Protein 2b of Cucumber mosaic virus strains IA and SD preferentially suppresses RDR6-dependent silencing pathway
- 20 Downloads
The 2b protein of Cucumber mosaic virus (CMV) subgroup IB strain IA (IA2b) suppresses the sense transgene-induced post-transcriptional gene silencing (S-PTGS) but not the inverted repeat-induced post-transcriptional gene silencing (IR-PTGS) of a tobacco microsome-localized α-linolenate synthase gene (NtFAD3). In contrast, the 2b protein of CMV subgroup IB strain SD (SD2b) has been reported to suppress IR-PTGS. We overexpressed the SD2b gene in tobacco, and this transgenic line was crossed with the transgenic plants showing S-PTGS and IR-PTGS of the NtFAD3 gene. The phenotype of offspring showed that SD2b inhibited S-PTGS but not IR-PTGS. Next, we determined the suppressor activity of IA2b and SD2b proteins in a transient IR-PTGS assay. The transient expression of firefly luciferase (LUC) gene was efficiently decreased by IR-PTGS. Co-infiltration of SD2b and IA2b gene partially suppressed IR-PTGS of the LUC gene in the wild-type plants; however, these 2b proteins did not suppress IR-PTGS in the RNA-dependent RNA polymerase6 (RDR6) knockdown plants. It has been reported that RDR6-dependent secondary small interfering RNA synthesis does not occur in the IR-PTGS, when targeting endogenous genes such as NtFAD3, but is efficiently induced in the IR-PTGS of the reporter transgenes. These results indicate that the SD2b and IA2b preferentially suppress the RDR6-dependent silencing pathway but do not suppress the RDR6-independent IR-PTGS pathway.
KeywordsAgroinfiltration Cucumber mosaic virus 2b protein IR-PTGS RDR6 S-PTGS Secondary siRNA synthesis
The authors would like to thank Enago (http://www.enago.jp) for the English language review.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
- González I, Matínez L, Rakitina DV, Lewsey MG, Atencio FA, Llave C, Kalinina NO, Carr JP, Palukaitis P, Canto T (2010) Cucumber mosaic virus 2b protein subcellular targets and interactions: their significance to RNA silencing suppressor activity. Mol Plant Microbe Interact 23:294–303CrossRefGoogle Scholar
- Parent JS, Jauvion V, Bouché N, Béclin C, Hachet M, Zytnicki M, Vaucheret H (2015) Post-transcriptional gene silencing triggered by sense transgenes involves uncapped antisense RNA and differs from silencing intentionally triggered by antisense transgenes. Nucleic Acids Res 43:8464–8475CrossRefGoogle Scholar
- Roossinck MJ, Zhang L, Hellwald KH (1999) Rearrangements in the 5′ nontranslated region and phylogenetic analyses of cucumber mosaic virus RNA 3 indicate radial evolution of three subgroups. J Virol 73:6752–6758Google Scholar
- Shen WX, Au PCK, Shi BJ, Smith NA, Dennis ES, Guo HS, Zhou CY, Wang MB (2015) Satellite RNAs interfere with the function of viral RNA silencing suppressors. Front Plant Sci 6:281Google Scholar