The genome of the Cauliflower mosaic virus, a plant pararetrovirus, is highly methylated in the nucleus

Abstract

Cytosine methylation is an important defense against invasive DNAs. Here, cytosine methylation profiles of a plant pararetrovirus, Cauliflower mosaic virus (CaMV), was investigated. Nuclear CaMV DNA is highly methylated throughout the genome including at transcription regulatory regions, but the virion DNA is unmethylated. In vitro CG methylation of the viral 35S promoter reduces transcription from the downstream gene. Although nuclear CaMV DNA is highly methylated, its transcripts are accumulated in the nucleus. The data suggest that a small population of unmethylated viral genomes produced through reversetranscription are constantly delivered back to the nucleus. Small RNA profiles suggest that methylation of the CaMV DNA may be due to de novo methylation through 21, 22 and 24-nt small RNAs with adenines at their 5' terminus.

Comparative Plant Transcriptome Profiling of Arabidopsis thaliana Col-0 and Camelina sativa var.CelineInfested with Myzus persicae Aphids Acquiring Circulative and Noncirculative Viruses Reveals Virus- and Plant-Specific Alterations Relevant to Aphid Feeding Behavior and Transmission

“…Celine (log 2 FC = 3.82 for Csa18g032680), and not significantly deregulated in TuYV-infected A. thaliana Col-0. This gene codes for an XH/XS domain-containing protein, which probably functions in siRNA-directed DNA methylation and might contribute to methylation and transcriptional silencing of CaMV double-stranded DNA (dsDNA) in the nucleus ( 46 ). Taken together, CaMV infection strongly affected silencing-related genes in both hosts, but the deregulations were host specific, with downregulations dominating in A. thaliana Col-0 and upregulations in C. sativa var.…”

Comparative plant transcriptome profiling of Arabidopsis and Camelina infested withMyzus persicaeaphids acquiring circulative and non-circulative viruses reveals virus- and plant-specific alterations relevant to aphid feeding behavior and transmission

“…It was strongly upregulated in CaMV-infected Camelina and Arabidopsis, less strongly upregulated in TuYV-infected Camelina and not significantly deregulated in TuYV-infected Arabidopsis. This gene codes for a XH/XS domain-containing protein, which probably functions in siRNA-directed DNA methylation and might contribute to methylation and transcriptional silencing of CaMV dsDNA in the nucleus (Omae et al, 2020). Taken together, CaMV infection strongly affected silencing-related genes in both hosts, but the deregulations were host-specific, with downregulations dominating in Arabidopsis, and upregulations in Camelina.…”

Stress & Granules : regulation of Cauliflower mosaic virus disease in Arabidopsis thaliana

“…(Matzke & Mosher, 2014). Viruses that transcribe their genome in the nucleus, like geminiviruses and caulimoviruses, are targeted by the RdDM pathway and their viral minichromosomes are highly methylated (Omae et al, 2020;Raja et al, 2008). dsRNA structures also commonly occur during virus replication in the cytoplasm and independent of their origin, dsRNAs are commonly recognized by RNAse-III-type endonucleases, the dicer-like proteins (DCLs), which additionally require DOUBLE-STRANDED RNA BINDING (DRB) proteins for their action (Hiraguri et al, 2005).…”