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Background Alfalfa mosaic virus (AMV) is an important virus affecting many vegetable crops in Egypt. In this study, virus isolates were collected from naturally infected potato, tomato, alfalfa and clover plants that showed suspected symptoms of AMV in different locations of Beheira and Alexandria governorates during the 2019–2020 growing season. The relative incidence of the virus ranged from 11–25% based on visual observations of symptoms and ELISA testing. A total of 41 samples were tested by ELISA using polyclonal antisera for AMV. Four AMV isolates collected from different host plants, named AM1 from potato, AM2 from tomato, AM3 from alfalfa and AM4 from alfalfa, were maintained on Nicotiana glutinosa plants for further characterization of AMV. Results Electron micrographs of the purified viral preparation showed spheroidal particles with a diameter of 18 nm and three bacilliform particles with lengths of roughly 55, 68, and 110 nm and diameters identical to those of the spheroidal particles. The CP gene sequence comparisons of four AMV isolates (AM1, AM2, AM3 and AM4) showed the highest nucleotide identity of 99.7% with the Gomchi isolate from South Korea infecting Gomchi (Ligularia fischeri ) plants. Phylogenetic analysis showed that the present isolates were grouped together into a distinct separate clade (GPI) along with the Gomchi isolate from South Korea. Similarly, the deduced amino acid sequence comparisons of Egyptian AMV isolates revealed that amino acids Q 29 , S 30 , T 34 , V 92 and V 175 were conserved among the Egyptian isolates in GPI. Conclusion The present study found strong evolutionary evidence for the genetic diversity of AMV isolates by the identification of potential recombination events involving parents from GPI and GPII lineages. Additionally, the study found that Egyptian AMV isolates are genetically stable with low nucleotide diversity. Genetic analysis of the AMV population suggested that the AMV populations differ geographically, and AMV CP gene is under mild purifying selection. Furthermore, the study proposed that the Egyptian AMV population had common evolutionary ancestors with the Asian AMV population. Antioxidant enzymes activity was assessed on N. glutinosa plants in response to infection with each AMV isolate studied, and the results revealed that the enzyme activity varied.

RNA interference (RNAi) is a sequence-specific, posttranscriptional gene silencing (PTGS) process in plants that is mediated by dsRNA homologous to the silenced gene(s). In this study, we report an efficient method to produce dsRNA using a bacterial expression system. Two fragments of the Sugarcane Mosaic Virus (SCMV) CP (coat protein) gene were amplified by RT-PCR, and cloned into the inverted-repeat cloning vector pUCCRNAi. The two recombinant plasmids were transformed individually into E. coli HT115, an RNase-III deficient strain, and dsRNA was induced by isopropyl-β-d-thiogalactopyranoside (IPTG). The crude extracts of E. coli HT115 containing large amounts of dsRNA were applied to plants as a spray and the experiment confirmed a preventative efficacy. Our findings demonstrated that spraying crude dsRNA-containing extracts inhibited SCMV infection, and the dsRNA derived from an upstream region (CP1) was more effective than was dsRNA derived from a downstream region (CP2) of the SCMV CP gene. The results provide a valuable tool for plant viral control using dsRNA and the PTGS approach.

We report the chloroplast (cp) genome sequence of tartary buckwheat (Fagopyrum tataricum) obtained by next-generation sequencing technology and compared this with the previously reported common buckwheat (F. esculentum ssp. ancestrale) cp genome. The cp genome of F. tataricum has a total sequence length of 159,272 bp, which is 327 bp shorter than the common buckwheat cp genome. The cp gene content, order, and orientation are similar to those of common buckwheat, but with some structural variation at tandem and palindromic repeat frequencies and junction areas. A total of seven InDels (around 100 bp) were found within the intergenic sequences and the ycf1 gene. Copy number variation of the 21-bp tandem repeat varied in F. tataricum (four repeats) and F. esculentum (one repeat), and the InDel of the ycf1 gene was 63 bp long. Nucleotide and amino acid have highly conserved coding sequence with about 98% homology and four genes--rpoC2, ycf3, accD, and clpP--have high synonymous (Ks) value. PCR based InDel markers were applied to diverse genetic resources of F. tataricum and F. esculentum, and the amplicon size was identical to that expected in silico. Therefore, these InDel markers are informative biomarkers to practically distinguish raw or processed buckwheat products derived from F. tataricum and F. esculentum.

