Dokument: In silico exploration of paths toward C4 metabolism
| Titel: | In silico exploration of paths toward C4 metabolism | |||||||
| Weiterer Titel: | In silico Erforschung von Wegen in Richtung C4 Metabolismus | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=49454 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20190507-111424-0 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Sundermann, Esther M. [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Lercher, Martin [Gutachter] Prof. Dr. Weber, Andreas [Gutachter] | |||||||
| Stichwörter: | C3 photosynthesis, C4 photosynthesis, C3-C4 photosynthesis, photosynthetic nitrogen-use efficiency, C4 evolution, C4 ecology, leaf nitrogen level, Flaveria, environment, phenotypic plasticity, resource allocation, systems modeling | |||||||
| Dewey Dezimal-Klassifikation: | 000 Informatik, Informationswissenschaft, allgemeine Werke » 004 Datenverarbeitung; Informatik | |||||||
| Beschreibung: | Photosynthesis sustains nearly all life on earth. Its key enzyme Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) has a dual function: it catalyzes the reaction with either CO2 or O2. When catalyzing the reaction with CO2, this is the initial step of the Calvin-Benson cycle that produces sugar. In contrast, the reaction with O2 starts photorespiration that results in drastic carbon and energy losses. In order to fix carbon from the atmosphere, the C3 photosynthetic pathway uses Rubisco exclusively. In contrast, C4 photosynthesis spatially separates the carbon fixation from Rubisco and the Calvin-Benson cycle. In C4 photosynthesis, the initial carbon fixation in the mesophyll cell is catalyzed by Phosphoenolpyruvatcarboxylase, which is the start of the C4 cycle. The C4 cycle facilitates the transport of carbon in form of organic acids into the bundle sheath, the location of Rubisco and the Calvin-Benson cycle. This CO2-concentrating mechanism allows plants to suppress photorespiration. The complex C4 metabolism evolved more than 60 times independently from the original C3 pathway. C4 evolution is presumably triggered by environmental factors that result in high photorespiratory rates, e. g., high temperatures.
In order to improve the understanding of the quantitative effect of environmental factors on the physiology and evolution of C3, C3-C4 intermediate, and C4 plants, we developed a detailed mathematical model. This mechanistic model represents the complex photosynthetic apparatus and explicitly accounts for the photosynthetic nitrogen and energy allocation, which includes the energy production based on linear and cyclic electron transport. It can be parametrized as C3, C4, and all intermediate photosynthetic types and considers the following environmental factors: light intensity, leaf nitrogen level, temperature, and CO2 and O2 gas concentrations. As the nitrogen and energy allocation is not understood in detail yet, the model assumes that resources are allocated such that the CO2 assimilation rate—which is used as a proxy for fitness—is maximized for a given environment. Based on the resource allocation, the model provides detailed information about physiological and molecular parameters. The mathematical model is validated with data of the model genus of C4 evolution, Flaveria. We explore to what extent observed resource allocation patterns in different photosynthetic types are optimally adapted to current conditions, and to what extend this pattern is optimally adapted to ancestral environments. The optimal resource allocation was calculated for a standard evolutionary scenario, which is inferred from literature, and for the growth conditions given in the experimental set-up. A comparison of the modeled physiological parameters with the empirical data indicates that the observed resource distribution in C4 plants still reflects optimality in ancestral environments. It further reveals that C4 plants show limited phenotypic plasticity regarding resource allocation. The limited phenotypic plasticity allows us to quantitatively infer ancestral environments from currently observed resource allocation patterns. To adjust from the ancestral environment to a given growth environment, plants need to re-allocate nitrogen. Our analysis shows a link between the low phenotypic plasticity in C4 plants and the need to re-allocate significantly more nitrogen between photosynthetic components for C4 compared to C3 relatives. Analyzing C3 and C4 Flaveria species in the inferred ancestral environment provides insight into the widely unknown effect of nitrogen availability on the physiology of C3 and C4 plants and on C4 photosynthesis evolution. A detailed comparison of the optimal nitrogen allocation in C3 and C4 plants shows that C4 plants require an increased investment not only into the C4 cycle but also the thylakoids. In addition to this qualitative information, our work allows us to add quantitative information on the physiological parameters, e. g., on the maximal electron transport rate. We find that low nitrogen availability increases the C4 advantage over C3 in photosynthetic nitrogen-use efficiency, i. e., CO2 assimilation rate per leaf nitrogen level. Moreover, a low nitrogen availability results in less required nitrogen re-allocation in order to transform an optimal C3 into an optimal C4 plant. This finding points to the possibility that nitrogen scarcity is an accelerator of C4 evolution. We test this hypothesis by analyzing evolutionary trajectories for various leaf nitrogen levels, which supports the presented hypothesis. | |||||||
| Quelle: | References are given in the document. | |||||||
| Rechtliche Vermerke: |  In silico exploration of paths toward C4 metabolism von Esther M. Sundermann ist lizenziert unter einer Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie » Entwicklungs- und Molekularbiologie der Pflanzen | |||||||
| Dokument erstellt am: | 07.05.2019 | |||||||
| Dateien geändert am: | 07.05.2019 | |||||||
| Promotionsantrag am: | 05.02.2019 | |||||||
| Datum der Promotion: | 15.04.2019 |
