Suppressor of RNA silencing encoded by Tomato yellow leaf curl virus-Israel

The Israeli isolate of Tomato yellow leaf curl geminivirus (TYLCV-Is) is a major tomato pathogen, causing extensive crop losses both in the New and Old World. Surprisingly, however, little is known about the molecular mechanisms of TYLCV-Is interactions with tomato cells. Here, we have identified a TYLCV-Is protein, V2, which acts as a suppressor of RNA silencing and which is unrelated to presently known viral suppressors. Specifically, V2, but not other proteins of TYLCV-Is, inhibited RNA silencing of a reporter transgene, GFP. This inhibition elevated the cellular levels of the GFP transcript and the GFP protein, but it had no apparent effect on the accumulation of GFP-specific short interfering RNAs (siRNAs), suggesting that TYLCV-Is V2 targets a step in the RNA silencing pathway which is subsequent to the Dicer-mediated cleavage of dsRNA. Visualization of the sub-cellular localization of TYLCV-Is V2 in plant protoplasts and tissues showed that this protein is associated with cytoplasmic strands and inclusion bodies in the cortical regions of the cell.