Suppression of post-transcriptional gene silencing by callus induction and virus infection reveals the existence of aberrant RNAs

Post-transcriptional silenced tobacco plants were used to study RNA interference (RNAi) at initial phases of plant development and in tissues with highly proliferating cells. Two transgenic lines harboring DeltaP3 construct, corresponding to part of the Andean potato mottle virus (APMoV) minor coat protein fused with the 3'-NTR, were used. Early post-transcriptional gene silencing (PTGS) activation and transgene degradation was observed on silenced plants. Silencing was suppressed when silenced line were submitted to callus formation or Potato virus Y (PVY) infection. Analyses of callus and virus-suppressed plants revealed the presence of aberrant high molecular weight transgene transcript species generally proposed in RNAi models but not experimentally demonstrated. (C) 2004 Elsevier Ireland Ltd. All rights reserved.