Organ-specific alterations in tobacco transcriptome caused by the PVX-derived P25 silencing suppressor transgene

The expression of the PVX-specific P25 silencing suppressor in transgenic tobacco plants caused significant up-regulation of 1350 transcripts, but down-regulation of only five transcripts in the leaves, and up- and down-regulation of 51 and 13 transcripts, respectively, in the flowers of these plants, as compared to the wild type control plants. Most of the changes occurred in the transcripts related to biotic and abiotic stresses, transcription regulation, signaling, metabolic pathways and cell wall modifications, and many of them appeared to be induced through up-regulation of the signaling pathways regulated by ethylene, jasmonic acid and salicylic acid. Correlations of these alterations with the protein profile and related biological functions were analyzed. Surprisingly, they did not cause significant alterations in the protein profile, and caused only very mild alteration in the phenotype of the P25-expressing transgenic plants.Expression of the PVX-specific P25 VSRS protein causes major alterations in the transcriptome of the leaves of transgenic tobacco plants, but very little of any effects in the young flowers of the same plants. The fairly stable protein profile in the leaves and lack of any major changes in the plant phenotype indicate that the complicated interplay and interactions between different regulatory levels are able to maintain homeostasis in the plants.RNA silencing is a highly conserved and versatile genetic surveillance and regulatory mechanism occurring in all higher eukaryotes. It is mediated by a large network of interacting effector molecules, and connected to several parallel regulatory and signaling pathways. It affects, both directly and indirectly, cellular processes varying from the cell cycle regulation and chromatin structure maintenance to transcriptional and posttranscriptional regulation, to stress and hormonal signaling, and to developmental differentiation [1-5]. Thus, RNA silencing plays a central role in manifestation of t