Physcomitrella patens is a model plant representing the group of mosses, which diverged from vascular plant ancestors early after land colonization. To investigate the unique characteristic of the composition and post-translational regulation of Physcomitrella patens photosynthetic apparatus, we have separated the thylakoids protein complexes in their subunits composition by means of two-dimensional large-pore Blue-Native/sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2D lpBN/SDS-PAGE), followed by protein in-gel tryptic digestion of single spots. To identify the kinase responsible for phosphorylation of the major thylakoid protein complex photosystem II, a mutant line lacking the ortholog of kinase STN8 in the model angiosperm Arabidopsis thaliana has been generated and the identified thylakoid protein phosphorylation pattern have been compared with the WT moss.