Identification of <i>Plum pox virus</i> Pathogenicity Determinants in Herbaceous and Woody Hosts

Salvador, Beatriz; Delgadillo, María Otilia; Sáenz, Pilar; Garcı́a, Juan Antonio; Simón‐Mateo, Carmen

doi:10.1094/mpmi-21-1-0020

Cited by 77 publications

(62 citation statements)

References 39 publications

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“…Similar results were obtained from at least two additional independent experiments. These results suggest that the full-length cDNA clone of PPV isolate VPH is infectious in its natural and experimental hosts and the pathogenicity discrepancy in peach and N. benthamiana possibly results from viral host adaptation, as previously reported for PPV (39)(40)(41).…”

Section: Resultssupporting

confidence: 81%

Plum Pox Virus 6K1 Protein Is Required for Viral Replication and Targets the Viral Replication Complex at the Early Stage of Infection

Cui

Wang

2016

J Virol

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The 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 Canadian Plum 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. The trans expression of 6K1 or the cis expression 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.T o establish their infection, positive-sense single-stranded RNA viruses remodel and recruit host cellular membranes to assemble the viral replication complex (VRC), which consists of both viral proteins and host factors, for robust viral replication (1-4). Therefore, t...

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Section: Resultssupporting

confidence: 81%

Plum Pox Virus 6K1 Protein Is Required for Viral Replication and Targets the Viral Replication Complex at the Early Stage of Infection

Cui

Wang

2016

J Virol

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“…For example, the papain-like leader proteases of Grapevine leafroll-associated virus-2, and -3a protein of Cowpea chlorotic mottle virus have been reported to fail to function in some hosts but not others (26,27). Host-specific infections by potyvirid species have been studied extensively, and P1, P3, 6K2, VPg, NIa-Pro, and CP have been found to be differential in certain hosts (28)(29)(30)(31)(32)(33). In general, different versions of these viral gene products function in specific hosts.…”

Section: Discussionmentioning

confidence: 99%

A plant virus evolved by acquiring multiple nonconserved genes to extend its host range

Satyanarayana

Robertson

Garnsey

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Viruses have evolved as combinations of genes whose products interact with cellular components to produce progeny virus throughout the plants. Some viral genes, particularly those that are involved in replication and assembly, tend to be relatively conserved, whereas other genes that have evolved for interactions with the specific host for movement and to counter host-defense systems tend to be less conserved. Closteroviridae encode 1-5 nonconserved ORFs. Citrus tristeza virus (CTV), a Closterovirus, possesses nonconserved p33, p18, and p13 genes that are expendable for systemic infection of the two laboratory hosts, Citrus macrophylla and Mexican lime. In this study, we show that the extended host range of CTV requires these nonconserved genes. The p33 gene was required to systemically infect sour orange and lemon trees, whereas either the p33 or the p18 gene was sufficient for systemic infection of grapefruit trees and the p33 or the p13 gene was sufficient for systemic infection of calamondin plants. Thus, these three genes are required for systemic infection of the full host range of CTV, but different genes were specific for different hosts. Remarkably, either of two genes was sufficient for infection of some citrus hybrids. These findings suggest that CTV acquired multiple nonconserved genes (p33, p18, and p13) and, as a result, gained the ability to interact with multiple hosts, thus extending its host range during the course of evolution. These results greatly extend the complexity of known virus-plant interactions.gene addition | host-specific activity | long-distance transport

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“…For biolistic inoculation, the Helios Gene Gun System (Bio-Rad) was used as previously described (47). For manual inoculation of plants using plasmids, 6 g of DNA from the indicated constructs was spread on two leaves of plants that had previously been dusted with Carborundum.…”

Section: Plantsmentioning

confidence: 99%

A Novel Role of the Potyviral Helper Component Proteinase Contributes To Enhance the Yield of Viral Particles

Vallí

Gallo

Calvo

et al. 2014

J Virol

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The helper component proteinase (HCPro) is an indispensable, multifunctional protein of members of the genus Potyvirus and other viruses of the family Potyviridae. This viral factor is directly involved in diverse steps of viral infection, such as aphid transmission, polyprotein processing, and suppression of host antiviral RNA silencing. In this paper, we show that although a chimeric virus based on the potyvirus Plum pox virus lacking HCPro, which was replaced by a heterologous silencing suppressor, caused an efficient infection in Nicotiana benthamiana plants, its viral progeny had very reduced infectivity. Making use of different approaches, here, we provide direct evidence of a previously unknown function of HCPro in which the viral factor enhances the stability of its cognate capsid protein (CP), positively affecting the yield of virions and consequently improving the infectivity of the viral progeny. Site-directed mutagenesis revealed that the ability of HCPro to stabilize CP and enhance the yield of infectious viral particles is not linked to any of its previously known activities and helped us to delimit the region of HCPro involved in this function in the central region of the protein. Moreover, the function is highly specific and cannot be fulfilled by the HCPro of a heterologous potyvirus. The importance of this novel requirement in regulating the sorting of the viral genome to be subjected to replication, translation, and encapsidation, thus contributing to the synchronization of these viral processes, is discussed. IMPORTANCEPotyviruses form one of the most numerous groups of plant viruses and are a major cause of crop loss worldwide. It is well known that these pathogens make use of virus-derived multitasking proteins, as well as dedicated host factors, to successfully infect their hosts. Here, we describe a novel requirement for the proper yield and infectivity of potyviral progeny. In this case, such a function is performed by the extensively studied viral factor HCPro, which seems to use an unknown mechanism that is not linked to its previously described activities. To our knowledge, this is the first time that a factor different from capsid protein (CP) has been shown to be directly involved in the yield of potyviral particles. Based on the data presented here, we hypothesize that this capacity of HCPro might be involved in the coordination of mutually exclusive activities of the viral genome by controlling correct assembly of CP in stable virions.

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Identification of Plum pox virus Pathogenicity Determinants in Herbaceous and Woody Hosts

Cited by 77 publications

References 39 publications

Plum Pox Virus 6K1 Protein Is Required for Viral Replication and Targets the Viral Replication Complex at the Early Stage of Infection

Plum Pox Virus 6K1 Protein Is Required for Viral Replication and Targets the Viral Replication Complex at the Early Stage of Infection

A plant virus evolved by acquiring multiple nonconserved genes to extend its host range

A Novel Role of the Potyviral Helper Component Proteinase Contributes To Enhance the Yield of Viral Particles

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