An Antagonistic Pair of FT Homologs Mediates the Control of Flowering Time in Sugar Beet

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Science  03 Dec 2010:
Vol. 330, Issue 6009, pp. 1397-1400
DOI: 10.1126/science.1197004

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Flowering time regulation is important for plants to maximize their reproductive output. By investigating copies of genes that are strong and central activators of flowering in many different species (homologs of the FT gene in Arabidopsis), Pin et al. (p. 1397) found that during evolution, the regulation of flowering time in sugar beet (Beta vulgaris) has come under the control of two FT-like genes. Functional differences in these genes owing to small mutations in a critical domain have caused a duplicated copy of the flowering promoter FT to turn into a flowering repressor in sugar beet. These changes may explain why cultivated beets are unable to flower until their second year after passing through the winter, a behavior important for increasing crop yield.


Cultivated beets (Beta vulgaris ssp. vulgaris) are unable to form reproductive shoots during the first year of their life cycle. Flowering only occurs if plants get vernalized, that is, 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 beets 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 represses flowering and its down-regulation is crucial for the vernalization response in beets. These data suggest that the beet has evolved a different strategy relative to Arabidopsis and cereals to regulate vernalization.

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