Group Of Plant Viruses Research Articles

Three-fold expansion of the genetic diversity of blunerviruses through plant (meta)transcriptome data-mining

Kitaviruses are plant-infecting, non-systemic disease-causing viruses with multipartite single-stranded RNA genomes. Despite their importance, knowledge on kitaviruses is limited in comparison with other plant virus groups, mainly because of the lesser number of identified and characterized kitaviruses and their isolates. In the present study, we explored plant (meta)transcriptome data available in public domain and identified genome sequences of eighteen putative novel blunerviruses in eighteen plant species, including four gymnosperm and four monocot species. Four RNA segments (RNAs 1–4) of eleven identified viruses were recovered, whilst at least two RNA segments were recovered for the remaining viruses. Phylogenetic analysis grouped the identified viruses with known blunerviruses. Based on genome organization, sequence identities of encoded proteins with known blunerviruses and phylogeny, the identified viruses are regarded as new members of the genus Blunervirus. The study paves way for initiating further studies on understanding biological properties, economic importance and geographical distribution of identified blunerviruses.

Exploring Virus Diversity in the Potato leafhopper (Empoasca fabae), an Economically Important Agricultural Pest.

The potato leafhopper (Empoasca fabae, PLH) is a serious pest that feeds on a wide range of agricultural crops and is found throughout the United States but is not known to be a vector for plant-infecting viruses. We probed the diversity of virus sequences in field populations of PLH collected from four Midwestern states: Illinois, Indiana, Iowa, and Minnesota. High-throughput sequencing data from total RNAs extracted from PLH were used to assemble sequences of fifteen positive-stranded RNA viruses, two negative-stranded RNA viruses, and one DNA virus. These sequences included ten previously described plant viruses and eight putative insect-infecting viruses. All but one of the insect-specific viruses were novel and included three solemoviruses, one iflavirus, one phenuivirus, one lispivirus, and one ambidensovirus. Detailed analyses of the novel genome sequences and their evolutionary relationships with related family members were conducted. Our study revealed a diverse group of plant viruses circulating in the PLH population and discovered novel insect viruses, expanding knowledge on the untapped virus diversity in economically important crop pests. Our findings also highlight the importance of monitoring the emergence and circulation of plant-infecting viruses in agriculturally important arthropod pests.

Plant Immunity against Tobamoviruses.

Tobamoviruses are a group of plant viruses that pose a significant threat to agricultural crops worldwide. In this review, we focus on plant immunity against tobamoviruses, including pattern-triggered immunity (PTI), effector-triggered immunity (ETI), the RNA-targeting pathway, phytohormones, reactive oxygen species (ROS), and autophagy. Further, we highlight the genetic resources for resistance against tobamoviruses in plant breeding and discuss future directions on plant protection against tobamoviruses.

Identification and characterization of two closely related virga-like viruses latently infecting rubber trees (Hevea brasiliensis).

A novel virga-like virus, provisionally named Rubber tree latent virus 2 (RTLV2), was identified from rubber tree (Hevea brasiliensis). It is a close relative of the previously reported Rubber tree latent virus 1 (RTLV1). The complete genomes of RTLV1 and RTLV2 were sequenced and comparatively analyzed in terms of genome organization, putative gene products and phylogenetic relationship. Both RTLV1 and RTLV2 have positive-sense single-stranded RNA genomes that encode seven open reading frames (ORFs), forming a similar genomic layout. In phylogenetic analyses based on replicase and coat protein amino acid sequences, RTLV1 and RTLV2 were clustered with unclassified virga-like viruses. They are distinct from currently recognized plant virus families. RTLV1 and RTLV2 can be distinguished from members of Virgaviridae by the presence of a putative coat protein duplex and a poly(A) tail at the 3'-terminus. The authenticity of RTLV1 and RTLV2 as infectious viruses was confirmed through field investigations and transmissibility assays. In conclusion, RTLV1 and RTLV2 represent a novel plant virus group that does not readily fit into current virus families.

