FLOWERING LOCUS C-dependent and -independent regulation of the circadian clock by the autonomous and vernalization pathways.
BACKGROUND
The circadian system drives pervasive biological rhythms in plants. Circadian clocks integrate endogenous timing information with environmental signals, in order to match rhythmic outputs to the local day/night cycle. Multiple signaling pathways affect the circadian system, in ways that are likely to be adaptively significant. Our previous studies of natural genetic variation in Arabidopsis thaliana accessions implicated FLOWERING LOCUS C (FLC) as a circadian-clock regulator. The MADS-box transcription factor FLC is best known as a regulator of flowering time. Its activity is regulated by many regulatory genes in the "autonomous" and vernalization-dependent flowering pathways. We tested whether these same pathways affect the circadian system.


RESULTS
Genes in the autonomous flowering pathway, including FLC, were found to regulate circadian period in Arabidopsis. The mechanisms involved are similar, but not identical, to the control of flowering time. By mutant analyses, we demonstrate a graded effect of FLC expression upon circadian period. Related MADS-box genes had less effect on clock function. We also reveal an unexpected vernalization-dependent alteration of periodicity.


CONCLUSIONS
This study has aided in the understanding of FLC's role in the clock, as it reveals that the network affecting circadian timing is partially overlapping with the floral-regulatory network. We also show a link between vernalization and circadian period. This finding may be of ecological relevance for developmental programming in other plant species.
Salathia
Neeraj
N
Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK. nsalathia@cgr.harvard.edu
Davis
Seth J
SJ
Lynn
James R
JR
Michaels
Scott D
SD
Amasino
Richard M
RM
Millar
Andrew J
AJ
D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001683:Biological Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D035264:Flowers / Q000502:physiology*; D018628:Gene Dosage; D026161:MADS Domain Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D012621:Seasons
D029681:Arabidopsis Proteins; C418902:At5g10140 protein, Arabidopsis; D026161:MADS Domain Proteins