Kitaviridae , a newly recognized virus family, includes plant viruses infecting crops of great global importance, notably citrus. Despite its significant impact on citrus agricultural production, the molecular mechanisms underlying kitavirus infections remain largely unknown. Here, we engineered a recombinant citrus leprosis virus C (CiLV-C, genus Cilevirus ) expressing green fluorescent protein (GFP) and demonstrated its feasibility for studying the biology of cilevirus. Genetic manipulation of rCiLV-C-GFP revealed that vRNA1 is essential for replication and can self-replicate independently, while vRNA2 is crucial for movement. The intergenic region between the polymerase and capsid protein (CP) acts as a promoter for CP gene expression. Frameshift and deletion analyses provided key insights into replication, movement, and morphogenesis. We reported that CP is critical for viral RNA accumulation, while movement protein (p32) facilitates viral spread. The putative glycoprotein (p61) is not structurally essential, as its deletion did not affect virion assembly, whereas the putative matrix protein (p24) is critical for morphogenesis, likely acting as a structural protein. Deletion of the RNA silencing suppressor (RSS, p15) and p15-p61 attenuated symptoms, implicating them as virulence factors. Additional analyses revealed that CP enhances vRNA accumulation through a mechanism independent of RSS. CP exhibits RNA-binding properties and interacts with eukaryotic initiation factor 4A (eIF4A), suggesting a role in translation. Overexpression of eIF4A increased CiLV-C RNA accumulation, while eIF4A knockdown reduced it, indicating that CP may recruit eIF4A to promote replication. Similar results were observed with turnip crinkle virus (TCV), and notably, the TCV CP efficiently restored RNA accumulation of a CP-defective CiLV-C, suggesting the existence of a conserved, CP-dependent, replication-related mechanism shared across distinct virus families. Our findings support the proposal of an initial model that elucidates the mechanism through which the CPs drive the production of high levels of vRNA manipulating host eIFs.

Background Characterization of the key factors determining gene expression level has been of significant interest. Previous studies on the relationship among evolutionary rates, codon usage bias, and expression level mostly focused on either nuclear genes or unicellular/multicellular organisms but few in chloroplast (cp) genes. Ophioglossum vulgatum is a unique fern and has important scientific and medicinal values. In this study, we sequenced its cp genome and transcriptome to estimate the evolutionary rates ( dN and dS ), selective pressure ( dN / dS ), gene expression level, codon usage bias, and their correlations. Results The correlation coefficients between dN, dS, and dN / dS , and Transcripts Per Million (TPM) average values were -0.278 ( P  = 0.027 < 0.05), -0.331 ( P  = 0.008 < 0.05), and -0.311 ( P  = 0.013 < 0.05), respectively. The codon adaptation index (CAI) and tRNA adaptation index (tAI) were significantly positively correlated with TPM average values ( P  < 0.05). Conclusions Our results indicated that when the gene expression level was higher, the evolutionary rates and selective pressure were lower, but the codon usage bias was stronger. We provided evidence from cp gene data which supported the E-R (E stands for gene expression level and R stands for evolutionary rate) anti-correlation.

Papaya ringspot virus biotype-P is a detrimental pathogen of economically important papaya and cucurbits worldwide. The mutation prone feature of this virus perhaps accounts for its geographical dissemination. In this study, investigations of the atypical PRSV-P strain was conducted based on phylogenetic, recombination and genetic differentiation analyses considering of it’s likely spread across India and Bangladesh. Full length genomic sequences of 38 PRSV isolates and 35 CP gene sequences were subjected to recombination analysis. A total of 61 recombination events were detected in aligned complete PRSV genome sequences. 3 events were detected in complete genome of PRSV strain PK whereas one was in its CP gene sequence. The PRSV-PK appeared to be recombinant of a major parent from Bangladesh. However, the genetic differentiation based on full length genomic sequences revealed less frequent gene flow between virus PRSV-PK and the population from America, India, Colombia, other Asian Countries and Australia. Whereas, frequent gene flow exists between Pakistan and Bangladesh virus populations. These results provided evidence correlating geographical position and genetic distances. We speculate that the genetic variations and evolutionary dynamics of this virus may challenge the resistance developed in papaya against PRSV and give rise to virus lineage because of its atypical emergence where geographic spread is already occurring.

