title: Branching patterns in leaf starches from Arabidopsis mutants deficient in diverse starch synthases.
abstract: This is the first report on the cluster structure of transitory starch from Arabidopsis leaves. In addition to wild type, the molecular structures of leaf starch from mutants deficient in starch synthases (SS) including single enzyme mutants ss1-, ss2-, or ss3-, and also double mutants ss1-ss2- and ss1-ss3- were characterized. The mutations resulted in increased amylose content. Clusters from whole starch were isolated by partial hydrolysis using α-amylase of Bacillus amyloliquefaciens. The clusters were then further hydrolyzed with concentrated α-amylase of B. amyloliquefaciens to produce building blocks (α-limit dextrins). Structures of the clusters and their building blocks were characterized by chromatography of samples before and after debranching treatment. While the mutations increased the size of clusters, the reasons were different as reflected by the composition of their unit chains and building blocks. In general, all mutants contained more of a-chains that preferentially increased the number of small building blocks with only two chains. The clusters of the double mutant ss1-ss3- were very large and possessed also more of large building blocks with four or more chains. The results from transitory starch are compared with those from agriculturally important crops in the context that to what extent the Arabidopsis can be a true biotechnological reflection for starch modifications through genetic means.
authors.affiliation: School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. Electronic address: fzhu5@yahoo.com.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhu
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave, St Paul, MN, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Bertoft
authors.affiliation: Unité de Glycobiologie Structurale et Fonctionnelle, UMR8576 CNRS-Université Lille 1, Sciences et Technologies, F-59655 Villeneuve d'Ascq Cedex, France; Miniaturisation pour l'analyse, la synthèse et la protéomique, USR3290 CNRS-Université Lille 1, Sciences et Technologies, F-59655 Villeneuve d'Ascq cedex, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Szydlowski
authors.affiliation: Unité de Glycobiologie Structurale et Fonctionnelle, UMR8576 CNRS-Université Lille 1, Sciences et Technologies, F-59655 Villeneuve d'Ascq Cedex, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: d'Hulst
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave, St Paul, MN, USA.
authors.forename: Koushik
authors.initials: K
authors.lastname: Seetharaman
mesh_terms: D000688:Amylose / Q000737:chemistry; D017360:Arabidopsis / Q000737:chemistry* / Q000201:enzymology / Q000235:genetics*; D057005:Bioengineering; D006868:Hydrolysis; D009154:Mutation; D018515:Plant Leaves / Q000737:chemistry*; D013213:Starch / Q000737:chemistry*; D013214:Starch Synthase / Q000172:deficiency*
chemical_list: D013213:Starch; D000688:Amylose; D013214:Starch Synthase
keywords: Arabidopsis; Building block; Cluster; Starch structure; Starch synthase; Transitory starch