Wassenegger, M.M.WasseneggerSpieker, R.L.R.L.SpiekerThalmeir, S.S.ThalmeirGast, F.-U.F.-U.GastRiedel, L.L.RiedelSänger, H.L.H.L.Sänger2022-03-032022-03-031996https://publica.fraunhofer.de/handle/publica/18946210.1006/viro.1996.0646Mechanical inoculation of Nicotiana tabacum with the PSTVd isolate KF 440-2 from the host plant tomato resulted in the de novo emergence, replication, and accumulation of a new "tobacco variant," designated PSTVd NT. It produces no symptoms in tobacco but, like PSTV KF 440-2, severe ones in tomato. The sequence analysis of PSTVd NT revealed a single nucleotide substitution from C -> U at position 259. Autonomous viroid replication was also induced in tobacco by genomic integration of oligomeric cDNA copies of PSTVd KF 440-2. Although these cDNAs contained the original tomato-specific C259, the circular PSTVd RNA subsequently accumulating in tobacco also exhibited the C259 -> U259 substitution. In the secondary structure of PSTVd, nucleotide 259 is part of an internal loop analogous to loop E of eukaryotic 5S rRNA and presumed to be the only bulged extrahelical nucleotide of this loop. The C259 in PSTVd KF 440-2 and in practically all other isolates and the U259 in PSTVd NT of the loop E-like structure might be involved in protein binding and in viroid processing. The new variant PSTVd NT is genetically stable in both tobacco and tomato.en570610620660579journal article