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Sabharwal, Pallavi, i Handanahal S. Savithri. "Functional Characterization of Pepper Vein Banding Virus-Encoded Proteins and Their Interactions: Implications in Potyvirus Infection". Viruses 12, nr 9 (17.09.2020): 1037. http://dx.doi.org/10.3390/v12091037.
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Pepper vein banding virus (PVBV) is a distinct species in the Potyvirus genus which infects economically important plants in several parts of India. Like other potyviruses, PVBV encodes multifunctional proteins, with several interaction partners, having implications at different stages of the potyviral infection. In this review, we summarize the functional characterization of different PVBV-encoded proteins with an emphasis on their interaction partners governing the multifunctionality of potyviral proteins. Intrinsically disordered domains/regions of these proteins play an important role in their interactions with other proteins. Deciphering the function of PVBV-encoded proteins and their interactions with cognitive partners will help in understanding the putative mechanisms by which the potyviral proteins are regulated at different stages of the viral life-cycle. This review also discusses PVBV virus-like particles (VLPs) and their potential applications in nanotechnology. Further, virus-like nanoparticle-cell interactions and intracellular fate of PVBV VLPs are also discussed.
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Guo, Deyin, Carl Spetz, Mart Saarma i Jari P. T. Valkonen. "Two Potato Proteins, Including a Novel RING Finger Protein (HIP1), Interact with the Potyviral Multifunctional Protein HCpro". Molecular Plant-Microbe Interactions® 16, nr 5 (maj 2003): 405–10. http://dx.doi.org/10.1094/mpmi.2003.16.5.405.
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Potyviral helper-component proteinase (HCpro) is a multifunctional protein exerting its cellular functions in interaction with putative host proteins. In this study, cellular protein partners of the HCpro encoded by Potato virus A (PVA) (genus Potyvirus) were screened in a potato leaf cDNA library using a yeast two-hybrid system. Two cellular proteins were obtained that interact specifically with PVA HCpro in yeast and in the two in vitro binding assays used. Both proteins are encoded by single-copy genes in the potato genome. Analysis of the deduced amino acid sequences revealed that one (HIP1) of the two HCpro interactors is a novel RING finger protein. The sequence of the other protein (HIP2) showed no resemblance to the protein sequences available from databanks and has known biological functions.
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Solovyev, Andrey G., Anastasia K. Atabekova, Alexander A. Lezzhov, Anna D. Solovieva, Denis A. Chergintsev i Sergey Y. Morozov. "Distinct Mechanisms of Endomembrane Reorganization Determine Dissimilar Transport Pathways in Plant RNA Viruses". Plants 11, nr 18 (15.09.2022): 2403. http://dx.doi.org/10.3390/plants11182403.
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Plant viruses exploit the endomembrane system of infected cells for their replication and cell-to-cell transport. The replication of viral RNA genomes occurs in the cytoplasm in association with reorganized endomembrane compartments induced by virus-encoded proteins and is coupled with the virus intercellular transport via plasmodesmata that connect neighboring cells in plant tissues. The transport of virus genomes to and through plasmodesmata requires virus-encoded movement proteins (MPs). Distantly related plant viruses encode different MP sets, or virus transport systems, which vary in the number of MPs and their properties, suggesting their functional differences. Here, we discuss two distinct virus transport pathways based on either the modification of the endoplasmic reticulum tubules or the formation of motile vesicles detached from the endoplasmic reticulum and targeted to endosomes. The viruses with the movement proteins encoded by the triple gene block exemplify the first, and the potyviral system is the example of the second type. These transport systems use unrelated mechanisms of endomembrane reorganization. We emphasize that the mode of virus interaction with cell endomembranes determines the mechanism of plant virus cell-to-cell transport.
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Genovés, A., J. A. Navarro i V. Pallás. "Functional analysis of the five melon necrotic spot virus genome-encoded proteins". Journal of General Virology 87, nr 8 (1.08.2006): 2371–80. http://dx.doi.org/10.1099/vir.0.81793-0.
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Function of the melon necrotic spot virus (MNSV) genome-encoded proteins (p29, p89, p7A, p7B and p42) has been studied. Protein-expression mutants of an infectious, full-length cDNA clone of a Spanish MNSV-Al isolate and a recombinant green fluorescent protein (GFP)-expressing virus were used in infection bioassays on melon plants. Results revealed that p29 and p89 are both essential for virus replication, whereas small proteins p7A and p7B are sufficient to support viral movement between adjacent cells operating in trans. It is also demonstrated that, in addition to its structural role as coat protein, p42 is an important factor controlling symptoms and is required for systemic transport. Moreover, both p42 and p7B, among all of the MNSV-encoded proteins, were able to delay RNA silencing in transient-expression assays on GFP-transgenic Nicotiana benthamiana plants. Finally, the presence of p42 also produced an enhancing effect on local spread similar to that of potyviral helper component proteinase (HC-Pro), probably due to its RNA silencing-suppression ability.
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Merits, Andres, Minna-Liisa Rajamäki, Päivi Lindholm, Pia Runeberg-Roos, Tuija Kekarainen, Pietri Puustinen, Katri Mäkeläinen, Jari P. T. Valkonen i Mart Saarma. "Proteolytic processing of potyviral proteins and polyprotein processing intermediates in insect and plant cells". Journal of General Virology 83, nr 5 (1.05.2002): 1211–21. http://dx.doi.org/10.1099/0022-1317-83-5-1211.
