scholarly journals A Unique 5′ Translation Element Discovered in Triticum Mosaic Virus

2015 ◽  
Vol 89 (24) ◽  
pp. 12427-12440 ◽  
Author(s):  
Robyn Roberts ◽  
Jincan Zhang ◽  
Laura K. Mayberry ◽  
Satyanarayana Tatineni ◽  
Karen S. Browning ◽  
...  
Keyword(s):  
Mosaic Virus ◽  
Translation Initiation ◽  
Plant Virus ◽  
Plant Viruses ◽  
Leader Sequence ◽  
Content Type ◽  
Internal Translation ◽  
Positive Strand Rna ◽  
Independent Translation

ABSTRACTSeveral plant viruses encode elements at the 5′ end of their RNAs, which, unlike most cellular mRNAs, can initiate translation in the absence of a 5′ m7GpppG cap. Here, we describe an exceptionally long (739-nucleotide [nt]) leader sequence in triticum mosaic virus (TriMV), a recently emerged wheat pathogen that belongs to thePotyviridaefamily of positive-strand RNA viruses. We demonstrate that the TriMV 5′ leader drives strong cap-independent translation in both wheat germ extract and oat protoplasts through a novel, noncanonical translation mechanism. Translation preferentially initiates at the 13th start codon within the leader sequence independently of eIF4E but involves eIF4G. We truncated the 5′ leader to a 300-nucleotide sequence that drives cap-independent translation from the 5′ end. We show that within this sequence, translation activity relies on a stem-loop structure identified at nucleotide positions 469 to 490. The disruption of the stem significantly impairs the function of the 5′ untranslated region (UTR) in driving translation and competing against a capped RNA. Additionally, the TriMV 5′ UTR can direct translation from an internal position of a bicistronic mRNA, and unlike cap-driven translation, it is unimpaired when the 5′ end is blocked by a strong hairpin in a monocistronic reporter. However, the disruption of the identified stem structure eliminates such a translational advantage. Our results reveal a potent and uniquely controlled translation enhancer that may provide new insights into mechanisms of plant virus translational regulation.IMPORTANCEMany members of thePotyviridaefamily rely on their 5′ end for translation. Here, we show that the 739-nucleotide-long triticum mosaic virus 5′ leader bears a powerful translation element with features distinct from those described for other plant viruses. Despite the presence of 12 AUG start codons within the TriMV 5′ UTR, translation initiates primarily at the 13th AUG codon. The TriMV 5′ UTR is capable of driving cap-independent translationin vitroandin vivo, is independent of eIF4E, and can drive internal translation initiation. A hairpin structure at nucleotide positions 469 to 490 is required for the cap-independent translation and internal translation initiation abilities of the element and plays a role in the ability of the TriMV UTR to compete against a capped RNAin vitro. Our results reveal a novel translation enhancer that may provide new insights into the large diversity of plant virus translation mechanisms.

scholarly journals Identification of Plant Virus Receptor Candidates in the Stylets of Their Aphid Vectors

2018 ◽  
Vol 92 (14) ◽  
Author(s):  
Craig G. Webster ◽  
Elodie Pichon ◽  
Manuella van Munster ◽  
Baptiste Monsion ◽  
Maëlle Deshoux ◽  
...  
Keyword(s):  
Mosaic Virus ◽  
Myzus Persicae ◽  
Plant Virus ◽  
Plant Viruses ◽  
Cauliflower Mosaic Virus ◽  
Insect Vectors ◽  
Virus Receptor ◽  
Content Type ◽  
Cuticular Proteins

