
authors.lastname: Ball
authors.forename: Christophe
authors.initials: C
authors.lastname: D'Hulst
authors.forename: Angel
authors.initials: A
authors.lastname: Mérida
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins; D009154:Mutation; D010641:Phenotype; D018087:Plastids / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013213:Starch / Q000096:biosynthesis*; D013214:Starch Synthase / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D012333:RNA, Messenger; D013213:Starch; D013214:Starch Synthase; C520418:starch synthase IV, Arabidopsis