Viroids: sequence variability and evolution of pathogenic RNAšek J. (2002): Viroids: sequence variability and evolution of pathogenic RNA. Plant Protect. Sci., 38: 173-176.
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Viroids as the smallest pathogenic circular single-stranded pathogenic RNAs form populations of quasi-species, which
has been recently identified by thermodynamic methods like TGGE pre-selection and heteroduplex analysis. It was found
that replication under thermal stress led to enormously high level of viroid mutagenesis. Mostly multiple mutants having
non-random distribution of base changes were found. A specific “hot spots” were identified in the regions, where
a characteristic “pathogenicity domains” are localised in different viroids of the pospiviroidae family. Specific viroid
microevolution was observed upon artificial inoculation of non-host plant species. Our results suggest that viroid propagation
under physiological stress can be assumed as important factor, which is among others, responsible for an appearance
of viroid quasi-species in the nature. Evolution and new viroid patotypes could accumulate due to environmental stress
including various pollutants may be a potential danger for cultured plants.
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