CONSTANS and ASYMMETRIC LEAVES 1 complex is involved in the induction of FLOWERING LOCUS T in photoperiodic flowering in Arabidopsis

Plant J. 2012 Jan;69(2):332-42. doi: 10.1111/j.1365-313X.2011.04793.x. Epub 2011 Nov 18.


Plants monitor changes in day length to coordinate flowering with favorable seasons to increase their fitness. The day-length specific induction of FLOWERING LOCUS T (FT) regulated by CONSTANS (CO) is the crucial aspect of photoperiodic flowering in Arabidopsis thaliana. Recent studies have elucidated some mechanisms of CO-dependent FT induction. Here, we demonstrate another mechanism of CO-dependent FT regulation. Our results indicate that CO protein partially regulates FT transcription by forming a complex with ASYMMETRIC LEAVES 1 (AS1) protein, which regulates leaf development partly by controlling gibberellin (GA) levels. We identified AS1 as a CO-interacting protein in yeast and verified their interaction in vitro and in planta. We also showed that the temporal and spatial expression pattern of AS1 overlapped with that of CO. In addition, as1 mutants showed GA-independent delayed flowering under different light/dark conditions. FT expression levels in the as1 mutants and the SUC2:CO-HA/as1 line under long-day and 12-h light/12-h dark conditions were reduced compared with wild-type plants and the SUC2:HA-CO line, respectively. Moreover, AS1 bound directly to the specific regions of the FT promoter in vivo. These results indicate that CO forms a functional complex with AS1 to regulate FT expression and that AS1 plays different roles in two regulatory pathways, both of which concomitantly regulate the precise timing of flowering.

Publication types

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

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / physiology*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Flowers / genetics
  • Flowers / growth & development
  • Flowers / physiology*
  • Gene Expression Regulation, Plant / genetics*
  • Mutation
  • Phenotype
  • Photoperiod
  • Plant Leaves / genetics
  • Plant Leaves / metabolism
  • Plants, Genetically Modified / genetics
  • Plants, Genetically Modified / metabolism
  • Promoter Regions, Genetic
  • Protein Interaction Mapping
  • Signal Transduction / genetics
  • Time Factors
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Two-Hybrid System Techniques


  • ASYMMETRIC LEAVES1 protein, Arabidopsis
  • Arabidopsis Proteins
  • CONSTANS protein, Arabidopsis
  • DNA-Binding Proteins
  • FT protein, Arabidopsis
  • Transcription Factors