Genome Reconstruction of Grapevine Virus M and In Silico miRNA Prediction for Sequence-Specific Gene Silencing.

Understanding the dissemination of viruses and viroids identified through virome analysis of major grapevine rootstocks and RPA-based detection of prevalent grapevine virus B

Pathogen‐tested material of grapevine varieties and rootstocks

Grapevine is one of the most economically important fruit crops cultivated worldwide. However, grapevine is highly susceptible to virus infections and exposed to the most diverse forms of viral diseases compared to other fruit crops, and virus-induced incompatibility affects plant growth to different degrees ranging from decline to death. The influence of virus-induced incompatibility could be mitigated to an acceptable level by using appropriate rootstocks. However, the viral tolerance of various grapevine rootstocks with diverse genetic backgrounds remains unclear, along with the identification of the specific viral tolerance factors. In this study, the viral tolerance of 21 grapevine rootstocks was evaluated in a green grafting system. Cabernet Franc varieties infected with a single virus [grapevine leafroll associated virus-1 (GLRaV-1)], a co-infection of two viruses (GLRaV-1 plus grapevine virus A—GVA), and no infection were used as the scions, respectively. The vegetative growth and photosynthetic function of the grafts were analyzed 4 months after grafting. The results indicated that some rootstocks could alleviate the influence of the virus infection, with vegetative growth and photosynthetic function sustained at a normal level, whereas other rootstocks were susceptible to the virus infection, resulting in a decline in the growth and photosynthetic function of the grafts. Our research provides evidence for the existence and diversity of viral tolerance among grapevine rootstocks, offering important information for appropriate rootstock selection in the establishment of new vineyards and in the breeding of grapevine rootstocks with enhanced viral tolerance.

Virology meets Proteomics.

Viral infections cause profound alterations in host cells. Here, we explore the interactions between proteins of the Alphavirus Sindbis and host factors during the course of mammalian cell infection. Using a mutant virus expressing the viral nsP3 protein tagged with green fluorescent protein (GFP) we directly observed nsP3 localization and isolated nsP3-interacting proteins at various times after infection. These results revealed that host factor recruitment to nsP3-containing complexes was time dependent, with a specific early and persistent recruitment of G3BP and a later recruitment of 14-3-3 proteins. Expression of GFP-tagged G3BP allowed reciprocal isolation of nsP3 in Sindbis infected cells, as well as the identification of novel G3BP-interacting proteins in both uninfected and infected cells. Note-worthy interactions include nuclear pore complex components whose interactions with G3BP were reduced upon Sindbis infection. This suggests that G3BP is a nuclear transport factor, as hypothesized previously, and that viral infection may alter RNA transport. Immunoelectron microscopy showed that a portion of Sindbis nsP3 is localized at the nuclear envelope, suggesting a possible site of G3BP recruitment to nsP3-containing complexes. Our results demonstrate the utility of using a standard GFP tag to both track viral protein localization and elucidate specific viral-host interactions over time in infected mammalian cells.

As the knowledge of biomolecules is increasing from the last decades, it is helping the researchers to understand the unsolved issues regarding virology. Recent technologies in high-throughput sequencing are providing the swift generation of SARS-CoV-2 genomic data with the basic inside of viral infection. Owing to various virus-host protein interactions, high-throughput technologies are unable to provide complete details of viral pathogenesis. Identifying the virus-host protein interactions using bioinformatics approaches can assist in understanding the mechanism of SARS-CoV-2 infection and pathogenesis. In this chapter, recent integrative bioinformatics approaches are discussed to help the virologists and computational biologists in the identification of structurally similar proteins of human and SARS-CoV-2 virus, and to predict the potential of virus-host interactions. Considering experimental and time limitations for effective viral drug development, computational aided drug design (CADD) can reduce the gap between drug prediction and development. More research with respect to evolutionary solutions could be helpful to make a new pipeline for virus-host protein-protein interactions and provide more understanding to disclose the cases of host switch, and also expand the virulence of the pathogen and host range in developing viral infections.

