Green algae CO2capture is powered by alternative electron pathways of photosynthesis

Abstract

AbstractOn Earth, microalgae contribute to about half of global net photosynthesis. During photosynthesis, sunlight is converted into chemical energy (ATP and NADPH) used by metabolism to convert CO2into biomass. Alternative electron pathways of photosynthesis have been proposed to generate additional ATP that is required for sustaining CO2fixation, but the relative importance of each pathway remains elusive. Here, we dissect and quantify the contribution of cyclic, pseudo-cyclic and chloroplast to mitochondria electron flows for their ability to sustain net photosynthesis in the microalgaChlamydomonas reinhardtii. We show that each pathway has the potential to energize substantial CO2fixation, can compensate each other, and that the additional energy requirement to fix CO2is more than 3 times higher than previous estimations. We further show that all pathways have very different efficiencies at energizing CO2fixation, with the chloroplast-mitochondria interaction being the most efficient, thus laying bioenergetic foundations for biotechnological improvement of CO2capture.