Regulatory mechanisms across networks of the circadian clock and senescence pathways

Abstract

The circadian clock serves the fitness of higher plants by controlling various aspects of plant growth and development ranging from photosynthesis to flowering and defense mechanisms. The key components of the core oscillator mediate the circadian output through transcriptional or post-transcriptional mechanisms by phase-wise expression and repression of numerous genes. Senescence on the other hand is a tightly regulated developmental process that facilitates the remobilization of nutrients and leads to inevitable death of the plant in the end. Thus, senescence is critical for flowering, ripening of fruits, biomass production and the yield of crop plants. The circadian clock and senescence are tightly interwoven in many eukaryotes. However, in plants the intricacy of regulations by the circadian oscillator for triggering the onset or progress of senescence is not known in detail. Clock regulation during senescence is known through several cross-signaling networks, such as age-dependent, hormone-mediated and dark-induced. The present review aims to expound on the recent advances in understanding the cross-network regulations of the circadian clock during different types of senescence in plants.