Characterization of plant miRNAs and small RNAs derived from potato spindle tuber viroid (PSTVd) in infected tomato.

To defend against invading pathogens, plants possess RNA silencing mechanisms involving small RNAs (miRNAs, siRNAs). Also viroids - plant infectious, non-coding, unencapsidated RNA - cause the production of viroid-specific small RNAs (vsRNA), but viroids do escape the cytoplasmic silencing mechanism. Viroids with minor sequence variations can produce different symptoms in infected plants, suggesting an involvement of vsRNAs in symptom production.

Accumulation of viroid-specific small RNAs and increase in nucleolytic activities linked to viroid-caused pathogenesis.

Strong viroid-caused pathogenesis was achieved in tomato cv. Rutgers by biolistic transfer of severe or lethal potato spindle tuber viroid (PSTVd) strains, while other tomato genotypes (e.g.