Analysis of RNA silencing suppressor activity by TGBP1 of Pepino Mosaic virus
Plant viruses are natural targets of RNA silencing by siRNAs (small interfering RNAs). The goal of the presented research was to determine whether the triple gene block protein 1 (TGBp1) of 'Pepino mosaic potexirus' (PepMV) is a silencing suppressor and allows virus infection to proceed. Similar to ' Potato virus X' TGBp1, PepMV TGBp1 restored silenced reporter gene expression in systemic but not in local, infiltrated leaves. This suppression restricted silencing to the veins and adjacent tissue in the systemic leaves. MicroTom tomato expressing TGBp1 showed mild developmental abnormalities at ambient temperatures and severe abnormalities, similar to Pepino mosaic disease symptoms, after transfer to 15°C. PepMV infection affected 'TGB1 '-transgenic plants more than non-transgenic plants, as evidenced by a higher death percentage. Together these results suggest that PepMV TGBp1 is a suppressor of systemic silencing by siRNAs and also suppresses the silencing by miRNA (microRNAs) of mRNA involved in normal plant development.