Genetic Variability Among U.S.-Sentinel Cotton Plot Cotton Leafroll Dwarf Virus and Globally Available Reference Isolates Based on ORF0 Diversity.

The aphid-transmitted polerovirus, cotton leafroll dwarf virus (CLRDV), first characterized from symptomatic cotton plants in South America, has been identified in commercial cotton plantings in the United States. Here, the CLRDV intraspecific diversity was investigated by comparative sequence analysis of the most divergent CLRDV coding region, ORF0/P0. Bayesian analysis of ORF0 sequences for U.S. and reference populations resolved three well-supported sister clades comprising one U.S. and two South American lineages. Principal component analysis (PCA) identified seven statistically supported intraspecific populations. The Bayesian phylogeny and PCA dendrogram-inferred relationships were congruent. Population analysis of ORF0 sequences indicated most lineages have evolved under negative selection, albeit certain sites/isolates evolved under positive selection. Both U.S. and South American isolates exhibited extensive ORF0 diversity. At least two U.S. invasion foci were associated with their founder populations in Alabama-Georgia and eastern Texas. The Alabama-Georgia founder is implicated as the source of recent widespread expansion and establishment of secondary disease foci throughout the southeastern-central United States. Based on the geographically restricted distribution, spread of another extant Texas population appeared impeded by a population bottleneck. Extant CLRDV isolates represent several putative introductions potentially associated with catastrophic weather events dispersing viruliferous cotton aphids of unknown origin(s).

High Incidence of Strawberry Polerovirus 1 in the Czech Republic and Its Vectors, Genetic Variability and Recombination.

In total, 332 strawberry plants from 33 different locations in the Czech Republic with or without disease symptoms were screened by RT-PCR for the presence of strawberry polerovirus 1 (SPV1) and five other viruses: strawberry mottle virus, strawberry crinkle virus, strawberry mild yellow edge virus, strawberry vein banding virus, and strawberry virus 1. SPV1 was detected in 115 tested strawberry plants (35%), including 89 mixed infections. No correlation between symptoms and the detected viruses was found. To identify potential invertebrate SPV1 vectors, strawberry-associated invertebrate species were screened by RT-PCR, and the virus was found in the aphids Aphis forbesi, A. gossypii, A. ruborum, A.sanquisorbae, Aulacorthum solani, Chaetosiphon fragaefolii, Myzus ascalonicus, and several other non-aphid invertebrate species. SPV1 was also detected in aphid honeydew. Subsequent tests of C. fragaefolii and A.gossypii virus transmission ability showed that at least 4 h of acquisition time were needed to acquire the virus. However, 1 day was sufficient for inoculation using C. fragaefolii. In conclusion, being aphid-transmitted like other tested viruses SPV1 was nevertheless the most frequently detected agent. Czech SPV1 isolates belonged to at least two phylogenetic clusters. The sequence analysis also indicated that recombination events influence evolution of SPV1 genomes.

Cotton Leafroll Dwarf Virus US Genomes Comprise Divergent Subpopulations and Harbor Extensive Variability.

Cotton leafroll dwarf virus (CLRDV) was first reported in the United States (US) in 2017 from cotton plants in Alabama (AL) and has become widespread in cotton-growing states of the southern US. To investigate the genomic variability among CLRDV isolates in the US, complete genomes of the virus were obtained from infected cotton plants displaying mild to severe symptoms from AL, Florida, and Texas. Eight CLRDV genomes were determined, ranging in size from 5865 to 5867 bp, and shared highest nucleotide identity with other CLRDV isolates in the US, at 95.9-98.7%. Open reading frame (ORF) 0, encoding the P0 silencing suppressor, was the most variable gene, sharing 88.5-99.6% and 81.2-89.3% amino acid similarity with CLRDV isolates reported in cotton growing states in the US and in Argentina and Brazil in South America, respectively. Based on Bayesian analysis, the complete CLRDV genomes from cotton in the US formed a monophyletic group comprising three relatively divergent sister clades, whereas CLRDV genotypes from South America clustered as closely related sister-groups, separate from US isolates, patterns reminiscent of phylogeographical structuring. The CLRDV isolates exhibited a complex pattern of recombination, with most breakpoints evident in ORFs 2 and 3, and ORF5. Despite extensive nucleotide diversity among all available CLRDV genomes, purifying selection (dN/dS < 1) was implicated as the primary selective force acting on viral protein evolution.

