Elucidating the functional aspects of different domains of bean common mosaic virus coat protein

The pollen virome: A review of pollen-associated viruses and consequences for plants and their interactions with pollinators

The movement of pollen grains from anthers to stigmas, often by insect pollinator vectors, is essential for plant reproduction. However, pollen is also a unique vehicle for viral spread. Pollen-associated plant viruses reside on the outside or inside of pollen grains, infect susceptible individuals through vertical or horizontal infection pathways, and can decrease plant fitness. These viruses are transferred with pollen between plants by pollinator vectors as they forage for floral resources; thus, pollen-associated viral spread is mediated by floral and pollen grain phenotypes and pollinator traits, much like pollination. Most of what is currently known about pollen-associated viruses was discovered through infection and transmission experiments in controlled settings, usually involving one virus and one plant species of agricultural or horticultural interest. In this review, we first provide an updated, comprehensive list of the recognized pollen-associated viruses. Then, we summarize virus, plant, pollinator vector, and landscape traits that can affect pollen-associated virus transmission, infection, and distribution. Next, we highlight the consequences of plant-pollinator-virus interactions that emerge in complex communities of co-flowering plants and pollinator vectors, such as pollen-associated virus spread between plant species and viral jumps from plant to pollinator hosts. We conclude by emphasizing the need for collaborative research that bridges pollen biology, virology, and pollination biology.

High-mobility group box 1 protein promotes dengue virus replication by interacting with untranslated regions of viral genome

Dengue virus (DENV) is most prevalent arthropod-borne human pathogen belongs to Flaviviridae family causes thousands of deaths annually. HMGB1 is highly conserved, ubiquitously expressed, non-histone nuclear protein which plays important role in diseases like metabolic disorders, cancer, and viral infections. However, the importance of HMGB1 in DENV infection is understudied. In this study, we observed that DENV-2 induces cytoplasmic translocation and secretion of HMGB1. Interestingly, inhibition of HMGB1 secretion by ethyl pyruvate (EP) enhanced viral propagation while silencing of HMGB1 resulted in abrogated viral replication in DENV-2 infected A549 cells. RNA-Electrophoretic mobility shift assay and immunoprecipitation showed that HMGB1 interacts with 5'-3' UTRs of DENV-2 genome. This interaction further stimulates production of proinflammatory cytokines like TNF-α, IL-6 and IL-1β which have been implicated in pathogenesis of severe DENV disease. Together, our finding suggests that DENV-2 modulates HMGB1 translocation and HMGB1-DENV-2 UTRs RNA interaction further induces proinflammatory cytokines production in A549 cells. This study discloses HMGB1 as an important host factor contributing to disease pathogenesis and hence can be targeted as an alternative approach for antiviral development against DENV virus infection.

Restriction-free cloning for molecular manipulation and augmented expression of banana bunchy top viral coat protein

Banana bunchy top virus (BBTV) causing bunchy top disease, is one of the most devastating diseases of banana and plantain. All the six genomic components of isolates from different parts of the world have been well characterised, with most of the studies focusing on replicase gene and coat protein gene. Overexpression of coat protein (CP) in Escherichia coli system can contribute significantly in structural as well as immunological studies. In the present investigation, the full length BBTV CP was cloned to pGEX-4T-2 expression vector and overexpressed in various Escherichia coli strains to obtain high quality and quantity of the CP. An augmented overexpression and stability of recombinant coat protein was achieved by molecular manipulation of the clone by restriction-free (RF) cloning platform. The RF cloning was employed to replace the thrombin cleavage site in the vector backbone, which was also present in the protein of interest, and to incorporate TEV protease site to cleave fusion protein at this specific site, and separate the affinity tag. The RF method allows direct transformation of the PCR product to undergo ligation in vivo and obtain the transformants thereby avoiding the restriction digestion and ligation of the product to the linearized plasmid. From a litre culture, 1.084 mg/ml of fusion protein with GST tag was obtained after GSH sepharose affinity column chromatography. The fluorescence spectra indicated partial disordered tertiary structure of the fusion protein. Cleavage of tag was attempted using TEV protease overexpressed and purified in the laboratory.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-03017-x.

Interaction of potyvirus helper component-proteinase (HcPro) with RuBisCO and nucleosome in viral infections of plants

Bean common mosaic virus (BCMV) causes severe disease in Phaseolus vulgaris plants. One of its non structural protein, the helper-component proteinase (HcPro) involves in multiple roles in aphid transmission, RNA binding, suppression of gene silencing and protease activity. The multifunctional role of HcPro hint towards its regulation at multiple host cellular sites. The mechanisms of these regulatory activities are poorly understood. Therefore, it is very important to study the molecular level interaction of HcPro with different cellular components. In this study, we demonstrate that the HcPro interacts with RuBisCo, an enzyme of chloroplast origin which might plays a crucial role in virus infection. A further line of experiments were carried out with factors of nuclear origin. Due to nucleic acid binding activity of HcPro, it showed interaction with dsDNA of nucleosome, as ascertained through electrophoretic mobility shift assay (EMSA). Interestingly, HcPro interacts with host nucleoprotein histones, H3 and H4. The gel-overlay assay and native electrophoresis-western blot analysis (NEWeB) revealed a direct interaction of BCMV HcPro with host nucleosome and with histones. These findings suggest that the BCMV through HcPro, not only utilize the host cytoplasmic components but also use host nuclear factors for its propagation and disease development.

Purification and Characterization of Prolyl Hydroxylase 3/Pyruvate Kinase Isoform 2 Protein Complex

The prolyl hydroxylase 3 (PHD3) protein is less abundant in normal oxygen conditions (normoxia) but increases under deficient oxygen condition (hypoxia). Since cancerous cells often thrive in hypoxic conditions and predominantly express the Pyruvate kinase isoforms 2 (PKM2), the PHD3/PKM2 interaction might be particularly important in cancer development. In the present study, the PHD3/PKM2 complex was co-expressed and purified by size-exclusion chromatography. The interaction of PHD3 with PKM2 was confirmed in Native gel as well as western blot analysis. The PHD3/PKM2 complex formed discreet crystals under suitable conditions, and diffraction data revealed that crystal belonged to the P1 space group with 3.0 Å resolution. This is the first crystal report of PHD3/PKM2 complex as well as this study demonstrates a direct physical binding through protein-protein interaction. The structural analysis of complex will provide the information regarding the amino acid residues critical for the catalytic mechanism. Based on the structural information thus obtained, pharmacological interference with the PHD3/PKM2 interaction could be used as a novel strategy to reduce the cancer progression.

Differential expression of structural and functional proteins during bean common mosaic virus-host plant interaction

Bean common mosaic virus (BCMV), the most common seed-borne pathogen in Phaseolus vulgaris L. is known to cause severe loss in productivity across the globe. In the present study, proteomic analyses were performed for leaf samples from control (healthy) and susceptible BCMV infected plants. The differential expression of proteins was evaluated using two-dimensional gel electrophoresis (2-DE). Approximately, 1098 proteins were spotted, amongst which 107 proteins were observed to be statistically significant with differential expression. The functional categorization of the differential proteins illustrated that they were involved in biotic/abiotic stress (18%), energy and carbon metabolism (11%), photosynthesis (46%), protein biosynthesis (10%), chaperoning (5%), chlorophyll (5%) and polyunsaturated fatty acid biosynthesis (5%). This is the first report on the comparative proteome study of compatible plant-BCMV interactions in P. vulgaris which contributes largely to the understanding of protein-mediated disease resistance/susceptible mechanisms.