Potato leafroll virus reduces Buchnera aphidocola titer and alters vector transcriptome responses

Viruses in the Luteoviridae family, such as Potato leafroll virus (PLRV), are transmitted by aphids in a circulative and nonpropagative mode. This means the virions enter the aphid body through the gut when they feed from infected plants and then the virions circulate through the hemolymph to enter the salivary glands before being released into the saliva. Although these viruses do not replicate in their insect vectors, previous studies have demonstrated viruliferous aphid behavior is altered and the obligate symbiont of aphids, Buchnera aphidocola, may be involved in transmission. Here we provide the transcriptome of green peach aphids (Myzus persicae) carrying PLRV and virus-free control aphids using Illumina sequencing. Over 150 million paired-end reads were obtained through Illumina sequencing, with an average of 19 million reads per library. The comparative analysis identified 134 differentially expressed genes (DEGs) between the M. persicae transcriptomes, including 64 and 70 genes that were up- and down-regulated in aphids carrying PLRV, respectively. Using functional classification in the GO databases, 80 of the DEGs were assigned to 391 functional subcategories at category level 2. The most highly up-regulated genes in aphids carrying PLRV were cytochrome p450s, genes related to cuticle production, and genes related to development, while genes related to heat shock proteins, histones, and histone modification were the most down-regulated. PLRV aphids had reduced Buchnera titer and lower abundance of several Buchnera transcripts related to stress responses and metabolism. These results suggest carrying PLRV may reduce both aphid and Buchnera genes in response to stress. This work provides valuable basis for further investigation into the complicated mechanisms of circulative and nonpropagative transmission.

Nanobiotechnological Approaches to Enhance Potato Resistance against Potato Leafroll Virus (PLRV) Using Glycyrrhizic Acid Ammonium Salt and Salicylic Acid Nanoparticles

The present research was aiming to study In-Silico the effect of Glycyrrhizic Acid ammonium salt (GAS) and Salicylic acid (SA) on the coat protein of potato leafroll virus (PLRV). In addition, in-vitro studying the effect of (GAS NPs) and Salicylic acid (SA NPs) nanoparticles at concentrations 0.15, 0.30, 1.25 and 2.5 mM, respectively, to control, decline or reduce the presence of PLRV in potato plants Solanum tuberosum L. selena. (GAS NPs) and (SA NPs) were applied in the MS medium at concentrations 0.15, 0.30, 1.25 and 2.5 mM, respectively. Results revealed that, enhancement or decline the PLRV according to the initiation of specific pathways. The expression level of Kinase 3 gene increased significantly due to the two used concentrations of GAS NPs. While the expression of callose gene was upregulated significantly in response to treatment of PLRV infected plant with (GAS NPs) with concentration (0.30 mM). Treatment with (SA NPs) caused upregulation significance only of callose gene at (2.5 mM) concentration. The molecular modeling results of used compounds (glycyrrhizic acid ammonium salt and salicylic acid) showed highest score of binding and the best rms define value with a very good binding mode and perfect interactions with amino acids of the three subunits (A, B and C) forming the protein coat of leaf roll virus. Glycyrrhizic acid ammonium salt and salicylic acid nanoparticles could be perfect solution to produce potato plant free virus in-vitro. Further larger studies are needed to investigate the role of the studied compounds in vivo.

Crystal structure of the potato leafroll virus coat protein and implications for viral assembly

Luteoviruses, poleroviruses, and enamoviruses are insect-transmitted, agricultural pathogens that infect a wide array of staple food crops. Previous cryo-electron microscopy studies of virus-like particles indicate that luteovirid viral capsids are built from a structural coat protein that organizes with T=3 icosahedral symmetry. Here we present the crystal structure of a truncated version of the coat protein monomer from potato leafroll virus at 1.57-Å resolution. In the crystal lattice, monomers pack into flat sheets that preserve the two-fold and three-fold axes of icosahedral symmetry and show minimal structural deviations when compared to the full-length subunits of the assembled virus-like particle. These observations have important implications in viral assembly and maturation, suggesting that the CP N-terminus and its interactions with RNA serve as a key driver for generating capsid curvature.

The green peach aphid, Myzus persicae, transcriptome in response to a circulative, nonpropagative polerovirus, Potato leafroll virus.