Identification of two novel poleroviruses and the occurrence of Tobacco bushy top disease causal agents in natural plants.

Tobacco bushy top disease (TBTD) is a devastating tobacco disease in the southwestern region of China. TBTD in the Yunnan Province is often caused by co-infections of several plant viruses: tobacco bushy top virus (TBTV), tobacco vein distorting virus (TVDV), tobacco bushy top virus satellite RNA (TBTVsatRNA) and tobacco vein distorting virus-associated RNA (TVDVaRNA). Through this study, two new poleroviruses were identified in two TBTD symptomatic tobacco plants and these two novel viruses are tentatively named as tobacco polerovirus 1 (TPV1) and tobacco polerovirus 2 (TPV2), respectively. Analyses of 244 tobacco samples collected from tobacco fields in the Yunnan Province through RT-PCR showed that a total of 80 samples were infected with TPV1 and/or TPV2, and the infection rates of TPV1 and TPV2 were 8.61% and 29.51%, respectively. Thirty-three TPV1 and/or TPV2-infected tobacco samples were selected for further test for TBTV, TVDV, TBTVsatRNA and TVDVaRNA infections. The results showed that many TPV1 and/or TPV2-infected plants were also infected with two or more other assayed viruses. In this study, we also surveyed TBTV, TVDV, TBTVsatRNA and TVDVaRNA infections in a total of 1713 leaf samples collected from field plants belonging to 29 plant species in 13 plant families and from 11 provinces/autonomous regions in China. TVDV had the highest infection rates of 37.5%, while TVDVaRNA, TBTV and TBTVsatRNA were found to be at 23.0%, 12.4% and 8.1%, respectively. In addition, TVDV, TBTV, TBTVsatRNA and TVDVaRNA were firstly detected of co-infection on 10 plants such as broad bean, pea, oilseed rape, pumpkin, tomato, crofton weed etc., and 1 to 4 of the TBTD causal agents were present in the samples collected from Guizhou, Hainan, Henan, Liaoning, Inner mongolia and Tibet autonomous regions. The results indicated that TBTD causal agents are expanding its host range and posing a risk to other crop in the field.

Genomic characterization of two novel viruses infecting Barleria cristata L. from the genera Orthotospovirus and Polerovirus.

Barleria cristata L. has become naturalized in South Africa, where it is commonly used as an ornamental. In 2019, plants of B. cristata showing putative viral symptoms were collected from two locations in Gauteng, South Africa. RNAtag-seq libraries were prepared and sequenced using an Illumina HiSeq 2500 platform. De novo assembly of the resulting data revealed the presence of a novel member of the family Tospoviridae associated with the plants from both locations, and this virus was given the tentative name "barleria chlorosis-associated virus". Segments L, M, and S have lengths of 8752, 4760, and 2906 nt, respectively. Additionally, one of the samples was associated with a novel polerovirus, provisionally named "barleria polerovirus 1", with a complete genome length of 6096 nt. This is the first study to show the association of viruses with a member of the genus Barleria.

Comparative genomics reveals insights into genetic variability and molecular evolution among sugarcane yellow leaf virus populations.

Yellow leaf disease caused by sugarcane yellow leaf virus (SCYLV) is one of the most prevalent diseases worldwide. In this study, six near-complete genome sequences of SCYLV were determined to be 5775-5881 bp in length. Phylogenetic analysis revealed that the two SCYLV isolates from Réunion Island, France, and four from China were clustered into REU and CUB genotypes, respectively, based on 50 genomic sequences (this study = 6, GenBank = 44). Meanwhile, all 50 isolates were clustered into three phylogroups (G1-G3). Twelve significant recombinant events occurred in intra- and inter-phylogroups between geographical origins and host crops. Most recombinant hotspots were distributed in coat protein read-through protein (RTD), followed by ORF0 (P0) and ORF1 (P1). High genetic divergences of 12.4% for genomic sequences and 6.0-24.9% for individual genes were determined at nucleotide levels. The highest nucleotide diversity (π) was found in P0, followed by P1 and RdRP. In addition, purifying selection was a main factor restricting variability in SCYLV populations. Infrequent gene flow between Africa and the two subpopulations (Asia and America) were found, whereas frequent gene flow between Asia and America subpopulations was observed. Taken together, our findings facilitate understanding of genetic diversity and evolutionary dynamics of SCYLV.