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Processing of the polyprotein encoded by Potato virus A (PVA; genus Potyvirus) was studied using expression of the complete PVA polyprotein or its mutants from recombinant baculoviruses in insect cells. The time-course of polyprotein processing by the main viral proteinase (NIaPro) was examined with the pulse–chase method. The sites at the P3/6K1, CI-6K2 and VPg/NIaPro junctions were processed slowly, in contrast to other proteolytic cleavage sites which were processed at a high rate. The CI-6K2 polyprotein was observed in the baculovirus system and in infected plant cells. In both cell types the majority of CI-6K2 was found in the membrane fraction, in contrast to fully processed CI. Deletion of the genomic region encoding the 6K1 protein prevented proper proteolytic separation of P3 from CI, but did not affect processing of VPg, NIaPro, NIb or CP from the polyprotein. The 6K2-encoding sequence could be removed without any detectable effect on polyprotein processing. However, deletion of either the 6K1 or 6K2 protein-encoding regions rendered PVA non-infectious. Mutations at the 6K2/VPg cleavage site reduced virus infectivity in plants, but had a less pronounced, albeit detectable, effect on proteolytic processing in the baculovirus system. The results of this study indicate that NIaPro catalyses proteolytic cleavages preferentially in cis, and that the 6K1/CI and NIb/CP sites can also be processed in trans. Both 6K peptides are indispensable for virus replication, and proteolytic separation of the 6K2 protein from the adjacent proteins by NIaPro is important for the rate of virus replication and movement.
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Nunna, Haritha, Feng Qu i Satyanarayana Tatineni. "P3 and NIa-Pro of Turnip Mosaic Virus Are Independent Elicitors of Superinfection Exclusion". Viruses 15, nr 7 (28.06.2023): 1459. http://dx.doi.org/10.3390/v15071459.
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Superinfection exclusion (SIE) is an antagonistic interaction between identical or closely related viruses in host cells. Previous studies by us and others led to the hypothesis that SIE was elicited by one or more proteins encoded in the genomes of primary viruses. Here, we tested this hypothesis using Turnip mosaic virus (TuMV), a member of the genus Potyvirus of the family Potyviridae, with significant economic consequences. To this end, individual TuMV-encoded proteins were transiently expressed in the cells of Nicotiana benthamiana leaves, followed by challenging them with a modified TuMV expressing the green fluorescent protein (TuMV-GFP). Three days after TuMV-GFP delivery, these cells were examined for the replication-dependent expression of GFP. Cells expressing TuMV P1, HC-Pro, 6K1, CI, 6K2, NIa-VPg, NIb, or CP proteins permitted an efficient expression of GFP, suggesting that these proteins failed to block the replication of a superinfecting TuMV-GFP. By contrast, N. benthamiana cells expressing TuMV P3 or NIa-Pro did not express visible GFP fluorescence, suggesting that both of them could elicit potent SIE against TuMV-GFP. The SIE elicitor activity of P3 and NIa-Pro was further confirmed by their heterologous expression from a different potyvirus, potato virus A (PVA). Plants systemically infected with PVA variants expressing TuMV P3 or NIa-Pro blocked subsequent infection by TuMV-GFP. A +1-frameshift mutation in P3 and NIa-Pro cistrons facilitated superinfection by TuMV-GFP, suggesting that the P3 and NIa-Pro proteins, but not the RNA, are involved in SIE activity. Additionally, deletion mutagenesis identified P3 amino acids 3 to 200 of 352 and NIa-Pro amino acids 3 to 40 and 181 to 242 of 242 as essential for SIE elicitation. Collectively, our study demonstrates that TuMV encodes two spatially separated proteins that act independently to exert SIE on superinfecting TuMV. These results lay the foundation for further mechanistic interrogations of SIE in this virus.
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Cui, Hongguang, i Aiming Wang. "Plum Pox Virus6K1 Protein Is Required for Viral Replication and Targets the Viral Replication Complex at the Early Stage of Infection". Journal of Virology 90, nr 10 (9.03.2016): 5119–31. http://dx.doi.org/10.1128/jvi.00024-16.
