Transcriptional regulation of Beta-phaseolin gene expression /
The overall objective of the research presented here is to
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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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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742145711&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The overall objective of the research presented here is to increase understanding of the mechanisms that regulate transcription of the []-phaseolin gene (phas). Expression of phas is rigorously confined to the developing seed, both in bean and transgenic tobacco plants. Expression of the diphtheria toxin A-chain (DT-A) coding region driven by the phas promoter in transgenic tobacco, produced plants that were phenotypically normal in vegetative tissues, but were male sterile due to initiation of DT-A expression at the onset of microsporogenesis. When wild-type pollen was used to fertilize DT-A-transformed plants, 50% of the resulting embryos aborted at the heart stage. The remaining seeds developed normally and yielded kanamycin-sensitive seedlings. To analyze the seed specific expression conferred by the proximal 295 bp of the promoter (p295), this region was dissected into three elements: a 68 bp element (68mer: -295 to -227), a middle region (-227 to -109) and a basal promoter (-109 to +20). The transcriptional activity of the 68mer and middle regions in combination with the basal phas promoter or the heterologous CaMV 35S basal promoter (-64 to +6) fused to the reporter gene gus was tested in transgenic plants. No expression in vegetative tissues was found for any of the constructs, and elements interacted synergistically to yield high levels of expression. p295 transformed seeds expressed gus in embryo and endosperm, whereas p227 was expressed primarily in the embryo. Constructs containing 2 copies of the 68mer element were preferentially expressed in the endosperm. These results illustrate the modular nature of the proximal phas promoter, where distinct elements contribute to high levels of expression in different parts of the seed. Investigation of the far upstream phas promoter region and 3' end suggested the presence of matrix attachment regions (MARs). These regions are A/T-rich and bound to nuclear matrices in vitro. A gus fusion construct containing the full length phas promoter and 3' end (pl470/phas) that included both MAR elements exhibited higher expression levels and lower plant- to-plant variation in transgenic tobacco plants than did a similar construct lacking MAR sequences. These results are consistent with the presence of functional MARs flanking the phas gene. |
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| Item Description: | Vita. "Major Subject: Biology". In title, symbol for Greek letter Beta is used. |
| Physical Description: | viii, 80 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |