Abstract
Panicum mosaic virus (PMV) has a positive-sense, single-stranded RNA genome that serves as the mRNA for two 5'-proximal genes, p48 and p112. The p112 open reading frame (ORF) has a GDD-motif, a feature of virus RNA-dependent RNA polymerases. Replication assays in protoplasts showed that p48 and p112 are sufficient for replication of PMV and its satellite virus (SPMV). Differential centrifugation of extracts from PMV-infected plants showed that the p48 and p112 proteins are membrane-associated. The same fractions exhibited RNA polymerase activity in vitro on viral RNA templates, suggesting that p48 and p112 represent the viral replication proteins. Moreover, we identified a domain spanning amino acids 306 to 405 on the p48 and p112 PMV ORFs that is common to the Tombusviridae. Alanine scanning mutagenesis of the conserved domain (CD) revealed that several substitutions were lethal or severely debilitated PMV accumulation. Other substitutions did not affect RNA accumulation, yet they caused variable phenotypes suggestive of plant-dependent effects on systemic invasion and symptom induction. The mutants that were most debilitating to PMV replication were hydrophobic amino acids that we hypothesize are important for membrane localization and functional replicase activity.
Highlights
Panicum mosaic virus (PMV), a 4.3 kb positive-sense ssRNA virus, is the type member of the Panicovirus genus in the Tombusviridae [1,2]
In this study we examined the role of p48 and p112 and the defined conserved domain (CD) in replication and pathogenicity of PMV and SPMV
SiFnyifgmeucptrtioenm6s roefsYp3o3n0seAs palnuds SrePpMliVcaotinonproobssoermveildletduring mixed Symptom responses and replication observed during mixed infections of Y330A plus SPMV on proso millet. (A) Y330A+SPMV-infected plants with no obvious symptoms or mild mosaic symptoms
Summary
Panicum mosaic virus (PMV), a 4.3 kb positive-sense ssRNA virus, is the type member of the Panicovirus genus in the Tombusviridae [1,2]. Like other members of this family [3,4], PMV encodes two proteins expressed from the 5'proximal half of the ssRNA genome (Fig. 1). For most members of the Tombusviridae the first open reading frame (ORF) encodes a protein of approximately 25–30 kDa. In contrast, the molecular weight of the PMV 5'-proximal encoded protein is considerably higher (48 kDa). A second protein that is expressed as a translational read-through product usually generates an 80 to 100 kDa protein; instead, PMV encodes a protein of 112 kDa. In all cases, the downstream portion of the larger translational product contains the GDD-motif, a characteristic feature of RNA-dependent RNA polymerases [5]. PMV serves as the helper for a satellite virus (SPMV), satellite RNAs and an SPMVderived defective interfering RNA (DI) [1,6,7,8,9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
