Spatiotemporal analysis of localized circadian arrhythmias in plant roots

The circadian system in plants is characterized by substantial cellular oscillations over an approximately 24-h period. Interactions between cellular oscillators trigger phase resets near the root meristem, resulting in localized regions of arrhythmic expression of the clock gene CCA1. The arrhythmicity of the circadian rhythm significantly impacts physiologic processes and growth; however, the exact nature of these arrhythmic regions remains unknown. In this study, we analyzed spatiotemporal patterns in CCA1 expression in arrhythmic regions using a nondestructive imaging technique. We found that formation of root arrhythmic regions involves the emergence of small spiral waves. Near the small spiral waves, the synchrony of cellular oscillations was low. Our findings provide experimental evidence that the arrhythmias are based on desynchronization of cellular oscillators and enhance our understanding of the role of circadian phenomena in root growth.