Pod pepper vein yellows virus, a new recombinant polerovirus infecting Capsicum frutescens in Yunnan province, China.

Pepper vein yellows viruses (PeVYV) are phloem-restricted viruses in the genus Polerovirus, family Luteoviridae. Typical viral symptoms of PeVYV including interveinal yellowing of leaves and upward leaf curling were observed in pod pepper plants (Capsicum frutescens) growing in Wenshan city, Yunnan province, China. The complete genome sequence of a virus from a sample of these plants was determined by next-generation sequencing and RT-PCR. Pod pepper vein yellows virus (PoPeVYV) (MT188667) has a genome of 6015 nucleotides, and the characteristic genome organization of a member of the genus Polerovirus. In the 5' half of its genome (encoding P0 to P4), PoPeVYV is most similar (93.1% nt identity) to PeVYV-3 (Pepper vein yellows virus 3) (KP326573) but diverges greatly in the 3'-part encoding P5, where it is most similar (91.7% nt identity) to tobacco vein distorting virus (TVDV, EF529624) suggesting a recombinant origin. Recombination analysis predicted a single recombination event affecting nucleotide positions 4126 to 5192 nt, with PeVYV-3 as the major parent but with the region 4126-5192 nt derived from TVDV as the minor parent. A full-length clone of PoPeVYV was constructed and shown to be infectious in C. frutescens by RT-PCR and the presence of icosahedral viral particles.

Pepper vein yellows virus 9: a novel polerovirus isolated from chili pepper in Indonesia.

In 2017, a leaf sample from a single chili pepper (Capsicum annuum) plant exhibiting yellowing was collected from Aceh province, Indonesia. Total RNA was extracted from this sample, and RNA-Seq analysis was conducted. Putative infecting viruses were detected by mapping the obtained reads to the full-length viral genome sequences available in the GenBank database (7457 sequences) and the de novo-assembled contigs. RNA-Seq analysis detected polerovirus, begomovirus, and amalgavirus sequences, and the polerovirus-like sequences showed strong similarity to those of previously reported pepper vein yellows viruses (PeVYVs). The complete viral genome sequence obtained by RT-PCR had a length of 6023 nt, had the typical genome organization of a polerovirus and showed a high degree of sequence similarity to PeVYV-2 from Israel. Moreover, the predicted amino acid sequence of the P0 protein of the Indonesian isolate was 85.1% to 88.8% identical to those of other PeVYVs. In accordance with the polerovirus species demarcation criteria, this isolate should be assigned to a new polerovirus species, and we propose the name "pepper vein yellows virus 9" (PeVYV-9) for this virus.

Complete genome sequence of a novel grapevine-infecting member of the genus Polerovirus, grapevine polerovirus 1.

Double-stranded RNAs and total RNAs purified from grapevine (Vitis vinifera) phloem scrapings of two varieties held in the INRAE (France) grapevine germplasm collection were analyzed by high-throughput sequencing. BLAST annotation revealed contigs with homology to Polerovirus genus members. The full genome sequence of one isolate (KT) was determined (5651 nucleotides [nt]), and a partial sequence representing about half of the genome was assembled for a second isolate (KS) that was found to share 95% nt sequence identity with the KT isolate. The genome has a typical polerovirus organization, containing six open reading frames (ORFs) as well as a putative additional ORF3a. Based on genome organization and phylogenetic relationships, the new virus belongs to the genus Polerovirus but, similar to the recently described persimmon polerovirus 1, is characterized by a highly divergent coat-protein/readthrough domain. Considering the species demarcation criteria for the family Luteoviridae, these two isolates, together with a closely related sequence recently deposited in the GenBank database (LC507098), represent a new Polerovirus species for which the name "Grapevine polerovirus 1" is proposed.

Lack of transmission of Sugarcane yellow leaf virus in Florida from Columbus grass and sugarcane to sugarcane with aphids or mites.