Current status, breeding strategies and future prospects for managing chilli leaf curl virus disease and associated begomoviruses in Chilli (Capsicum spp.).

Chilli leaf curl virus disease caused by begomoviruses, has emerged as a major threat to global chilli production, causing severe yield losses and economic harm. Begomoviruses are a highly successful and emerging group of plant viruses that are primarily transmitted by whiteflies belonging to the Bemisia tabaci complex. The most effective method for mitigating chilli leaf curl virus disease losses is breeding for host resistance to Begomovirus. This review highlights the current situation of chilli leaf curl virus disease and associated begomoviruses in chilli production, stressing the significant issues that breeders and growers confront. In addition, the various breeding methods used to generate begomovirus resistant chilli cultivars, and also the complicated connections between the host plant, vector and the virus are discussed. This review highlights the importance of resistance breeding, emphasising the importance of multidisciplinary approaches that combine the best of traditional breeding with cutting-edge genomic technologies. subsequently, the article highlights the challenges that must be overcome in order to effectively deploy begomovirus resistant chilli varieties across diverse agroecological zones and farming systems, as well as understanding the pathogen thus providing the opportunities for improving the sustainability and profitability of chilli production.

WRKY1 represses the WHIRLY1 transcription factor to positively regulate plant defense against geminivirus infection.

Geminiviruses constitute the largest group of known plant viruses and cause devastating diseases and economic losses in many crops worldwide. Due to limited naturally occurring resistance genes, understanding plant antiviral defense against geminiviruses is critical for finding host factors of geminiviruses and development of strategies for geminivirus control. Here we identified NbWRKY1 as a positive regulator of plant defense against geminivirus infection. Using tomato yellow leaf curl China virus/tomato yellow leaf curl China betasatellite (TYLCCNV/TYLCCNB) as a representative geminivirus, we found that NbWRKY1 was upregulated in response to TYLCCNV/TYLCCNB infection. Overexpression of NbWRKY1 attenuated TYLCCNV/TYLCCNB infection, whereas knockdown of NbWRKY1 enhanced plant susceptibility to TYLCCNV/TYLCCNB. We further revealed that NbWRKY1 bound to the promoter of the NbWHIRLY1 (NbWhy1) transcription factor and inhibited the transcription of NbWhy1. Consistently, NbWhy1 negatively regulates plant response against TYLCCNV/TYLCCNB. Overexpression of NbWhy1 significantly accelerated TYLCCNV/TYLCCNB infection. Conversely, knockdown of NbWhy1 led to impaired geminivirus infection. Furthermore, we demonstrated that NbWhy1 interfered with the antiviral RNAi defense and disrupted the interaction between calmodulin 3 and calmodulin-binding transcription activator-3. Moreover, the NbWRKY1-NbWhy1 also confers plant antiviral response toward tomato yellow leaf curl virus infection. Taken together, our findings suggest that NbWRKY1 positively regulates plant defense to geminivirus infection by repressing NbWhy1. We propose that the NbWRKY1-NbWhy1 cascade could be further employed to control geminiviruses.

Occurrence and distribution of geminiviruses in China

Geminiviruses are a group of plant viruses that cause severe diseases in many economically important crops worldwide, leading to devastating losses to agricultural production. Here we summarize the occurrence and distribution of geminiviruses in China, which provides valuable information for further epidemiological studies and supports the development of effective disease management strategies.

ABA INSENSITIVE 5 confers geminivirus resistance via suppression of the viral promoter activity in plants

Geminiviruses are a large group of plant viruses that have been a serious threat to worldwide agriculture. Transcription of the virus-encoded genes is necessary for geminiviruses to complete their life cycle, but the host proteins which directly target geminivirus promoters for suppression of viral gene transcription remain to be identified. Using Beet severe curly top virus (BSCTV) which causes severe plant symptoms as a system, we performed a yeast one-hybrid screening and identified ABA INSENSITIVE 5 (ABI5), a critical transcription factor in Abscisic acid (ABA) signaling transduction, as an interactor with the viral promoter. Further data showed that an ABA-responsive element in the viral promoter is necessary for its interaction with ABI5 and symptom development. Overexpression of ABI5 suppresses the transcription activity of the viral promoter and BSCTV infection in Nicotiana benthamiana and Arabidopsis; whilst depletion of ABI5 enhances the infection of BSCTV in Arabidopsis. Taken together, our study uncovered the function of ABI5 in the plant-virus interaction and will provide us with a new strategy to protect crops from geminivirus infection.

Short 5' Untranslated Region Enables Optimal Translation of Plant Virus Tricistronic RNA via Leaky Scanning.

Regardless of the general model of translation in eukaryotic cells, a number of studies suggested that many mRNAs encode multiple proteins. Leaky scanning, which supplies ribosomes to downstream open reading frames (ORFs) by readthrough of upstream ORFs, has great potential to translate polycistronic mRNAs. However, the mRNA elements controlling leaky scanning and their biological relevance have rarely been elucidated, with exceptions such as the Kozak sequence. Here, we have analyzed the strategy of a plant RNA virus to translate three movement proteins from a single RNA molecule through leaky scanning. The in planta and in vitro results indicate thatthe significantly shorter 5' untranslated region (UTR) of the most upstream ORF promotes leaky scanning, potentially fine-tuning the translation efficiency of the three proteins in a single RNA molecule to optimize viral propagation. Our results suggest that the remarkably short length of the leader sequence, like the Kozak sequence, is a translational regulatory element with a biologically important role, as previous studies have shown biochemically. IMPORTANCEPotexvirus, a group of plant viruses, infect a variety of crops, including cultivated crops. It has been thought that the three transition proteins that are essential for the cell-to-cell transfer of potexviruses are translated from two subgenomic RNAs, sgRNA1 and sgRNA2. However, sgRNA2 has not been clearly detected. In this study, we have shown that sgRNA1, but not sgRNA2, is the major translation template for the three movement proteins. In addition, we determined the transcription start site of sgRNA1 in flexiviruses and found that the efficiency of leaky scanning caused by the short 5' UTR of sgRNA1, a widely conserved feature, regulates the translation of the three movement proteins. When we tested the infection of viruses with mutations introduced into the length of the 5' UTR, we found that the movement efficiency of the virus was affected. Our results provide important additional information on the protein translation strategy of flexiviruses, including Potexvirus, and provide a basis for research on their control as well as the need to reevaluate the short 5' UTR as a translational regulatory element with an important role in vivo.

Presence of a Mitovirus Is Associated with Alteration of the Mitochondrial Proteome, as Revealed by Protein-Protein Interaction (PPI) and Co-Expression Network Models in Chenopodium quinoa Plants.

