By Dalian Institute of Chemical Physics, Chinese Academy Sciences
January 15, 2023
It has been widely accepted that CO2 assimilation takes place in light-independent responses, for example, through the Calvin-Benson Cycle in the stroma. Here, an unusual light-driven CO2 assimilation (into methanol) by the PSII core complex in photosynthesis was reported.
Light-Driven CO2 Assimilation by Photosystem II and Its Relation to Photosynthesis
Photosynthesis is the best natural process transforming sunshine into chemical energy on a huge scale and keeping life in the world. There are essentially two successive phases of oxygenic photosynthesis, of which the light-dependent reactions in photosystem II (PSII), and in photosystem I (PSI), make it possible for the oxidation of H2O into molecular oxygen, and production of lowering power (NADPH and ATP), while CO2 assimilation is generally known to happen long after oxygen development and NADP+ reduction, through light-independent reactions in the stroma.
There is broad agreement that throughout light-dependent reactions CO2 (or bicarbonate) is not reduced as a substrate, but plays a special stimulatory function in O2 evolution, namely the so-called “bicarbonate result.” The function of bicarbonate impact in addition to the bicarbonate binding sites in PSII have actually been intensively studied because the 1970s, with some essential conclusions reached so far. Nevertheless, CO2 (or bicarbonate) in PSII is believed to just play supporting roles during water oxidation, instead of being “taken in” by PSII.
Recently, a team of researchers, for the very first time, reported a light-driven CO2 assimilation by PSII core complex, where the formation of methanol (CH3OH), in addition to the oxygen development, is validated by in-situ mass spectrometry, gas chromatography, and isotopic labeling experiments.
It has actually been extensively accepted that CO2 assimilation takes place in light-independent reactions, for example, through the Calvin-Benson Cycle in the stroma. Here, an unusual light-driven CO2 assimilation (into methanol) by the PSII core complex in photosynthesis was reported. Such an unusual CO2 assimilation is likely to be a synchronised occasion along with the usual electron transfer occurring in regular light-independent assimilation.
The team included researchers from Dalian University of Technology, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, China, and the University of Illinois at Urbana-Champaign, USA.
Such an uncommon CO2 assimilation is most likely to be a simultaneous event together with the usual electron transfer happening in typical light-independent assimilation. This discovery is remarkable and is of excellent significance as it might substantially customize our understanding of the system of photosynthesis. The results were released in the Chinese Journal of Catalysis.
Referrals: “Light-driven CO2 assimilation by photosystem II and its relation to photosynthesis” by Yuehui Li, Duanhui Si, Wangyin Wang, Song Xue, Wenzhe Shang, Zhanyou Chi, Can Li, Ce Hao, Govindjee and Yantao Shi, 2 December 2022, Chinese Journal of Catalysis.DOI: 10.1016/ S1872-2067( 22 )64170-6.