Sugarcane yellow leaf virus (SCYLV), the causal agent of yellow leaf disease, naturally infects at least three plant species in Florida: sugarcane (Saccharum spp.), the weed Columbus grass (Sorghum almum) and cultivated sorghum (S. bicolor). All three hosts are also colonized by the sugarcane aphid (Melanaphis sacchari), the main vector of SCYLV worldwide. To understand the high incidence of SCYLV observed in sugarcane commercial fields and in germplasm collections, we investigated the transmission efficiency of SCYLV from sugarcane and Columbus grass to sugarcane using the sugarcane aphid and a spider mite (Oligonychus grypus) that also tested positive for SCYLV in Florida. Healthy and SCYLV-infected leaf pieces of sugarcane and Columbus grass carrying viruliferous aphids or spider mites were transferred to virus-free plants of the yellow leaf susceptible sugarcane cultivar CP96-1252. Three- and 6-months post inoculation, the 108 aphid-inoculated plants of Columbus grass and the 90 mite-inoculated plants of sugarcane tested negative for SCYLV by tissue blot immunoassay (TBIA) or reverse transcription polymerase chain reaction (RT-PCR). Similar results were obtained for 162 aphid-inoculated plants of sugarcane, except for two plants that tested positive for SCYLV by TBIA and RT-PCR. In two field experiments planted with SCYLV-free and virus-infected sugarcane (cultivar CP96-1252), only 18-28% of healthy plants became infected during a 24- to 28-month period. SCYLV prevalence in these field experiments did not differ between aphicide treated and untreated plots. Incidence of M. sacchari haplotypes in the Everglades agricultural area also indicated that the predominant haplotype that is currently colonizing sugarcane was not a vector of SCYLV in Florida. Lack of virus transmission by the spider mite suggested that this arthropod only acquired the virus when feeding on infected plants but was unable to transmit SCYLV. The current vector of SCYLV in Florida remains to be identified.

Complete genome sequence of a novel putative polerovirus detected in grapevine.

Next-generation sequencing detected a novel virus from grapevine cultivar 'Kishmish Chjornyj' from Russia. Its complete genome sequence of 5625 nucleotides includes seven open reading frames encoding seven putative proteins similar to those of members of the genus Polerovirus in the family Luteoviridae. The novel virus showed graft-transmissibility and was tentatively named "grapevine polerovirus 1" (GPoV-1). Phylogenetic analysis using complete genome sequences of GPoV-1 and members of the family Luteoviridae indicated that although GPoV-1 is a member of the genus Polerovirus, it is unique within its clade. GPoV-1 is the first polerovirus detected in grapevine.

RNA sequence analysis of diseased groundnut (Arachis hypogaea) reveals the full genome of groundnut rosette assistor virus (GRAV).

The complete genome sequences for two variant isolates of groundnut rosette assistor virus (GRAV) have been determined from symptomatic groundnut plants in western Kenya. The sequences of the two GRAV isolates (sc7.1 and sc7.2) are 84.2% identical at the nucleotide level and 98.5% identical at the coat protein level. The variants sc7.1 and sc7.2 comprise 5850 and 5879 nucleotides respectively, and show similar genome organizations with 7 predicted ORFs (P0, P1, P2, P3a, P3 (coat protein, CP), P4 (movement protein, MP) and P5 (coat protein-readthrough protein, CP-RT). Currently, GRAV is an unassigned virus in the Luteoviridae family, due to the fact that only the sequence of the coat protein was previously obtained. The presence of both ORF0 and ORF 4 within the genome sequence determined in the current work suggest that GRAV should be classified as a member of the genus Polerovirus.

Complete genome sequence of a novel polerovirus in Ornithogalum thyrsoides from South Africa.

Ornithogalum thyrsoides, commonly known as chincherinchee, is an indigenous ornamental plant widely cultivated in South Africa. It is commercially valued as a flowering pot plant and for the production of cut flowers. Virus infections resulting in the development of severe necrotic mosaic symptoms threaten the success of commercial cultivation. The virome of an O. thyrsoides plant displaying necrotic mosaic symptoms was determined using high-throughput sequencing (HTS). In this plant, ornithogalum mosaic virus and ornithogalum virus 3 were identified, as well as a previously unknown virus. The full genome sequence of this virus was confirmed by Sanger sequencing using overlapping amplicons combined with rapid amplification of cDNA ends (RACE). Based on genome organisation and phylogenetic analysis, this novel virus can be classified as a polerovirus.

Discovery of Four Novel Viruses Associated with Flower Yellowing Disease of Green Sichuan Pepper (Zanthoxylum Armatum) by Virome Analysis.

