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Mitochondrial phosphoenolpyruvate carboxylase contributes to carbon fixation in the diatom Phaeodactylum tricornutum at low inorganic carbon concentrations

Mitochondrial phosphoenolpyruvate carboxylase contributes to carbon fixation in the diatom Phaeodactylum tricornutum at low inorganic carbon concentrations

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YU, Guilan, Kensuke NAKAJIMA, Ansgar GRUBER, Carolina RIO BARTULOS, Alexander F. SCHOBER, Bernard LEPETIT, Elizabeth YOHANNES, Yusuke MATSUDA, Peter G. KROTH, 2022. Mitochondrial phosphoenolpyruvate carboxylase contributes to carbon fixation in the diatom Phaeodactylum tricornutum at low inorganic carbon concentrations. In: The New Phytologist. Wiley. 235(4), pp. 1379-1393. ISSN 0028-646X. eISSN 1469-8137. Available under: doi: 10.1111/nph.18268

@article{Yu2022-08Mitoc-57699, title={Mitochondrial phosphoenolpyruvate carboxylase contributes to carbon fixation in the diatom Phaeodactylum tricornutum at low inorganic carbon concentrations}, year={2022}, doi={10.1111/nph.18268}, number={4}, volume={235}, issn={0028-646X}, journal={The New Phytologist}, pages={1379--1393}, author={Yu, Guilan and Nakajima, Kensuke and Gruber, Ansgar and Rio Bartulos, Carolina and Schober, Alexander F. and Lepetit, Bernard and Yohannes, Elizabeth and Matsuda, Yusuke and Kroth, Peter G.} }

eng Kroth, Peter G. Rio Bartulos, Carolina Mitochondrial phosphoenolpyruvate carboxylase contributes to carbon fixation in the diatom Phaeodactylum tricornutum at low inorganic carbon concentrations Gruber, Ansgar Nakajima, Kensuke 2022-05-30T12:20:24Z Rio Bartulos, Carolina Schober, Alexander F. Yu, Guilan 2022-05-30T12:20:24Z Photosynthetic carbon fixation is often limited by CO<sub>2</sub> availability, which led to the evolution of CO<sub>2</sub> concentrating mechanisms (CCMs). Some diatoms possess CCMs that employ biochemical fixation of bicarbonate, similar to C<sub>4</sub> plants, but it is controversially discussed whether biochemical CCMs are a commonly found in diatoms.<br />In the diatom Phaeodactylum tricornutum, Phosphoenolpyruvate Carboxylase (PEPC) is present in two isoforms, PEPC1 in the plastids and PEPC2 in the mitochondria. We used real-time quantitative PCR, western blots, and enzymatic assays to examine PEPC expression and PEPC activities, under low and high concentrations of dissolved inorganic carbon (DIC).<br />We generated and analyzed individual knockout cell lines of PEPC1 and PEPC2, as well as a PEPC1/2 double-knockout strain. While we could not detect an altered phenotype in the PEPC1 knockout strains at ambient, low or high DIC concentrations, PEPC2 and the double-knockout strains grown under ambient air or lower DIC availability, showed reduced growth and photosynthetic affinity to DIC, while behaving similarly as WT cells at high DIC concentrations. These mutants furthermore exhibited significantly lower <sup>13</sup>C/<sup>12</sup>C ratios compared to WT.<br />Our data implies that in P. tricornutum at least parts of the CCM relies on biochemical bicarbonate fixation catalyzed by the mitochondrial PEPC2. Yohannes, Elizabeth Matsuda, Yusuke Matsuda, Yusuke Nakajima, Kensuke Yohannes, Elizabeth Schober, Alexander F. Yu, Guilan terms-of-use Kroth, Peter G. Gruber, Ansgar 2022-08 Lepetit, Bernard Lepetit, Bernard

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