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ABSTRACTThe potyviral RNA genome encodes two polyproteins that are proteolytically processed by three viral protease domains into 11 mature proteins. Extensive molecular studies have identified functions for the majority of the viral proteins. For example, 6K2, one of the two smallest potyviral proteins, is an integral membrane protein and induces the endoplasmic reticulum (ER)-originated replication vesicles that target the chloroplast for robust viral replication. However, the functional role of 6K1, the other smallest protein, remains uncharacterized. In this study, we developed a series of recombinant full-length viral cDNA clones derived from a CanadianPlum pox virus(PPV) isolate. We found that deletion of any of the short motifs of 6K1 (each of which ranged from 5 to 13 amino acids), most of the 6K1 sequence (but with the conserved sequence of the cleavage sites being retained), or all of the 6K1 sequence in the PPV infectious clone abolished viral replication. Thetransexpression of 6K1 or thecisexpression of a dislocated 6K1 failed to rescue the loss-of-replication phenotype, suggesting the temporal and spatial requirement of 6K1 for viral replication. Disruption of the N- or C-terminal cleavage site of 6K1, which prevented the release of 6K1 from the polyprotein, either partially or completely inhibited viral replication, suggesting the functional importance of the mature 6K1. We further found that green fluorescent protein-tagged 6K1 formed punctate inclusions at the viral early infection stage and colocalized with chloroplast-bound viral replicase elements 6K2 and NIb. Taken together, our results suggest that 6K1 is required for viral replication and is an important viral element of the viral replication complex at the early infection stage.IMPORTANCEPotyviruses account for more than 30% of known plant viruses and consist of many agriculturally important viruses. The genomes of potyviruses encode two polyproteins that are proteolytically processed into 11 mature proteins, with the majority of them having been at least partially functionally characterized. However, the functional role of a small protein named 6K1 remains obscure. In this study, we showed that deletion of 6K1 or a short motif/region of 6K1 in the full-length cDNA clones of plum pox virus abolishes viral replication and that mutation of the N- or C-terminal cleavage sites of 6K1 to prevent its release from the polyprotein greatly attenuates or completely inhibits viral replication, suggesting its important role in potyviral infection. We report that 6K1 forms punctate structures and targets the replication vesicles in PPV-infected plant leaf cells at the early infection stage. Our data reveal that 6K1 is an important viral protein of the potyviral replication complex.
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Bera, Sayanta, Gabriella D. Arena, Swayamjit Ray, Sydney Flannigan i Clare L. Casteel. "The Potyviral Protein 6K1 Reduces Plant Proteases Activity during Turnip mosaic virus Infection". Viruses 14, nr 6 (20.06.2022): 1341. http://dx.doi.org/10.3390/v14061341.
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Potyviral genomes encode just 11 major proteins and multifunctionality is associated with most of these proteins at different stages of the virus infection cycle. Some potyviral proteins modulate phytohormones and protein degradation pathways and have either pro- or anti-viral/insect vector functions. Our previous work demonstrated that the potyviral protein 6K1 has an antagonistic effect on vectors when expressed transiently in host plants, suggesting plant defenses are regulated. However, to our knowledge the mechanisms of how 6K1 alters plant defenses and how 6K1 functions are regulated are still limited. Here we show that the 6K1 from Turnip mosaic virus (TuMV) reduces the abundance of transcripts related to jasmonic acid biosynthesis and cysteine protease inhibitors when expressed in Nicotiana benthamiana relative to controls. 6K1 stability increased when cysteine protease activity was inhibited chemically, showing a mechanism to the rapid turnover of 6K1 when expressed in trans. Using RNAseq, qRT-PCR, and enzymatic assays, we demonstrate TuMV reprograms plant protein degradation pathways on the transcriptional level and increases 6K1 stability at later stages in the infection process. Moreover, we show 6K1 decreases plant protease activity in infected plants and increases TuMV accumulation in systemic leaves compared to controls. These results suggest 6K1 has a pro-viral function in addition to the anti-insect vector function we observed previously. Although the host targets of 6K1 and the impacts of 6K1-induced changes in protease activity on insect vectors are still unknown, this study enhances our understanding of the complex interactions occurring between plants, potyviruses, and vectors.
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Kang, Hara, Yong Jae Lee, Jae Hwan Goo i Woo Jin Park. "Determination of the substrate specificity of turnip mosaic virus NIa protease using a genetic method". Journal of General Virology 82, nr 12 (1.12.2001): 3115–17. http://dx.doi.org/10.1099/0022-1317-82-12-3115.
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The RNA genome of turnip mosaic potyvirus (TuMV) encodes a large polyprotein that is processed to mature proteins by virus-encoded proteases. The TuMV NIa protease is responsible for the cleavage of the polyprotein at seven different locations. These cleavage sites are defined by a conserved sequence motif Val-Xaa-His-Gln↓, with the scissile bond located after Gln. To determine the substrate specificity of the NIa protease, amino acid sequences cleaved by the NIa protease were obtained from randomized sequence libraries using a screening method referred to as GASP (genetic assay for site-specific proteolysis). Based on statistical analysis of the obtained sequences, a consensus substrate sequence was deduced: Yaa-Val-Arg-His-Gln↓Ser, with Yaa being an aliphatic amino acid and the scissile bond being located between Gln and Ser. This result is consistent with the conserved cleavage sequence motif, and should provide insight into the molecular activity of the NIa protease.
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Martín, María Teresa, Carlos López Otín, Sonia Laín i Juan Antonio García. "Determination of polyprotein processing sites by amino terminal sequencing of nonstructural proteins encoded by plum pox potyvirus". Virus Research 15, nr 2 (luty 1990): 97–106. http://dx.doi.org/10.1016/0168-1702(90)90001-r.
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Jossey, Sushma, Houston A. Hobbs i Leslie L. Domier. "Role of Soybean mosaic virus–Encoded Proteins in Seed and Aphid Transmission in Soybean". Phytopathology® 103, nr 9 (wrzesień 2013): 941–48. http://dx.doi.org/10.1094/phyto-09-12-0248-r.
