Figure 6.

The molecular factors regulating the thermal control of bud break in hybrid aspen. Dormancy release results from exposure to extended low temperatures; warm temperatures promote bud break and growth. Low temperature suppresses expression of SVL, a negative regulator of the growth-promoting FT/GA pathway. SVL promotes ABA biosynthesis and receptors via a positive feedback loop resulting in high levels of ABA to maintain dormancy and inhibit dormancy release. The pathways shown are based on studies of poplar trees but most of the components are known to be actively involved in regulating similar responses in other species.