Metabolite pools and carbon flow during C4 photosynthesis in maize : 13CO2 labeling kinetics and cell type fractionation
© The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.
| Publié dans: | Journal of experimental botany. - 1985. - 68(2017), 2 vom: 29. Jan., Seite 283-298 |
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| Auteur principal: | |
| Autres auteurs: | , , , , , , |
| Format: | Article en ligne |
| Langue: | English |
| Publié: |
2017
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| Accès à la collection: | Journal of experimental botany |
| Sujets: | Journal Article Research Support, Non-U.S. Gov't 13C labeling C4 photosynthesis CO2-concentrating shuttle carbon flow maize. Carbon Isotopes Carbon Dioxide 142M471B3J plus... |
| Résumé: | © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology. Worldwide efforts to engineer C4 photosynthesis into C3 crops require a deep understanding of how this complex pathway operates. CO2 is incorporated into four-carbon metabolites in the mesophyll, which move to the bundle sheath where they are decarboxylated to concentrate CO2 around RuBisCO. We performed dynamic 13CO2 labeling in maize to analyze C flow in C4 photosynthesis. The overall labeling kinetics reflected the topology of C4 photosynthesis. Analyses of cell-specific labeling patterns after fractionation to enrich bundle sheath and mesophyll cells revealed concentration gradients to drive intercellular diffusion of malate, but not pyruvate, in the major CO2-concentrating shuttle. They also revealed intercellular concentration gradients of aspartate, alanine, and phosphenolpyruvate to drive a second phosphoenolpyruvate carboxykinase (PEPCK)-type shuttle, which carries 10-14% of the carbon into the bundle sheath. Gradients also exist to drive intercellular exchange of 3-phosphoglycerate and triose-phosphate. There is rapid carbon exchange between the Calvin-Benson cycle and the CO2-concentrating shuttle, equivalent to ~10% of carbon gain. In contrast, very little C leaks from the large pools of metabolites in the C concentration shuttle into respiratory metabolism. We postulate that the presence of multiple shuttles, alongside carbon transfer between them and the Calvin-Benson cycle, confers great flexibility in C4 photosynthesis |
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| Description: | Date Completed 02.02.2018 Date Revised 27.03.2024 published: Print-Electronic Citation Status MEDLINE |
| ISSN: | 1460-2431 |
| DOI: | 10.1093/jxb/erw414 |