Abstract
The cucumber mosaic virus (CMV) 2b viral suppressor of RNA silencing (VSR) inhibits host responses to jasmonic acid (JA), a chemical signal regulating resistance to insects. Previous experiments with a CMV subgroup IA strain and its 2b gene deletion mutant suggested that VSRs might neutralize aphid (Myzus persicae) resistance by inhibiting JA-regulated gene expression. To further investigate this, we examined JA-regulated gene expression and aphid performance in Nicotiana benthamiana infected with Potato virus X, Potato virus Y, Tobacco mosaic virus and a subgroup II CMV strain, as well as in transgenic plants expressing corresponding VSRs (p25, HC-Pro, 126 kDa and 2b). All the viruses or their VSRs inhibited JA-induced gene expression. However, this did not always correlate with enhanced aphid performance. Thus, VSRs are not the sole viral determinants of virus-induced changes in host–aphid interactions and interference with JA-regulated gene expression cannot completely explain enhanced aphid performance on virus-infected plants.
Highlights
Interference with jasmonic acid-regulated gene expression is a general property of viral suppressors of RNA silencing but only partly explains virus-induced changes in plant–aphid interactions
We examined jasmonic acid (JA)-regulated gene expression and aphid performance in Nicotiana benthamiana infected with Potato virus X, Potato virus Y, Tobacco mosaic virus and a subgroup II cucumber mosaic virus (CMV) strain, as well as in transgenic plants expressing corresponding viral suppressor of RNA silencing (VSR) (p25, HC-Pro, 126 kDa and 2b)
In Arabidopsis thaliana, the 2b VSR encoded by a subgroup IA CMV strain (Fny-CMV) interacted strongly with AGO1 and interfered with microRNAregulated gene expression and plant development, whereas 2b proteins of subgroup II strains (LS-CMV and Q-CMV) did not interact as strongly with AGO1 or induce such strong developmental defects in the host (Zhang et al, 2006; Lewsey et al, 2007)
Summary
In Arabidopsis thaliana, the 2b VSR encoded by a subgroup IA CMV strain (Fny-CMV) interacted strongly with AGO1 and interfered with microRNAregulated gene expression and plant development, whereas 2b proteins of subgroup II strains (LS-CMV and Q-CMV) did not interact as strongly with AGO1 or induce such strong developmental defects in the host (Zhang et al, 2006; Lewsey et al, 2007). It was reported that VSRs encoded by certain other aphid-transmitted viruses have the ability to enhance JA-mediated signalling: HC-Pro derived from the potyvirus tabacco etch virus and the P6 protein from cauliflower mosaic virus enhanced responses to JA when expressed in transgenic A. thaliana (Endres et al, 2010; Love et al, 2012).
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