Photosynthetic organisms exhibit a variety of responses to changes in light intensity, including differential biosynthesis of chlorophyll-protein complexes. Cultures of Rhodobacter capsulatus grown anaerobically with a low intensity of light (2 W/m²) contained about four times as much B800-850 light harvesting complex as cells grown under high light intensity (140 W/m²). The mRNA transcripts encoding B800-850 beta and alpha peptides were analyzed by Northern blot, S1 nuclease protection and capping with guanylyl transferase. It was found that the steady-state levels of B800-850 mRNAs in high light-grown cultures was about four times as great as in cells grown under low light intensity. Therefore the lesser amounts of mature B800-850 peptide gene products found in cells grown with high light intensity were the result of a posttranscriptional regulatory process. It was also found that there were two polycistronic messages encoding the B800-850 peptides. These messages shared a common 3' terminus but differed in their 5' end segments as a result of transcription initiation at two discrete sites. Moreover the half life of B800-850 mRNAs was about 10 minutes in cells grown with high light and approximately 19 minutes in low light-grown cultures. Transcriptional and translational fusions were constructed between the B800-850 transcription initiation region (from this point on referred to as the puc transcription initiation region; see Fig. 1) and the Escherichia coli lacZ gene. From these studies it was concluded that the rates of transcription initiation of the puc (B800-850) genes was higher in cells grown with high light illumination than in low light-grown cultures, and that the relative amount of B800-850 complexes under these conditions was controlled by a translational or a posttranslational mechanism. The translational and transcriptional fusions were also used for examination of oxygen regulated expression of the puc genes. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/28362 |
| Date | January 1988 |
| Creators | Zucconi, Anthony |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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