An emerging virus-like flower yellowing disease (FYD) of green Sichuan pepper (Zanthoxylum armatum v. novemfolius) has been recently reported. Four new RNA viruses were discovered in the FYD-affected plant by the virome analysis using high-throughput sequencing of transcriptome and small RNAs. The complete genomes were determined, and based on the sequence and phylogenetic analysis, they are considered to be new members of the genera Nepovirus (Secoviridae), Idaeovirus (unassigned), Enamovirus (Luteoviridae), and Nucleorhabdovirus (Rhabdoviridae), respectively. Therefore, the tentative names corresponding to these viruses are green Sichuan pepper-nepovirus (GSPNeV), -idaeovirus (GSPIV), -enamovirus (GSPEV), and -nucleorhabdovirus (GSPNuV). The viral population analysis showed that GSPNeV and GSPIV were dominant in the virome. The small RNA profiles of these viruses are in accordance with the typical virus-plant interaction model for Arabidopsis thaliana. Rapid and sensitive RT-PCR assays were developed for viral detection, and used to access the geographical distributions. The results revealed a correlation between GSPNeV and the FYD. The viruses pose potential threats to the normal production of green Sichuan pepper in the affected areas due to their natural transmission and wide spread in fields. Collectively, our results provide useful information regarding taxonomy, transmission and pathogenicity of the viruses as well as management of the FYD.

Transmission of a New Polerovirus Infecting Pepper by the Whitefly Bemisia tabaci.

Many animal and plant viruses depend on arthropods for their transmission. Virus-vector interactions are highly specific, and only one vector or one of a group of vectors from the same family is able to transmit a given virus. Poleroviruses (Luteoviridae) are phloem-restricted RNA plant viruses that are exclusively transmitted by aphids. Multiple aphid-transmitted polerovirus species commonly infect pepper, causing vein yellowing, leaf rolling, and fruit discoloration. Despite low aphid populations, a recent outbreak with such severe symptoms in many bell pepper farms in Israel led to reinvestigation of the disease and its insect vector. Here we report that this outbreak was caused by a new whitefly (Bemisia tabaci)-transmitted polerovirus, which we named Pepper whitefly-borne vein yellows virus (PeWBVYV). PeWBVYV is highly (>95%) homologous to Pepper vein yellows virus (PeVYV) from Israel and Greece on its 5' end half, while it is homologous to African eggplant yellows virus (AeYV) on its 3' half. Koch's postulates were proven by constructing a PeWBVYV infectious clone causing the pepper disease, which was in turn transmitted to test pepper plants by B. tabaci but not by aphids. PeWBVYV represents the first report of a whitefly-transmitted polerovirus.IMPORTANCE The high specificity of virus-vector interactions limits the possibility of a given virus changing vectors. Our report describes a new virus from a family of viruses strictly transmitted by aphids which is now transmitted by whiteflies (Bemisia tabaci) and not by aphids. This report presents the first description of polerovirus transmission by whiteflies. Whiteflies are highly resistant to insecticides and disperse over long distances, carrying virus inoculum. Thus, the report of such unusual polerovirus transmission by a supervector has extensive implications for the epidemiology of the virus disease, with ramifications concerning the international trade of agricultural commodities.

Faba bean polerovirus 1 (FBPV-1); a new polerovirus infecting legume crops in Australia.

A new polerovirus species with the proposed name faba bean polerovirus 1 (FBPV-1) was found in winter legume crops and weeds in New South Wales, Australia. We describe the complete genome sequence of 5,631 nucleotides, containing all putative open reading frames, from two isolates, one from faba bean (Vicia faba) and one from chickpea (Cicer arietinum). FBPV-1 has a genome organization typical of poleroviruses with six open reading frames. However, recombination analysis strongly supports a recombination event in which the 5' portion of FBPV-1, which encodes for proteins P0, P1 and P1-P2, appears to be from a novel parent with a closest nucleotide identity of only 66% to chickpea chlorotic stunt virus. The 3' portion of FBPV-1 encodes for proteins P3, P4 and P3-P5 and shares 94% nucleotide identity to a turnip yellows virus isolate from Western Australia.

Novel bird's-foot trefoil RNA viruses provide insights into a clade of legume-associated enamoviruses and rhabdoviruses.

