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Contribution of carbon fixed by Rubisco and PEPC to phloem export in the Crassulacean acid metabolism plant Kalanchoë daigremontiana
Crassulacean acid metabolism (CAM) plants exhibit a complex interplay between CO(2) fixation by phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco), and carbon demand for CAM maintenance and growth. This study investigated the flux of carbon from PEPC...
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Formato: | Texto |
Lenguaje: | English |
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Oxford University Press
2010
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2837257/ https://www.ncbi.nlm.nih.gov/pubmed/20159885 http://dx.doi.org/10.1093/jxb/erq006 |
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author | Wild, Birgit Wanek, Wolfgang Postl, Wolfgang Richter, Andreas |
author_facet | Wild, Birgit Wanek, Wolfgang Postl, Wolfgang Richter, Andreas |
author_sort | Wild, Birgit |
collection | PubMed |
description | Crassulacean acid metabolism (CAM) plants exhibit a complex interplay between CO(2) fixation by phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco), and carbon demand for CAM maintenance and growth. This study investigated the flux of carbon from PEPC and direct Rubisco fixation to different leaf carbon pools and to phloem sap over the diurnal cycle. Concentrations and carbon isotope compositions of starch, soluble sugars, and organic acids were determined in leaves and phloem exudates of Kalanchoë daigremontiana Hamet et Perr., and related to CO(2) fixation by PEPC and Rubisco. Three types of leaf carbon pools could be distinguished. (i) Starch and malate pools were dominant and showed a pattern of reciprocal mobilization and accumulation (85/54 and 13/48 mg C g(−1) DW, respective, at the beginning/end of phase I). The carbon isotope composition of these pools was compatible with predominant PEPC fixation (δ(13)C values of –13 and –11‰ for starch and malate compared to –11‰ of PEPC fixed carbon). (ii) Isotopic composition (–17‰ and –14‰) and concentration of glucose and fructose (2 and 3 mg C g(−1) DW, respectively) were not affected by diurnal metabolism, suggesting a low turnover. (iii) Sucrose (1–3 mg C g(−1) DW), in contrast, exhibited large diurnal changes in δ(13)C values (from –17‰ in the evening to –12‰ in the morning), which were not matched by net changes in sucrose concentration. This suggests a high sucrose turnover, fed by nocturnal starch degradation and direct Rubisco fixation during the day. A detailed dissection of the carbon fixation and mobilization pattern in K. daigremontiana revealed that direct fixation of Rubisco during the light accounted for 30% of phloem sucrose, but only 15% of fixed carbon, indicating that carbon from direct Rubisco fixation was preferentially used for leaf export. |
format | Text |
id | pubmed-2837257 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2010 |
publisher | Oxford University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-28372572010-03-15 Contribution of carbon fixed by Rubisco and PEPC to phloem export in the Crassulacean acid metabolism plant Kalanchoë daigremontiana Wild, Birgit Wanek, Wolfgang Postl, Wolfgang Richter, Andreas J Exp Bot Research Papers Crassulacean acid metabolism (CAM) plants exhibit a complex interplay between CO(2) fixation by phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco), and carbon demand for CAM maintenance and growth. This study investigated the flux of carbon from PEPC and direct Rubisco fixation to different leaf carbon pools and to phloem sap over the diurnal cycle. Concentrations and carbon isotope compositions of starch, soluble sugars, and organic acids were determined in leaves and phloem exudates of Kalanchoë daigremontiana Hamet et Perr., and related to CO(2) fixation by PEPC and Rubisco. Three types of leaf carbon pools could be distinguished. (i) Starch and malate pools were dominant and showed a pattern of reciprocal mobilization and accumulation (85/54 and 13/48 mg C g(−1) DW, respective, at the beginning/end of phase I). The carbon isotope composition of these pools was compatible with predominant PEPC fixation (δ(13)C values of –13 and –11‰ for starch and malate compared to –11‰ of PEPC fixed carbon). (ii) Isotopic composition (–17‰ and –14‰) and concentration of glucose and fructose (2 and 3 mg C g(−1) DW, respectively) were not affected by diurnal metabolism, suggesting a low turnover. (iii) Sucrose (1–3 mg C g(−1) DW), in contrast, exhibited large diurnal changes in δ(13)C values (from –17‰ in the evening to –12‰ in the morning), which were not matched by net changes in sucrose concentration. This suggests a high sucrose turnover, fed by nocturnal starch degradation and direct Rubisco fixation during the day. A detailed dissection of the carbon fixation and mobilization pattern in K. daigremontiana revealed that direct fixation of Rubisco during the light accounted for 30% of phloem sucrose, but only 15% of fixed carbon, indicating that carbon from direct Rubisco fixation was preferentially used for leaf export. Oxford University Press 2010-03 2010-02-16 /pmc/articles/PMC2837257/ /pubmed/20159885 http://dx.doi.org/10.1093/jxb/erq006 Text en © 2010 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details) |
spellingShingle | Research Papers Wild, Birgit Wanek, Wolfgang Postl, Wolfgang Richter, Andreas Contribution of carbon fixed by Rubisco and PEPC to phloem export in the Crassulacean acid metabolism plant Kalanchoë daigremontiana |
title | Contribution of carbon fixed by Rubisco and PEPC to phloem export in the Crassulacean acid metabolism plant Kalanchoë daigremontiana |
title_full | Contribution of carbon fixed by Rubisco and PEPC to phloem export in the Crassulacean acid metabolism plant Kalanchoë daigremontiana |
title_fullStr | Contribution of carbon fixed by Rubisco and PEPC to phloem export in the Crassulacean acid metabolism plant Kalanchoë daigremontiana |
title_full_unstemmed | Contribution of carbon fixed by Rubisco and PEPC to phloem export in the Crassulacean acid metabolism plant Kalanchoë daigremontiana |
title_short | Contribution of carbon fixed by Rubisco and PEPC to phloem export in the Crassulacean acid metabolism plant Kalanchoë daigremontiana |
title_sort | contribution of carbon fixed by rubisco and pepc to phloem export in the crassulacean acid metabolism plant kalanchoë daigremontiana |
topic | Research Papers |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2837257/ https://www.ncbi.nlm.nih.gov/pubmed/20159885 http://dx.doi.org/10.1093/jxb/erq006 |
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