combination with the phylogenetic evidence, we discuss the suitability of O. tauri as a model species to study protein kinase signalling. This data-mining approach was augmented by experimental identification of 5,563 phosphorylated O. tauri peptides from 107 liquid-chromatography-coupled mass spectrometry experiments. These correspond to 3,994 uniquely identified phosphorylations of 2,214 peptide sequences of 1,252 proteins, including several conserved protein kinases, discussed below. In the process of identifying and categorising kinases in O. tauri, we identified a novel gene locus, corrected 9 existing gene models, and patched sequencing gaps in 25 gene loci with sequence information from Ostreococcus lucimarinus data to generate a more complete database for peptide identification. Protein domain diagrams are attached as Additional file 2: O. tauri protein kinase and phosphatase survey A survey of the 7,989 gene models currently annotated in the O. tauri genome revealed 133 genes encoding Hindle et al. Phosphatases, in contrast, do not scale with the size of the genome. The Human Phosphatase Portal reports 135 protein phosphatases of which 107 are Protein Tyrosine Phosphatases. The remaining 28 S/T phosphatases consist of two families, Metal Dependent Protein Phosphatases and Phosphoserine Protein Phosphatases. A. thaliana contains 131 phosphatases of which 10 are PTPs and the remaining S/T phosphatases contain 38 PPPs and 83 PPMs. S. cerevisiae contains 25 protein phosphatases, which are composed of 6 PTPs, 12 PPPs and 7 PPMs. The PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19802338 O. tauri genome contains 32 protein phosphatases, which are composed of 8 PTPs, 10 PPPs and 14 PPMs. The higher proportions of S/T phosphatases to PTPs in O. tauri resemble the proportions found in higher A. thaliana more than S. cerevisiae and H. sapiens. The dominance of the PPM family within the S/T phosphatases in O. tauri is consistent with A. thaliana and H. sapiens but is in contrast to S. cerevisiae. A categorisation of kinases into families by sequence similarity and phylogenetic analysis with the A. thaliana, S. cerevisiae, and H. sapiens kinomes confirmed the presence in O. tauri of all major ePK families present in the green lineage. We also observed six small, conserved families of ePK-related protein kinases, which are classified as other-ePKs and five families of aPKs. No Receptor-Like Kinases were found in O. tauri. The main ePK families account for a large proportion of the kinome in all the eukaryotes. O. tauri contains 13 TKL-like kinases, which is consistent with a large expansion of this family in the green lineage. In contrast the TKL family is absent in S. cerevisiae and many other fungal genomes. For such a small kinome, O. tauri contains a surprising abundance of 20 ABC1-like kinases, which have few functionallycharacterised orthologs in other species. Recent experimental technologies for targeted gene knock-out in O. tauri will Rutin site therefore greatly assist in the elucidation of their function. Within ePK subfamilies, not all branches are equally conserved, as is evident in the following phylogenetic analyses. The TOR pathway: PIKK, CMGC and AGC kinase families Target of rapamycin mediated signalling is vital to the regulation of growth and the key components exist throughout eukaryotes. Here, we describe the phylogenetic relationships within 
the kinase families that participate in the TOR signalling pathway, aPK PI3K-related kinases, and the ePK CMGC and AGC kinases. PI3K-related k