Simple SummaryPlants often harbor persistent plant virus infection transmitted only vertically through seeds, resulting in no obvious symptoms (cryptic infections). Several studies have shown that such cryptic infections provide resilience against abiotic (and biotic) stress. We have recently discovered a new group of cryptic plant viruses infecting mitochondria (plant mitovirus). Mitochondria are cellular organelles displaying a pivotal role in protecting cells from the stress of nature . Here, we look at the proteomic alterations caused by the mitovirus cryptic infection of Chenopodium quinoa by Systems Biology approaches allowing one to evaluate data at holistic level. Quinoa is a domesticated plant species with many exciting features of abiotic stress resistance, and it is distinguished by its exceptional nutritional characteristics, such as the content and quality of proteins, minerals, lipids, and tocopherols. These features determined the growing interest for the quinoa crop by the scientific community and international organizations since they provide opportunities to produce high-value grains in arid, high-salt and high-UV agroecological environments. We discovered that quinoa lines hosting mitovirus activate some metabolic processes that might help them face drought. These findings present a new perspective for breeding crop plants through the augmented genome provided by accessory cryptic viruses to be investigated in the future.Plant mitoviruses belong to Mitoviridae family and consist of positive single-stranded RNA genomes replicating exclusively in host mitochondria. We previously reported the biological characterization of a replicating plant mitovirus, designated Chenopodium quinoa mitovirus 1 (CqMV1), in some Chenopodium quinoa accessions. In this study, we analyzed the mitochondrial proteome from leaves of quinoa, infected and not infected by CqMV1. Furthermore, by protein–protein interaction and co-expression network models, we provided a system perspective of how CqMV1 affects mitochondrial functionality. We found that CqMV1 is associated with changes in mitochondrial protein expression in a mild but well-defined way. In quinoa-infected plants, we observed up-regulation of functional modules involved in amino acid catabolism, mitochondrial respiratory chain, proteolysis, folding/stress response and redox homeostasis. In this context, some proteins, including BCE2 (lipoamide acyltransferase component of branched-chain alpha-keto acid dehydrogenase complex), DELTA-OAT (ornithine aminotransferase) and GR-RBP2 (glycine-rich RNA-binding protein 2) were interesting because all up-regulated and network hubs in infected plants; together with other hubs, including CAT (catalase) and APX3 (L-ascorbate peroxidase 3), they play a role in stress response and redox homeostasis. These proteins could be related to the higher tolerance degree to drought we observed in CqMV1-infected plants. Although a specific causative link could not be established by our experimental approach at this stage, the results suggest a new mechanistic hypothesis that demands further in-depth functional studies.

Alternanthera yellow vein virus (AYVV); a betasatellite independent begomovirus infecting Sonchus palustris in Pakistan.

Satellites associated begomoviruses are the most diverse group of plant viruses in tropical and subtropical regions. In Pakistan, during field surveys in 2019-2020, Sonchus palustris (a weed plant) was observed showing begomovirus symptoms i.e., vein yellowing and mosaic patterns on leaves. Rolling circle amplification from total isolated DNA of symptomatic leaves was performed to amplify circular viral genomes. Subsequent cloning and sequencing showed that a new strain of Alternanthera yellow vein virus (AlYVV) is associated with vein yellowing disease of S. palustris. The identity percentage analysis through BLAST search and SDT analysis showed that the new strain is 94-98% identical to AlYVV isolates reported from Pakistan, India and China. In phylogenetic tree, it clustered with AlYVV-[PK:E prostrata:15-KX710155], AlYVV-[PK:E prostrata:13]-KX906697] and AlYVV-[PK:E prostrata:11]-KX906694] previously reported from Pakistan. There was no detectable level of betasatellite or any other satellite molecule in the samples studied here. Phylogenetic analysis of Rep and CP genes of AlYVV with corresponding genes of closely related viruses circulating in Southeast Asia showed intra-specific recombination involving both complementary and virion sense region of virus. Relaxed clock and Bayesian Skyline Plot analysis based on CP gene sequences indicated slight higher substitution rates (4.75 x 10-3 substitutions/nucleotide/year). In the Indian subcontinent satellite-associated monopartite begomoviruses predominately infect crops and non-crop plants. But AlYVV is found infecting mostly non-crop plants independent of satellite molecules. We hypothesize here that AlYVV evolved as a true monopartite begomovirus in the Indian sub-continent and could be a great threat to introduced crops under suitable conditions. Such studies are crucial to understand probable future epidemics of begomoviruses in the region.

