RNA silencing proteins in PVA infection

High molecular weight ribonucleoprotein complexes associated with PVA infection, which contain in addition to helper component-proteinase (HCPro) many viral and host proteins [1], have many of these proteins in common with the PVA-induced RNA granules [2]. The host proteins include ARGONAUTE 1 (AGO1) and VARICOSE (VCS), which both have antiviral roles in plants.

Translational repression is a mechanism employed by RNA silencing to regulate gene expression. VCS has a role in miRNA-regulated translational repression in plants. We are specifically interested in investigating the role of translational repression in potyvirus infection. VCS, AGO1 and few other plant proteins functioning in translational repression are under investigation. We initiated investigations on this subject with turnip mosaic virus and Arabidopisis mutants in collaboration with Dr. Aiming Wang (Agriculture and Agri-Food Canada).

Our recent work demonstrated that HCPro has subverted both AGO1 and VCS to serve in pro-viral roles during PVA infection [3,4]. We propose that HCPro recruits VCS, which serves as a scaffolding platform to assemble an RNP complex around viral RNA, to which AGO1 binds through HCPro. Importantly, these proteins are required for the systemic spread of viral infection and the formation of stable viral particles. Translation of these results into an application is our future goal.

  1. Ivanov, K.I., Eskelin, K., Bašić, M., De, S., Lõhmus, A., Varjosalo, M., and Mäkinen K. (2016). ”Molecular insights into the function of the viral RNA silencing suppressor HC-pro” The Plant Journal, 85, 30–45.
  2. Hafren, A., Lõhmus, A, and Mäkinen, K. (2015) “Formation of Potato virus A-induced RNA granules and viral translation are interrelated processes required for optimal virus accumulation” PLOS Pathogens, 11(12):e1005314. doi: 10.1371/journal.ppat.1005314.
  3. De, S., Pollari, M., Varjosalo, M., and Mäkinen K. 2020. “Association of host protein VARICOSE with HCPro within a multiprotein complex is crucial for RNA silencing suppression, translation, encapsidation and systemic spread of potato virus A infection” PLOS Pathogens. provisionally accepted.
  4. Pollalri, M., De, S., Wang, A., and Mäkinen K. 2020. "The potyviral silencing suppressor HCPro recruits and employs host ARGONAUTE1 in pro-viral functions" PLOS Pathogens, provisionally accepted.