Dokument: Of robust kleptoplasts and versatile embryoplasts
| Titel: | Of robust kleptoplasts and versatile embryoplasts | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=39066 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20160818-084418-9 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | de Vries, Jan [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Martin, William [Gutachter] Dr. Gould, Sven B. [Gutachter] | |||||||
| Stichwörter: | photosynthetic sea slugs, kleptoplasty, plastid evolution, functional genomics | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 580 Pflanzen (Botanik) | |||||||
| Beschreibung: | Photosynthesis in eukaryotes arose through endosymbiotic acquisition of a cyanobacterium. This endosymbiont turned into the heritable photosynthetic organelle of eukaryotes: the plastid. Various eukaryotes that lack heritable plastids engage in interactions with phototrophs to gain access to photosynthesis. Kleptoplasty is a very unique kind of symbiosis, in which a heterotrophic eukaryote steals plastids (kleptoplasts) from a photosynthetic one. This thesis focuses on the molecular mechanisms that mediate the only known case of functional kleptoplasty from the animal world, that occurring in some species of the sacoglossan sea slugs. Sacoglossans sequester plastids from their macroalgal food sources and store them in the cytosol of the digestive epithelial cells that envelop their digestive tract. Within the animal cytosol, kleptoplasts retain their photosynthetic activity, which in some slugs has been reported to last up to several months. Sacoglossan slugs that retain active plastids long-term display a remarkable starvation tolerance. It was long thought that photosynthates provided by the slugs’ kleptoplasts were the basis of starvation tolerance. At the same time, kleptoplasts were thought to be chaperoned by products of genes that the slugs had acquired from their food alga through lateral gene transfer. Results of the present thesis challenge both of these concepts. Comparative analysis of two congeneric slugs with different modes of plastid retention revealed that, although carbon is fixed by the slugs' kleptoplasts, it has little influence on their starvation tolerance. Starvation tolerance is a property dependent on the animal. Global gene expression analyses showed that both slug species respond very little towards perturbations of the kleptoplasts’ photosynthetic performance. The kleptoplasts, as a consequence, are not dependent on being fostered by their slug host. The absence of transcripts for algal nuclear genes (above noise level) indicates that the slug nuclear chromosomes have not been enriched with laterally acquired algal genes. In slugs that maintain their kleptoplasts for more than four weeks, the kleptoplasts’ photochemistry perpetuates as measured through spectrofluorometry. Such kleptoplasts appear to have intrinsic properties that render them robust. To identify potential factors conferring plastid robustness, gene contents of algal and embryophytic plastid genomes were compared. These analyses uncovered the presence of specific genes, such as ftsH, which codes for an essential protein in the photosystem II repair cycle, in plastid genomes of kleptoplasts. It is conceivable that these genes equip the stolen algal plastids with a toolkit for greater in situ control over photosystem maintenance relative to plastids lacking genes such as ftsH. Comparisons of plastid genome content identified further genes unique to algal plastids, drawing a distinguishable line between algal and land plant plastids. This suggests the existence of a shift from in situ to nuclear control over plastid function during the evolutionary process of land plant origin. This postulated shift of control might explain why only the plastids of land plants can differentiate into such a broad range of plastid types. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie » Ökologische Pflanzenphysiologie | |||||||
| Dokument erstellt am: | 18.08.2016 | |||||||
| Dateien geändert am: | 18.08.2016 | |||||||
| Promotionsantrag am: | 15.03.2016 | |||||||
| Datum der Promotion: | 22.07.2016 |
