Regulation of plastid gene expression during chloroplast biogenesis in barley /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | The results of my research show that the activation of plastid DNA synthesis occurred early in barley leaf chloroplast development. High rates of DNA synthesis were observed in the leaf basal meristem or dark-grown plants where plastid transcription activity was low. DNA synthesis activity decreased in later stages of chloroplast development. Plastid transcription activity increased 10-fold in elongating cells which had ceased dividing; light was not required to activate plastid gene transcription. Plastid DNA copy number increased from 130 to 210. Plastid transcription activity declined rapidly in illuminated plants with increasing leaf cell age and plastid DNA copy number also declined but with a slower time course. In dark-grown seedlings, plastid transcription activity declined more slowly than in illuminated plants while DNA copy number remained constant with increasing cell age. These data show that plastid transcription activity and DNA copy number increase early in chloroplast development and that transcription activity per DNA template varies up to 5-fold during barley leaf biogenesis. Plastid numbers per cell increased from 15 to 60 in developing mesophyll cells, however, the decline in DNA copy number continued after plastid division ceased. Therefore the reduction in DNA copy number in illuminated seedlings was due to degradation. The relative transcription rates of several plastid genes varied up to 67-fold during chloroplast development. Genes encoding components of the transcription/translation apparatus were preferentially expressed earlier in chloroplast development than genes encoding the photosynthetic apparatus. The relative stability of mRNAs from selected plastid genes also varied with development. These results demonstrate that transcription is an important determinant of RNA levels in developing barley chloroplasts, and show modulation of RNA stability for a few genes. A procedure is described to visualize plastid nucleic acid binding proteins separated on LDS-PAGE gels. This procedure was used to show that ribosomal proteins are the most abundant nucleic acid binding proteins in the chloroplast. Other low abundance nucleic acid binding proteins are detected in membrane and fractions enriched in the plastid DNA-protein (nucleoid) complex. The levels of some of these proteins varied with chloroplast development. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Biochemistry." |
| Physical Description: | x, 140 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |