Reproductive success in plants requires careful timing of the developmental transition from leaf to flower production. In Arabidopsis, a central regulator of this transition is the floral inhibitor FLOWERING LOCUS C (FLC). FLC is positively regulated by the FRIGIDA(FRI) pathway, and is negatively regulated by the autonomous floral-promotion pathway and by vernalization (a period of cold that triggers flowering). Sang Yeol Kim and Scott Michaels now report that SUPPRESSOR OF FRI 4 (SUF4), a zinc-finger-containing transcription factor, is required for delayed flowering in winter-annual Arabidopsis -spring-flowering plants that germinate in the autumn (see ). The authors show that SUF4 is required for the upregulation of FLCexpression (but not that of nearby genes) by FRI. In suf4mutants, they report, histone H3 lysine 4 trimethylation at FLC is reduced, which suppresses FLC expression through modification of its chromatin structure. Thus, the authors propose, SUF4 is a new factor that specifically recruits chromatin-modifying complexes to the FLC locus to control flower development.