ABSTRACTIn accordance with the European Legislation and the recently developed national system for production of certified vine growing material, 1295 samples from grapevine varieties and rootstocks were checked for their virus status in the period of 2004–2006. The results obtained showed that total of 30.50% of the ELISA tested Vitis vinifera vines and rootstocks were infected by one (86.08%) or more viruses (13.92). The most widespread virus was Grapevine flack virus (GFkV) (23.3%), followed by Grapevine fanleaf virus (GFLV) (5.05%) and Grapevine leafroll associated viruses 1 and 3 (GLRaV 1 and 3) (3.34% and 2.78%), respectively. Grapevine Bulgarian latent virus (GBLV) (0.37%) was scarcely represented, while Arabis mosaic virus (ArMV), Grapevine leafroll associated viruses 2 and 7 (GLRaV 2 and 7), Grapevine virus A (GVA) and Grapevine virus B (GVB) were completely absent. The mixed infection showed eight virus combinations. The associations of GFkV + GLRaV 1 (8.3%) and GFLV + GLRaV3 (8.3%) were the most widespread ones.All tested for ArMV, GFLV and GBLV wild vines (Vitis vinifera ssp. sylvestris) were virus free.

Quantitative omics and its application to study virus-host interactions—a new frontier

Rethinking hepatitis C viral kinetics: Insights into host-virus interactions in ‘difficult-to-treat’ groups and implications for novel treatment approaches

The incidence of grapevine virus infections in Korean vineyards was investigated from July to October, 2020. A total of 177 petiole samples were collected from two or three different cultivars in each of four different regions; these were examined by reverse transcription-polymerase chain reaction assay for the presence of 14 major viruses. The overall occurrence of grapevine viruses was 91.0%, and the level of incidence was high irrespective of region or cultivar. The predominant viruses were grapevine leafroll-associated virus 3 (80.2%), grapevine fleck virus (70.6%), and grapevine rupestris stem pitting-associated virus (49.2%). Most grapevines were infected with multiple viruses, suggesting that Korean vineyards are likely to suffer economic losses resulting from viral diseases. This is the first extensive survey performed in Korea to observe the outbreak status of diverse grapevine viruses; surveys of this type can provide important information for the management of grapevine viruses in Korea.

We investigated the prevalence of viruses infecting grapevines in Virginia, identity of disease vectors, and potential factors affecting virus incidence. Tested viruses were grapevine leafroll-associated virus (GLRaV-1 and -4), grapevine fleck virus (GFkV), grapevine virus A (GVA), grapevine virus B (GVB), grapevine rupestris stem pitting-associated virus (GRSPaV), tomato ringspot virus (ToRSV), grapevine vein clearing virus (GVCV), grapevine red blotch virus (GRBV), and grapevine Pinot gris virus (GPGV). We documented wide distributions of GRSPaV (54%) and GRBV (24%) and common occurrences of grape (Pseudococcus maritimus) and Gill’s (Ferrisia gilli) mealybugs among vineyards. This is the first report of GLRaV-1, GLRaV-4, GVA, GVB, GRSPaV, and obscure mealybug (Pseudococcus viburni) in Virginia. We also documented significant association (P ≤ 0.05) of the presence of mealybugs and GVA and GVB. With younger vines, significantly lower incidences were found for viruses that were listed (i.e., tested for a certification) by the Foundation Planting Service’s and the National Clean Plant Network’s grape programs. On the other hand, there was a lack of the age effect on incidence of GRSPaV and GRBV, which were not listed until recently. These results suggest the importance of clean plant material and vector management for grapevine virus disease management in Virginia.

Grapevine is one of the economically and culturally important perennial fruit crops. More than 60 viruses infect grapevines and adversely affect their growth and development. Latent infection of most viruses in grapevines leads to chronic modulation of gene expression at transcriptional and post-transcriptional levels. Plant small RNAs (sRNAs) consist of microRNA (miRNA) and small interfering RNA (siRNA). miRNAs are expressed from the plant genome while most siRNAs are derived from double-stranded RNA molecules which are intermediates during virus replication. In a previous study, we constructed four cDNA libraries of sRNAs that were enriched from three virus-infected grapevines and one virus-free grapevine. Majority of siRNAs align most closely with the genomes of DNA viruses in the genus Badnavirus, family Caulimoviridae that led to the discovery of a new Grapevine vein clearing virus in grapevines. In this study, we conducted a comprehensive analysis of miRNAs in the four cDNA libraries and identified novel and stress-related miRNAs. The results indicated that miRNA abundance was influenced by virus infection. A total of 54 new miRNAs were identified and characterized, six of which, VITIS-MIR17, 18, 19, 20, 21, and 22, were detected only in virus-infected samples. One target of VITIS-MIR18 is the gene coding a non-apical meristem protein (GSVIVT00035370001), a transcription factor in the regulation of plant development and stress responses. Among the virus infection-induced known miRNAs, miRNA168 and miRNA3623 likely regulate grapevine's defense response, miRNA319 and miRNA395 modulate the expression of genes that are involved in nutrient metabolisms while miRNA396 plays a role in the regulation of cell division and cell cycle. The abiotic stress-induced miR169 and mi398 were negatively regulated by virus infection in grapevines. In addition, variety-specific miRNAs were discovered and compiled. The newly discovered miRNAs expand the miRNA profiles in the Vitis species. The characteristics of variety-specific and virus infection-associated miRNAs help understand the biology underlying the development and defense response of grapevines.

