The Roles of Circadian Clock Genes in Plant Temperature Stress Responses.

Plants monitor day length and memorize changes in temperature signals throughout the day, creating circadian rhythms that support the timely control of physiological and metabolic processes. The DEHYDRATION-RESPONSE ELEMENT-BINDING PROTEIN 1/C-REPEAT BINDING FACTOR ( DREB1/CBF ) transcription factors are known as master regulators for the acquisition of cold stress tolerance, whereas PHYTOCHROME INTERACTING FACTOR 4 ( PIF4 ) is involved in plant adaptation to heat stress through thermomorphogenesis. Recent studies have shown that circadian clock genes control plant responses to temperature. Temperature-responsive transcriptomes show a diurnal cycle and peak expression levels at specific times of throughout the day. Circadian clock genes play essential roles in allowing plants to maintain homeostasis by accommodating temperature changes within the normal temperature range or by altering protein properties and morphogenesis at the cellular level for plant survival and growth under temperature stress conditions. Recent studies revealed that the central oscillator genes CIRCADIAN CLOCK ASSOCIATED 1 / LATE ELONGATED HYPOCOTYL ( CCA1/LHY ) and PSEUDO-RESPONSE REGULATOR5 / 7 / 9 ( PRR5 / 7 / 9 ), as well as the EVENING COMPLEX ( EC ) genes REVEILLE4/REVEILLE8 ( REV4 / REV8 ), were involved in the DREB1 pathway of the cold signaling transcription factor and regulated the thermomorphogenesis gene PIF4 . Further studies showed that another central oscillator, TIMING OF CAB EXPRESSION 1 ( TOC1 ), and the regulatory protein ZEITLUPE ( ZTL ) are also involved. These studies led to attempts to utilize circadian clock genes for the acquisition of temperature-stress resistance in crops. In this review, we highlight circadian rhythm regulation and the clock genes involved in plant responses to temperature changes, as well as strategies for plant survival in a rapidly changing global climate.