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Soybean mosaic virus (SMV) is seed and aphid transmitted and can cause significant reductions in yield and seed quality in soybean (Glycine max). The roles in seed and aphid transmission of selected SMV-encoded proteins were investigated by constructing mutants in and chimeric recombinants between SMV 413 (efficiently aphid and seed transmitted) and an isolate of SMV G2 (not aphid or seed transmitted). As previously reported, the DAG amino acid sequence motif near the amino terminus of the coat protein (CP) was the major determinant in differences in aphid transmissibility of the two SMV isolates, and helper component proteinase (HC-Pro) played a secondary role. Seed transmission of SMV was influenced by P1, HC-Pro, and CP. Replacement of the P1 coding region of SMV 413 with that of SMV G2 significantly enhanced seed transmissibility of SMV 413. Substitution in SMV 413 of the two amino acids that varied in the CPs of the two isolates with those from SMV G2, G to D in the DAG motif and Q to P near the carboxyl terminus, significantly reduced seed transmission. The Q-to-P substitution in SMV 413 also abolished virus-induced seed-coat mottling in plant introduction 68671. This is the first report associating P1, CP, and the DAG motif with seed transmission of a potyvirus and suggests that HC-Pro interactions with CP are important for multiple functions in the virus infection cycle.
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Merits, Andres, Deyin Guo, Lilian Järvekülg i Mart Saarma. "Biochemical and Genetic Evidence for Interactions between Potato A Potyvirus-Encoded Proteins P1 and P3 and Proteins of the Putative Replication Complex". Virology 263, nr 1 (październik 1999): 15–22. http://dx.doi.org/10.1006/viro.1999.9926.
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Huang, Chih-Hung, Chia-Hsing Tai, Ruey-Song Lin, Chung-Jan Chang i Fuh-Jyh Jan. "Biological, Pathological, and Molecular Characteristics of a New Potyvirus, Dendrobium Chlorotic Mosaic Virus, Infecting Dendrobium Orchid". Plant Disease 103, nr 7 (lipiec 2019): 1605–12. http://dx.doi.org/10.1094/pdis-10-18-1839-re.
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Dendrobium smillieae is one of the popular orchids in Taiwan. This report describes a new potyvirus tentatively named Dendrobium chlorotic mosaic virus (DeCMV) causing chlorotic and mosaic symptoms in D. smillieae. Enzyme-linked immunosorbent assay (ELISA) tests using six antisera against orchid-infecting viruses revealed that only a monoclonal antibody against the potyvirus group reacted positively with crude saps prepared from a symptomatic dendrobium orchid. Potyvirus-like, flexuous, filamentous particles were observed under an electron microscope, measuring approximately 700 to 800 nm in length and 11 to 12 nm in diameter. Sequence analyses revealed that DeCMV coat protein gene shared 59.6 to 66.0% nucleotide sequence identity and 57.6 to 66.0% amino acid sequence identity, whereas the DeCMV complete genome shared 54.1 to 57.3% nucleotide sequence identity and 43.7 to 49.5% amino acid sequence identity with those other known potyviruses. These similarity levels were much lower than the criteria set for species demarcation in potyviruses. Thus, DeCMV can be considered a new potyvirus. The whole DeCMV genome contains 10,041 nucleotides (GenBank accession no. MK241979) and encodes a polyprotein that is predicted to produce 10 proteins by proteolytic cleavage. In a pathogenicity test, results of inoculation assays demonstrated that DeCMV can be transmitted to dendrobium orchids by grafting and mechanical inoculation, as verified by ELISA and western blot analyses using the DeCMV polyclonal antiserum and by reverse transcription polymerase chain reaction using the coat protein gene-specific primers. The inoculated orchids developed similar chlorotic and mosaic symptoms. In conclusion, DeCMV is a novel orchid-infecting potyvirus, and this is the first report of a new potyvirus that infects dendrobium orchids in Taiwan.
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ANDRADE, Carlos G., Emanuel M. Da SILVA, Carla RAGONEZI i Miguel Â. A. PINHEIRO DE CARVALHO. "Viral diagnosis in cultivars of Ipomoea batatas (L.) Lam." Notulae Botanicae Horti Agrobotanici Cluj-Napoca 49, nr 1 (24.03.2021): 12222. http://dx.doi.org/10.15835/nbha49112222.
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Ipomoea batatas (L.) Lam. commonly known as sweet potato, is an important staple food worldwide, mainly due to its high nutritional value and yield. However, vegetative reproduction of sweet potato makes it more susceptible to viral infections, which threatens its productivity, quality, and difficult long-term preservation in germplasm banks. Also, it can act as a virus reservoir infecting the rest of the plant accessions in the bank collections. Hence, this work aimed to screen Begomovirus, Potyvirus, and Carlavirus infections in 16 traditional sweet potato cultivars from the germplasm collection of the ISOPlexis Germplasm Bank, Madeira, Portugal. The infection prevalence by these viruses among cultivars was 81.25%, 25.00%, and 6.25%, respectively; being ISOP1011 the only accession coinfected by Potyvirus and Carlavirus. The accessions ISOP1006, ISOP1010, and ISOP1047 were also coinfected by Begomovirus and Potyvirus, highlighting their vulnerability to viral infections. The ISOP1005 and ISOP1027 accessions were the only ones not infected by any of these viruses. The analysis of the partial sequence obtained from the Carlavirus detected in the accession ISOP1011, revealed the existence of an ORF that encodes for 93 amino acids of the catalytic domain of an RNA-directed RNA polymerase related to the Tymovirus protein family, as could be confirmed by comparison with proteins stored in UniProtKB. Multiple sequence alignment with these proteins showed that Motifs A and B of the catalytic domain were conserved. The search for sequence similarity with sequences deposited in GenBank reported a high sequence identity with Sweet potato yellow mottle virus (SPYMV) and Sweet potato chlorotic fleck virus (SPCFV). However, the 9-11% discrepancy in nucleotide sequence identity and a phylogenetic analysis carried out using the maximum probability method suggests the virus isolated from ISOP1011 is a new divergent strain of the SPCFV species.
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Cuellar, Wilmer J., Fred Tairo, Jan F. Kreuze i Jari P. T. Valkonen. "Analysis of gene content in sweet potato chlorotic stunt virus RNA1 reveals the presence of the p22 RNA silencing suppressor in only a few isolates: implications for viral evolution and synergism". Journal of General Virology 89, nr 2 (1.02.2008): 573–82. http://dx.doi.org/10.1099/vir.0.83471-0.
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Sweet potato chlorotic stunt virus (genus Crinivirus) belongs to the family Closteroviridae, members of which have a conserved overall genomic organization but are variable in gene content. In the bipartite criniviruses, heterogeneity is pronounced in the 3′-proximal region of RNA1, which in sweet potato chlorotic stuat virus (SPCSV) encodes two novel proteins, RNase3 (RNase III endonuclease) and p22 (RNA silencing suppressor). This study showed that two Ugandan SPCSV isolates contained the p22 gene, in contrast to three isolates of the East African strain from Tanzania and Peru and an isolate of the West African strain from Israel, which were missing a 767 nt fragment of RNA1 that included the p22 gene. Regardless of the presence of p22, all tested SPCSV isolates acted synergistically with potyvirus sweet potato feathery mottle virus (SPFMV; genus Potyvirus, family Potyviridae) in co-infected sweetpotato plants (Ipomoea batatas), which greatly enhanced SPFMV titres and caused severe sweetpotato virus disease (SPVD). Therefore, the results indicate that any efforts to engineer pathogen-derived RNA silencing-based resistance to SPCSV and SPVD in sweetpotato should not rely on p22 as the transgene. The data from this study demonstrate that isolates of this virus species can vary in the genes encoding RNA silencing suppressor proteins. This study also provides the first example of intraspecific variability in gene content of the family Closteroviridae and may be a new example of the recombination-mediated gene gain that is characteristic of virus evolution in this virus family.
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Chen, T. C., C. W. Huang, F. L. Liu, C. H. Lin i S. D. Yeh. "EXPRESSION OF S RNA-ENCODED PROTEINS OF THRIPS-BORNE WATERMELON SILVER MOTTLE TOSPOVIRUS IN SQUASH BY ZUCCHINI YELLOW MOSAIC POTYVIRUS VECTOR". Acta Horticulturae, nr 722 (październik 2006): 313–20. http://dx.doi.org/10.17660/actahortic.2006.722.39.
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Chase, Ornela, Giannina Bambaren i Juan José López-Moya. "Deciphering the RNA Silencing Suppressor Function in the Potyvirus SPV2". Proceedings 50, nr 1 (9.06.2020): 26. http://dx.doi.org/10.3390/proceedings2020050026.
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In most eukaryotes, RNA silencing is a key element in the regulation of gene expression and defense against pathogens. Plants have developed a defensive barrier against exogenous microorganisms, such as plant-infecting viruses, by specifically targeting and degrading the viral RNAs and thus limiting the negative effects of the diseases caused by them. On the other hand, plant viruses encode for suppressor proteins that repress the host-silencing machinery, hence allowing viral replication and infection establishment. Our current project focuses on the characterization of gene products contributing to the RNA silencing suppressor (RSS) function of Sweet potato virus 2 (SPV2), genus Potyvirus, family Potyviridae. SPV2 infects sweet potatoes (Ipomoea batatas, family Convolvulaceae), one of the most important staple food crops worldwide. Infections by potyvirids result in the high yield losses of sweet potatoes, especially from coinfection with unrelated viruses, and our final goal is to develop efficient control strategies. Our preliminary results analyzing the P1 and HCPro proteases of SPV2, transiently expressed in N. benthamiana together with a reporter GFP construct, revealed that HCPro constitutes a strong RSS. This is a novel finding, and we are currently characterizing the functions of other gene products.
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Goh, Chul Jun, i Yoonsoo Hahn. "Analysis of proteolytic processing sites in potyvirus polyproteins revealed differential amino acid preferences of NIa-Pro protease in each of seven cleavage sites". PLOS ONE 16, nr 1 (25.01.2021): e0245853. http://dx.doi.org/10.1371/journal.pone.0245853.
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Potyviruses encode a large polyprotein that undergoes proteolytic processing, producing 10 mature proteins: P1, HC-Pro, P3, 6K1, CI, 6K2, VPg, NIa-Pro, NIb-RdRp, and CP. While P1/HC-Pro and HC-Pro/P3 junctions are cleaved by P1 and HC-Pro, respectively, the remaining seven are processed by NIa-Pro. In this study, we analyzed 135 polyprotein sequences from approved potyvirus species and deduced the consensus amino acid residues at five positions (from −4 to +1, where a protease cleaves between −1 and +1) in each of nine cleavage sites. In general, the newly deduced consensus sequences were consistent with the previous ones. However, seven NIa-Pro cleavage sites showed distinct amino acid preferences despite being processed by the same protease. At position −2, histidine was the dominant amino acid residue in most cleavage sites (57.8–60.7% of analyzed sequences), except for the NIa-Pro/NIb-RdRp junction where it was absent. At position −1, glutamine was highly dominant in most sites (88.2–97.8%), except for the VPg/NIa-Pro junction where glutamic acid was found in all the analyzed proteins (100%). At position +1, serine was the most abundant residue (47.4–86.7%) in five out of seven sites, while alanine (52.6%) and glycine (82.2%) were the most abundant in the P3/6K1 and 6K2/VPg junctions, respectively. These findings suggest that each NIa-Pro cleavage site is finely tuned for differential characteristics of proteolytic reactions. The newly deduced consensus sequences may be useful resources for the development of models and methods to accurately predict potyvirus polyprotein processing sites.