Western blot immunoassay and enzyme-linked immunosorbent assay using different monoclonal antibodies (MAb) and polyclonal antisera (PA) revealed mixed infections of serologically related and unrelated grapevine leafroll associated viruses (GLRaVs) and grapevine corky bark associated virus (GCBaV) in symptomatic grapevines. A PA designated rootstock-scion incompatibility (RSI)-24 kDa, grapevine corky bark PA, and GLRaV-2b MAb reacted to polypeptides of approximately 24 kDa isolated from grapevines exhibiting rootstock-scion incompatibility, leafroll, and corky bark disease symptoms, suggesting that these isolates are infected with closely related viruses. A PA designated GLRaV-2 US detected virus specific polypeptides of 38, 37, 36, and 24 kDa, while a polyclonal antiserum designated GLRaV-2 FR detected a single virus-specific polypeptide of approximately 24 kDa. The reactivity of GLRaV-2 US to various polypeptides suggests that the immunogen used to produce this antiserum was a mixture of viruses. Apical meristems were excised and cultured to eliminate the infection of viruses in the grapevines showing RSI symptoms and in the cultivar French Colombard infected with GLRaV-1. The elimination of these viruses was confirmed by Western blot assay. These studies show that the Western blot assay can be used to detect and differentiate grapevine disease-associated closteroviruses.

Rugose wood is one of the most important disease syndromes of grapevine, and it has been associated with at least three viruses: grapevine rupestris stem pitting-associated virus (GRSPaV), grapevine virus A (GVA), and grapevine virus B (GVB). All three viruses show a worldwide distribution pattern, and their genetic composition has been the focus of extensive research in past years. Despite their first record in Greece almost 20 years ago, there is a lack of knowledge on the distribution and genetic variability of their populations in Greek vineyards. In this context, we investigated the distribution of GRSPaV, GVA, and GVB in rootstocks, self-rooted vines, and grafted grapevine cultivars originating from different geographic regions that represent important viticultural areas of Greece. Three new reverse transcription-PCR assays were developed for the reliable detection of GRSPaV, GVA, and GVB. Our results indicated that GVA is the most prevalent in Greek vineyards, followed by GRSPaV and GVB. However, virus incidence differed among self-rooted and grafted grapevine cultivars or rootstocks tested. Selected isolates from each virus were further molecularly characterized to determine their phylogenetic relationships. All three viruses exhibited high nucleotide diversity, which was depicted in the constructed phylogenetic trees. Isolates from Greece were placed in various phylogroups, reinforcing the scenario of multiple introductions of GVA, GVB, and GRSPaV in Greece and highlighting the effect of different transmission modes in the evolutionary course of the three viruses.

In eukaryotes, microRNAs (miRNAs) serve as regulators of many biological processes, including virus infection. An miRNA can generally target diverse genes during virus-host interactions. However, the regulation of gene expression by multiple miRNAs has not yet been extensively explored during virus infection. This study found that the Spaztle (Spz)-Toll-Dorsal-antilipopolysaccharide factor (ALF) signaling pathway plays a very important role in antiviral immunity against invasion of white spot syndrome virus (WSSV) in shrimp (Marsupenaeus japonicus). Dorsal, the central gene in the Toll pathway, was targeted by two viral miRNAs (WSSV-miR-N13 and WSSV-miR-N23) during WSSV infection. The regulation of Dorsal expression by viral miRNAs suppressed the Spz-Toll-Dorsal-ALF signaling pathway in shrimp in vivo, leading to virus infection. Our study contributes novel insights into the viral miRNA-mediated Toll signaling pathway during the virus-host interaction.IMPORTANCE An miRNA can target diverse genes during virus-host interactions. However, the regulation of gene expression by multiple miRNAs during virus infection has not yet been extensively explored. The results of this study indicated that the shrimp Dorsal gene, the central gene in the Toll pathway, was targeted by two viral miRNAs during infection with white spot syndrome virus. Regulation of Dorsal expression by viral miRNAs suppressed the Spz-Toll-Dorsal-ALF signaling pathway in shrimp in vivo, leading to virus infection. Our study provides new insight into the viral miRNA-mediated Toll signaling pathway in virus-host interactions.