The effects of bromoviral coat protein gene sequence exchanges on virus-host interactions
Pratt, Steven D.
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The goal of this research was to provide insight into how bromoviral nucleotide sequences, and specifically the sequence of the coat protein gene, affect virus-host interactions. The interactions we were specifically interested in were host range, infectivity, symptoms and their severity, and viral transport. This research was accomplished by using recombinant DNA techniques to produce three classes of coat protein mutants: those in which a single amino acid was altered, chimeric clones in which portions of the coat protein gene sequence were exchanged between brome mosaic virus (BMV) and cowpea chlorotic mottle virus (CCMV), and a single clone in which the coat protein gene of CCMV was replaced by that of BMV. Upon assay in whole plants, the point mutants proved most capable of infection and systemic spread. These clones all produced symptoms (though not all as severe as those produced by the wild-type virus) and spread systemically in their normal hosts. The partial coat protein gene transfers did not appear capable of producing infection in the hosts of either virus. However, the entire coat protein gene exchange did produce systemic symptoms in cowpea, although no virus could be detected in leaves. These observations are preliminary, but they do appear to indicate that even small alterations in the coat protein can affect symptoms produced and their severity.