AC2 and AC4 proteins of Tomato yellow leaf curl China virus and Tobacco curly shoot virus mediate suppression of RNA silencing

Tomato yellow leaf curl China virus Y10 isolate (TYLCCNV-Y10) alone could systemically infect host plants such as Nicotiana benthamiana without symptoms. In contrast, Tobacco curly shoot virus Y35 isolate (TbCSV-Y35) alone induces leaf curl symptoms in N. benthamiana. When inoculated into transgenic N. benthamiana plants expressing GFP gene (line 16c), TYLCCNV-Y10 neither reverses the established GFP silencing nor blocks the onset of GFP silencing. In contrast, TbCSV-Y35 can partially reverse the established GFP silencing and block the onset of GFP silencing in new leaves. In the patch co-infiltration assays, the AC2 and AC4 proteins of TYLCCNV-Y10 and TbCSV-Y35 could suppress local GFP silencing and delay systemic GFP silencing, suggesting that they are suppressors of RNA silencing. Comparison of the accumulation levels of GFP mRNA in the co-infiltration patches showed that Y10 AC2 and Y35 AC2 proteins had similar efficiency for suppression of RNA silencing. However, Y35 AC4 protein functioned as a stronger suppressor of RNA silencing than Y10 AC4 protein. There-fore, the pathogenicity difference between TbCSV-Y35 and TYLCCNV-Y10 may be related to the functional difference in their AC4 proteins.

AC2 and AC4 proteins of <Emphasis Type="Italic">Tomato yellow leaf curl China virus</Emphasis> and <Emphasis Type="Italic">Tobacco curly shoot virus</Emphasis> mediate suppression of RNA silencing

Tomato yellow leaf curl China virus Y10 isolate (TYLCCNV-Y10) alone could systemically infect host plants such as Nicotiana benthamiana without symptoms. In con- trast, Tobacco curly shoot virus Y35 isolate (TbCSV-Y35) alone induces leaf curl symptoms in N. benthamiana. When inoculated into transgenic N. benthamiana plants expressing GFP gene (line 16c), TYLCCNV-Y10 neither reverses the established GFP silencing nor blocks the onset of GFP si- lencing. In contrast, TbCSV-Y35 can partially reverse the established GFP silencing and block the onset of GFP silenc- ing in new leaves. In the patch co-infiltration assays, the AC2 and AC4 proteins of TYLCCNV-Y10 and TbCSV-Y35 could suppress local GFP silencing and delay systemic GFP silenc- ing, suggesting that they are suppressors of RNA silencing. Comparison of the accumulation levels of GFP mRNA in the co-infiltration patches showed that Y10 AC2 and Y35 AC2 proteins had similar efficiency for suppression of RNA si- lencing. However, Y35 AC4 protein functioned as a stronger suppressor of RNA silencing than Y10 AC4 protein. There- fore, the pathogenicity difference between TbCSV-Y35 and TYLCCNV-Y10 may be related to the functional difference in their AC4 proteins.