Complex epistatic interactions between ELF3, PRR9, and PRR7 regulates the circadian clock and plant physiology

Abstract

AbstractCircadian clocks are endogenous timekeeping mechanisms that coordinate internal physiological responses with the external environment. EARLY FLOWERING3 (ELF3), PSEUDO RESPONSE REGULATOR (PRR9), and PRR7 are essential components of the plant circadian clock and facilitate entrainment of the clock to internal and external stimuli. Previous studies have highlighted a critical role for ELF3 in repressing the expression ofPRR9andPRR7. However, the functional significance of activity in regulating circadian clock dynamics and plant development is unknown. To explore this regulatory dynamic further, we firstly employed mathematical modelling to simulate the effect of theprr9/prr7mutation on theelf3circadian phenotype. These simulations suggested that simultaneous mutations inprr9/prr7could rescue theelf3circadian arrythmia. Following these simulations, we generated all Arabidopsiself3/prr9/prr7mutant combinations and investigated their circadian and developmental phenotypes. Although these assays could not replicate the results from the mathematical modelling, our results have revealed a complex epistatic relationship between ELF3 and PRR9/7 in regulating different aspects of plant development. ELF3 was essential for hypocotyl development under ambient and warm temperatures, while PRR9 was critical for root thermomorphogenesis. Finally, mutations inprr9andprr7rescued the photoperiod insensitive flowering phenotype of theelf3mutant. Together, our results highlight the importance of investigating the genetic relationship amongst plant circadian genes.