A Partial C4 Photosynthetic Biochemical Pathway in Rice
Introduction of a C4 photosynthetic pathway into C3 rice (Oryza sativa) requires installation of a biochemical pump that concentrates CO2 at the site of carboxylation in modified bundle sheath cells. To investigate the feasibility of this, we generated a quadruple line that simultaneously accumulate...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2020-10-01
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| Series: | Frontiers in Plant Science |
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| Online Access: | https://www.frontiersin.org/article/10.3389/fpls.2020.564463/full |
| _version_ | 1819016375876714496 |
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| author | HsiangChun Lin Stéphanie Arrivault Robert A. Coe Shanta Karki Sarah Covshoff Efren Bagunu John E. Lunn Mark Stitt Robert T. Furbank Julian M. Hibberd William Paul Quick William Paul Quick |
| author_facet | HsiangChun Lin Stéphanie Arrivault Robert A. Coe Shanta Karki Sarah Covshoff Efren Bagunu John E. Lunn Mark Stitt Robert T. Furbank Julian M. Hibberd William Paul Quick William Paul Quick |
| author_sort | HsiangChun Lin |
| collection | DOAJ |
| description | Introduction of a C4 photosynthetic pathway into C3 rice (Oryza sativa) requires installation of a biochemical pump that concentrates CO2 at the site of carboxylation in modified bundle sheath cells. To investigate the feasibility of this, we generated a quadruple line that simultaneously accumulates four of the core C4 photosynthetic enzymes from the NADP-malic enzyme subtype, phosphoenolpyruvate carboxylase (ZmPEPC), NADP-malate dehydrogenase (ZmNADP-MDH), NADP-malic enzyme (ZmNADP-ME), and pyruvate phosphate dikinase (ZmPPDK). This led to enhanced enzyme activity and mild phenotypic perturbations but was largely neutral in its effects on photosynthetic rate. Measurements of the flux of 13CO2 through photosynthetic metabolism revealed a significant increase in the incorporation of 13C into malate, consistent with increased fixation of 13CO2 via PEP carboxylase in lines expressing the maize PEPC enzyme. However, there was no significant differences in labeling of 3-phosphoglycerate (3PGA) indicating that there was no carbon flux through NADP-ME into the Calvin-Benson cycle. There was also no significant difference in labeling of phosphoenolpyruvate (PEP) indicating that there was no carbon flux through PPDK. Crossing the quadruple line with a line with reduced glycine decarboxylase H-protein (OsGDCH) abundance led to a photosynthetic phenotype characteristic of the reduced OsGDCH line and higher labeling of malate, aspartate and citrate than in the quintuple line. There was evidence of 13C labeling of aspartate indicating 13CO2 fixation into oxaloacetate by PEPC and conversion to aspartate by the endogenous aspartate aminotransferase activity. While Kranz anatomy or other anatomical modifications have not yet been installed in these plants to enable a fully functional C4 cycle, these results demonstrate for the first-time a partial flux through the carboxylation phase of NADP-ME C4 metabolism in transgenic rice containing two of the key metabolic steps in the C4 pathway. |
| first_indexed | 2024-12-21T02:46:38Z |
| format | Article |
| id | doaj.art-1304bc0718af40c781f3a94fc51ba7ec |
| institution | Directory Open Access Journal |
| issn | 1664-462X |
| language | English |
| last_indexed | 2024-12-21T02:46:38Z |
| publishDate | 2020-10-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Plant Science |