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Waltermann, Angelika, i Edgar Maiss. "Detection of 6K1 as a mature protein of 6 kDa in plum pox virus-infected Nicotiana benthamiana". Journal of General Virology 87, nr 8 (1.08.2006): 2381–86. http://dx.doi.org/10.1099/vir.0.81873-0.
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The RNA genome of Plum pox virus (PPV) encodes one large polyprotein that is subsequently cleaved into mature viral proteins. One of the products of proteolytic processing, the 6K1 protein, has not yet been identified in vivo for any member of the genus Potyvirus. In this study, 6K1-specific polyclonal antiserum was raised against PPV 6K1 expressed in Escherichia coli as a translational fusion with the N terminus of avian troponin C and an unusual metal-binding cluster of troponin T-1. For detection of 6K1 in vivo, a pPPV-H6K1-NAT infectious clone was constructed, enabling concentration of histidine-tagged 6K1 by affinity chromatography. Affinity-purified 6K1 was detected in locally infected Nicotiana benthamiana leaves at 4, 7 and 14 days post-inoculation (d.p.i.) and, in addition, in systemically infected leaves at 14 d.p.i., 6K1 was detected exclusively as a protein of 6 kDa and no polyprotein precursors were identified with the raised anti-6K1 antiserum.
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Cañizares, M. Carmen, Rosa Lozano-Durán, Tomás Canto, Eduardo R. Bejarano, David M. Bisaro, Jesús Navas-Castillo i Enrique Moriones. "Effects of the Crinivirus Coat Protein–Interacting Plant Protein SAHH on Post-Transcriptional RNA Silencing and Its Suppression". Molecular Plant-Microbe Interactions® 26, nr 9 (wrzesień 2013): 1004–15. http://dx.doi.org/10.1094/mpmi-02-13-0037-r.
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In plants, post-transcriptional gene silencing (PTGS) is a sequence-specific mechanism of RNA degradation induced by double-stranded RNA (dsRNA), which is processed into small interfering RNAs (siRNAs). siRNAs are methylated and, thereby, stabilized by the activity of the S-adenosylmethionine-dependent RNA methyltransferase HEN1. PTGS is amplified by host-encoded RNA-dependent RNA polymerases (RDR), which generate dsRNA that is processed into secondary siRNAs. To counteract this RNA silencing-mediated response of the host, plant viruses express proteins with silencing suppression activity. Here, we report that the coat protein (CP) of crinivirus (family Closteroviridae, genus Crinivirus) Tomato chlorosis virus, a known suppressor of silencing, interacts with S-adenosylhomocysteine hydrolase (SAHH), a plant protein essential for sustaining the methyl cycle and S-adenosylmethionine-dependent methyltransferase activity. Our results show that, by contributing to an increased accumulation of secondary siRNAs generated by the action of RDR6, SAHH enhances local RNA silencing. Although downregulation of SAHH prevents local silencing, it enhances the spread of systemic silencing. Our results also show that SAHH is important in the suppression of local RNA silencing not only by the crinivirus Tomato chlorosis virus CP but also by the multifunctional helper component-proteinase of the potyvirus Potato virus Y.
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Choi, Il-Ryong, Kempton M. Horken, Drake C. Stenger i Roy French. "Mapping of the P1 proteinase cleavage site in the polyprotein of Wheat streak mosaic virus (genus Tritimovirus)". Journal of General Virology 83, nr 2 (1.02.2002): 443–50. http://dx.doi.org/10.1099/0022-1317-83-2-443.
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Monopartite members of the family Potyviridae utilize three virus-encoded proteinases to cleave the viral polyprotein into mature proteins. The amino-terminal region of the viral polyprotein is autolytically cleaved by the P1 proteinase. A domain required for P1 proteinase activity of Wheat streak mosaic virus (WSMV) was mapped using a series of templates with nested 3′-truncations or 5′-deletions to program in vitro transcription–translation reactions. The WSMV P1 proteinase cleavage site was mapped to a position downstream of amino acid residue 348 and upstream of amino acid residue 353, with the peptide bond between amino acid residues Y352 and G353 the most probable site of hydrolysis. An alignment of potyvirus polyprotein sequences in the carboxy-terminal region of the P1 domain revealed WSMV P1 contained conserved H257, D267, S303 and FIVXG325–329 residues upstream of the cleavage site that are typical of serine proteinases and shown by others to be required for P1 proteolysis in Tobacco etch virus. Insertion of the GUS reporter gene immediately downstream of the P1 cleavage site in a full-length clone of WSMV resulted in systemic infection and GUS expression upon inoculation of plants with in vitro transcripts. When cleaved by P1 at the amino terminus and NIa proteinase at a site engineered in the carboxy-terminus, active GUS protein expressed by WSMV in infected wheat had electrophoretic mobility similar to wild-type GUS protein.
