A phospho-dawn of protein modification anticipates light onset in the picoeukaryote Ostreococcus tauri

Zeenat B. Noordally, Matthew M. Hindle, Sarah F. Martin, Daniel D. Seaton, T. Ian Simpson, Thierry Le Bihan*, Andrew J. Millar*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Diel regulation of protein levels and protein modification had been less studied than transcript rhythms. Here, we compare transcriptome data under light-dark cycles with partial proteome and phosphoproteome data, assayed using shotgun MS, from the alga Ostreococcus tauri, the smallest free-living eukaryote. A total of 10% of quantified proteins but two-thirds of phosphoproteins were rhythmic. Mathematical modelling showed that light-stimulated protein synthesis can account for the observed clustering of protein peaks in the daytime. Prompted by night-peaking and apparently dark-stable proteins, we also tested cultures under prolonged darkness, where the proteome changed less than under the diel cycle. Among the dark-stable proteins were prasinophyte-specific sequences that were also reported to accumulate when O. tauri formed lipid droplets. In the phosphoproteome, 39% of rhythmic phospho-sites reached peak levels just before dawn. This anticipatory phosphorylation suggests that a clock-regulated phospho-dawn prepares green cells for daytime functions. Acid-directed and proline-directed protein phosphorylation sites were regulated in antiphase, implicating the clock-related casein kinases 1 and 2 in phase-specific regulation, alternating with the CMGC protein kinase family. Understanding the dynamic phosphoprotein network should be facilitated by the minimal kinome and proteome of O. tauri. The data are available from ProteomeXchange, with identifiers PXD001734, PXD001735, and PXD002909.

Original languageEnglish
Pages (from-to)5514–5531
Number of pages18
JournalJournal of Experimental Botany
Issue number18
Early online date22 Jul 2023
Publication statusPublished - 29 Sept 2023

Keywords / Materials (for Non-textual outputs)

  • Light signalling
  • marine microalgae
  • phosphoproteomics
  • photoperiod
  • photosynthetic pico-eukaryotes
  • proteomics
  • systems biology


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