title: Oscillation of mRNA level and activity of granule-bound starch synthase I in Arabidopsis leaves during the day/night cycle.
abstract: Granule-bound starch synthase (GBSSI) is one of the most extensively studied enzymes of the starch synthesis pathway and its role in the synthesis of amylose has been well established. However, few studies have been carried out to characterize the regulation of GBSSI gene. Regulation of starch synthesis genes is especially interesting in photosynthetic tissues, where starch is subjected to a periodical alternation of synthesis and degradation during the day/night cycle. In this report we show a circadian oscillation of GBSSI mRNA levels in leaves of Arabidopsis during the day/night cycle, and provide evidence that GBSSI expression is controlled by the transcription factors CCA1 and LHY. Over-expression of both CCA1 and LHY genes causes the elimination of GBSSI mRNA oscillation. Binding shift assays indicate that this control may be exerted through a direct interaction of those regulatory proteins with the GBSSI promoter. Oscillation is not observed on the GBSSI protein levels, which remains constant along the cycle. However, GBSSI activity shows a clear oscillation with a period of 24 h that is altered in transgenic plants over-expressing CCA1. Possible mechanisms controlling GBSSI activity during the day/night cycle are discussed.
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis CSIC-USE, Avda Américo Vespucio s/n. Isla de la Cartuja, 41092-Sevilla.
authors.forename: Germán
authors.initials: G
authors.lastname: Tenorio
authors.forename: Alicia
authors.initials: A
authors.lastname: Orea
authors.forename: José M
authors.initials: JM
authors.lastname: Romero
authors.forename: Angel
authors.initials: A
authors.lastname: Mérida
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002940:Circadian Rhythm / Q000502:physiology*; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D009154:Mutation; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D013214:Starch Synthase / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C114425:CCA1 protein, Arabidopsis; D018744:DNA, Plant; D004268:DNA-Binding Proteins; C113192:LHY protein, Arabidopsis; D012333:RNA, Messenger; D014157:Transcription Factors; C434607:granule-bound starch synthase I; D013214:Starch Synthase