Top Three Strategies of ss(+)RNA Plant Viruses: Great Opportunists and Ecosystem Tuners with a Small Genome

ss(+)RNA viruses represent the dominant group of plant viruses. They owe their evolutionary superiority to the large number of mutations that occur during replication, courtesy of RNA-dependent RNA polymerase. Natural selection rewards successful viral subtypes, whose effective tuning of the ecosystem regulates the interactions between its participants. Thus, ss(+)RNA viruses act as shuttles for the functionally important genes of the participants in symbiotic relationships within the ecosystem, of which the most common ecological triad is “plant–virus–insect”. Due to their short life cycle and large number of offspring, RNA viruses act as skillful tuners of the ecosystem, which benefits both viruses and the system as a whole. A fundamental understanding of this aspect of the role played by viruses in the ecosystem makes it possible to apply this knowledge to the creation of DNA insecticides. In fact, since the genes that viruses are involved in transferring are functionally important for both insects and plants, silencing these genes (for example, in insects) can be used to regulate the pest population. RNA viruses are increasingly treated not as micropathogens but as necessary regulators of ecosystem balance.

A group I WRKY transcription factor regulates mulberry mosaic dwarf-associated virus-triggered cell death in Nicotiana benthamiana.

Geminiviruses constitute the largest group of known plant viruses and cause devastating losses to a wide range of crops and woody plants globally. Mulberry mosaic dwarf‐associated virus (MMDaV), identified from Chinese mulberry trees via small RNA‐based deep sequencing, is a divergent monopartite geminivirus belonging to the genus Mulcrilevirus of the family Geminiviridae. Previous studies have shown that plants employ multiple layers of defence to protect themselves from geminivirus infection. The interplay between plant and MMDaV is nevertheless less studied. This study presents evidence that MMDaV triggers hypersensitive response (HR)‐mediated antiviral defence in Nicotiana benthamiana plants. We show that the RepA protein of MMDaV is engaged in HR‐type cell death induction. We find that the RepA mutants with compromised nuclear localization ability impair their capabilities of cell death induction. Virus‐induced gene silencing of the key components of the R protein‐mediated signalling pathway reveals that down‐regulation of the nucleus‐targeting NbWRKY1 alleviates the cell death induction activity of RepA. We further demonstrate that RepA up‐regulates the transcript level of NbWRKY1. Furthermore, expression of RepA in N. benthamiana confers plant resistance against two begomoviruses. We propose that plant resistance against RepA can be potentially used to improve plant defence against geminiviruses in crops.

Illuminating the Plant Rhabdovirus Landscape through Metatranscriptomics Data.

Rhabdoviruses infect a large number of plant species and cause significant crop diseases. They have a negative-sense, single-stranded unsegmented or bisegmented RNA genome. The number of plant-associated rhabdovirid sequences has grown in the last few years in concert with the extensive use of high-throughput sequencing platforms. Here, we report the discovery of 27 novel rhabdovirus genomes associated with 25 different host plant species and one insect, which were hidden in public databases. These viral sequences were identified through homology searches in more than 3000 plant and insect transcriptomes from the National Center for Biotechnology Information (NCBI) Sequence Read Archive (SRA) using known plant rhabdovirus sequences as the query. The identification, assembly and curation of raw SRA reads resulted in sixteen viral genome sequences with full-length coding regions and ten partial genomes. Highlights of the obtained sequences include viruses with unique and novel genome organizations among known plant rhabdoviruses. Phylogenetic analysis showed that thirteen of the novel viruses were related to cytorhabdoviruses, one to alphanucleorhabdoviruses, five to betanucleorhabdoviruses, one to dichorhaviruses and seven to varicosaviruses. These findings resulted in the most complete phylogeny of plant rhabdoviruses to date and shed new light on the phylogenetic relationships and evolutionary landscape of this group of plant viruses. Furthermore, this study provided additional evidence for the complexity and diversity of plant rhabdovirus genomes and demonstrated that analyzing SRA public data provides an invaluable tool to accelerate virus discovery, gain evolutionary insights and refine virus taxonomy.

Infectious clone construction and pathogenicity confirmation of Cotton leaf curl Multan virus (CLCuMuV), Ramie mosaic virus (RamV) and Corchorus yellow vein Vietnam virus (CoYVV) by southern blot analysis.

