BIG: a calossin-like protein required for polar auxin transport in Arabidopsis

Genes Dev. 2001 Aug 1;15(15):1985-97. doi: 10.1101/gad.905201.


Polar auxin transport is crucial for the regulation of auxin action and required for some light-regulated responses during plant development. We have found that two mutants of Arabidopsis-doc1, which displays altered expression of light-regulated genes, and tir3, known for its reduced auxin transport-have similar defects and define mutations in a single gene that we have renamed BIG. BIG is very similar to the Drosophila gene Calossin/Pushover, a member of a gene family also present in Caenorhabditis elegans and human genomes. The protein encoded by BIG is extraordinary in size, 560 kD, and contains several putative Zn-finger domains. Expression-profiling experiments indicate that altered expression of multiple light-regulated genes in doc1 mutants can be suppressed by elevated levels of auxin caused by overexpression of an auxin biosynthetic gene, suggesting that normal auxin distribution is required to maintain low-level expression of these genes in the dark. Double mutants of tir3 with the auxin mutants pin1, pid, and axr1 display severe defects in auxin-dependent growth of the inflorescence. Chemical inhibitors of auxin transport change the intracellular localization of the auxin efflux carrier PIN1 in doc1/tir3 mutants, supporting the idea that BIG is required for normal auxin efflux.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arabidopsis / genetics
  • Arabidopsis / physiology*
  • Arabidopsis Proteins*
  • Caenorhabditis elegans / genetics
  • Calmodulin-Binding Proteins / chemistry
  • Calmodulin-Binding Proteins / genetics*
  • Calmodulin-Binding Proteins / metabolism*
  • Chromosome Mapping
  • Darkness
  • Drosophila / genetics
  • Drosophila Proteins*
  • Gene Expression Regulation, Developmental
  • Gene Expression Regulation, Plant*
  • Genes, Plant
  • Genome, Human
  • Humans
  • Indoleacetic Acids / metabolism*
  • Insect Proteins / chemistry
  • Insect Proteins / genetics
  • Light
  • Molecular Sequence Data
  • Mutation
  • Plant Proteins / chemistry
  • Plant Proteins / genetics*
  • Plant Proteins / metabolism
  • RNA, Messenger / genetics
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Transcription, Genetic


  • Arabidopsis Proteins
  • BIG protein, Arabidopsis
  • Calmodulin-Binding Proteins
  • Drosophila Proteins
  • Indoleacetic Acids
  • Insect Proteins
  • Plant Proteins
  • RNA, Messenger
  • poe protein, Drosophila