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Fig. 2. The effect of temperature changes on FT induction. FLC, a strong floral regulator, associates with the first intron of the FT gene and represses the expression of the gene. Vernalization removes FLC repression of the FT locus. In short days, low temperature (?16°C) increases the occupancy of H2A.Z nucleosomes on the FT locus, resulting in the inhibition of PIF4 binding to the FT promoter under this condition. However, high temperature (?27°C) stimulates the de-association of H2A.Z from the FT locus and induces CO accumulation in the afternoon. These cause the formation of a CO-PIF4 complex that binds to the FT promoter and activates its transcription. SVP represses FT expression by binding to the FT promoter in response to low temperature in long days. Temperature fluctuations increase SVP activity at dusk and CO stability, which are also regulated by photoperiod, at night in long days, leading to changes in the gene expression profiles of FT in a day length-dependent manner.
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