Geminiviruses are insect-transmissible, economically vital group of plant viruses, which cause significant losses to crop production and ornamental plants across the world. During this study, infectious clones of three devastating begomoviruses, i.e., Cotton leaf curl Multan virus (CLCuMuV), Ramie mosaic virus (RamV) and Corchorus yellow vein Vietnam virus (CoYVV) were constructed by following novel protocol. All infectious clones were confirmed by cloning and sequencing. All of the infectious clones were agro-inoculated in Agrobacterium. After the agro-infiltrations, all clones were injected into Nicotiana benthamiana and jute plants under controlled condition. After 28 days of inoculation, plants exhibited typical symptoms of their corresponding viruses. All the symptomatic and asymptomatic leaves were collected from inoculated plants for further analysis. The southern blot analysis was used to confirm the infection of studied begomoviruses. At the end, all the products were sequenced and analyzed.

Research Advances in Potyviruses: From the Laboratory Bench to the Field.

Potyviruses (viruses in the genus Potyvirus, family Potyviridae) constitute the largest group of known plant-infecting RNA viruses and include many agriculturally important viruses that cause devastating epidemics and significant yield losses in many crops worldwide. Several potyviruses are recognized as the most economically important viral pathogens. Therefore, potyviruses are more studied than other groups of plant viruses. In the past decade, a large amount of knowledge has been generated to better understand potyviruses and their infection process. In this review, we list the top 10 economically important potyviruses and present a brief profile of each. We highlight recent exciting findings on the novel genome expression strategy and the biological functions of potyviral proteins and discuss recent advances in molecular plant-potyvirus interactions, particularly regarding the coevolutionary arms race. Finally, we summarize current disease control strategies, with a focus on biotechnology-based genetic resistance, and point out future research directions.

A proteomic approach reveals possible molecular mechanisms and roles for endosymbiotic bacteria in begomovirus transmission by whiteflies.

BackgroundMany plant viruses are vector-borne and depend on arthropods for transmission between host plants. Begomoviruses, the largest, most damaging and emerging group of plant viruses, infect hundreds of plant species, and new virus species of the group are discovered each year. Begomoviruses are transmitted by members of the whitefly Bemisia tabaci species complex in a persistent-circulative manner. Tomato yellow leaf curl virus (TYLCV) is one of the most devastating begomoviruses worldwide and causes major losses in tomato crops, as well as in many agriculturally important plant species. Different B. tabaci populations vary in their virus transmission abilities; however, the causes for these variations are attributed among others to genetic differences among vector populations, as well as to differences in the bacterial symbionts housed within B. tabaci.ResultsHere, we performed discovery proteomic analyses in 9 whitefly populations from both Middle East Asia Minor I (MEAM1, formerly known as B biotype) and Mediterranean (MED, formerly known as Q biotype) species. We analysed our proteomic results on the basis of the different TYLCV transmission abilities of the various populations included in the study. The results provide the first comprehensive list of candidate insect and bacterial symbiont (mainly Rickettsia) proteins associated with virus transmission.ConclusionsOur data demonstrate that the proteomic signatures of better vector populations differ considerably when compared with less efficient vector populations in the 2 whitefly species tested in this study. While MEAM1 efficient vector populations have a more lenient immune system, the Q efficient vector populations have higher abundance of proteins possibly implicated in virus passage through cells. Both species show a strong link of the facultative symbiont Rickettsia to virus transmission.

Divergent Symptoms Caused by Geminivirus-Encoded C4 Proteins Correlate with Their Ability To Bind NbSKη.

