title: CRM1/BIG-mediated auxin action regulates Arabidopsis inflorescence development.
abstract: The shape of the inflorescence in Arabidopsis thaliana ecotype Columbia is a raceme with individual flowers developing acropetally. The ecotype Landsberg harboring the erecta (er) mutation shows a corymb-like inflorescence, namely a compact inflorescence with a flattened arrangement of flower buds at the tip. To gain insight into inflorescence development, we previously isolated corymb-like inflorescence mutants, named corymbosa1 (crm1), and found that the corymb-like inflorescence in crm1-1 was due to reduced cell elongation of pedicels and stem internodes. Double mutants of crm1 with er and crm2, and crm1-1 crm2-1 er-105 triple mutants show an additive phenotype. crm1-1 is caused by a mutation in BIG, which is required for polar auxin transport. CRM1/BIG is expressed in inflorescence meristems, floral meristems and vascular tissues. We analyzed a collection of 12 reduced lateral root formation (rlr) mutants, which are allelic to crm1-1, and categorized the mutants into three classes, depending on the plant developmental defects. Although all 12 alleles had new stop codons, the phenotype of heterozygous crm1-1/doc1-1 and Northern blotting suggest that new crm1/big mutant alleles are hypomorphic. Auxin-responsive DR5rev::GFP expression was decreased in crm1-1 vasculature of pedicels and stem internodes. PINFORMED1 (PIN1) and CRM1/BIG are expressed in vasculature of pedicels and stem internodes. The severity of corymb-like inflorescence in crm1/big mutants correlated with increased levels of PIN1. Our results suggest that CRM1/BIG controls the elongation of the pedicels and stem internodes through auxin action.
authors.affiliation: Laboratory of Plant Science, Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Tokyo, Japan.
authors.forename: Nobutoshi
authors.initials: N
authors.lastname: Yamaguchi
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Suzuki
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Fukaki
authors.forename: Miyo
authors.initials: M
authors.lastname: Morita-Terao
authors.forename: Masao
authors.initials: M
authors.lastname: Tasaka
authors.forename: Yoshibumi
authors.initials: Y
authors.lastname: Komeda
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002148:Calmodulin-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D035264:Flowers / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010937:Plant Growth Regulators / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000254:growth & development / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D029681:Arabidopsis Proteins; C434262:BIG protein, Arabidopsis; D002148:Calmodulin-Binding Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis; D010937:Plant Growth Regulators