Transient expression of intron-containing transgenes generates non-spliced aberrant pre-mRNAs that are processed into siRNAs. Nicotiana benthamiana

SRNA deep sequencing (sRNA-seq) of different agroinfiltrated transgenes revealed the presence of sRNAs mapping to the entire non-spliced pre-mRNA suggesting that RDRs (most likely RDR6) processed aberrant non-spliced pre-mRNAs. Primary and secondary sRNAs with lengths of 18-25-nucleotides (nt) were detected, with the most prominent sRNA size class of 22-nt. SRNAs also mapped to the terminator sequence, indicating that RDR substrates also comprised read-through transcripts devoid of polyadenylation tail.