Characterization of plant miRNAs and small RNAs derived from potato spindle tuber viroid (PSTVd) strains of different severity 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, which suggests an involvement of vsRNAs in symptom production. We analyze by deep sequencing the spectrum of vsRNAs induced by different PSTVd strains, which cause mild, intermediate and strong symptoms, respectively, upon infection of tomato plants cv Heinz.