Research Emphasis:

In my Plant Virology laboratory, we study the molecular mechanisms that determine whether a plant is susceptible or resistant to virus infection. Although there are multiple factors that influence the ability of a virus to infect a plant, crucial events are viral movement and the evasion of resistance responses, including RNA silencing or interference (RNAi). To investigate some of these aspects we use Tomato bushy stunt virus (TBSV) as a model system. TBSV has an RNA genome with five genes of which two (encoding for proteins designated P22 and P19) are involved in virus spread and which can also act as elicitors of resistance responses. P22 is required for cell-to-cell movement and P19 performs host-specific activities for virus transport. P19 is also a suppressor of RNAi through sequestration of short interfering RNAs (siRNAs) that are consequently unavailable to program any Argonaute (AGO) in the RNA-induced silencing complex (RISC). We are currently conducting experiments to examine the biochemical properties of P22 and P19 and to examine their interaction with host proteins. We also use P19 mutants and biochemical isolation procedures to characterize a novel virus-induced RISC-like complex from plants, and through genetic approaches aim to identify AGO proteins involved in antiviral silencing. A biotechnologically directed effort deals with exploiting virus proteins (e.g., suppressors) and replicons to increase expression of value-added foreign genes in suspension cells or whole plants.

Teaching

PLPA 616: Methods in Molecular Biology of Plant-Microbe Interactions (2 cr.) The topics of this course focus on the concepts and techniques used in molecular plant pathology to study the interactions between hosts and pathogens. The emphasis is on understanding the rationale for implementing certain procedures and the theoretical concepts underlying the methodology.

PLPA 620: Plant Virology (3 cr. with lab). An overview of plant virology with an emphasis on the molecular biology of virus-host interactions; topics include virus replication, gene expression, movement, symptom induction, transmission, control, and topics from current literature. The laboratory focuses on virus inoculation, purification, and molecular diagnostics.

PLPA 665: Viral Vectors and Gene Therapy (3 cr.). Viruses are proving to be exceptional vehicles for the expression of recombinant protein. This course will describe several viral vector systems, their development and uses as research tools and for gene therapy.

PLPA 681; Seminar (1 cr.). Instruction in the preparation, presentation, and evaluation of research seminars.

BESC 484; Field Experience (3 cr.) (team-taught). A supervised research/internship experience conducted in the area of the student’s specialization. Writing-Intensive (3 cr.)

 

Recent Publications

Alvarado, V.Y., and Scholthof, H.B. (2012) AGO2: A new Argonaute compromising plant virus accumulation. Frontiers Plant-Microbe Interact. (in press).

Seaberg, B., Hsieh, Y.-C., Scholthof, K.-B.G. and Scholthof, H.B. (2012) Host impact on stability of a plant virus gene vector as measured by a newly adapted fluorescent local lesion assay. J. Virol. Meth. doi:10.1016/j.jviromet.2011.11.004

Scholthof, H.B., Alvarado, V.Y., Vega-Arreguin, J.C., Ciomperlik, J.J., Odokonyero, D., Brosseau, C., Jaubert, M., Zamora, A., and Moffett, P. (2011)^. Identification of an ARGONAUTE for antiviral RNA silencing in Nicotiana benthamiana. Plant Physiol., 156:1548-1555.

Ciomperlik, J., Omarov, R.T., and Scholthof, H.B. (2011). An antiviral RISC isolated from Tobacco rattle virus-infected plants. Virology 412:117-124

Scholthof, K.-B.G., and Scholthof, H.B. (2011). Induction and suppression of RNA silencing: Insights from plant viral infections – A BARD Workshop Report. Plant Molec. Biol. 75:205-210

Saxena, P., Hsieh, Y-C., (both share first co-authorship), Alvarado^, V.Y., Sainsbury,^, F., Saunders^. K., Lomonossoff, G., and Scholthof, H.B. (2011).^. Improved foreign gene expression in plants using a virus-encoded suppressor of RNA silencing modified to be developmentally harmless. Plant Biotech. J. 9:703-712.

Everett, A, Scholthof, H.B., and Scholthof, K.-B. G. (2010) Satellite panicum mosaic virus coat protein enhances the performance of plant virus gene vectors. Virology 396:37-46.

Alvarado, V., and Scholthof, H.B. (2009). Plant responses against invasive nucleic acids:  RNA silencing and its suppression by plant viral pathogens. Sem. Cell Develop. Biol. 20:1032–1040.

Hsieh, Y.-C., Omarov, R.T., and Scholthof, H.B. (2008). Diverse and newly recognized effects associated with siRNA binding site modifications on the Tomato bushy stunt virus P19 silencing suppressor. J. Virol. 83:2188-2000.

Qiu, W, and Scholthof, H.B. (2008).Tomato bushy stunt virus gene vectors. Curr. Protoc. Microbiol. 7:16I.4.1-16I.4.16

Scholthof, H.B. Heterologous expression of viral RNAi suppressors: RISC management. (2007). Plant Physiol. 145:1110-1117

Omarov, R., Ciomperlik, J., and Scholthof, H.B. (2007). RNAi-associated ssRNA-specific ribonucleases in Tombusvirus P19 mutant-infected plants and evidence for a discrete siRNA-containing effector complex. Proc. Natl. Acad. Sci. USA 104:1714-1719

Scholthof, H.B. (2006). The Tombusvirus-encoded P19: from irrelevance to elegance. Nat. Rev. Microbiol. 4:405-411

Omarov, R., Sparks, K.,Smith, L., Zindovic, J., and Scholthof, H.B. (2006). Biological relevance of a stable biochemical interaction between the tombusvirus-encoded P19 and siRNAs. J. Virol. 80:3000-3008

Skare, J.M., Wijkamp, I., Denham, I., Rezende, J.A.M., Kitajima, E.W., Park, J.W., Desvoyes, B., Rush, C.M., Michels, G., Scholthof, K.-B. G., and Scholthof, H.B. (2006). A new eriophyid mite-borne membrane-enveloped virus complex isolated from plants. Virology 347:343-353.