Figure 11.

A Model for the Control of Seed Germination under Low-GA Conditions.

Environmental conditions influence the levels of bioactive GA accumulating upon seed imbibition. When GA levels are low, RGL2 protein overaccumulates, which stimulates endogenous ABA synthesis. This probably involves XERICO and as yet unknown factors (X). In turn, an increase in ABA synthesis sustains ABI5 mRNA and protein expression and activity (through phosphorylation by SnRK2-type kinases) but also RGL2 mRNA levels.