Figure 1.

GA Biosynthesis Pathways and Models of BR-GA Interactions.

BZR1 is a key positive regulator of the BR growth response. According to the “GA signaling” model (Bai et al., 2012; Gallego-Bartolomé et al., 2012; Li et al., 2012), DELLA proteins (negative regulators of GA signaling that are degraded by bioactive GA) physically interact with BZR1, thereby reducing the BR growth response. The “GA synthesis” model of BR-GA interaction, shown in red (Tong et al., 2014) or blue (Unterholzner et al., 2015), suggests that, in addition to this, BRs are master regulators of GA biosynthesis and metabolism.