Abstract
Photosystem I is a chlorophyll protein complex, which consists of 14 subunits and a number of cofactors and mediates the electron transfer from plastocyanin to ferredoxin. PsaL is one of the peripheral subunits of photosystem I and has been proposed to be involved in state transitions in plants. However, the detail of its role in state transitions remains elusive. We have generated knockdown transformants of PSAL gene by using RNAi technique from the green alga Chlamydomonas reinhardtii. We isolated 3 lines of transformant in which the accumulation of PsaL protein decreased to <3% of that in cw-15, the host strain. Although the transformants (PsaL-RNAi) accumulated normal level of PSI reaction center, they showed a significant decrease in the accumulation of PsaH. Low temperature fluorescence spectra showed that PsaL-RNAi cells were impaired in the induction of state 2 during the state transitions. We are now analyzing the formation of PSI-LHCI/II supercomplex in state 2 in the PsaL-RNAi strains and also growth of the cells under fluctuating light conditions.
