CRM1/BIG-mediated auxin action regulates Arabidopsis inflorescence development

Plant Cell Physiol. 2007 Sep;48(9):1275-90. doi: 10.1093/pcp/pcm094. Epub 2007 Jul 24.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Arabidopsis / genetics*
  • Arabidopsis / growth & development*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Arabidopsis Proteins / physiology*
  • Calmodulin-Binding Proteins / genetics
  • Calmodulin-Binding Proteins / metabolism
  • Calmodulin-Binding Proteins / physiology*
  • Flowers / anatomy & histology
  • Flowers / genetics
  • Flowers / growth & development*
  • Gene Expression Regulation, Plant
  • Genes, Plant
  • Indoleacetic Acids / metabolism*
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism
  • Molecular Sequence Data
  • Mutation
  • Plant Growth Regulators / metabolism*
  • Plant Leaves / metabolism
  • Plants, Genetically Modified / growth & development
  • Plants, Genetically Modified / metabolism
  • Up-Regulation


  • Arabidopsis Proteins
  • BIG protein, Arabidopsis
  • Calmodulin-Binding Proteins
  • Indoleacetic Acids
  • Membrane Transport Proteins
  • PIN1 protein, Arabidopsis
  • Plant Growth Regulators

Associated data

  • GENBANK/AF507018