Mutations in the huge Arabidopsis gene BIG affect a range of hormone and light responses

Plant J. 2003 Jul;35(1):57-70. doi: 10.1046/j.1365-313x.2003.01779.x.


In independent genetic screens, for shade-avoidance response and cytokinin sensitivity, we identified two Arabidopsis mutants, attenuated shade avoidance 1 (asa1) and umbrella1 (umb1), which have very similar pleiotropic phenotypes. asa1 and umb1 are allelic to tir3-1, and are caused by mutations in BIG, which is required for normal auxin efflux. They have a compact rosette, fewer lateral roots, delayed flowering, more secondary inflorescence, smaller seeds and, in the Laer-0 background, much shorter internodes between adjacent flowers, suggesting an interaction between BIG and ERECTA. These mutants have organ-specific defects in response to cytokinins, ethylene, N-1-naphthylphthalamic acid (NPA) and gibberellin (GA). The phenotype of the asa1 ga1-3 double mutant is consistent with defects in GA signalling. There are subtle effects in responses to auxins, abscisic acid and brassinolide. Elongation growth associated with shade avoidance in phyA phyB null mutants is suppressed by asa1 in all organs other than the hypocotyl. Therefore, we here provide evidence that BIG is a key player not just in auxin signalling, but in a multitude of light and hormone pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Arabidopsis / drug effects*
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / radiation effects*
  • Arabidopsis Proteins / metabolism
  • Base Sequence
  • Calmodulin-Binding Proteins / genetics*
  • Genes, Plant / genetics
  • Light*
  • Mutation / genetics
  • Phenotype
  • Phototropism / drug effects
  • Phototropism / radiation effects
  • Plant Growth Regulators / metabolism
  • Plant Growth Regulators / pharmacology*
  • Plant Leaves / drug effects
  • Plant Leaves / metabolism
  • Plant Proteins / genetics*
  • Plant Roots / drug effects
  • Plant Roots / metabolism
  • Protein-Serine-Threonine Kinases / metabolism
  • Receptors, Cell Surface / metabolism
  • Signal Transduction / drug effects*
  • Signal Transduction / radiation effects*


  • Arabidopsis Proteins
  • BIG protein, Arabidopsis
  • Calmodulin-Binding Proteins
  • Plant Growth Regulators
  • Plant Proteins
  • Receptors, Cell Surface
  • ER protein, Arabidopsis
  • Protein-Serine-Threonine Kinases