Efficiency of Nitrous Acid as An Inactivating and Mutagenic Agent of Intact Tobacco Mosaic Virus and Its Isolated Nucleic Acid 1

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RESUMO

When tobacco mosaic virus (TMV) and its isolated nucleic acid (TMV-RNA) were treated with nitrous acid, the nucleic acid was inactivated six times faster than the intact virus. Inactivation of both the infectious entities was exponential with treatment time to 0.1% level of survival. Eight different mutant phenotypes were scored after inactivation of TMV and TMV-RNA to 50, 10, 1.0, and 0.1% survival levels. Significantly more mutants in relation to unaltered isolates were induced at all levels of survival upon nitrous acid treatment of TMV than of TMV-RNA. Furthermore, the proportion of two specific mutant phenotypes was significantly greater in treated TMV than in treated TMV-RNA. No qualitative differences, however, were observed between the mutational spectra of nitrous acid-treated TMV and TMV-RNA. These results indicate that, in the intact virus, the viral capsid protects some of the sites involved in lethality; thus, proportionately more mutants are induced on nitrous acid treatment of TMV versus TMV-RNA.

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