Virus encoded RNA-silencing suppressors (RSSs) are the key components evolved by the viruses to counter RNA-silencing defense of plants. Whitefly-transmitted begomoviruses infecting tomato crop code for five different proteins, ORF AC4, ORF AC2 and ORF AV2 in DNA-A component, ORF BV1 in DNA-B and ORF 𝛽C1 in satellite DNA 𝛽 which are predicted to function as silencing suppressors. In the present study suppressor function of ORF 𝛽C1 of three betasatellites Tomato leaf curl Bangalore betasatellite ToLCBB-[IN:Hess:08], Cotton leaf curl Multan betasatellite CLCuMB–[IN:Sri:02] and Luffa leaf distortion betasatellite LuLDB-[IN:Lu:04] were examined. Agroinfiltration of GFP-silenced Nicotiana tabaccum cv. Xanthi with the cells expressing 𝛽C1 protein resulted in reversal of silenced GFP expression. GFP-siRNA level was more than 50-fold lower compared to silenced plants in plants infiltrated with 𝛽C1 gene from ToLCBB. However, in the case of 35S-𝛽C1 CLCuMB and 35S-𝛽C1 LuLDB construct, although GFP was expressed, siRNA level was not reduced, indicating that the step at which 𝛽C1 interfere in RNA-silencing pathway is different.
Volume 44 | Issue 5
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