Science Report: FKF1 Conveys Timing Information for CONSTANS Stabilization in Photoperiodic Flowering

Science 25 May 2012: Vol. 336 no. 6084 pp. 1045-1049

DOI: 10.1126/science.1219644

REPORT

FKF1 Conveys Timing Information for CONSTANS Stabilization in Photoperiodic Flowering

Young Hun Song1, Robert W. Smith2, Benjamin J. To1, Andrew J. Millar2, Takato Imaizumi1,*

+ Author Affiliations

1Department of Biology, University of Washington, Seattle, WA 98195, USA.

2School of Biological Sciences and SynthSys, University of Edinburgh, Edinburgh EH9 3JD, UK.

↵*To whom correspondence should be addressed. E-mail: takato@u.washington.edu

ABSTRACT

Plants use day-length information to coordinate flowering time with the appropriate season to maximize reproduction. In Arabidopsis, the long day–specific expression of CONSTANS (CO) protein is crucial for flowering induction. Although light signaling regulates CO protein stability, the mechanism by which CO is stabilized in the long-day afternoon has remained elusive. Here, we demonstrate that FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (FKF1) protein stabilizes CO protein in the afternoon in long days. FKF1 interacts with CO through its LOV domain, and blue light enhances this interaction. In addition, FKF1 simultaneously removes CYCLING DOF FACTOR 1 (CDF1), which represses CO and FLOWERING LOCUS T (FT) transcription. Together with CO transcriptional regulation, FKF1 protein controls robust FT mRNA induction through multiple feedforward mechanisms that accurately control flowering timing.