The Role of ZEITLUPE in the Control of Circadian Period in Plants
David Somers (Plant Cellular and Molecular Biology, The Ohio State University)
(October 16, 2003 11:30 AM - 12:30 PM)
At the molecular core of the circadian clock lies a transcription/translation autoregulatory feedback loop. Cyclic expression of at least some of the components of the circadian central oscillator is essential to maintain circadian rhythmicity. High amplitude cycling of mRNA and protein abundance, protein phosphorylation and nuclear/cytoplasmic shuttling have all been implicated in the maintenance of circadian period. We have used a newly characterized Arabidopsis suspension cell culture to establish that the rhythmic changes in the levels of the novel clock-associated F-box protein, ZEITLUPE, are post-transcriptionally controlled through different circadian phase-specific degradation rates. This proteolysis is proteasome dependent, implicating ZTL itself as substrate for ubiquitination. This demonstration of circadian phase-regulated degradation of an F-box protein, which itself controls circadian period, suggests a novel regulatory feedback mechanism among known circadian systems. Evidence for an additional level of light- and dark-dependent control of ZTL function will also be presented.