{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,14]],"date-time":"2026-10-14T21:44:29Z","timestamp":1792014269393,"version":"4.4.0"},"reference-count":0,"publisher":"Oxford University Press (OUP)","license":[{"start":{"date-parts":[[2026,10,14]],"date-time":"2026-10-14T00:00:00Z","timestamp":1791936000000},"content-version":"am","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE\/OXYGENASE (RUBISCO) and the Calvin-Benson-Bassham (CBB) cycle assimilate most of the inorganic carbon on earth. Conserved CP12 proteins control diurnal C-assimilation of the CBB cycle. Their function originated in cyanobacteria that deactivate GLYCERALDEHYDE 3-PHOSPHATE DEHYDROGENASE (GAPDH) and PHOSPHORIBULOKINASE (PRK) during darkness by redox-regulated complex-formation with CP12. This mechanism indicates metabolic regulation of C-assimilation. We measured C-assimilation in vivo at the day\/night transition by dynamic 13CO2 labeling and 1-C-positional monitoring of 13C-incorporation into 3-phosphoglycerate (3PGA) and aspartate of Synechocystis sp. PCC 6803 grown with high (5%) CO2 supply. Unlike wild type, a \u0394cp12 mutant accumulated ribulose-1,5-bisphosphate (RuBP) and assimilated 13CO2 in darkness. We validated these observations by proteome measurements and orthogonal quantifications of RUBISCO abundances and specific activities. Complementation of \u0394cp12 with native CP12 and point-mutants of its GAPDH- and PRK-binding domains demonstrated that defective complex formation is causal for aberrant C-assimilation during darkness and that RuBP accumulation correlates significantly with the time-shifted 13C-incorporation into 3PGA. RUBISCO carboxylase activity is present throughout the diurnal cycle and depends on CP12-controlled substrate availability. 13C-positional analyses suggest dysregulated RuBP regeneration in \u0394cp12 during darkness via futile metabolic cycling through gluconeogenesis and the oxidative pentose phosphate path. We propose that blocked regeneration and rapid depletion of RuBP contributes to the regulation of RUBISCO activity at day-night transitions.<\/jats:p>","DOI":"10.1093\/plcell\/koag301","type":"journal-article","created":{"date-parts":[[2026,10,13]],"date-time":"2026-10-13T11:33:19Z","timestamp":1791891199000},"source":"Crossref","is-referenced-by-count":0,"title":["RuBP availability contributes to the regulation of RUBISCO activity in\n                    <i>Synechocystis<\/i>"],"prefix":"10.1093","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3249-0441","authenticated-orcid":false,"given":"Luisa","family":"Wittemeier","sequence":"first","affiliation":[{"name":"Max-Planck-Institute of Molecular Plant Physiology , Am M\u00fchlenberg 1, 14476 Potsdam-Golm ,","place":["Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0516-6950","authenticated-orcid":false,"given":"St\u00e9phanie","family":"Arrivault","sequence":"additional","affiliation":[{"name":"Max-Planck-Institute of Molecular Plant Physiology , Am M\u00fchlenberg 1, 14476 Potsdam-Golm ,","place":["Germany"]},{"name":"Martin-Luther-University, Institute of Pharmacy , Hoher Weg 8, 06120 Halle ,","place":["Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Niels","family":"Neumann","sequence":"additional","affiliation":[{"name":"Department of Quantitative Proteomics, Interfaculty Institute for Cell Biology, Eberhard Karls University T\u00fcbingen , 72076 T\u00fcbingen ,","place":["Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1206-2458","authenticated-orcid":false,"given":"Boris","family":"Ma\u010dek","sequence":"additional","affiliation":[{"name":"Department of Quantitative Proteomics, Interfaculty Institute for Cell Biology, Eberhard Karls University T\u00fcbingen , 72076 T\u00fcbingen ,","place":["Germany"]},{"name":"Cluster of Excellence GreenRobust, Eberhard Karls University T\u00fcbingen , 72076 T\u00fcbingen ,","place":["Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6780-9889","authenticated-orcid":false,"given":"Nils","family":"Schmidt","sequence":"additional","affiliation":[{"name":"Plant Physiology Department, Institute of Biological Sciences, Rostock University , Albert-Einstein-Stra\u00dfe 3, 18059 Rostock ,","place":["Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2059-2061","authenticated-orcid":false,"given":"Martin","family":"Hagemann","sequence":"additional","affiliation":[{"name":"Plant Physiology Department, Institute of Biological Sciences, Rostock University , Albert-Einstein-Stra\u00dfe 3, 18059 Rostock ,","place":["Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9675-4883","authenticated-orcid":false,"given":"Joachim","family":"Kopka","sequence":"additional","affiliation":[{"name":"Max-Planck-Institute of Molecular Plant Physiology , Am M\u00fchlenberg 1, 14476 Potsdam-Golm ,","place":["Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2026,10,14]]},"container-title":["The Plant Cell"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/academic.oup.com\/plcell\/advance-article-pdf\/doi\/10.1093\/plcell\/koag301\/71948571\/koag301.pdf","content-type":"application\/pdf","content-version":"am","intended-application":"syndication"},{"URL":"https:\/\/academic.oup.com\/plcell\/advance-article-pdf\/doi\/10.1093\/plcell\/koag301\/71948571\/koag301.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,14]],"date-time":"2026-10-14T20:46:09Z","timestamp":1792010769000},"score":1,"resource":{"primary":{"URL":"https:\/\/academic.oup.com\/plcell\/advance-article\/doi\/10.1093\/plcell\/koag301\/8916656"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,10,14]]},"references-count":0,"URL":"https:\/\/doi.org\/10.1093\/plcell\/koag301","relation":{},"ISSN":["1040-4651","1532-298X"],"issn-type":[{"value":"1040-4651","type":"print"},{"value":"1532-298X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,10,14]]},"article-number":"koag301"}}