{"database":"biostudies-literature","file_versions":[],"scores":null,"additional":{"submitter":["Torres-Romero I"],"funding":["Eidgenössische Technische Hochschule Zürich (ETH)","Eidgenössische Technische Hochschule Zürich","Swiss National Science Foundation"],"pagination":["e2318570121"],"full_dataset_link":["https://www.ebi.ac.uk/biostudies/studies/S-EPMC11214045"],"repository":["biostudies-literature"],"omics_type":["Unknown"],"volume":["121(26)"],"pubmed_abstract":["Hydrogen isotope ratios (δ<sup>2</sup>H) represent an important natural tracer of metabolic processes, but quantitative models of processes controlling H-fractionation in aquatic photosynthetic organisms are lacking. Here, we elucidate the underlying physiological controls of <sup>2</sup>H/<sup>1</sup>H fractionation in algal lipids by systematically manipulating temperature, light, and CO<sub>2</sub>(aq) in continuous cultures of the haptophyte <i>Gephyrocapsa oceanica</i>. We analyze the hydrogen isotope fractionation in alkenones (α<sub>alkenone</sub>), a class of acyl lipids specific to this species and other haptophyte algae. We find a strong decrease in the α<sub>alkenone</sub> with increasing CO<sub>2</sub>(aq) and confirm α<sub>alkenone</sub> correlates with temperature and light. Based on the known biosynthesis pathways, we develop a cellular model of the δ<sup>2</sup>H of algal acyl lipids to evaluate processes contributing to these controls on fractionation. Simulations show that longer residence times of NADPH in the chloroplast favor a greater exchange of NADPH with <sup>2</sup>H-richer intracellular water, increasing α<sub>alkenone</sub>. Higher chloroplast CO<sub>2</sub>(aq) and temperature shorten NADPH residence time by enhancing the carbon fixation and lipid synthesis rates. The inverse correlation of α<sub>alkenone</sub> to CO<sub>2</sub>(aq) in our cultures suggests that carbon concentrating mechanisms (CCM) do not achieve a constant saturation of CO<sub>2</sub> at the Rubisco site, but rather that chloroplast CO<sub>2</sub> varies with external CO<sub>2</sub>(aq). The pervasive inverse correlation of α<sub>alkenone</sub> with CO<sub>2</sub>(aq) in the modern and preindustrial ocean also suggests that natural populations may not attain a constant saturation of Rubisco with the CCM. Rather than reconstructing growth water, α<sub>alkenone</sub> may be a powerful tool to elucidate the carbon limitation of photosynthesis."],"journal":["Proceedings of the National Academy of Sciences of the United States of America"],"pubmed_title":["Hydrogen isotope fractionation is controlled by CO<sub>2</sub> in coccolithophore lipids."],"pmcid":["PMC11214045"],"funding_grant_id":["200021","SEED-17 21-2","182070","Core funding","200021_182070"],"pubmed_authors":["Jaggi M","Clark AJ","Stoll HM","Zhang H","Torres-Romero I","McLeod RE","Wijker RS"],"additional_accession":[]},"is_claimable":false,"name":"Hydrogen isotope fractionation is controlled by CO<sub>2</sub> in coccolithophore lipids.","description":"Hydrogen isotope ratios (δ<sup>2</sup>H) represent an important natural tracer of metabolic processes, but quantitative models of processes controlling H-fractionation in aquatic photosynthetic organisms are lacking. Here, we elucidate the underlying physiological controls of <sup>2</sup>H/<sup>1</sup>H fractionation in algal lipids by systematically manipulating temperature, light, and CO<sub>2</sub>(aq) in continuous cultures of the haptophyte <i>Gephyrocapsa oceanica</i>. We analyze the hydrogen isotope fractionation in alkenones (α<sub>alkenone</sub>), a class of acyl lipids specific to this species and other haptophyte algae. We find a strong decrease in the α<sub>alkenone</sub> with increasing CO<sub>2</sub>(aq) and confirm α<sub>alkenone</sub> correlates with temperature and light. Based on the known biosynthesis pathways, we develop a cellular model of the δ<sup>2</sup>H of algal acyl lipids to evaluate processes contributing to these controls on fractionation. Simulations show that longer residence times of NADPH in the chloroplast favor a greater exchange of NADPH with <sup>2</sup>H-richer intracellular water, increasing α<sub>alkenone</sub>. Higher chloroplast CO<sub>2</sub>(aq) and temperature shorten NADPH residence time by enhancing the carbon fixation and lipid synthesis rates. The inverse correlation of α<sub>alkenone</sub> to CO<sub>2</sub>(aq) in our cultures suggests that carbon concentrating mechanisms (CCM) do not achieve a constant saturation of CO<sub>2</sub> at the Rubisco site, but rather that chloroplast CO<sub>2</sub> varies with external CO<sub>2</sub>(aq). The pervasive inverse correlation of α<sub>alkenone</sub> with CO<sub>2</sub>(aq) in the modern and preindustrial ocean also suggests that natural populations may not attain a constant saturation of Rubisco with the CCM. Rather than reconstructing growth water, α<sub>alkenone</sub> may be a powerful tool to elucidate the carbon limitation of photosynthesis.","dates":{"release":"2024-01-01T00:00:00Z","publication":"2024 Jun","modification":"2026-06-01T17:38:45.974Z","creation":"2025-04-04T21:45:09.26Z"},"accession":"S-EPMC11214045","cross_references":{"pubmed":["38905238"],"doi":["10.1073/pnas.2318570121"]}}