The Importance of the Plant Circadian Clock to Confer Heat Tolerance

Most eukaryotic organisms display specialized cellular and behavioral oscillations with a period of approximately 24 hours, which are called circadian rhythms. The biological clock generates a rhythm that conveys temporal information over a day. Through this system, most eukaryotic organisms appropriately respond to daily or seasonal environmental changes by regulating their physiology and development in a time-dependent manner, conferring the organism with an adaptive advantage. In plants, the endogenous timing system also controls many important physiological processes including flower opening, hormone synthesis, metabolic pathways and gene expression so that these sessile species may survive efficiently in changing environments. Temperature compensation (TC) is one of the defining features of the clock mechanism. Under this mechanism, the pace of the clock, or period, remains stable over a broad range of physiologically relevant temperatures, which is unlikely to happen in other biochemical reactions. Thus, this mechanism allows organisms to sustain their ordinary life in various thermal environments by providing an accurate measure of the passage of time, regardless of the ambient temperature. Considering the current global climate changes our planet is undergoing, understanding the fundamental mechanism underlying TC cannot be overemphasized. In this review, we discuss the molecular organization of the plant circadian clock and the concept of TC, as well as the significance of plant TC in conferring fitness under the current increasing thermal environments.