Figure 6: A revised model of the molecular network controlling vernalization-induced flowering in cereals.
From: Direct links between the vernalization response and other key traits of cereal crops
Prolonged exposure to low temperatures (vernalization) induces transcription of VRN1 during winter. Then the VRN1 protein binds to the promoter of FT1/VRN3 (1). This enhances the expression of FT1 in long days. VRN1 also binds to the promoters of VRN2 (2), blocking the expression of this floral repressor and allowing activation of FT1 (3). VRN1 binds to the promoter of ODDSOC2 and downregulates this gene (4), allowing the increased expression of other floral promoters (5). Binding of VRN1 to the promoters of CBF genes (6) contributes to decreased cold acclimation potential as plants develop towards flowering. Indirect regulation of VRN1 by FT1 can further activate the expression of the VRN1 gene in leaves, in long days (7) and can trigger the floral initiation in some genetic backgrounds, but does not play a primary role in vernalization-induced flowering. Direct interactions are indicated by solid black connectors. Regulatory interactions that could be direct or indirect (status unknown) are indicated by thin blue dashed lines. Indirect feedback regulation of VRN1 by FT1 is indicated by a thin red dashed line56. Blue upwards arrows indicate increased expression, red arrows facing downwards indicate decreased expression.
