title: Disruption of a DNA topoisomerase I gene affects morphogenesis in Arabidopsis.
abstract: The genesis of phyllotaxis, which often is associated with the Fibonacci series of numbers, is an old unsolved puzzle in plant morphogenesis. Here, we show that disruption of an Arabidopsis topoisomerase (topo) I gene named TOP1alpha affects phyllotaxis and plant architecture. The divergence angles and internode lengths between two successive flowers were more random in the top1alpha mutant than in the wild type. The top1alpha plants sporadically produced multiple flowers from one node, and the number of floral organ primordia often was different. The mutation also caused the twisting of inflorescences and individual flowers and the serration of leaf margins. These morphological abnormalities indicate that TOP1alpha may play a critical role in the maintenance of a regular pattern of organ initiation. The top1alpha mutant transformed with the RNA interference construct for TOP1beta, another topo I gene arrayed tandemly with TOP1alpha, was found to be lethal at young seedling stages, suggesting that topo I activity is essential in plants.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan. perfect@sci.hokudai.ac.jp
authors.forename: Taku
authors.initials: T
authors.lastname: Takahashi
authors.forename: Shio
authors.initials: S
authors.lastname: Matsuhara
authors.forename: Mitsutomo
authors.initials: M
authors.lastname: Abe
authors.forename: Yoshibumi
authors.initials: Y
authors.lastname: Komeda
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002166:Camptothecin / Q000494:pharmacology; D003001:Cloning, Molecular; D004264:DNA Topoisomerases, Type I / Q000235:genetics* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D009154:Mutation; D010641:Phenotype; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D004791:Enzyme Inhibitors; D018749:RNA, Plant; D004264:DNA Topoisomerases, Type I; C469258:TOP1alpha protein, Arabidopsis; C469259:TOP1beta protein, Arabidopsis; D002166:Camptothecin