title: Modulation of amylose content by structure-based modification of OsGBSS1 activity in rice (Oryza sativa L.).
abstract: The rice Waxy (Wx) gene encodes granule-bound starch synthase 1 (EC 2.4.1.242), OsGBSS1, which is responsible for amylose synthesis in rice seed endosperm. In this study, we determined the functional contribution of eight amino acids on the activity of OsGBSS1 by introducing site-directed mutated Wx gene constructs into the wx mutant glutinous rice. The eight amino acid residues are suspected to play roles in OsGBSS1 structure maintenance or function based on homologous enzyme sequence alignment and homology modelling. Both OsGBSS1 activity and amylose content were analysed in homozygous transgenic lines carrying the mutated OsGBSS1 (Wx) genes. Our results indicate that mutations at diverse sites in OsGBSS1 reduces its activity by affecting its starch-binding capacity, its ADP-glucose-binding capability or its protein stability. Our results shed new light on the structural basis of OsGBSS1 activity and the mechanisms of OsGBSS1 activity on amylose synthesis in vivo. This study also demonstrates that it is feasible to finely modulate amylose content in rice grains by modifying the OsGBSS1 activity.
authors: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China; Graduate School of the Chinese Academy of Sciences, Beijing, China.
authors: Derui
authors: D
authors: Liu
authors: Wei
authors: W
authors: Wang
authors: Xiuling
authors: X
authors: Cai
mesh_terms: D000245:Adenosine Diphosphate Glucose / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000688:Amylose / Q000378:metabolism*; D003433:Crosses, Genetic; D018506:Gene Expression Regulation, Plant; D006720:Homozygote; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D055550:Protein Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013214:Starch Synthase / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D000245:Adenosine Diphosphate Glucose; D000688:Amylose; D013214:Starch Synthase
keywords: ADPG-binding capacity; OsGBSS1; Swiss-Pdbviewer; amylose content; site-directed mutagenesis; starch-binding capacity