Abstract (Expand)
BioRxiv preprint, 4 April 2018. Abstract:
Daily light-dark cycles (LD) drive dynamic regulation of plant and algal transcriptomes via photoreceptor pathways and 24-hour, circadian rhythms. Diel regulation … of protein levels and modifications has been less studied. Ostreococcus tauri, the smallest free-living eukaryote, provides a minimal model proteome for the green lineage. Here, we compare transcriptome data under LD to the algal proteome and phosphoproteome, assayed using shotgun mass-spectrometry. Under 10% of 855 quantified proteins were rhythmic but two-thirds of 860 phosphoproteins showed rhythmic modification(s). Most rhythmic proteins peaked in the daytime. Model simulations showed that light-stimulated protein synthesis largely accounts for this distribution of protein peaks. Prompted by apparently dark-stable proteins, we sampled during prolonged dark adaptation, where stable RNAs and very limited change to the proteome suggested a quiescent, cellular “dark state”. In LD, acid-directed and proline-directed protein phosphorylation sites were regulated in antiphase. Strikingly, 39% of rhythmic phospho-sites reached peak levels just before dawn. This anticipatory phosphorylation is distinct from light-responsive translation but consistent with plant phosphoprotein profiles, suggesting that a clock-regulated phospho-dawn prepares green cells for daytime functions.
Authors: Zeenat B. Noordally, Matthew M. Hindle, Sarah F. Martin, Daniel D. Seaton, Ian Simpson, Thierry Le Bihan, Andrew J. Millar
Date Published: No date defined
Publication Type: Not specified
DOI: 10.1101/287862
Citation: Circadian protein regulation in the green lineage I. A phospho-dawn anticipates light onset before proteins peak in daytime.
