Post-transcriptional gene silencing of RNA-2 in brome mosaic virus /
Transgenic Nicotiana benthamiana plants expressions biome mosaic virus (BMV) p2 protein complemented replication of RNAs1+3 but, surprisingly, supported little or no replication of RNA-2. The transient RNA did not behave as a defective interfering RNA, nor was RNA-2 silencing mediated through the RN...
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731681551&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Transgenic Nicotiana benthamiana plants expressions biome mosaic virus (BMV) p2 protein complemented replication of RNAs1+3 but, surprisingly, supported little or no replication of RNA-2. The transient RNA did not behave as a defective interfering RNA, nor was RNA-2 silencing mediated through the RNA-2 minus strand promoter sequence. Kinetic analyses showed identical degradation rates for RNAs-2 and -3, greatly detracting from the concept of an induction of an RNA-2 specify degradation system. Deletion analysis identified a 462 nt sequence which may contribute to RNA-2 specific silencing. However, an evaluation of the replication of RNA-3 chimeric constructs bearing several regions of RNA-2 suggested that the silencing operates in an RNA-2 context-specific manner. When R₁ progeny of a p2 transgenic line that severely debilitated RNA-2 accumulation were tested for virus resistance, three different classes of reactions were observed. In Class 1 and Class 3 plants, the virus moved systemically and showed various extents of RNA-2 silencing. However, in Class 2 plants, there was a stochastic onset of post-transcriptional silencing in the systemic leaves that was reminiscent obvious recovery seen In other plant virus systems. Plants showing recovery tended to have a greater number of transient loci than did those exhibiting component-specific silencing. The induction of silencing did not appear to be dependent solely on the combined steady state levels of the transient and viral RNA. Some plants transformed with a p2 frameshift construct showed a phenotype that silenced expression of all three BMV RNAs, but none showed RNA-2 specific silencing. P2 transgenic plants were able to support systemic migration of RNAs-1 and -3. However, superinfection of these plants with virion RNA revealed that specific silencing of RNA-2 was maintained. While the precise relationship between the two types of silencing (RNA-2 specific and global BMV RNAs) remains unclear, it is likely that these findings reported reflect early events in the induction of recovery from virus infection. |
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| Item Description: | Vita. "Major Subject: Biology". |
| Physical Description: | x, 85 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 68-84). |