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Saha, Shreya, Anders Hafren i Kristiina Mäkinen. "Dynamics of Protein Accumulation from the 3′ End of Viral RNA Are Different from Those in the Rest of the Genome in Potato Virus A Infection". Journal of Virology 93, nr 19 (24.07.2019). http://dx.doi.org/10.1128/jvi.00721-19.
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ABSTRACT One large open reading frame (ORF) encodes 10 potyviral proteins. We compared the accumulation of cylindrical inclusion (CI) protein from the middle, coat protein (CP) from the 3′end, and Renilla luciferase (RLUC) from two distinct locations in potato virus A (PVA) RNA. 5′ RLUC was expressed from an rluc gene inserted between the P1 and helper component proteinase (HCPro) cistrons, and 3′ RLUC was expressed from the gene inserted between the RNA polymerase and CP cistrons. Viral protein and RNA accumulation were quantitated (i) when expressed from PVA RNA in the presence of ectopically expressed genome-linked viral protein (VPg) and auxiliary proteins and (ii) at different time points during natural infection. The rate and timing of 3′ RLUC and CP accumulation were found to be different from those of 5′ RLUC and CI. Ectopic expression of VPg boosted PVA RNA, 3′ RLUC, and, together with HCPro, CP accumulation, whereas 5′ RLUC and CI accumulation remained unaffected regardless of the increased viral RNA amount. In natural infection, the rate of the noteworthy minute early accumulation of 3′ RLUC accelerated toward the end of infection. 5′ RLUC accumulation, which was already pronounced at 2 days postinfection, increased moderately and stabilized to a constant level by day 5, whereas PVA RNA and CP levels continued to increase throughout the infection. We propose that these observations connect with the mechanisms by which potyvirus infection limits CP accumulation during early infection and specifically supports its accumulation late in infection, but follow-up studies are required to understand the mechanism of how this occurs. IMPORTANCE The results of this study suggest that the dynamics of potyviral protein accumulation are regulated differentially from the 3′ end of viral RNA than from the rest of the genome, the significance of which would be to satisfy the needs of replication early and particle assembly late in infection.
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Qin, Li, Wentao Shen, Zhongfa Tang, Weiyao Hu, Lingna Shangguan, Yaodi Wang, Decai Tuo i in. "A Newly Identified Virus in the Family Potyviridae Encodes Two Leader Cysteine Proteases in Tandem That Evolved Contrasting RNA Silencing Suppression Functions". Journal of Virology 95, nr 1 (14.10.2020). http://dx.doi.org/10.1128/jvi.01414-20.
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ABSTRACT Potyviridae is the largest family of plant-infecting RNA viruses and includes many agriculturally and economically important viral pathogens. The viruses in the family, known as potyvirids, possess single-stranded, positive-sense RNA genomes with polyprotein processing as a gene expression strategy. The N-terminal regions of potyvirid polyproteins vary greatly in sequence. Previously, we identified a novel virus species within the family, Areca palm necrotic spindle-spot virus (ANSSV), which was predicted to encode two cysteine proteases, HCPro1 and HCPro2, in tandem at the N-terminal region. Here, we present evidence showing self-cleavage activity of these two proteins and define their cis-cleavage sites. We demonstrate that HCPro2 is a viral suppressor of RNA silencing (VSR), and both the variable N-terminal and conserved C-terminal (protease domain) moieties have antisilencing activity. Intriguingly, the N-terminal region of HCPro1 also has RNA silencing suppression activity, which is, however, suppressed by its C-terminal protease domain, leading to the functional divergence of HCPro1 and HCPro2 in RNA silencing suppression. Moreover, the deletion of HCPro1 or HCPro2 in a newly created infectious clone abolishes viral infection, and the deletion mutants cannot be rescued by addition of corresponding counterparts of a potyvirus. Altogether, these data suggest that the two closely related leader proteases of ANSSV have evolved differential and essential functions to concertedly maintain viral viability. IMPORTANCE The Potyviridae represent the largest group of known plant RNA viruses and account for more than half of the viral crop damage worldwide. The leader proteases of viruses within the family vary greatly in size and arrangement and play key roles during the infection. Here, we experimentally demonstrate the presence of a distinct pattern of leader proteases, HCPro1 and HCPro2 in tandem, in a newly identified member within the family. Moreover, HCPro1 and HCPro2, which are closely related and typically characterized with a short size, have evolved contrasting RNA silencing suppression activity and seem to function in a coordinated manner to maintain viral infectivity. Altogether, the new knowledge fills a missing piece in the evolutionary relationship history of potyvirids and improves our understanding of the diversification of potyvirid genomes.
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Cheng, Xiaofei, i Aiming Wang. "The Potyvirus Silencing Suppressor Protein VPg Mediates Degradation of SGS3 via Ubiquitination and Autophagy Pathways". Journal of Virology 91, nr 1 (19.10.2016). http://dx.doi.org/10.1128/jvi.01478-16.
