Dokument: Understanding the Bundle Sheath in C4 Evolution–Forward Genetic and Transcriptomic Approaches
| Titel: | Understanding the Bundle Sheath in C4 Evolution–Forward Genetic and Transcriptomic Approaches | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=42586 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20170612-102448-5 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Döring, Florian [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Westhoff, Peter [Gutachter] Prof. Dr. Korff Schmising, Maria von [Gutachter] | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie | |||||||
| Beschreibung: | In the presence of high CO2 concentrations, the oxygenase activity of RubisCO is effectively suppressed, and hence, photorespiration is strongly reduced in C4 plants. Nevertheless, small amounts of 2-PG are produced in the bundle sheath of C4 plants that need to be detoxified by the photorespiratory pathway.
In this study, it was analyzed whether the expression of genes related to photorespiration becomes bundle sheath-specific in the fully optimized C4 species Sorghum bicolor. By the use of transcriptome analysis, qPCR, and in situ hybridization, it was shown that all genes of the core photorespiratory cycle are at least preferentially, if not specifically, expressed in the bundle sheath, except for GLYK, which is expressed to a much higher degree in the mesophyll than in the bundle sheath. These results support the assumption that the photorespiratory pathway is shifted almost completely to the bundle sheath in plants after they established true C4 photosynthesis. The reduction and exclusion of most photorespiratory genes from the mesophyll represents an optimization and enhances the nitrogen-use efficiency of the C4 grass Sorghum bicolor. The evolution of C4 photosynthesis proceeds step by step and each small change contributes to the general fitness of the plant. Large and organelle-rich bundle sheath cells are a requirement before a CO2 shuttle toward the bundle sheath can develop. However, the genetic basis of these changes remains unknown so far. In this study, two forward genetic screens (EMS and activation tagging) were established in Arabidopsis thaliana to identify genes involved in bundle sheath ontogeny and maintenance (BSOM genes). Two reporter gene lines that express either luciferase or chloroplast-targeted GFP in the bundle sheath and vasculature were created and used as a genetic background in both mutant screens. Differences in the reporter gene signal in Arabidopsis leaves were used as a proxy to isolate mutants with potentially altered bundle sheath anatomy. It was shown that both screens resulted in numerous primary mutants with increased or decreased reporter gene activity. High- resolution light microscopy and transmission electron microscopy could reveal that the bundle sheath anatomy is affected in four EMS-generated mutant lines and activation tagging mutant line AT-2. Furthermore, BSOM2, a gene that encodes an ABA efflux transporter, was mapped from activation tagging line AT-2. It was shown that both the overexpression and knockout of BSOM2 results in more bundle sheath cells and an enlarged vasculature. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie » Entwicklungs- und Molekularbiologie der Pflanzen | |||||||
| Dokument erstellt am: | 12.06.2017 | |||||||
| Dateien geändert am: | 12.06.2017 | |||||||
| Promotionsantrag am: | 20.03.2017 | |||||||
| Datum der Promotion: | 31.05.2017 |
