Role of viral and host factors in systemic infection by tobacco etch potyvirus /
This dissertation focuses on characterizing roles of viral and host factors in establishment of systemic infection by tobacco etch potyvirus (TEV). The roles of capsid protein (CP) and CP coding sequence in TEV genome amplification were analyzed using a series of frameshift-stop codon and correspond...
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| Format: | Thesis Book |
| Language: | English |
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[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=731681221&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | This dissertation focuses on characterizing roles of viral and host factors in establishment of systemic infection by tobacco etch potyvirus (TEV). The roles of capsid protein (CP) and CP coding sequence in TEV genome amplification were analyzed using a series of frameshift-stop codon and corresponding 3' deletion mutants. Analysis of mutants indicated that efficient genome amplification required translation of CP-coding sequence between codons 138-189. Analysis of series of 5' deletion mutants lacking up to CP codon 210 indicated that although the first 210 residues and the sequence coding them were nonessential, genome amplification absolutely required a cis-active RNA sequence between codons 211-246. Computer-based models indicated that this region formed a series of stem-loop structures with 3' nontranslated RNA sequences. To investigate host functions necessary for systemic TEV infection, the Arabidopsis thaliana-TEV system was developed. Screens of Arabidopsis for susceptibility to TEV revealed that although several ecotypes supported genome replication and cell-to-cell movement in inoculated leaves, only four ecotypes including C24 and La-er sustained systemic infection. Investigation of genetic basis for restriction in the Columbia ecotype using C24 x Col-3 crosses and backcrosses, and La-er x Col-0 recombinant inbred lines, indicated that restriction was mediated by a dominant locus on chromosome 1 designated RTM1 (restricted TEV movement 1). No visible or microscopic cell-death lesions or PR-la gene expression was evident in inoculated leaves of the restrictive ecotype. The restriction was active in several mutants with defects in HR/SAR-type defense response pathways suggesting that it was substantially different from classical gene-for-gene resistance. To gain insight into the role of RIM1 in TEV restriction, it was isolated using a combination of map-based and mutational approaches. Based on fine-structure mapping experiments, RIM1 was localized between two closely linked molecular markers within a bacterial artificial chromosome (BAC) contig. Transgenic complementation data from cosmids derived from BACS spanning this interval identified a 6 kb genomic region comprising three open reading frames (ORFs) that could potentially encode RTM1. Sequence analysis of mutant alleles confirmed ORF 3 as the region encoding RTM1. Database searches revealed that RTM1 was homologous to myrosinase-binding proteins and jacalin-like lectins from plants. |
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| Item Description: | Vita. "Major Subject: Biology". |
| Physical Description: | x, 126 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 89-122). |