Fifty years of research on the “Bicarbonate effect” in photosystem II: A mini-review Swain Barsha Bhushan, Mishra Smrutirekha, Mohapatra Pradipta Kumar* Department of Botany, Ravenshaw University, Cuttack-753003, Odisha, India *Corresponding author email id: pradiptamoha@yahoo.com
Online published on 11 November, 2023. Abstract Cyanobacteria, algae, and plants fix CO2 in photosynthesis by utilizing the chemical energy generated in the light reaction. Photosystem II (PS II) plays a vital role in the photosynthetic energy fixation and oxygen evolution. Since the discovery of the stimulatory effect of CO2 on the Hill reaction (non-cyclic electron transfer in the light reaction), researchers from different laboratories around the world have shared their perspectives on this unique role of CO2. After approximately twenty-eight years of confusion regarding the role of CO2 in photosynthesis (dating back to James Franck's 1945 finding of increased oxygen evolution in the presence of CO2; Franck J (1945) Reviews of Modern Physics, 17:112-119), Alan Stemler and Govindjee from the University of Illinois at Urbana-Champaign (UIUC) established, in 1973, the effect of bicarbonate (HCO3-) on PS II but were unable to pinpoint the exact binding site. Ongoing research in Govindjee's laboratory and other research facilities worldwide (e.g., Canada, China, Israel, Finland, Switzerland, France, Germany, and The Netherlands) has predominantly focused on the effect of HCO3- on the (electron) acceptor side of PS II. However, key suggestions have been made regarding the effect of HCO 3- on the electron donor side (of PS II) by Alan Stemler (USA) and Vyacheslav Klimov (Russia). Yanyou Wu (China) has also put forth an argument suggesting that bicarbonate may partly serve as a source of oxygen in the light reaction of photosynthesis. In this review, we provide a brief historical account of the conceptual progression of the “bicarbonate effect” and present current perspectives on both the (electron) acceptor and donor sides of PS II. Additionally, we briefly discuss the prevailing opinion on the carbonic anhydrase-like function of PS II for CO2 hydration in oxygenic photosynthesis. Top Keywords Acceptor side of PS II, Bicarbonate effect, Carbonic anhydrase, Donor side of PS II, Non-heme iron, Photosystem II, Plastoquinone. Top |