Photosystem I (PSI) consists of at least eleven subunits in the thylakoid membrane, and mediates photosynthetic electron transfer from plastocyanin to ferredoxin. PsaD subunit, which is located at the stromal surface of the PSI, is thought to be the docking site of ferredoxin, and encoded by the nuclear gene PsaD-1(AT4G02770) and PsaD-2 (AT1G03130) .
