STRESSing the role of the plant circadian clock

• Matching internal circadian time with the environment confers fitness advantages in plants.
• Regulation of stress signaling by the circadian clock enhances the ability of plants to prepare for stress.
• Stress signaling appears to influence clock activity to ensure synchronization of acute responses under stress.
• Circadian gating defines an efficient way to increase resistance to stress without substantially decreasing plant growth.

The circadian clock is a timekeeper mechanism that is able to regulate biological activities with a period of 24 h. Proper matching of the internal circadian time with the environment not only confers fitness advantages but also allows the clock to temporally gate the responses to environmental stresses. By restricting the time of maximal responsiveness, the circadian gating defines an efficient way to increase resistance to stress without substantially decreasing plant growth. Stress signaling in turn appears to influence the clock activity. The feedback regulation might be important to maximize metabolic efficiency under challenging environmental conditions. This review focuses on recent research advances exploring the intricate connection between the clock and osmotic stresses. The role of the circadian clock favoring the proper balance between immune responses and cellular metabolism is also discussed.