The electron transport in psbS-silenced rice

Abstract

A part of light energy absorbed in photosystem II (PSII) is used for photosynthetic electron transport and the rest is dissipated as heat and fluorescence. While there are methods to estimate the allocation of the absorbed light energy by chlorophyll fluorescence (for example, Dermming-Adams et al., 1996; Kramer et al., 2004; Hendrickson et al., 2004), none of them have become experimentally approved. For this purpose we generated lines of psbS knockdown rice in which both of psbS genes were efficiently silenced. The silencing of psbS genes resulted in a decrease in the allocation of the absorbed light energy in PSII to TD in antenna (D), and an increase in that to TD in closed PSII centers, designated as excess (E), in wide range of light intensities, whereas energy allocation to the electron transport (P) did not change, suggesting that the main site of dissipation was shifted from antenna to PSII centers in PsbS-silenced lines. This also means that the rate-limiting step of photosynthetic electron transport was not at the light absorption even under low light but at acceptor side of PSII in the electron transport.