Viruses in the Luteoviridae family, such as Potato leafroll virus (PLRV), are transmitted by aphids in a circulative and nonpropagative mode. This means the virions enter the aphid body through the gut when they feed from infected plants and then the virions circulate through the hemolymph to enter the salivary glands before being released into the saliva. Although these viruses do not replicate in their insect vectors, previous studies have demonstrated viruliferous aphid behavior is altered and the obligate symbiont of aphids, Buchnera aphidocola, may be involved in transmission. Here we provide the transcriptome of green peach aphids (Myzus persicae) carrying PLRV and virus-free control aphids using Illumina sequencing. Over 150 million paired-end reads were obtained through Illumina sequencing, with an average of 19 million reads per library. The comparative analysis identified 134 differentially expressed genes (DEGs) between the M. persicae transcriptomes, including 64 and 70 genes that were down- and up-regulated in aphids carrying PLRV, respectively. Using functional classification in the GO databases, 80 of the DEGs were assigned to 391 functional subcategories at category level 2. The most highly up-regulated genes in aphids carrying PLRV were cytochrome p450s, genes related to cuticle production, and genes related to development, while genes related to histone and histone modification were the most down-regulated. PLRV aphids had reduced Buchnera titer and lower abundance of several Buchnera transcripts related to stress responses and metabolism. These results suggest carrying PLRV may reduce both aphid and Buchnera genes in response to stress. This work provides valuable basis for further investigation into the complicated mechanisms of circulative and nonpropogative transmission.

The innate immunity protein C1QBP functions as a negative regulator of circulative transmission of Potato leafroll virus by aphids

ABSTRACTThe vast majority of plant viruses are transmitted by insect vectors with many crucial aspects of the transmission process being mediated by key protein-protein interactions. Yet, very few vector proteins interacting with virus have been identified and functionally characterized. Potato leafroll virus (PLRV) is transmitted most effectively by Myzus persicae, the green peach aphid, in a circulative, non-propagative manner. Using an affinity purification strategy coupled to high-resolution mass spectrometry (AP-MS), we identified 11 proteins from M. persicae displaying high probability of interaction with PLRV and an additional 23 vector proteins with medium confidence interaction scores. Two of these proteins were confirmed to directly interact with the structural proteins of PLRV and other luteovirid species via yeast two-hybrid with an additional vector protein displaying binding specificity. Immunolocalization of one of these direct PLRV-interacting proteins, an orthologue of the human innate immunity protein complement component 1 Q subcomponent-binding protein (C1QBP), shows that MpC1QBP partially co-localizes with PLRV within cytoplasmic puncta and along the periphery of aphid gut epithelial cells. Chemical inhibition of C1QBP in the aphid leads to increased PLRV acquisition and subsequently increased titer in inoculated plants, supporting the role of C1QBP as a negative regulator of PLRV accumulation in M. persicae. We hypothesize that the innate immune function of C1QBP is conserved in aphids and represents the first instance of aphids mounting an immune response to a non-propagative plant virus. This study presents the first use of AP-MS for the in vivo isolation of functionally relevant insect vector-virus protein complexes.

Inhibition of potato leafroll virus multiplication and systemic translocation by siRNA constructs against putative ATPase fold of movement protein

Viruses cause many severe plant diseases, resulting in immense losses of crop yield worldwide. Therefore, developing novel approaches to control plant viruses is crucial to meet the demands of a growing world population. Recently, RNA interference (RNAi) has been widely used to develop virus-resistant plants. Once genome replication and assembly of virion particles is completed inside the host plant, mature virions or sometimes naked viral genomes spread cell-to-cell through plasmodesmata by interacting with the virus-encoded movement protein (MP). We used the RNAi approach to suppress MP gene expression, which in turn prevented potato leafroll virus (PLRV) systemic infection in Solanum tuberosum cv. Khufri Ashoka. Potato plants agroinfiltrated with MP siRNA constructs exhibited no rolling symptoms upon PLRV infection, indicating that the silencing of MP gene expression is an efficient method for generating PLRV-resistant potato plants. Further, we identified novel ATPase motifs in MP that may be involved in DNA binding and translocation through plasmodesmata. We also showed that the ATPase activity of MP was stimulated in the presence of DNA/RNA. Overall, our findings provide a robust technology to generate PLRV-resistant potato plants, which can be extended to other species. Moreover, this approach also contributes to the study of genome translocation mechanisms of plant viruses.

Potato virus Y and Potato leafroll virus management under climate change in sub-Saharan Africa

Potato has increased in importance as a staple food in sub-Saharan Africa, where its production is faced with a multitude of challenges, including plant disease development and spread under changing climatic conditions. The economically most important plant viruses affecting potatoes globally are Potato virus Y (PVY) and Potato leafroll virus (PLRV). Disease management relies mostly on the use of insecticides, cultural control and seed certification schemes. A major obstacle in many sub-Saharan Africa countries is the availability of disease-free quality seed potatoes. Establishment and implementation of quality control through specialised seed production systems and certification schemes is critical to improve seed potato quality and reduce PVY and PLRV sources. Seed could be further improved by breeding virus-resistant varieties adapted to different environmental conditions combined with management measures tailored for smallholder or commercial farmers to specific agricultural requirements. Innovative technologies – including more sensitive testing, remote sensing, machine learning and predictive models – provide new tools for the management of PVY and PLRV, but require support for adoption and implementation in sub-Saharan Africa.