Recognition of CCA1 alternative protein isoforms during temperature acclimation

Key message CCA1 alpha and CCA1 beta protein variants respond to environmental light and temperature cues, and higher temperature promotes CCA1 beta protein production and causes its retention detectable in the cytoplasm. CIRCADIAN CLOCK ASSOCIATED1 (CCA1), as the core transcription factor of circadian clock, is involved in the regulation of endogenous circadian rhythm in Arabidopsis. Previous studies have shown that CCA1 consists of two abundant splice variants, fully spliced CCA1 alpha and intron-retaining CCA1 beta. CCA1 beta is believed to form a nonfunctional heterodimer with CCA1 alpha and its closed-related homolog LHY. Many studies have established that CCA1 beta is a transcription product, while how CCA1 beta protein is produced and how two CCA1 isoforms respond to environmental cues have not been elucidated. In this study, we identified CCA1 alpha and CCA1 beta protein variants under different photoperiods with warm or cold temperature cycles, respectively. Our results showed that CCA1 protein production is regulated by prolonged light exposure and warm temperature. The protein levels of CCA1 alpha and CCA1 beta peak in the morning, but the detection of CCA1 beta is dependent on immunoprecipitation enrichment at 22 degrees C. Higher temperature of 37 degrees C promotes CCA1 beta protein production and causes its retention to be detectable in the cytoplasm. Overall, our results indicate that two splice variants of the CCA1 protein respond to environmental light and temperature signals and may, therefore, maintain the circadian rhythms and give individuals the ability to adapt to environment.

Automated summary

The study identified that CCA1 alpha and CCA1 beta protein variants respond to light and temperature cues, with higher temperatures promoting CCA1 beta protein production. The levels of CCA1 proteins peak in the morning and the detection of CCA1 beta is dependent on specific conditions at 22 degrees Celsius.