NPH4/ARF7 and ARF19 promote leaf expansion and auxin-induced lateral root formation

Plant J. 2005 Jul;43(1):118-30. doi: 10.1111/j.1365-313X.2005.02432.x.


Auxin response factors (ARFs) bind auxin response promoter elements and mediate transcriptional responses to auxin. Five of the 22 ARF genes in Arabidopsis thaliana encode ARFs with glutamine-rich middle domains. Four of these can activate transcription and have been ascribed developmental functions. We show that ARF19, the fifth Q-rich ARF, also activates transcription. Mutations in ARF19 have little effect on their own, but in combination with mutations in NPH4/ARF7, encoding the most closely related ARF, they cause several phenotypes including a drastic decrease in lateral and adventitious root formation and a decrease in leaf cell expansion. These results indicate that auxin induces lateral roots and leaf expansion by activating NPH4/ARF7 and ARF19. Auxin induces the ARF19 gene, and NPH4/ARF7 and ARF19 together are required for expression of one of the arf19 mutant alleles, suggesting that a positive feedback loop regulates leaf expansion and/or lateral root induction.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / growth & development*
  • Arabidopsis Proteins / physiology*
  • Dose-Response Relationship, Drug
  • Gene Expression Regulation, Plant
  • Indoleacetic Acids / pharmacology
  • Indoleacetic Acids / physiology
  • Phenotype
  • Plant Leaves / growth & development*
  • Plant Roots / growth & development*
  • Trans-Activators / physiology*
  • Transcription Factors / physiology*
  • Transcription, Genetic


  • ARF19 protein, Arabidopsis
  • ARF7 protein, Arabidopsis
  • Arabidopsis Proteins
  • Indoleacetic Acids
  • Trans-Activators
  • Transcription Factors
  • indoleacetic acid