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In tobacco and Nicotiana benthamiana, limited cross-protection against cucumber mosaic virus strain Fny (Fny-CMV) was provided by prior inoculation with a deletion mutant lacking the 2b silencing-suppressor protein gene (Fny-CMVΔ2b). Cross-protection by Fny-CMVΔ2b did not result from induction of systemic RNA silencing. We investigated whether protection occurs through induction of localized RNA silencing by using Arabidopsis thaliana plants harbouring mutations in genes encoding the dicer-like (DCL) endoribonucleases 2, 3 and 4 involved in antiviral silencing. In wild-type A. thaliana (Col-0) plants, Fny-CMVΔ2b was symptomless and cross-protected against Fny-CMV infection. Cross-protection by Fny-CMVΔ2b against Fny-CMV infection was not abolished in dcl2, dcl3 or dcl4 mutant plants and was strongest in dcl2/4 double mutants, although in these plants and in dcl4 mutants, Fny-CMVΔ2b replicated to high levels and induced strong symptoms. The results suggest that Fny-CMVΔ2b/Fny-CMV cross-protection is not completely dependent on RNA silencing and also involves competition between these viruses.
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Journal of General Virology vol. 90 , part 9, pp. 2288–2292
Supplementary Fig. S1. Symptoms in cross-protection experiments using Fny-CMV and Fny-CMVΔ2b in dcl3-1 mutant and dcl2-1/3-1/4-2 triple mutant A. thaliana .
Supplementary Fig S2. Typical Fny-CMV- and Fny-CMVΔ2b-induced symptoms in wild-type and dcl2-1/4-2 double mutant A. thaliana .
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