AccliPhot ESRs are published in Plant and Cell Physiology
In oxygenic photosynthesis, light produces ATP plus NADPH via linear electron transfer, i.e. the in-series activity of the two photosystems: PS1 and PS2. This process, however, is thought not to be sufficient to provide enough ATP per NADPH for carbon assimilation in the Calvin-Benson-Bassham cycle (Allen 2002). Thus, it is assumed that additional ATP can be generated by alternative electron pathways. These circuits produce an electrochemical proton gradient without NADPH synthesis, and, although they often represent a small proportion of the linear electron flow, they could have a huge importance in optimizing CO2 assimilation. InViridiplantae, there is a consensus that alternative electron flow comprises cyclic electron flow around PS1 (Shikanai 2007) and the water to water cycles. The latter processes include photosynthetic O2 reduction via the Mehler reaction at PS1 (Asada 2000), the plastoquinone terminal oxidase downstream of PS2 (Zehr and Kudela 2009), photorespiration (the oxygenase activity of Rubisco, (Ort and Baker 2002)) and the export of reducing equivalents towards the mitochondrial oxidases, through the malate shuttle (Kinoshita et al. 2011). In this review, we summarize current knowledge about the role of the water to water cycles in photosynthesis, with a special focus on their occurrence and physiological roles in microalgae.
Curien, Gilles, Serena Flori, Valeria Villanova, Leonardo Magneschi, Cécile Giustini, Giorgio Forti, Michel Matringe, Dimitris Petroutsos, Marcel Kuntz, and Giovanni Finazzi. "The water to water cycles in microalgae." Plant and Cell Physiology (2016): pcw048.
Author: Fiona Moejes