| This project going to be… | Experimental (lab/field based) |
| Email | eugene.savenkov@slu.se |
| Position held | Associate Professor |
| Title of Project | Investigating the role of viral non-coding ribonuclease-resistant RNAs in virus pathogenicity |
| Institution Department and Address | Almas allé 5, BioCenter SLU, Dept of Plant Biology, The Swedish University of Agricultural Sciences |
| Uppsala, Uppland 75007 |
| Sweden |
| Full Name of Supervisor | Eugene Savenkov |
| Date of Project Commencement | 19/06/2023 |
| Duration (weeks) | 10 |
| Brief Description of Project | The student will join the Plant Virology group at the Swedish University of Agricultural Sciences for summer placement. The student’s project will be based on Potato mop-top virus (PMTV), a virus causing potato “spraing” disease. The student will also have the opportunity to gain experience in handling and working with infectious clones of plant viruses including virus complementation studies to identify and characterise viral suppressors of RNA silencing (VSRs). Previously, phylogenetic analysis identified three major genotypes for PMTV RNA-CP. Genomic RNA-CP of one of these genotypes appeared to be longer than that of the rest of genotypes (3253 nt vs. 3134 nt). The difference in length is due to the presence of a tandem repeat of the “coremin” motif in the 3´-untranslated region of RNA-CP. “Coremin” motif is required for stalling Xrn1, a major exoribonuclease involved in the RNA metabolism and, thus, leads to accumulation of exoribonuclease-resistant RNAs (xrRNAs). Folded RNA elements that block processive cellular exoribonuclease RNA decay machinery to yield biologically active viral non-coding RNAs were initially discovered in flaviviruses infecting humans and animals. Subsequently, it has become evident that xrRNAs are produced by many viruses including plant viruses. Whereas xrRNAs contribute to pathogenicity of human and animal viruses, the role of xrRNAs in plant virus infectious remains elusive. This project aims to investigate whether PMTV xrRNAs contribute to suppression of RNA silencing, one the major resistance mechanisms against plant viruses. Therefore, the project’s main focus will be to employ a complementation assay suitable in identifying silencing suppression activity for even weak VSRs. The identification of VSR activity is achieved using an assay based on complementation of cell-to-cell movement of turnip crinkle virus (TCV), the genome of which was modified by swapping a capsid protein (CP) gene of the virus with a reporter gene for Green Fluorescent Protein (GFP). The cell-to-cell movement of TCV in host plants requires expression of its CP, a well-characterized VSR. Thus, in the absence of CP expression, TCV-GFP is not able to move efficiently to neighbouring cells and is confined to single cells due to induction of antiviral silencing. Several xrRNA constructs will be tested using this assay including full-length RNA-CP, its mutants for the “coremin” region and xrRNAs of various size (truncated from the 3´-end). The effect of xrRNA on antiviral silencing will also be tested in combination with expression of the PMTV 8K protein, a “weak” VSR, to address a possible synergism between 8K and xrRNAs in counteracting antiviral silencing. The effect of knock down of xrRNAs on virus replication, movement and accumulation in systemically infected leaves will be tested as well. The project will improve our understanding of the molecular mechanisms underlying plant disease and provide student with an insight into plant pathology. |
| Attach the recommended reading for the project | 1. Savenkov E.I. (2021) Pomoviruses (Virgaviridae): in Encyclopedia of Virology, 4th edition, Vol. 3: 603-611. |
| 2. Kalyandurg P.B., Tahmasebi A., Vetukuri R.R., Kushwaha S.K., Lezzhov A.A., Solovyev A.G., Grenville-Briggs L.J., Savenkov E.I. (2019) Efficient RNA silencing suppression activity of Potato Mop-Top Virus 8K protein is driven by variability and positive selection. Virology, 535: 111-121. |
| 3. Dilweg I.W. , Gultyaev A.P., Olsthoorn R.C. (2019) Structural features of an Xrn1-resistant plant virus RNA. RNA Biology, 16: 838-845. |
| 4. Kalyandurg P., Gil J. F., Lukhovitskaya N.I., Flores B., Müller G., Chuquillanqui C., Palomino L., Monjane A., Barker I., Kreuze J., Savenkov E. I. (2017) Molecular and pathobiological characterization of 61 Potato mop-top virus full-length cDNAs reveals great variability of the virus in the centre of potato domestication, novel genotypes and evidence for recombination. Molecular Plant Pathology, 18: 864-877. |
