Abstract
An increasing body of evidence points at a role of the plant hormones jasmonates (JAs) in determining the outcome of plant-virus interactions. Geminiviruses, small DNA viruses infecting a wide range of plant species worldwide, encode a multifunctional protein, C2, which is essential for full pathogenicity. The C2 protein has been shown to suppress the JA response, although the current view on the extent of this effect and the underlying molecular mechanisms is incomplete. In this work, we use a combination of exogenous hormone treatments, microarray analysis, and pathogen infections to analyze, in detail, the suppression of the JA response exerted by C2. Our results indicate that C2 specifically affects certain JA-induced responses, namely defence and secondary metabolism, and show that plants expressing C2 are more susceptible to pathogen attack. We propose a model in which C2 might interfere with the JA response at several levels.
Highlights
Geminiviruses are a large family of plant viruses with circular, single-stranded DNA genomes packaged within geminate particles [1], which infect a broad range of staple and fiber crops worldwide and cause devastating diseases that lead to serious economic losses
As a first step to further understand the effect of C2 on the plant response to jasmonic acid (JA), we carried out a root growth inhibition assay in increasing concentrations of methyl-jasmonate (MeJA)
Given that C2 has been shown to affect the function of several SCF complexes in the plant [4], it would be feasible to speculate that the lower sensitivity to jasmonates displayed by the transgenic
Summary
Geminiviruses are a large family of plant viruses with circular, single-stranded (ss) DNA genomes packaged within geminate particles [1], which infect a broad range of staple and fiber crops worldwide and cause devastating diseases that lead to serious economic losses. The transcriptional inhibition of the jasmonate signalling pathway and the decreased JA responses in plants expressing C2 from TYLCV or TYLCSV [4] may be linked to an impairment of the function of the jasmonate receptor, the SCFCOI1 complex, given the effect of these proteins on the CSN complex and the SCF ubiquitin E3 ligases, in general. Both the exact molecular mechanisms underlying this effect and its extent remain to be determined. C2-expressing plants show a suppression of JA-mediated defence processes as well as JA-dependent secondary metabolism, which may involve additional, specific protein-protein interactions
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