Flowering responses to seasonal cues: what's new?

• Natural variation in FT proteins generates promoters or repressors of flowering.
• Long noncoding RNAs expressed at FLC correlate with its inactivation during cold.
• FT proteins bind lipids as well as different classes of transcription factor.
• Age dependent flowering in response to vernalization is conferred by miR156.

Seasonal cues of day length or winter cold trigger flowering of many species. Forward and reverse genetic approaches are revealing the mechanisms by which these responses are conferred. Homologues of the Arabidopsis thaliana protein FLOWERING LOCUS T (FT) are widely used to mediate seasonal responses to day length and act as graft-transmissible promoters or repressors of flowering. Winter cold in A. thaliana promotes flowering by repressing transcription of the MADS box gene FLOWERING LOCUS C (FLC). The mechanism by which this occurs involves a complex interplay of different forms of long noncoding RNAs induced at the FLC locus during cold and changes in the chromatin of FLC. In perennial relatives of A. thaliana, flowering also requires the age-dependent downregulation of miRNA156 before winter.