Transcriptional and post-transcriptional regulation of plastid gene expression during barley chloroplast development /
The expression of chloroplast psbD-psbC operons was examined from five cereals and three dicot species. Despite differences in the structure and expression of the cereal and dicot psbD-psbC operons, the accumulation of blue light-induced psbD-psbC mRNAs was conserved in all species studied. In addi...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742744361&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The expression of chloroplast psbD-psbC operons was examined from five cereals and three dicot species. Despite differences in the structure and expression of the cereal and dicot psbD-psbC operons, the accumulation of blue light-induced psbD-psbC mRNAs was conserved in all species studied. In addition, sequences surrounding the blue light-responsive psbD-psbC promoter (LRP) are highly conserved. The barley LRP, spanning from -121 to +64 relative to the transcription initiation site, contains two blocks of conserved sequences. The first, referred to as the AAG box, is located between -36 and -64 upstream of the transcription initiation site and contains two AAG repeats. The second, referred to as the PGT (plastid GT) box, is located between -71 and -100 and shows sequence homology to GT motifs in light-regulated nuclear promoters. Each motif interacts with a sequence-specific DNA-binding factor, termed AGF (AAG binding factor) and PGTF (PGT binding factor), respectively. Deletion analyses demonstrated that the AAG box is required for transcription of the LRP. Furthermore, point mutations in the AAG cis-element decreased binding of AGF and inhibited transcription from the LRP. Therefore, AGF is an essential factor required for transcription of the LRP. Meanwhile, DNA-binding of PGTF was decreased by an ADP-dependent protein kinase in plastids. It is likely that PGTF is involved in blue light regulation of the LRP. Point mutation analyses revealed that the sequence homologous to a prokaryotic '- 1O' promoter element is required for transcription from the LRP. Changes in plastid RNA stability were examined during barley chloroplast development. Of the plastid RNAs examined, a 2.6 kb unspliced precursor of tRNA(lys) exhibited the shortest half-life, which was estimated to be 3 hrs. The 16S RRNA and psba MRNA had the longest relative half-life, which was greater than 40 hrs. The stability of the 16S RRNA and mRNAs for rpoa, psba and rbcl increased independent of light and was further modulated during barley chloroplast development. The increase in psba MRNA stability helps support continued synthesis of D 1 required in illuminated plants. |
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| Item Description: | Vita. "Major Subject: Biochemistry". |
| Physical Description: | xii, 161 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |