Molecular and biochemical characterization of a molluscan/algal chloroplast endosymbiosis /
Early in its life cycle, the marine mollusc Elysia chlorotica (Gould) forms an intracellular endosymbiotic association with chloroplasts of the chromophytic alga, Vaucheria litorea (C. Agardh). As a result, the dark green sea slug can be sustained in culture solely by photoautotrophic CO₂ fixation...
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
2001.
|
| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=728907311&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Early in its life cycle, the marine mollusc Elysia chlorotica (Gould) forms an intracellular endosymbiotic association with chloroplasts of the chromophytic alga, Vaucheria litorea (C. Agardh). As a result, the dark green sea slug can be sustained in culture solely by photoautotrophic CO₂ fixation for at least 9 months when provided with only light and a source of CO₂. This endosymbiotic relationship must be re-established with each generation since the plastids are not integrated into the germline of the mollusc. It has been demonstrated that the mollusc endosymbiotic chloroplasts maintain functional levels of chloroplast-encoded proteins that participate in the transfer of electrons during photosynthesis. Among these polypeptides are the core photosystem I and II heterodimers PsaA/B and D1/D2, respectively, as well as several cytochrome complex proteins, and the large and small subunits of Rubisco. Maintenance of these polypeptide levels over the 9 months of culture is due, in part, to de novo protein synthesis in the chloroplasts. Levels of one putative nuclear encoded protein, a light harvesting complex protein homologue, was also maintained throughout the 9 month culture period. Mollusc plastid chlorophyll a and c levels remained comparable to that of alga for 6 months, after which time a significant decrease in both chlorophylls was observed. V. litorea chloroplasts were also isolated in order to ascertain the robustness of the isolated plastids. Ferricyanide-dependent O₂ intactness assays showed approximately 65% of the algal plastids to be structurally intact even after 48 h, whereas spinach chloroplasts dropped to only 26% intact after 24 h. Phase contrast microscopy of plastids isolated from the alga and mollusc demonstrated similar structural intactness percentages, while in vitro protein synthesis of algal plastids exhibited only a slight decrease in chloroplast translational efficiency of thylakoid and soluble plastid proteins. Therefore, it is believed that the acquisition of these plastids by the mollusc is aided by their unique stability, allowing for the remarkable levels of production and processing of transcripts, proteins, and pigments by the captured chloroplasts devoid of the 'normal' algal nuclear contribution. |
|---|---|
| Item Description: | Vita. "Major Subject: Molecular and Environmental Plant Sciences". |
| Physical Description: | x, 108 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 91-107). |