Abstract
DNA cytosine methylation is one of the main epigenetic mechanisms in higher eukaryotes and is considered to play a key role in transcriptional gene silencing. In plants, cytosine methylation can occur in all sequence contexts (CG, CHG, and CHH), and its levels are controlled by multiple pathways, including de novo methylation, maintenance methylation, and demethylation. Modulation of DNA methylation represents a potentially robust mechanism to adjust gene expression following exposure to different stresses. However, the potential involvement of epigenetics in plant-virus interactions has been scarcely explored, especially with regard to RNA viruses. Here, we studied the impact of a symptomless viral infection on the epigenetic status of the host genome. We focused our attention on the interaction between Nicotiana benthamiana and Pelargonium line pattern virus (PLPV, family Tombusviridae), and analyzed cytosine methylation in the repetitive genomic element corresponding to ribosomal DNA (rDNA). Through a combination of bisulfite sequencing and RT-qPCR, we obtained data showing that PLPV infection gives rise to a reduction in methylation at CG sites of the rDNA promoter. Such a reduction correlated with an increase and decrease, respectively, in the expression levels of some key demethylases and of MET1, the DNA methyltransferase responsible for the maintenance of CG methylation. Hypomethylation of rDNA promoter was associated with a five-fold augmentation of rRNA precursor levels. The PLPV protein p37, reported as a suppressor of post-transcriptional gene silencing, did not lead to the same effects when expressed alone and, thus, it is unlikely to act as suppressor of transcriptional gene silencing. Collectively, the results suggest that PLPV infection as a whole is able to modulate host transcriptional activity through changes in the cytosine methylation pattern arising from misregulation of methyltransferases/demethylases balance.
Highlights
Viruses, as obligate intracellular parasites, establish complex relationships with their hosts [1,2].This type of relationship imposes numerous challenges on both the infecting virus and the host partner [3,4]
Pelargonium line pattern virus (PLPV) Infection Is Associated with Hypomethylation of the Promoter Region of 45S ribosomal DNA (rDNA)
This type of unit is arranged into clusters consisting of modules of an almost identical sequence that are separated from each other by an intergenic spacer (IGS) region and encode the pre-rRNA of the three largest rRNAs, 18S, 5.8S, and 25S in plants, whose sequences are flanked by external (5’ETS and 3 ́ETS) and internal (ITS1 and ITS2) transcribed spacers (Figure 1)
Summary
As obligate intracellular parasites, establish complex relationships with their hosts [1,2].This type of relationship imposes numerous challenges on both the infecting virus and the host partner [3,4]. The host, on its side, deploys a set of defense mechanisms against the virus in an attempt to restrict or block the infection process [7] In such a scenario, it is not surprising that hosts suffering from active virus infections exhibit important physiological, biochemical, and metabolic changes that in some occasions, though not always, lead to symptom development [8]. It is not surprising that hosts suffering from active virus infections exhibit important physiological, biochemical, and metabolic changes that in some occasions, though not always, lead to symptom development [8] These changes may imply alterations in host gene expression at both transcriptional and post-transcriptional levels [9,10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
