A nuclear-replicating viroid antagonizes infectivity and accumulation of a geminivirus by upregulating methylation-related genes and inducing hypermethylation of viral DNA

Research output: Contribution to journalArticlepeer-review


  • Enza Maria Torchetti
  • Mattia Pegoraro
  • Beatriz Navarro
  • Francesco Di Serio
  • Emanuela Noris

Colleges, School and Institutes

External organisations

  • Institute for Sustainable Plant Protection, National Research Council of Italy, Bari, 70126, Italy.
  • Institute for Sustainable Plant Protection, National Research Council of Italy, Torino, 10135, Italy.


DNA methylation and post-transcriptional gene silencing play critical roles in controlling infection of single-stranded (ss) DNA geminiviruses and ssRNA viroids, respectively, but both pathogens can counteract these host defense mechanisms and promote their infectivity. Moreover, a specific role of DNA methylation in viroid-host interactions is not yet confirmed. Here, using an experimental system where two nuclear-replicating agents, the geminivirus tomato yellow leaf curl Sardinia virus (TYLCSV) and potato spindle tuber viroid (PSTVd), co-infect their common host tomato, we observed that PSTVd severely interferes with TYLCSV infectivity and accumulation, most likely as a consequence of strong activation of host DNA methylation pathways. In fact, PSTVd alone or in co-infection with TYLCSV significantly upregulates the expression of key genes governing DNA methylation in plants. Using methylation-sensitive restriction and bisulfite conversion assays, we further showed that PSTVd infection promotes a strong hypermethylation of TYLCSV DNA, thus supporting a mechanistic link with the antagonism of the viroid on the virus in co-infected tomato plants. These results describe the interaction between two nuclear-replicating pathogens and show that they differentially interfere with DNA methylation pathways.


Original languageEnglish
Article number35101
JournalScientific Reports
Publication statusPublished - 14 Oct 2016


  • Cell Nucleus/virology, DNA Methylation, DNA Replication, DNA, Viral/biosynthesis, Geminiviridae/growth & development, Lycopersicon esculentum/virology, Viral Interference, Viroids/growth & development