Abstract
Arabidopsis thaliana changes its architecture dependent on environmental conditions, among which light and temperature are prominent cue. Light regulates the plant growth in the quantity- and/or quality-dependent manner. Moderate high temperature promotes the cell elongation and low temperature suppresses it. Recently, Phytochrome Interacting Factor4 (PIF4), which is a positive cell elongation factor, has been identified as an integrator for the light- and temperature-signaling.
Here, we report destabilizations of PIF4 protein under blue light or low temperature (16 degrees) conditions. Blue light induced the PIF4 degradation mediated through the 26S proteasome pathway in a quantity-dependent manner, which required the Active Phytochrome Binding (APB) domain of PIF4 as like as red light does. On the other hand, ΔN-PIF4, which lacked the APB domain, was also degraded under low temperature-condition through the 26S proteasome pathway. These data suggest that the low temperature-induced degradation mechanism is distinguishable from the mechanism of light-induced degradation.