Abstract
Plants convert light energy into chemical energy via photosynthetic electron transport. There are two modes for the electron transport, linear electron flow (LEF) and cyclic electron flow (CEF). These two electron flow modes are switched by a mechanism called state transitions, which maintain photosynthetic efficiency under fluctuating light environments. Ferredoxin NADPH oxidoreductase (FNR) receives electrons from PSI through ferredoxin. It has been suggested that, FNR reduces NADP+ in state 1(LEF), while it participates in CEF in state 2. However, the localization and the exact function of FNR in the electron transfer switching and state transitions are as yet unclear. In this study, we identified the location of FNR using wild type of Chlamydmonas reinhardtii cells under state 1 and state 2 conditions. The result show that FNR was in the PSI-LHCI fraction (A3) in state 1, and in the PSI-LHCII fraction (A4) in state 2. Together with the results using PSI deficient mutant (ΔPSI) and Cytb6f deficient mutant (Fud6), we will discuss possible roles of FNR in regulating photosynthetic electron flow.
