Assembly of photosystem I in thylakoid membranes The light reactions of photosynthesis are carried out by a series of multiprotein complexes embedded in thylakoid membranes. Among them photosystem I (PSI) acting as plastocyanin ferderoxin oxidoreductase catalyzes the final reaction. Together with light harvesting antenna I PSI forms a high molecular weight supercomplex of ~600 kDa consisting of eighteen subunits and nearly two hundred co factors. Assembly of the various components into a functional thylakoid membrane complex requires precise coordination which is provided by the assembly machinery. Although this includes a small number of proteins (PSI assembly factors) that have been shown to play a role in the formation of PSI the process as a whole as well as the intricacy of its members remains largely unexplored. In the present work two approaches were used to find candidate PSI assembly factors. First EnsembleNet was used to select proteins thought to be functionally related to known PSI assembly factors in Arabidopsis thaliana (approach I) and second co immunoprecipitation (Co IP) of tagged PSI assembly factors in Nicotiana tabacum was performed (approach II). [...]