| spelling | doaj.art-1304bc0718af40c781f3a94fc51ba7ec2022-12-21T19:18:33ZengFrontiers Media S.A.Frontiers in Plant Science1664-462X2020-10-011110.3389/fpls.2020.564463564463A Partial C4 Photosynthetic Biochemical Pathway in RiceHsiangChun Lin0Stéphanie Arrivault1Robert A. Coe2Shanta Karki3Sarah Covshoff4Efren Bagunu5John E. Lunn6Mark Stitt7Robert T. Furbank8Julian M. Hibberd9William Paul Quick10William Paul Quick11C4 Rice Centre, International Rice Research Institute (IRRI), Los Baños, PhilippinesMax Planck Institute of Molecular Plant Physiology (MPI-MP), Potsdam, GermanyC4 Rice Centre, International Rice Research Institute (IRRI), Los Baños, PhilippinesNational Centre for Fruit Development, Kirtipur, NepalDepartment of Plant Sciences, University of Cambridge, Cambridge, United KingdomC4 Rice Centre, International Rice Research Institute (IRRI), Los Baños, PhilippinesMax Planck Institute of Molecular Plant Physiology (MPI-MP), Potsdam, GermanyMax Planck Institute of Molecular Plant Physiology (MPI-MP), Potsdam, GermanyARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, The Australian National University, Acton, ACT, AustraliaDepartment of Plant Sciences, University of Cambridge, Cambridge, United KingdomC4 Rice Centre, International Rice Research Institute (IRRI), Los Baños, PhilippinesDepartment of Animal and Plant Sciences, University of Sheffield, Sheffield, United KingdomIntroduction of a C4 photosynthetic pathway into C3 rice (Oryza sativa) requires installation of a biochemical pump that concentrates CO2 at the site of carboxylation in modified bundle sheath cells. To investigate the feasibility of this, we generated a quadruple line that simultaneously accumulates four of the core C4 photosynthetic enzymes from the NADP-malic enzyme subtype, phosphoenolpyruvate carboxylase (ZmPEPC), NADP-malate dehydrogenase (ZmNADP-MDH), NADP-malic enzyme (ZmNADP-ME), and pyruvate phosphate dikinase (ZmPPDK). This led to enhanced enzyme activity and mild phenotypic perturbations but was largely neutral in its effects on photosynthetic rate. Measurements of the flux of 13CO2 through photosynthetic metabolism revealed a significant increase in the incorporation of 13C into malate, consistent with increased fixation of 13CO2 via PEP carboxylase in lines expressing the maize PEPC enzyme. However, there was no significant differences in labeling of 3-phosphoglycerate (3PGA) indicating that there was no carbon flux through NADP-ME into the Calvin-Benson cycle. There was also no significant difference in labeling of phosphoenolpyruvate (PEP) indicating that there was no carbon flux through PPDK. Crossing the quadruple line with a line with reduced glycine decarboxylase H-protein (OsGDCH) abundance led to a photosynthetic phenotype characteristic of the reduced OsGDCH line and higher labeling of malate, aspartate and citrate than in the quintuple line. There was evidence of 13C labeling of aspartate indicating 13CO2 fixation into oxaloacetate by PEPC and conversion to aspartate by the endogenous aspartate aminotransferase activity. While Kranz anatomy or other anatomical modifications have not yet been installed in these plants to enable a fully functional C4 cycle, these results demonstrate for the first-time a partial flux through the carboxylation phase of NADP-ME C4 metabolism in transgenic rice containing two of the key metabolic steps in the C4 pathway.https://www.frontiersin.org/article/10.3389/fpls.2020.564463/fullC4 riceC4 photosynthesis13C labelingNADP-malic enzymemalateOryza sativa (rice) |
| spellingShingle | HsiangChun Lin Stéphanie Arrivault Robert A. Coe Shanta Karki Sarah Covshoff Efren Bagunu John E. Lunn Mark Stitt Robert T. Furbank Julian M. Hibberd William Paul Quick William Paul Quick A Partial C4 Photosynthetic Biochemical Pathway in Rice Frontiers in Plant Science C4 rice C4 photosynthesis 13C labeling NADP-malic enzyme malate Oryza sativa (rice) |
| title | A Partial C4 Photosynthetic Biochemical Pathway in Rice |
| title_full | A Partial C4 Photosynthetic Biochemical Pathway in Rice |
| title_fullStr | A Partial C4 Photosynthetic Biochemical Pathway in Rice |
| title_full_unstemmed | A Partial C4 Photosynthetic Biochemical Pathway in Rice |
| title_short | A Partial C4 Photosynthetic Biochemical Pathway in Rice |
| title_sort | partial c4 photosynthetic biochemical pathway in rice |
| topic | C4 rice C4 photosynthesis 13C labeling NADP-malic enzyme malate Oryza sativa (rice) |
| url | https://www.frontiersin.org/article/10.3389/fpls.2020.564463/full |
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