Revisiting the Roles of Tobamovirus Replicase Complex Proteins in Viral Replication and Silencing Suppression

Malpica-López, Nachelli and Rajeswaran, Rajendran and Beknazariants, Daria and Seguin, Jonathan and Golyaev, Victor and Farinelli, Laurent and Pooggin, Mikhail M.. (2018) Revisiting the Roles of Tobamovirus Replicase Complex Proteins in Viral Replication and Silencing Suppression. Molecular Plant-Microbe Interactions, 31 (1). pp. 125-144.

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Official URL: https://edoc.unibas.ch/71818/

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Tobamoviral replicase possesses an RNA-dependent RNA polymerase (RDR) domain and is translated from genomic (g)RNA via a stop codon readthrough mechanism at a one-to-ten ratio relative to a shorter protein lacking the RDR domain. The two proteins share methyltransferase and helicase domains and form a heterodimer implicated in gRNA replication. The shorter protein is also implicated in suppressing RNA silencing-based antiviral defenses. Using a stop codon mutant of Oilseed rape mosaic tobamovirus (ORMV), we demonstrate that the readthrough replicase (p182) is sufficient for gRNA replication and for subgenomic RNA transcription during systemic infection in Nicotiana benthamiana and Arabidopsis thaliana. However, the mutant virus displays milder symptoms and does not interfere with HEN1-mediated methylation of viral short interfering (si)RNAs or plant small (s)RNAs. The mutant virus tends to revert the stop codon, thereby restoring expression of the shorter protein (p125), even in the absence of plant Dicer-like activities that generate viral siRNAs. Plant RDR activities that generate endogenous siRNA precursors do not prevent replication or movement of the mutant virus, and double-stranded precursors of viral siRNAs representing the entire virus genome are likely synthesized by p182. Transgenic expression of p125 partially recapitulates the ORMV disease symptoms associated with overaccumulation of plant sRNAs. Taken together, the readthrough replicase p182 is sufficient for viral replication and transcription but not for silencing suppression. By contrast, the shorter p125 protein suppresses silencing, provokes severe disease symptoms, causes overaccumulation of unmethylated viral and plant sRNAs but it is not an essential component of the viral replicase complex.
Faculties and Departments:05 Faculty of Science
05 Faculty of Science > Departement Umweltwissenschaften
05 Faculty of Science > Departement Umweltwissenschaften > Ehemalige Einheiten Umweltwissenschaften > Pflanzenphysiologie Pathogenabwehr (Boller)
05 Faculty of Science > Departement Umweltwissenschaften > Integrative Biologie
UniBasel Contributors:Malpica López, Hortensia Nachelli
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Phytopathological Society
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:09 Nov 2020 16:46
Deposited On:09 Nov 2020 16:46

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