A new study led by Zhiyong Wang at Carnegie Institution for Science has
identified the system by which plants regulate their response to heat
differently between daytime and nighttime.
The protein called Phytochrome Interacting Factor 4 (PIF4) is crucial in
coordinating plant response to high temperature by activating genes that
help the plant deal with heat stress, but it only seems to be active during
daylight hours. Wang and his research team found that PIF4's daytime
activity is regulated by another protein called Timing of CAB Expression 1
(TOC1), which is a part of the biological circadian clock proteins that
accumulate at the end of the day. TOC1 binds to PIF4 and inhibits its
activity in the evening throughout the night. The disappearance of TOC1 at
dawn allows PIF4 to respond to warm temperature in the morning.