Role of circadian rhythm in plant system: An update from development to stress response

Plants have internal timekeeper known as a circadian clock that anticipates environmental cues such as light, temperature and regulates photoperiodic rhythmicity for the proper growth and fitness of the plants. The timing of the rhythms depends on the interaction between the external signal of the surrounding and internal systems of the organism. Initially, circadian clock was known to consist of only three modules i.e. input pathway, central oscillator and output pathway but recent studies showed that circadian clock consists of various complex transcriptional and translational feedback loops. Here we comprehensively summarize the molecular basis of the clock, various clock components and their regulation, input signals and their entrainment. In addition, we also discussed the output pathways in connection to development, biotic and abiotic stress resistance, In this review detail and updated knowledge of clock components and their regulation will help in the understanding of synchronization of plant's internal machinery with environmental signals as well as boost plant's fitness level thereby enhanced immunity.