Fig. 5.

Model for the extra early-flowering phenotype in exe mutants. This model is based on that proposed by Shimada et al. (2009). Under this model, VRN1 acts as an integrator of the vernalization and photoperiodic pathways, which are also coordinated with the autonomous pathway. VRN1 up-regulates the florigen gene WFT/VRN3. In exe mutants, the mechanism for suppressing the expression of VRN1 under SD conditions must be disrupted. High levels of accumulation of VRN1 transcripts induce WFT expression, resulting in the extra early-flowering phenotype. Note that exe mutants do not have an active VRN2 allele. Arrows and T-bars indicate promotion and suppression effects, respectively. Arrows with wider lines show stronger effects.