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

Abstract

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.

Interaction with host SGS3 is required for suppression of RNA silencing by tomato yellow leaf curl virus V2 protein

“…CFP signal is shown in green, YFP signal is shown in red, comparable levels of colocalizing green and red signals produce yellow color, and plastid autofluorescence is shown in mutant of TYLCV V2 was produced as described in ref. 23. All PCRs were performed by using a high-fidelity Pfu DNA polymerase (Promega), and their products were verified by DNA sequencing.…”

“…Specifically, CMV 2b binds AGO1 and inhibits its endonucleolytic activity (21), and P0 targets AGO1 for degradation (22). Here we report that an RNA-silencing suppressor of Tomato yellow curl leaf geminivirus (TYLCV), the V2 protein (23), interacts directly with the host SGS3 in planta, and that this interaction is required for V2's ability to suppress RNA silencing.…”

“…First, consistent with previous observations (23), we showed that the C84S/C86S mutant was indeed compromised in its ability to suppress RNA silencing. RNA silencing was detected by a visible increase in GFP expression after coinfiltration of a wild-type Nicotiana benthamiana plant with two strains of Agrobacterium, one that carries V2 or its mutant and the other that contains the RNA-silencing initiator and reporter gene, GFP (23). GFP expression, which could be observed 2 days postinfiltration (dpi) (data not shown), was almost completely silenced at 7 dpi.…”

“…RNA-silencing suppression was assayed as described in ref. 23. To detect RNA-silencing suppression in whole leaves, we used N. benthamiana leaves, which express high levels of GFP, allowing its visualization at low magnification.…”

Banana bunchy top disease (BBTD) symptom expression in banana and strategies for transgenic resistance: A review

“…PTGS used in the development of resistance against the viruses ACMV (Vanitharani et al, 2003, Vanderschuren et al, 2007, mungbean yellow mosaic virus (MYMV) (Pooggin et al, 2003), Sri Lankan cassava mosaic virus (SLCMV), East African cassava mosaic virus (EACMV) , TYLCV (Abhary et al, 2006, Fuentes et al, 2006Zrachya et al, 2007), bean golden mosaic virus (BGMV) (Bonfim et al, 2007), and TLCV (Ramesh et al, 2007). Although only in its early stages, research utilizing this process to achieve virus resistance is very promising in that any viral coding or noncoding sequences can be targeted and no protein need be expressed.…”