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ABSTRACT RNA silencing is an innate antiviral immunity response of plants and animals. To counteract this host immune response, viruses have evolved an effective strategy to protect themselves by the expression of viral suppressors of RNA silencing (VSRs). Most potyviruses encode two VSRs, helper component-proteinase (HC-Pro) and viral genome-linked protein (VPg). The molecular biology of the former has been well characterized, whereas how VPg exerts its function in the suppression of RNA silencing is yet to be understood. In this study, we show that infection by Turnip mosaic virus (TuMV) causes reduced levels of suppressor of gene silencing 3 (SGS3), a key component of the RNA silencing pathway that functions in double-stranded RNA synthesis for virus-derived small interfering RNA (vsiRNA) production. We also demonstrate that among 11 TuMV-encoded viral proteins, VPg is the only one that interacts with SGS3. We furthermore present evidence that the expression of VPg alone, independent of viral infection, is sufficient to induce the degradation of SGS3 and its intimate partner RNA-dependent RNA polymerase 6 (RDR6). Moreover, we discover that the VPg-mediated degradation of SGS3 occurs via both the 20S ubiquitin-proteasome and autophagy pathways. Taken together, our data suggest a role for VPg-mediated degradation of SGS3 in suppression of silencing by VPg. IMPORTANCE Potyviruses represent the largest group of known plant viruses and cause significant losses of many agriculturally important crops in the world. In order to establish infection, potyviruses must overcome the host antiviral silencing response. A viral protein called VPg has been shown to play a role in this process, but how it works is unclear. In this paper, we found that the VPg protein of Turnip mosaic virus (TuMV), which is a potyvirus, interacts with a host protein named SGS3, a key protein in the RNA silencing pathway. Moreover, this interaction leads to the degradation of SGS3 and its interacting and functional partner RDR6, which is another essential component of the RNA silencing pathway. We also identified the cellular pathways that are recruited for the VPg-mediated degradation of SGS3. Therefore, this work reveals a possible mechanism by which VPg sabotages host antiviral RNA silencing to promote virus infection.
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Martí, Maricarmen, Fernando Merwaiss, Anamarija Butković i José-Antonio Daròs. "Production of Potyvirus-Derived Nanoparticles Decorated with a Nanobody in Biofactory Plants". Frontiers in Bioengineering and Biotechnology 10 (31.03.2022). http://dx.doi.org/10.3389/fbioe.2022.877363.
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Viral nanoparticles (VNPs) have recently attracted attention for their use as building blocks for novel materials to support a range of functions of potential interest in nanotechnology and medicine. Viral capsids are ideal for presenting small epitopes by inserting them at an appropriate site on the selected coat protein (CP). VNPs presenting antibodies on their surfaces are considered highly promising tools for therapeutic and diagnostic purposes. Due to their size, nanobodies are an interesting alternative to classic antibodies for surface presentation. Nanobodies are the variable domains of heavy-chain (VHH) antibodies from animals belonging to the family Camelidae, which have several properties that make them attractive therapeutic molecules, such as their small size, simple structure, and high affinity and specificity. In this work, we have produced genetically encoded VNPs derived from two different potyviruses—the largest group of RNA viruses that infect plants—decorated with nanobodies. We have created a VNP derived from zucchini yellow mosaic virus (ZYMV) decorated with a nanobody against the green fluorescent protein (GFP) in zucchini (Cucurbita pepo) plants. As reported for other viruses, the expression of ZYMV-derived VNPs decorated with this nanobody was only made possible by including a picornavirus 2A splicing peptide between the fused proteins, which resulted in a mixed population of unmodified and decorated CPs. We have also produced tobacco etch virus (TEV)-derived VNPs in Nicotiana benthamiana plants decorated with the same nanobody against GFP. Strikingly, in this case, VNPs could be assembled by direct fusion of the nanobody to the viral CP with no 2A splicing involved, likely resulting in fully decorated VNPs. For both expression systems, correct assembly and purification of the recombinant VNPs was confirmed by transmission electron microscope; the functionality of the CP-fused nanobody was assessed by western blot and binding assays. In sum, here we report the production of genetically encoded plant-derived VNPs decorated with a nanobody. This system may be an attractive alternative for the sustainable production in plants of nanobody-containing nanomaterials for diagnostic and therapeutic purposes.
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Bello, Esther O., Yingshuai Yang, Yue Fang, Mengzhu Chai, Xue Jiang, Yameng Luan, Yuting Wang i in. "P1 of turnip mosaic virus interacts with NOD19 for vigorous infection". Frontiers in Microbiology 14 (23.06.2023). http://dx.doi.org/10.3389/fmicb.2023.1216950.
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P1 protein, the most divergent protein of virus members in the genus Potyvirus of the family Potyviridae, is required for robust infection and host adaptation. However, how P1 affects viral proliferation is still largely elusive. In this work, a total number of eight potential P1-interacting Arabidopsis proteins were identified by the yeast-two-hybrid screening using the turnip mosaic virus (TuMV)-encoded P1 protein as the bait. Among which, the stress upregulated NODULIN 19 (NOD19) was selected for further characterization. The bimolecular fluorescent complementation assay confirmed the interaction between TuMV P1 and NOD19. Expression profile, structure, and subcellular localization analyses showed that NOD19 is a membrane-associated protein expressed mainly in plant aerial parts. Viral infectivity assay showed that the infection of turnip mosaic virus and soybean mosaic virus was attenuated in the null mutant of Arabidopsis NOD19 and NOD19-knockdown soybean seedlings, respectively. Together, these data indicate that NOD19 is a P1-interacting host factor required for robust infection.