An antagonistic pair of FT homologs mediates the control of flowering time in sugar beet

Cultivated beets (Beta vulgaris) are unable to form reproductive shoots during the first year of their life cycle. Flowering only occurs if plants get vernalized, i.e. pass through the winter, and are subsequently exposed to an increasing day length (photoperiod) in spring. Here we show that the regulation of flowering time in beet is controlled by the interplay of two paralogs of the FLOWERING LOCUS T (FT) gene in Arabidopsis that have evolved antagonistic functions. BvFT2 is functionally conserved with FT and essential for flowering. In contrast, BvFT1, which is down-regulated in response to vernalization, represses flowering and is crucial for the vernalization response in beet. These data suggest that beet utilizes a different strategy relative to Arabidopsis and cereals to regulate vernalization.