Johansson M, McWatters HG, Bakó L, Takata N, Gyula P, Hall A, Somers DE, Millar AJ, Eriksson ME
Partners in time: EARLY BIRD associates with ZEITLUPE and regulates the speed of the Arabidopsis clock
Plant Physiology: 2011 155:2108-2122

Abstract
The circadian clock of the model plant Arabidopsis thaliana is made up of a complex series of interacting feedback loops whereby proteins regulate their own expression across day and night. early bird (ebi) is a circadian mutation that causes the clock to speed up: ebi plants have short circadian periods, early phase of clock gene expression and are early flowering. We show that EBI associates with ZEITLUPE (ZTL), known to act in the plant clock as a post-translational mediator of protein degradation. However, EBI is not degraded by its interaction with ZTL. Instead, ZTL counteracts the effect of EBI during the day and increases it at night, modulating the expression of key circadian components. The partnership of EBI with ZTL reveals a novel mechanism involved in controlling the complex transcription-translation feedback loops of the clock. This work highlights the importance of cross-talk between the ubiquitination pathway and transcriptional control for regulation of the plant clock.

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