Light-driven CO2 assimilation by photosystem II and its relation to photosynthesis

For natural oxygenic photosynthesis, there is a consensus that H 2 O is oxidized to molecular oxygen by photosystem II (PSII) in the grana, while CO 2 assimilation takes place, long after oxygen evolution, in light-independent reactions, for example, through the Calvin-Benson Cycle in the stroma. Here, we report, for the first time, light-driven CO 2 assimilation by the PSII core complex, where the formation of methanol, along with the oxygen evolution, is validated by in - situ mass spectrometry, gas chromatography and isotopic labeling experiments. Such an unusual CO 2 assimilation is likely to be a simultaneous event along with the usual electron transfer occurring in normal light–independent assimilation. This discovery is extraordinary and is of great significance as it may substantially modify our understanding of the mechanism of photosynthesis.