Convergence of signaling pathways in the control of differential cell growth in Arabidopsis

Dev Cell. 2004 Aug;7(2):193-204. doi: 10.1016/j.devcel.2004.07.002.


Seedling apical hook development involves a complex interplay of hormones and light in the regulation of differential cell growth. However, the underlying molecular mechanisms that integrate these diverse signals to control bending of the embryonic stem are poorly understood. The Arabidopsis ethylene-regulated HOOKLESS1 (HLS1) gene is essential for apical hook formation. Herein, we identify two auxin response regulators that act downstream of HLS1 to control cell elongation in the hypocotyl. Extragenic suppressors of hls1 were identified as mutations in AUXIN RESPONSE FACTOR 2 (ARF2). The level of ARF2 protein was decreased by ethylene, and this response required HLS1. Exposure to light decreased HLS1 protein levels and evoked a concomitant increase in ARF2 accumulation. These studies demonstrate that both ethylene and light signals affect differential cell growth by acting through HLS1 to modulate the auxin response factors, pinpointing HLS1 as a key integrator of the signaling pathways that control hypocotyl bending.

Publication types

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

MeSH terms

  • ADP-Ribosylation Factors / genetics
  • Alleles
  • Arabidopsis / genetics
  • Arabidopsis / physiology*
  • Cell Division
  • Cloning, Molecular
  • Ethylenes / pharmacology
  • Gene Expression Regulation, Plant
  • Immunoblotting
  • In Situ Hybridization
  • Indoleacetic Acids / metabolism
  • Models, Biological
  • Models, Genetic
  • Mutagenesis
  • Mutation
  • Phenotype
  • Plant Proteins / physiology
  • Plants, Genetically Modified
  • Plasmids / metabolism
  • RNA / metabolism
  • Saccharomyces cerevisiae Proteins*
  • Signal Transduction*
  • Time Factors
  • Transcription, Genetic


  • Ethylenes
  • HLS1 protein, Pisum sativum
  • Indoleacetic Acids
  • Plant Proteins
  • Saccharomyces cerevisiae Proteins
  • RNA
  • ethylene
  • ARF2 protein, S cerevisiae
  • ADP-Ribosylation Factors