Climate change does not only spell disaster for human life but for plant life as well, as graphically illustrated by agricultural crop suffering from recent bouts of heat waves. Even a minute increase in temperature can produce dramatic effects in a plant's growth. Arabidopsis, a mustard often used in studies, has shown that elevated temperatures cause the plants to grow longer stems and thinner leaves in order to cope with the heat stress.

A new research headed by Zhiyong Wang from the Carnegie Institution for Science, a private nonprofit organization dedicated to ground-breaking scientific research, has discovered the specific system plants use to regulate their various response to heat between daytime and nighttime.

Zhiyong's study has shed light on the exact mechanism as to why and how the circadian clock helps a plant's survival of heat stress, which was a mystery until today.

According to the paper published by Nature Communications, the protein Phytochrome Interacting Factor 4 (PIF4) is essential to a plant's response to a rise in temperature as it activates the stress-busting genes. However, PIF4 is only works during the day.

Looking into the factors that limits PIF4 activity to daytime, Wang and his colleagues found it is regulated by another protein called Timing of CAB Expression 1 (TOC1), 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 and through the night. The disappearance of TOC1 at dawn allows PIF4 to respond to warm temperature in the morning, Eureka Alert reported.

"Since the hottest temperatures usually occur around noon and continue through the early afternoon, a plant's survival during a heat wave is most threatened during this period. By tying the heat response to the circadian clock, plants maximize their chances of survival during heat waves," Wang explained.

Meanwhile, Director of Carnegie Plant Biology Sue Rhee said, "Zhiyong's new work reveals a potential energy-saving strategy in plants where heat-stress response genes are prevented from being turned on at night when there is less chance of heat stress. Using a circadian clock machinery to do this is quite elegant," Science Daily wrote.