The rotation of the Earth has generated cyclic changes in environmental factors. To fully exploit these predictable oscillatory factors for better fitness, plants have evolved an intricate endogenous timing system called the circadian clock. The plant circadian clock system perceives environmental cues like light and temperature through its input pathways. The input pathways then deliver these environmental cues to the core oscillators which are composed of interlocked transcription-translation feedback loops, generating self-sustaining circadian rhythms in various physiological processes through the output pathways (1, 2). Since most of the core oscillators are transcription factors, the plant circadian clock influences global transcription profoundly. Comprehensive transcriptomic studies suggest that 89% of transcripts in Arabidopsis cycle under certain conditions and the circadian clock system is responsible for the oscillatory expression of more than one-third of the genes in Arabidopsis (3). Strikingly, a study on plant transcriptome changes in response to salt, osmotic, and cold stresses suggests that 68% of the circadian oscillatory genes are involved in stress responses (4). It is now increasingly clear that the plant circadian clock plays an indispensable role in diverse plant stress responses (5). In PNAS, Cha et al. discover that SALT OVERLY SENSITIVE 1 (SOS1), a plasma membrane (PM) Na~+/H~+ antiporter, interacts with and stabilizes GIGANTEA (Gl), a core circadian clock component, to realize period compensation of plant circadian clock under daily fluctuating salt levels (6).
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