ABSTRACTPlant viruses transmitted by insects cause tremendous losses in most important crops around the world. The identification of receptors of plant viruses within their insect vectors is a key challenge to understanding the mechanisms of transmission and offers an avenue for future alternative control strategies to limit viral spread. We here report the identification of two cuticular proteins within aphid mouthparts, and we provide experimental support for the role of one of them in the transmission of a noncirculative virus. These two proteins, named Stylin-01 and Stylin-02, belong to the RR-1 cuticular protein subfamily and are highly conserved among aphid species. Using an immunolabeling approach, they were localized in the maxillary stylets of the pea aphidAcyrthosiphon pisumand the green peach aphidMyzus persicae, in the acrostyle, an organ earlier shown to harbor receptors of a noncirculative virus. A peptide motif present at the C termini of both Stylin-01 and Stylin-02 is readily accessible all over the surface of the acrostyle. Competition forin vitrobinding to the acrostyle was observed between an antibody targeting this peptide and the helper component protein P2 ofCauliflower mosaic virus. Furthermore, silencing thestylin-01but notstylin-02gene through RNA interference decreased the efficiency ofCauliflower mosaic virustransmission byMyzus persicae. These results identify the first cuticular proteins ever reported within arthropod mouthparts and distinguish Stylin-01 as the best candidate receptor for the aphid transmission of noncirculative plant viruses.IMPORTANCEMost noncirculative plant viruses transmitted by insect vectors bind to their mouthparts. They are acquired and inoculated within seconds when insects hop from plant to plant. The receptors involved remain totally elusive due to a long-standing technical bottleneck in working with insect cuticle. Here we characterize the role of the two first cuticular proteins ever identified in arthropod mouthparts. A domain of these proteins is directly accessible at the surface of the cuticle of the acrostyle, an organ at the tip of aphid stylets. The acrostyle has been shown to bind a plant virus, and we consistently demonstrated that one of the identified proteins is involved in viral transmission. Our findings provide an approach to identify proteins in insect mouthparts and point at an unprecedented gene candidate for a plant virus receptor.

scholarly journals Within-Host Multiplication and Speed of Colonization as Infection Traits Associated with Plant Virus Vertical Transmission

2019 ◽  
Vol 93 (23) ◽  
Author(s):  
Alberto Cobos ◽  
Nuria Montes ◽  
Marisa López-Herranz ◽  
Miriam Gil-Valle ◽  
Israel Pagán
Keyword(s):  
Arabidopsis Thaliana ◽  
Mosaic Virus ◽  
Vertical Transmission ◽  
Plant Virus ◽  
Seed Transmission ◽  
Plant Viruses ◽  
Content Type ◽  
Seed Survival ◽  
Virus Interactions ◽  
Number Of Seeds

ABSTRACT Although vertical transmission from parents to offspring through seeds is an important fitness component of many plant viruses, very little is known about the factors affecting this process. Viruses reach the seed by direct invasion of the embryo and/or by infection of the ovules or the pollen. Thus, it can be expected that the efficiency of seed transmission would be determined by (i) virus within-host multiplication and movement, (ii) the ability of the virus to invade gametic tissues, (iii) plant seed production upon infection, and (iv) seed survival in the presence of the virus. However, these predictions have seldom been experimentally tested. To address this question, we challenged 18 Arabidopsis thaliana accessions with Turnip mosaic virus and Cucumber mosaic virus. Using these plant-virus interactions, we analyzed the relationship between the effect of virus infection on rosette and inflorescence weights; short-, medium-, and long-term seed survival; virulence; the number of seeds produced per plant; virus within-host speed of movement; virus accumulation in the rosette and inflorescence; and efficiency of seed transmission measured as a percentage and as the total number of infected seeds. Our results indicate that the best estimators of percent seed transmission are the within-host speed of movement and multiplication in the inflorescence. Together with these two infection traits, virulence and the number of seeds produced per infected plant were also associated with the number of infected seeds. Our results provide support for theoretical predictions and contribute to an understanding of the determinants of a process central to plant-virus interactions. IMPORTANCE One of the major factors contributing to plant virus long-distance dispersal is the global trade of seeds. This is because more than 25% of plant viruses can infect seeds, which are the main mode of germplasm exchange/storage, and start new epidemics in areas where they were not previously present. Despite the relevance of this process for virus epidemiology and disease emergence, the infection traits associated with the efficiency of virus seed transmission are largely unknown. Using turnip mosaic and cucumber mosaic viruses and their natural host Arabidopsis thaliana as model systems, we have identified the within-host speed of virus colonization and multiplication in the reproductive structures as the main determinants of the efficiency of seed transmission. These results contribute to shedding light on the mechanisms by which plant viruses disperse and optimize their fitness and may help in the design of more-efficient strategies to prevent seed infection.

scholarly journals Mapping of sequences in the 5’ region and 3’ UTR of tomato ringspot virus RNA2 that facilitate cap-independent translation of reporter transcripts in vitro

