Figure 6.

Interaction between light, temperature, and hormonal pathways in the control of maize mesocotyl elongation. At constant 28°C (left), FR photoconverts PhyB-Pfr to PhyB-Pr, resulting in a derepression of elongation mediated by GA. In addition, ABA levels are reduced following EOD-FR exposure during night breaks in a PHYB-independent but FR-dependent manner, which strongly suggests a PHYA-mediated response. When a chilling treatment is applied during night breaks (right), ABA levels remain high and result in the repression of mesocotyl elongation. It is unclear if chilling reduces the GA response directly or through an independent pathway (e.g. PHYA or ABA). As mesocotyl tissues are longer in the phyB1 phyB2 double mutants than in the wild type following chilling treatments, some GA signaling likely persists following chill treatments. Gray arrows indicate a minor pathway and black arrows indicate the predominant pathway.