Article
- The EMBO Journal (1999) 18, 4679 - 4688
- doi:10.1093/emboj/18.17.4679
GIGANTEA: a circadian clock-controlled gene that regulates photoperiodic flowering in Arabidopsis and encodes a protein with several possible membrane-spanning domains
Sarah Fowler1, Karen Lee2, Hitoshi Onouchi2, Alon Samach2, Kim Richardson3, Bret Morris3, George Coupland2 and Jo Putterill1
- School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
- John Innes Centre, Colney Lane, Norwich NR4 7UH, UK
- Hort+Research, Mt Albert Research Centre, Private Bag 92169, Auckland, New Zealand
Correspondence to:
Jo Putterill, E-mail: j.putterill@auckland.ac.nz
Received 10 May 1999; Accepted 6 July 1999; Revised 6 July 1999
Abstract
Flowering of Arabidopsis is promoted by long days and delayed by short days. Mutations in the GIGANTEA (GI) gene delay flowering under long days but have little or no effect under short days. We have now isolated the GI gene and show that it encodes a novel, putative membrane protein. By comparing the sequence of the Arabidopsis gene with that of a likely rice orthologue and by sequencing mutant alleles, we identify regions of the GI protein that are likely to be important for its function. We show that GI expression is regulated by the circadian clock with a peak in transcript levels 8–10 h after dawn. The timing, height and duration of this peak are influenced by daylength. We analysed the interactions between GI and the LHY, CCA1 and ELF3 genes, previously shown to affect daylength responses; we show that the rhythmic pattern of GI expression is altered in the elf3, CCA1-OX and lhy genotypes, and that CCA1 and LHY expression are reduced by gi mutations. Our results are consistent with the idea that GI plays an important role in regulating the expression of flowering time genes during the promotion of flowering by photoperiod.
Keywords:
- Arabidopsis,
- flowering time,
- GIGANTEA,
- long day,
- photoperiod