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0249928
Author(s):  
Dinesh Babu Paudel ◽  
Hélène Sanfaçon
Keyword(s):  
Translation Initiation ◽  
Rna Virus ◽  
Ringspot Virus ◽  
General Mechanism ◽  
Coding Region ◽  
Initiation Mechanism ◽  
Tomato Ringspot Virus ◽  
Positive Strand Rna ◽  
Independent Translation

Tomato ringspot virus (ToRSV, genus Nepovirus, family Secoviridae, order Picornavirales) is a bipartite positive-strand RNA virus, with each RNA encoding one large polyprotein. ToRSV RNAs are linked to a 5’-viral genome-linked protein (VPg) and have a 3’ polyA tail, suggesting a non-canonical cap-independent translation initiation mechanism. The 3’ untranslated regions (UTRs) of RNA1 and RNA2 are unusually long (~1.5 kb) and share several large stretches of sequence identities. Several putative in-frame start codons are present in the 5’ regions of the viral RNAs, which are also highly conserved between the two RNAs. Using reporter transcripts containing the 5’ region and 3’ UTR of the RNA2 of ToRSV Rasp1 isolate (ToRSV-Rasp1) and in vitro wheat germ extract translation assays, we provide evidence that translation initiates exclusively at the first AUG, in spite of a poor codon context. We also show that both the 5’ region and 3’ UTR of RNA2 are required for efficient cap-independent translation of these transcripts. We identify translation-enhancing elements in the 5’ proximal coding region of the RNA2 polyprotein and in the RNA2 3’ UTR. Cap-dependent translation of control reporter transcripts was inhibited when RNAs consisting of the RNA2 3’ UTR were supplied in trans. Taken together, our results suggest the presence of a CITE in the ToRSV-Rasp1 RNA2 3’ UTR that recruits one or several translation factors and facilitates efficient cap-independent translation together with the 5’ region of the RNA. Non-overlapping deletion mutagenesis delineated the putative CITE to a 200 nts segment (nts 773–972) of the 1547 nt long 3’ UTR. We conclude that the general mechanism of ToRSV RNA2 translation initiation is similar to that previously reported for the RNAs of blackcurrant reversion virus, another nepovirus. However, the position, sequence and predicted structures of the translation-enhancing elements differed between the two viruses.

scholarly journals Towards plant resistance to viruses using protein-only RNase P

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Anthony Gobert ◽  
Yifat Quan ◽  
Mathilde Arrivé ◽  
Florent Waltz ◽  
Nathalie Da Silva ◽  
...  
Keyword(s):  
Mosaic Virus ◽  
Virus Replication ◽  
Yield Loss ◽  
Rnase P ◽  
Plant Viruses ◽  
Yellow Mosaic Virus ◽  
Resistance To Viruses ◽  
Target Plant

AbstractPlant viruses cause massive crop yield loss worldwide. Most plant viruses are RNA viruses, many of which contain a functional tRNA-like structure. RNase P has the enzymatic activity to catalyze the 5′ maturation of precursor tRNAs. It is also able to cleave tRNA-like structures. However, RNase P enzymes only accumulate in the nucleus, mitochondria, and chloroplasts rather than cytosol where virus replication takes place. Here, we report a biotechnology strategy based on the re-localization of plant protein-only RNase P to the cytosol (CytoRP) to target plant viruses tRNA-like structures and thus hamper virus replication. We demonstrate the cytosol localization of protein-only RNase P in Arabidopsis protoplasts. In addition, we provide in vitro evidences for CytoRP to cleave turnip yellow mosaic virus and oilseed rape mosaic virus. However, we observe varied in vivo results. The possible reasons have been discussed. Overall, the results provided here show the potential of using CytoRP for combating some plant viral diseases.

scholarly journals Topical Application of Double-Stranded RNA Targeting 2b and CP Genes of Cucumber mosaic virus Protects Plants against Local and Systemic Viral Infection

Plants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 963
Author(s):  
Maria C. Holeva ◽  
Athanasios Sklavounos ◽  
Rajendran Rajeswaran ◽  
Mikhail M. Pooggin ◽  
Andreas E. Voloudakis
Keyword(s):  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Topical Application ◽  
Plant Virus ◽  
Plant Protection ◽  
Post Inoculation ◽  
Tobacco Plants ◽  
Double Stranded Rna

