Proteomics section: 300ug of rotein extract from Ostreococcus tauri cells were reduced alkylated and trypsin digested. Phosphopeptide enrichment done on a Titanium dioxide column. LC-MS analysis performed on a cap-HPLC-MS (Orbitrap XL). Data analysis: Data were searched using Mascot. Peptide quantitation performed with Progenesis. Position of the phosphorylated amino acid confirmed with Maxquant and manual validation.