Lateral root formation is blocked by a gain-of-function mutation in the SOLITARY-ROOT/IAA14 gene of Arabidopsis

Plant J. 2002 Jan;29(2):153-68. doi: 10.1046/j.0960-7412.2001.01201.x.


Lateral root development is a post-embryonic organogenesis event that gives rise to most of the underground parts of higher plants. Auxin promotes lateral root formation, but the molecular mechanisms involved are still unknown. We have isolated a novel Arabidopsis mutant, solitary-root (slr), which has reduced sensitivity to auxin. This dominant slr-1 mutant completely lacks lateral roots, and this phenotype cannot be rescued by the application of exogenous auxin. Analysis with cell-cycle and cell-differentiation markers revealed that the slr-1 mutation blocks cell divisions of pericycle cells in lateral root initiation. The slr-1 mutant is also defective in root hair formation and in the gravitropic responses of its roots and hypocotyls. Map-based positional cloning and isolation of an intragenic suppressor mutant revealed that SLR encodes IAA14, a member of the Aux/IAA protein family. Green fluorescent protein-tagged mutant IAA14 protein was localized in the nucleus, and the gain-of-function slr-1/iaa14 mutation decreased auxin-inducible BA-GUS gene expression in the root, suggesting that SLR/IAA14 acts as a transcriptional repressor. These observations indicate that SLR/IAA14 is a key regulator in auxin-regulated growth and development, particularly in lateral root formation.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / genetics*
  • Arabidopsis / growth & development
  • Arabidopsis Proteins*
  • Cell Division / drug effects
  • Cell Nucleus / metabolism
  • Chromosome Mapping
  • DNA Mutational Analysis
  • Gene Expression Regulation, Plant / drug effects
  • Indoleacetic Acids / pharmacology
  • Molecular Sequence Data
  • Multigene Family
  • Mutation
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Phenotype
  • Plant Proteins / genetics*
  • Plant Proteins / metabolism
  • Plant Roots / drug effects
  • Plant Roots / genetics*
  • Plant Roots / growth & development
  • Plants, Genetically Modified
  • Sequence Homology, Amino Acid
  • Transcription Factors


  • AXR3 protein, Arabidopsis
  • Arabidopsis Proteins
  • Indoleacetic Acids
  • Nuclear Proteins
  • Plant Proteins
  • Transcription Factors
  • SLR1 protein, Brassica