The hypersensitive response induced by the V2 protein of a monopartite begomovirus is countered by the C2 protein

Abstract

A functional analysis of the V2 protein of two monopartite begomoviruses, Papaya leaf curl virus (PaLCuV) and Cotton leaf curl Kokhran virus (CLCuKoV), has been performed. Expression of the V2 gene from a Potato virus X (PVX) vector resulted in severe leaf curling followed by a hypersensitive response (HR) in Nicotiana benthamiana and N. tabacum, demonstrating that the V2 protein is a pathogenicity determinant and a target of host defence responses. Agroinfiltration of a PVX vector expressing the V2 protein resulted in cell death in the infiltrated area. Subsequently, a systemic HR developed that was associated with the long-distance spread of the virus and led to the death of the plant. V2 amino acid sequences encompassing a conserved putative protein kinase C (PKC) phosphorylation motif were shown to be essential for the elicitation of cell death. In co-inoculation experiments, the transient expression of the C2 protein of PaLCuV or Cotton leaf curl Multan virus under the control of the Cauliflower mosaic virus 35S promoter inhibited the HR induced by V2 in the agroinfiltrated area. These findings demonstrate that the V2 protein of monopartite begomoviruses is a pathogenicity determinant and induces an HR that can be suppressed by the C2 protein. The induction and suppression of HR have been demonstrated previously in bipartite begomoviruses and our results extend this to monopartite begomoviruses.

The six Tomato yellow leaf curl virus genes expressed individually in tomato induce different levels of plant stress response attenuation

“…The PVX expression system was shown to be productive for the expression of various begomovirus individual genes in N. benthamiana and tomato plants (Hussain et al 2007;Mubin et al 2010;Sharma and Ikegami 2010;Luna et al 2012). The recombinant PVX was infiltrated into N. benthamiana and tomato leaves, and the treated plants were maintained in a greenhouse for 30 days, during which symptoms were periodically recorded.…”

“…Analysis of the ToLCNDV-encoded genes pointed to the transcriptional activator protein (TrAP) (encoded by DNA A) as the factor mediating the anti-HR effect (Hussain et al 2005). Later on, the V2 protein of two monopartite begomoviruses, Papaya leaf curl virus (PaLCuV) and Cotton leaf curl Kokhran virus (CLCuKoV), was shown to be a pathogenicity determinant and a target of host defense responses in N. benthamiana and N. tabacum plants (Mubin et al 2010). C2/TrAP protein of PaLCuV or Cotton leaf curl Multan virus inhibited the HR induced by V2 in the virus-agroinfiltrated areas.…”

Transmission Specificity and Coinfection of Mastrevirus with Begomovirus

“…controls viral induced hypersensitive cell death (Hussain et al, 2007;Mubin et al, 2010), AC3 Replication enhancer protein (REn)…”

Mutational Analysis of Effectors Encoded by Monopartite Begomoviruses and Their Satellites

“…For example Stanley and Latham [58] have shown that V2 protein of Papaya leaf curl virus (PaLCuV) is potentially involved in the elicitation of cell death response. The deletion mutants (having deletions of 32 and 60 amino acids, respectively, at the N-terminal end of V2) exhibited a systemic HR in Nicotiana benthamiana plants.…”

“…Phosphorylation of MPs may also play a role in controlling the switch from viral replication to translation [36,37]. Few earlier studies showed that for PaLCuV V2, deletion of sequences encompassing this motif abrogates the ability to induce HR [58].…”