Here, we report the identification and characterization of two novel viruses associated with bird's-foot trefoil. Virus sequences related to those of enamoviruses (ssRNA (+); Luteoviridae; Enamovirus) and nucleorhabdoviruses (ssRNA (-); Rhabdoviridae; Nucleorhabdovirus) were detected in Lotus corniculatus transcriptome data. The genome of the tentatively named "bird's-foot trefoil-associated virus 1" (BFTV-1) is a 13,626-nt-long negative-sense ssRNA. BFTV-1 encodes six predicted gene products in the antigenome orientation in the canonical order 3'-N-P-P3-M-G-L-5'. The genome of the proposed "bird's-foot trefoil-associated virus 2" (BFTV-2) is 5,736 nt long with a typical 5΄-PO-P1-2-IGS-P3-P5-3' enamovirus genome structure. Phylogenetic analysis indicated that BFTV-1 is closely related to datura yellow vein nucleorhabdovirus and that BFTV-2 clusters into a monophyletic lineage of legume-associated enamoviruses. This subclade of highly related and co-divergent legume-associated viruses provides insights into the evolutionary history of the enamoviruses.

Molecular characterisation of a putative new polerovirus infecting pumpkin (Cucurbita pepo) in Kenya.

Next-generation sequencing of RNA extracted from a pumpkin plant with mosaic symptoms in Kenya identified the presence of a polerovirus sequence closely related to pepo aphid-borne yellows virus (PABYV). The near-complete polerovirus sequence comprised 5,810 nucleotides and contained seven putative open reading frames (ORFs) with a genome organisation typical of poleroviruses. BLASTp analysis of the translated sequences of ORFs 0, 1 and 2 revealed that their amino acid sequences differed by more than 10% from the corresponding protein sequences of other poleroviruses. These results suggest that this virus is a putative novel member of the genus Polerovirus, which has been provisionally named "pumpkin polerovirus" (PuPV).

In-field capable loop-mediated isothermal amplification detection of Turnip yellows virus in plants and its principal aphid vector Myzus persicae.

Widespread Turnip yellows virus (TuYV) infection causes severe seed yield and quality losses in rapeseed (Brassica napus) crops grown in broadacre agricultural systems worldwide. Current TuYV detection protocols are expensive and time consuming, and can have poor specificity and sensitivity. Typically, they are used as a diagnostic tool to test already symptomatic plants, limiting their practical value to reactive disease management. To improve diagnostic services so that they provide earlier, cheaper, faster, more specific and sensitive TuYV detection, novel and innovative protocols that utilise new technology are required. A reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed to detect TuYV in crude and total RNA extractions of leaf material and its principal aphid vector Myzus persicae. The assay was based on a set of six primers, highly sensitive and specific to TuYV, derived from a TuYV isolate originating from the south-west Australian grainbelt. TuYV was readily detected in 1 in 100 dilutions of (i) infected to uninfected leaf material, and (ii) viruliferous to non-viruliferous M. persicae. Furthermore, detection was successful in a majority of aphids stored for at least 8 weeks in various trapping and storage substances, including 30% ethylene glycol, sticky trap glue and 70% ethanol. This RT-LAMP assay protocol enables quicker and cheaper diagnosis for TuYV than currently adopted laboratory-based diagnostic techniques. Ultimately, it has the potential for earlier in-field TuYV detection in combination with aphid trapping surveillance programs.

The Interaction Dynamics of Two Potato Leafroll Virus Movement Proteins Affects Their Localization to the Outer Membranes of Mitochondria and Plastids.

The Luteoviridae is an agriculturally important family of viruses whose replication and transport are restricted to plant phloem. Their genomes encode for four proteins that regulate viral movement. These include two structural proteins that make up the capsid and two non-structural proteins known as P3a and P17. Little is known about how these proteins interact with each other and the host to coordinate virus movement within and between cells. We used quantitative, affinity purification-mass spectrometry to show that the P3a protein of Potato leafroll virus complexes with virus and that this interaction is partially dependent on P17. Bimolecular complementation assays (BiFC) were used to validate that P3a and P17 self-interact as well as directly interact with each other. Co-localization with fluorescent-based organelle markers demonstrates that P3a directs P17 to the mitochondrial outer membrane while P17 regulates the localization of the P3a-P17 heterodimer to plastids. Residues in the C-terminus of P3a were shown to regulate P3a association with host mitochondria by using mutational analysis and also varying BiFC tag orientation. Collectively, our work reveals that the PLRV movement proteins play a game of intracellular hopscotch along host organelles to transport the virus to the cell periphery.