Cucumber mosaic virus (CMV) is a destructive plant virus with worldwide distribution and the broadest host range of any known plant virus, as well as a model plant virus for understanding plant–virus interactions. Since the discovery of RNA interference (RNAi) as a major antiviral defense, RNAi-based technologies have been developed for plant protection against viral diseases. In plants and animals, a key trigger of RNAi is double-stranded RNA (dsRNA) processed by Dicer and Dicer-like (DCL) family proteins in small interfering RNAs (siRNAs). In the present study, dsRNAs for coat protein (CP) and 2b genes of CMV were produced in vitro and in vivo and applied onto tobacco plants representing a systemic solanaceous host as well as on a local host plant Chenopodium quinoa. Both dsRNA treatments protected plants from local and systemic infection with CMV, but not against infection with unrelated viruses, confirming sequence specificity of antiviral RNAi. Antiviral RNAi was effective when dsRNAs were applied simultaneously with or four days prior to CMV inoculation, but not four days post inoculation. In vivo-produced dsRNAs were more effective than the in vitro-produced; in treatments with in vivo dsRNAs, dsRNA-CP was more effective than dsRNA-2b, while the effects were opposite with in vitro dsRNAs. Illumina sequencing of small RNAs from in vivo dsRNA-CP treated and non-treated tobacco plants revealed that interference with CMV infection in systemic leaves coincides with strongly reduced accumulation of virus-derived 21- and 22-nucleotide (nt) siRNAs, likely generated by tobacco DCL4 and DCL2, respectively. While the 21-nt class of viral siRNAs was predominant in non-treated plants, 21-nt and 22-nt classes accumulated at almost equal (but low) levels in dsRNA treated plants, suggesting that dsRNA treatment may boost DCL2 activity. Taken together, our findings confirm the efficacy of topical application of dsRNA for plant protection against viruses and shed more light on the mechanism of antiviral RNAi.

scholarly journals 5′-UTR recruitment of the translation initiation factor eIF4GI or DAP5 drives cap-independent translation of a subset of human mRNAs

2020 ◽  
Vol 295 (33) ◽  
pp. 11693-11706 ◽  
Author(s):  
Solomon A. Haizel ◽  
Usha Bhardwaj ◽  
Ruben L. Gonzalez ◽  
Somdeb Mitra ◽  
Dixie J. Goss
Keyword(s):  
Translation Initiation ◽  
Tumor Hypoxia ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Luciferase Reporter ◽  
Binding Studies ◽  
Specific Subset ◽  
Independent Translation

During unfavorable conditions (e.g. tumor hypoxia or viral infection), canonical, cap-dependent mRNA translation is suppressed in human cells. Nonetheless, a subset of physiologically important mRNAs (e.g. hypoxia-inducible factor 1α [HIF-1α], fibroblast growth factor 9 [FGF-9], and p53) is still translated by an unknown, cap-independent mechanism. Additionally, expression levels of eukaryotic translation initiation factor 4GI (eIF4GI) and of its homolog, death-associated protein 5 (DAP5), are elevated. By examining the 5′ UTRs of HIF-1α, FGF-9, and p53 mRNAs and using fluorescence anisotropy binding studies, luciferase reporter-based in vitro translation assays, and mutational analyses, we demonstrate here that eIF4GI and DAP5 specifically bind to the 5′ UTRs of these cap-independently translated mRNAs. Surprisingly, we found that the eIF4E-binding domain of eIF4GI increases not only the binding affinity but also the selectivity among these mRNAs. We further demonstrate that the affinities of eIF4GI and DAP5 binding to these 5′ UTRs correlate with the efficiency with which these factors drive cap-independent translation of these mRNAs. Integrating the results of our binding and translation assays, we conclude that eIF4GI or DAP5 is critical for recruitment of a specific subset of mRNAs to the ribosome, providing mechanistic insight into their cap-independent translation.

scholarly journals Ultrabithorax and Antennapedia 5' untranslated regions promote developmentally regulated internal translation initiation.

