Abstract
Geminiviruses are important plant pathogens that affect crops around the world. In some geminivirus–host interactions, infected plants show recovery, a phenomenon characterized by symptom disappearance in newly emerging leaves. In pepper–Pepper golden mosaic virus (PepGMV) interaction, the host recovery process involves a silencing mechanism that includes both post-transcriptional (PTGS) and transcriptional (TGS) gene silencing pathways. Under field conditions, PepGMV is frequently found in mixed infections with Pepper huasteco yellow vein virus (PHYVV), another bipartite begomovirus. Mixed infected plants generally show a synergetic phenomenon and do not present recovery. Little is known about the molecular mechanism of this interaction. In the present study, we explored the effect of superinfection by PHYVV on a PepGMV-infected pepper plant showing recovery. Superinfection with PHYVV led to (a) the appearance of severe symptoms, (b) an increase of the levels of PepGMV DNA accumulation, (c) a decrease of the relative methylation levels of PepGMV DNA, and (d) an increase of chromatin activation marks present in viral minichromosomes. Finally, using heterologous expression and silencing suppression reporter systems, we found that PHYVV REn presents TGS silencing suppressor activity, whereas similar experiments suggest that Rep might be involved in suppressing PTGS.
Highlights
Geminiviruses are important plant pathogens that affect crops around the world
We have shown that pepper plants infected with Pepper golden mosaic virus (PepGMV) present a host recovery process three weeks after inoculation [6]
Pepper plants simultaneously inoculated with PepGMV and Pepper huasteco yellow vein virus (PHYVV) show an enhancement of the induced symptoms compared with the ones observed after individual infections
Summary
Geminiviruses are important plant pathogens that affect crops around the world. Their genomes are composed of circular, single-stranded DNA molecules packed into an icosahedral twinned particle [1]. The begomoviruses comprise the most diverse genus with around 400 species. They infect dicots, are transmitted by whiteflies, and include monopartite and bipartite species [3,4]. Bipartite begomoviruses encode six open reading frames (ORFs) distributed into two molecules called components A and B. Component A contains the capsid protein gene CP in the virion sense strand, whereas the complementary sense strand encodes the replication-associated protein Rep (an essential protein for viral replication), TrAP (a multifunctional protein involved in the activation of late viral genes and suppressor of host gene silencing), and REn (a protein that enhances viral DNA accumulation during the replication). The component B encodes two Viruses 2020, 12, 286; doi:10.3390/v12030286 www.mdpi.com/journal/viruses
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