Geminiviruses induce severe developmental abnormalities in plants. The C4/AC4 protein encoded by geminiviruses, especially those not associated with betasatellites, functions as a symptom determinant by hijacking a shaggy-related protein kinase (SKη) and interfering with its functions. Here, we report that the symptom determinant capabilities of C4 proteins encoded by different geminiviruses are divergent and tightly correlated with their abilities to interact with SKη from Nicotiana benthamiana (NbSKη). Swap of the minidomain of tomato leaf curl Yunnan virus (TLCYnV) C4 critical for the interaction with NbSKη increases the capacities of the C4 proteins encoded by tomato yellow leaf curl China virus (TYLCCNV) or tobacco curly shoot virus (TbCSV) to induce symptoms. The severity of symptoms induced by recombinant TYLCCNV C4 or TbCSV C4 correlates with the amount of NbSKη tethered to the plasma membrane by the viral protein. Moreover, a recombinant TYLCCNV harboring the minidomain of TLCYnV C4 induces more-severe symptoms than wild-type TYLCCNV. Thus, this study provides new insights into the mechanism by which different geminivirus-encoded C4 proteins possess divergent symptom determinant capabilities.IMPORTANCE Geminiviruses constitute the largest group of known plant viruses and cause devastating diseases in many economically important crops worldwide. Geminivirus-encoded C4 protein is a multifunctional protein. In this study, we found that the C4 proteins from different geminiviruses showed differential abilities to interact with NbSKη, which correlated with their symptom determinant capabilities. Moreover, a minidomain of tomato leaf curl Yunnan virus (TLCYnV) C4 that is indispensable for interacting with NbSKη and tethering it to the plasma membrane, thus leading to symptom induction, was determined. Supporting these findings, a recombinant geminivirus carrying the minidomain of TLCYnV C4 induced more-severe symptoms than the wild type. Therefore, these findings expand the scope of the interaction of NbSKη and C4-mediated symptom induction and thus contribute to further understanding of the multiple roles of C4.

Geminiviruses: Taxonomic Structure and Diversity in Genomic Organization.

Geminiviridae is one of the best-characterized and hence, one of the largest plant-virus families with the highest economic importance. Its members characteristically have a circular ssDNA genome within the encapsidation of twinned quasi-icosaheadral virions (18-38 nm size-range). Construction of a narrative review on geminiviruses, to have a clearer picture of their genomic structure and taxonomic status. A thorough search was conducted for papers and patents regarding geminiviruses, where relevant information was used to study their genomic organization, diversity and taxonomic structure. Geminiviruses have been classified into nine genera (viz., genus Begomovirus, Mastrevirus, Curtovirus, Topocuvirus, Becurtovirus, Turncurtovirus, Capulavirus, Eragrovirus and Grablovirus) having distinct genomic organizations, host ranges and insect vectors. Genomic organization of all genera generally shows the presence of 4-6 ORFs encoding for various proteins. For now, Citrus chlorotic dwarf-associated virus (CCDaV), Camellia chlorotic dwarf-associated virus (CaCDaV) and few other geminiviruses are still unassigned to any genera. The monopartite begomoviruses (and few mastreviruses) have been found associated with aplhasatellites and betasatellites (viz., ~1.3 kb circular ssDNA satellites). Recent reports suggest that deltasatellites potentially reduce the accumulation of helper-Begomovirus species in host plants. Some patents have revealed the methods to generate transgenic plants resistant to geminiviruses. Geminiviruses rapidly evolve and are a highly diverse group of plant-viruses. However, research has shown new horizons in tackling the acute begomoviral diseases in plants by generating a novel bio-control methodology in which deltasatellites can be used as bio-control agents and generate transgenic plants resistant to geminiviruses.

Structure of Turnip mosaic virus and its viral-like particles

Turnip mosaic virus (TuMV), a potyvirus, is a flexible filamentous plant virus that displays a helical arrangement of coat protein copies (CPs) bound to the ssRNA genome. TuMV is a bona fide representative of the Potyvirus genus, one of most abundant groups of plant viruses, which displays a very wide host range. We have studied by cryoEM the structure of TuMV virions and its viral-like particles (VLPs) to explore the role of the interactions between proteins and RNA in the assembly of the virions. The results show that the CP-RNA interaction is needed for the correct orientation of the CP N-terminal arm, a region that plays as a molecular staple between CP subunits in the fully assembled virion.