1997 ◽  
Vol 17 (3) ◽  
pp. 1714-1721 ◽  
Author(s):  
X Ye ◽  
P Fong ◽  
N Iizuka ◽  
D Choate ◽  
D R Cavener
Keyword(s):  
Translation Initiation ◽  
Untranslated Regions ◽  
Northern Analysis ◽  
Developmentally Regulated ◽  
Developmental Patterns ◽  
Internal Translation ◽  
Transgenic Drosophila ◽  
Independent Translation ◽  
Transgenic Strains

The 5' untranslated regions (UTRs) of the Drosophila Ubx and Antp genes were tested for their ability to promote cap-independent translation initiation. The Ubx and the Antp 5' UTR were inserted between the CAT and lacZ coding sequences in a dicistronic gene and tested for IRES activity in transgenic Drosophila. Northern analysis of the mRNAs showed the presence of the predicted full-length dicistronic mRNAs. High CAT activity was expressed from the first cistron from all of the dicistronic constructs introduced into the fly genome. The dicistronic transgenic strains bearing the Ubx and Antp IRES elements expressed significant levels of beta-galactosidase (betaGAL) from the second cistron whereas little or no betaGAL was expressed in the controls lacking the IRESs. In situ analysis of betaGAL expression in the transgenic strains indicates that expression of the second cistron is spatially and temporally regulated. Although the developmental patterns of expression directed by the Antp and Ubx IRESs overlap, they exhibit several differences indicating that these IRESs are not functionally equivalent.

scholarly journals Tombusvirus Y-Shaped Translational Enhancer Forms a Complex with eIF4F and Can Be Functionally Replaced by Heterologous Translational Enhancers

2012 ◽  
Vol 87 (3) ◽  
pp. 1872-1883 ◽  
Author(s):  
Beth L. Nicholson ◽  
Olga Zaslaver ◽  
Laura K. Mayberry ◽  
Karen S. Browning ◽  
K. Andrew White
Keyword(s):  
Plant Viruses ◽  
Related Factors ◽  
Content Type ◽  
Initiation Factors ◽  
Translational Enhancers ◽  
Translation Initiation Factors ◽  
New Information ◽  
Major Loss ◽  
High Degree

ABSTRACTCertain plus-strand RNA plant viruses that are uncapped and nonpolyadenylated rely on RNA elements in their 3′ untranslated region, termed 3′-cap-independent translational enhancers (3′CITEs), for efficient translation of their proteins. Here, we have investigated the properties of the Y-shaped class of 3′CITE present in the tombusvirusCarnation Italian ringspot virus(CIRV). While some types of 3′CITE have been found to function through recruitment of translation initiation factors to the viral genome, notrans-acting translation-related factors have yet been identified for the Y-shaped 3′CITE. Our results indicate that the CIRV 3′CITE complexes with eIF4F and eIFiso4F, with the former mediating translation more efficiently than the latter. In nature, some classes of 3′CITE are present in several different viral genera, suggesting that these elements hold a high degree of modularity. Here, we test this concept by engineering chimeric viruses containing heterologous 3′CITEs and show that the Y-shaped class of 3′CITE in CIRV can be replaced by two alternative types of 3′CITE, i.e., aPanicum mosaic virus-like 3′CITE or an I-shaped 3′CITE, without any major loss inin vitrotranslation or replication efficiency in protoplasts. The heterologous 3′CITEs also mediated whole-plant infections ofNicotiana benthamiana, where distinct symptoms were observed for each of the alternative 3′CITEs and 3′CITE evolution occurred during serial passaging. Our results supply new information on Y-shaped 3′CITE function and provide insights into 3′CITE virus-host compatibilities.

scholarly journals Human Norovirus NS3 Has RNA Helicase and Chaperoning Activities

2017 ◽  
Vol 92 (5) ◽  
Author(s):  
Teng-Feng Li ◽  
Myra Hosmillo ◽  
Hella Schwanke ◽  
Ting Shu ◽  
Zhaowei Wang ◽  
...  
Keyword(s):  
Rna Synthesis ◽  
Rna Viruses ◽  
Rna Helicase ◽  
Diverse Group ◽  
Rna Helicases ◽  
Human Norovirus ◽  
Content Type ◽  
Rna Remodeling ◽  
Positive Strand Rna

