Superinfection by PHYVV Alters the Recovery Process in PepGMV-Infected Pepper Plants.

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.

Quantitative proteomic analysis of Huh-7 cells infected with Dengue virus by label-free LC-MS.

Dengue is an important and growing public health problem worldwide with an estimated 100million new clinical cases annually. Currently, no licensed drug or vaccine is available. During natural infection in humans, liver cells constitute one of the main targets of dengue virus (DENV) replication. However, a clear understanding of dengue pathogenesis remains elusive. In order to gain a better reading of the cross talk between virus and host cell proteins, we used a proteomics approach to analyze the host response to DENV infection in a hepatic cell line Huh-7. Differences in proteome expression were assayed 24h post-infection using label-free LC-MS. Quantitative analysis revealed 155 differentially expressed proteins, 64 of which were up-regulated and 91 down-regulated. These results reveal an important decrease in the expression of enzymes involved in the glycolytic pathway, citrate cycle, and pyruvate metabolism. This study provides large-scale quantitative information regarding protein expression in the early stages of infection that should be useful for better compression of the pathogenesis of dengue. BIOLOGICAL SIGNIFICANCE: Dengue infection involves alterations in the homeostasis of the host cell. Defining the interactions between virus and cell proteins should provide a better understanding of how viruses propagate and cause disease. Here, we present for the first time the proteomic analysis of hepatocytes (Huh-7 cells) infected with DENV-2 by label-free LC-MS.