Fig. 4.

Molecular models for how TFL1 and FT act through the key amino acid. (A) TFL1 and FT recruit structurally related components X and Y depending on the identity of the key amino acid. Activated X complex then leads to repression of flowering, whereas activated Y complex promotes flowering. TFL1 and FT are structurally similar, as is X and Y. Therefore, swapping the key residue is sufficient for TFL1 and FT to swap partners and, thus, their effects on shoot meristem identity. (B) TFL1 and FT interact with the same component X. The key residue specifies whether the component functions as a repressor or an activator. Binding of FT to X induces some change (represented by blue shading of X) that leads to activation of flowering. TFL1 binds X and induces repression (pink). These changes depend on the key residue.