ABSTRACTRNA-remodeling proteins, including RNA helicases and chaperones, act to remodel RNA structures and/or protein-RNA interactions and are required for all processes involving RNAs. Although many viruses encode RNA helicases and chaperones, theirin vitroactivities and their roles in infected cells largely remain elusive. Noroviruses are a diverse group of positive-strand RNA viruses in the familyCaliciviridaeand constitute a significant and potentially fatal threat to human health. Here, we report that the protein NS3 encoded by human norovirus has both ATP-dependent RNA helicase activity that unwinds RNA helices and ATP-independent RNA-chaperoning activity that can remodel structured RNAs and facilitate strand annealing. Moreover, NS3 can facilitate viral RNA synthesisin vitroby norovirus polymerase. NS3 may therefore play an important role in norovirus RNA replication. Lastly, we demonstrate that the RNA-remodeling activity of NS3 is inhibited by guanidine hydrochloride, an FDA-approved compound, and, more importantly, that it reduces the replication of the norovirus replicon in cultured human cells. Altogether, these findings are the first to demonstrate the presence of RNA-remodeling activities encoded byCaliciviridaeand highlight the functional significance of NS3 in the noroviral life cycle.IMPORTANCENoroviruses are a diverse group of positive-strand RNA viruses, which annually cause hundreds of millions of human infections and over 200,000 deaths worldwide. For RNA viruses, cellular or virus-encoded RNA helicases and/or chaperones have long been considered to play pivotal roles in viral life cycles. However, neither RNA helicase nor chaperoning activity has been demonstrated to be associated with any norovirus-encoded proteins, and it is also unknown whether norovirus replication requires the participation of any viral or cellular RNA helicases/chaperones. We found that a norovirus protein, NS3, not only has ATP-dependent helicase activity, but also acts as an ATP-independent RNA chaperone. Also, NS3 can facilitatein vitroviral RNA synthesis, suggesting the important role of NS3 in norovirus replication. Moreover, NS3 activities can be inhibited by an FDA-approved compound, which also suppresses norovirus replicon replication in human cells, raising the possibility that NS3 could be a target for antinoroviral drug development.

scholarly journals Proteolytic processing of plant proteins by potyvirus NIa proteases

2021 ◽  
Author(s):  
Huogen Xiao ◽  
Etienne Lord ◽  
Hélène Sanfaçon
Keyword(s):  
Virus Infection ◽  
Plant Virus ◽  
Plant Viruses ◽  
Proteolytic Processing ◽  
Plum Pox Virus ◽  
Plant Proteins ◽  
Host Proteins ◽  
Prediction Approach

The NIa protease of potyviruses is a chymotrypsin-like cysteine protease related to the picornavirus 3C protease. It is also a multifunctional protein known to play multiple roles during virus infection. Picornavirus 3C proteases cleave hundreds of host proteins to facilitate virus infection. However, whether or not potyvirus NIa proteases cleave plant proteins has so far not been tested. Regular expression search using the cleavage site consensus sequence [EQN]xVxH[QE]/[SGTA] for the plum pox virus (PPV) protease identified 90-94 putative cleavage events in the proteomes of Prunus persica (a crop severely affected by PPV), Arabidopsis thaliana and Nicotiana benthamiana (two experimental hosts). In vitro processing assays confirmed cleavage of six A. thaliana and five P. persica proteins by the PPV protease. These proteins were also cleaved in vitro by the protease of turnip mosaic virus (TuMV), which has a similar specificity. We confirmed in vivo cleavage of a transiently expressed tagged version of AtEML2, an EMSY-like protein belonging to a family of nuclear histone readers known to be involved in pathogen resistance. Cleavage of AtEML2 was efficient and was observed in plants that co-expressed the PPV or TuMV NIa proteases or in plants that were infected with TuMV. We also show partial in vivo cleavage of AtDUF707, a membrane protein annotated as lysine ketoglutarate reductase trans-splicing protein. Although cleavage of the corresponding endogenous plant proteins remains to be confirmed, the results show that a plant virus protease can cleave host proteins during virus infection and highlight a new layer of plant-virus interactions. Importance Viruses are highly adaptive and use multiple molecular mechanisms to highjack or modify the cellular resources to their advantage. They must also counteract or evade host defense responses. One well-characterized mechanism used by vertebrate viruses is the proteolytic cleavage of host proteins to inhibit the activities of these proteins and/or to produce cleaved protein fragments that are beneficial to the virus infection cycle. Even though almost half of the known plant viruses encode at least one protease, it was not known whether plant viruses employ this strategy. Using an in silico prediction approach and the well-characterized specificity of potyvirus NIa proteases, we were able to identify hundreds of putative cleavage sites in plant proteins, several of which were validated by downstream experiments. It can be anticipated that many other plant virus proteases also cleave host proteins and that the identification of these cleavage events will lead to novel antiviral strategies.

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