A single nucleotide substitution converts potato spindle tuber viroid (PSTVd) from a noninfectious to an infectious RNA for nicotiana tabacum.
Mechanical 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.
Wassenegger
M
M
Max-Planck-Institut für Biochemie, Abteilung Viroidforschung, Martinsried, Germany.
Spieker
R L
RL
Thalmeir
S
S
Gast
F U
FU
Riedel
L
L
Sänger
H L
HL
D001482:Base Composition; D003562:Cytidine; D014644:Genetic Variation; D018551:Solanum lycopersicum / Q000821:virology; D008969:Molecular Sequence Data; D010942:Plant Viruses / Q000235:genetics / Q000472:pathogenicity*; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D012328:RNA Viruses / Q000235:genetics / Q000472:pathogenicity*; D012367:RNA, Viral / Q000302:isolation & purification; D014026:Nicotiana / Q000821:virology; D014529:Uridine; D014772:Viroids / Q000235:genetics / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics; D016662:Virus Integration; D014779:Virus Replication
D012367:RNA, Viral; D003562:Cytidine; D014529:Uridine