Factors that regulate psbA gene expression in Synechococcus elongatus PCC 7942 /
S. elongatus is a unicellular photoautotrophic cyanobacterium that carries out oxygenic (plant-type) photosynthesis and exhibits global circadian regulation of gene expression. In S. elongatus, a family of three psbA genes encodes the D1 protein of the photosystem II reaction center. The psbA genes...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2003.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=765154761&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | S. elongatus is a unicellular photoautotrophic cyanobacterium that carries out oxygenic (plant-type) photosynthesis and exhibits global circadian regulation of gene expression. In S. elongatus, a family of three psbA genes encodes the D1 protein of the photosystem II reaction center. The psbA genes encode two forms of the D1 protein and are differentially expressed in response to changes in light intensity. Chapter II presents biochemical methods for the partial purification of DNA-binding proteins from S. elongatus. We used these methods to obtain protein samples for electrophoretic mobility shift assays. These assays showed that one or more S. elongatus proteins binds to the untranslated leader region of psbAI, and that DNA sequences from the corresponding region of psbAII efficiently compete for binding. This suggests that psbAI and psbAII share a regulatory factor. Chapter III describes the isolation of a gene (psfR) that regulates psbAI activity. Overexpression of psfR results in increased expression of psbAI, but does not affect the circadian timing of psbAI expression. psfR overexpression affected some, but not all, of the genes we routinely survey for circadian expression. PsfR acts (directly or indirectly) on the psbAI basal promoter region. psfR knockout mutants exhibit wild-type psbAI expression, suggesting that other factors can regulate psbAI expression in the absence of functional PsfR. PsfR contains two receiver domains (found in bacterial two-component signal transduction systems), one of which lacks the conserved aspartyl residue required for phosphoryl transfer. PsfR also contains a GGDEF domain. The presence of these domains and the absence of a detectable conserved DNA-binding domain suggest that PsfR may regulate psbAI expression via protein-protein interactions or GGDEF activity (the production of cyclic dinucleotides) rather than direct interaction with the psbAI promoter. |
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| Item Description: | Vita. "Major Subject: Microbiology". |
| Physical Description: | xi, 122 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 113-120). |