Numerous, diverse plant viruses encode movement proteins (MPs) that aid the virus movement through plasmodesmata, the plant intercellular channels. MPs are essential for virus spread and propagation in distal tissues, and several unrelated MPs have been identified. The 30K superfamily of MPs (named after the molecular mass of tobacco mosaic virus MP, the classical model of plant virology) is the largest and most diverse MP variety, represented in 16 virus families, but its evolutionary origin remained obscure. Here, we show that the core structural domain of the 30K MPs is homologous to the jelly-roll domain of the capsid proteins (CPs) of small RNA and DNA viruses, in particular, those infecting plants. The closest similarity was observed between the 30K MPs and the CPs of the viruses in the families Bromoviridae and Geminiviridae . We hypothesize that the MPs evolved via duplication or horizontal acquisition of the CP gene in a virus that infected an ancestor of vascular plants, followed by neofunctionalization of one of the paralogous CPs, potentially through the acquisition of unique N- and C-terminal regions. During the subsequent coevolution of viruses with diversifying vascular plants, the 30K MP genes underwent explosive horizontal spread among emergent RNA and DNA viruses, likely permitting viruses of insects and fungi that coinfected plants to expand their host ranges, molding the contemporary plant virome.

The spread of cotton leaf curl disease in China, India and Pakistan is a recent phenomenon. Analysis of available sequence data determined that there is a substantial diversity of cotton-infecting geminiviruses in Pakistan. Phylogenetic analyses indicated that recombination between two major groups of viruses, cotton leaf curl Multan virus (CLCuMuV) and cotton leaf curl Kokhran virus (CLCuKoV), led to the emergence of several new viruses. Recombination detection programs and phylogenetic analyses showed that CLCuMuV and CLCuKoV are highly recombinant viruses. Indeed, CLCuKoV appeared to be a major donor virus for the coat protein (CP) gene, while CLCuMuV donated the Rep gene in the majority of recombination events. Using recombination free nucleotide datasets the substitution rates for CP and Rep genes were determined. We inferred similar nucleotide substitution rates for the CLCuMuV-Rep gene (4.96X10-4) and CLCuKoV-CP gene (2.706X10-4), whereas relatively higher substitution rates were observed for CLCuMuV-CP and CLCuKoV-Rep genes. The combination of sequences with equal and relatively low substitution rates, seemed to result in the emergence of viral isolates that caused epidemics in Pakistan and India. Our findings also suggest that CLCuMuV is spreading at an alarming rate, which can potentially be a threat to cotton production in the Indian subcontinent.

Background The roles of the choroid plexus (CP) and cerebrospinal fluid (CSF) production have drawn increasing attention in Alzheimer’s disease (AD) research. Specifically, studies document markedly decreased CSF production and turnover in moderate-to-severe AD. Moreover, reduced CP function and CSF turnover lead to impaired clearance of toxic metabolites, likely promote neuroinflammation, and may facilitate neuronal death during AD progression. We analyzed CP gene expression in AD compared with control subjects, specifically considering those genes involved with CSF production and CP structural integrity. Methods The Brown-Merck Gene Expression Omnibus (GEO) database (CP transcripts) was mined to examine changes in gene expression in AD compared to controls with a focus on assorted genes thought to play a role in CSF production. Specifically, genes coding for ion transporters in CP epithelium (CPE) and associated enzymes like Na–K-ATPase and carbonic anhydrase, aquaporins, mitochondrial transporters/enzymes, blood–cerebrospinal fluid barrier (BCSFB) stability proteins, and pro-inflammatory mediators were selected for investigation. Data were analyzed using t test p-value and fold-change analysis conducted by the GEO2R feature of the GEO database. Results Significant expression changes for several genes were observed in AD CP. These included disruptions to ion transporters (e.g., the solute carrier gene SLC4A5, p = 0.004) and associated enzyme expressions (e.g., carbonic anhydrase CA4, p = 0.0001), along with decreased expression of genes involved in BCSFB integrity (e.g., claudin CLDN5, p = 0.039) and mitochondrial ATP synthesis (e.g., adenosine triphosphate ATP5L, p = 0.0004). Together all changes point to disrupted solute transport at the blood–CSF interface in AD. Increased expression of pro-inflammatory (e.g., interleukin IL1RL1, p = 0.00001) and potential neurodegenerative genes (e.g., amyloid precursor APBA3, p = 0.002) also implicate disturbed CP function. Conclusions Because the altered expression of numerous transcripts in AD-CP help explain decreased CSF production in AD, these findings represent a first step towards identifying novel therapeutic targets in AD.

Carlavirus sigmasolani (Potato virus S, PVS) is a globally distributed plant virus infecting cultivated potato ( Solanum tuberosum ), causing yield losses and reduced tuber quality in the host crop, yet its evolutionary history, global dissemination and population genetic structure remain incompletely understood. In this study, we conducted comprehensive phylogenetic and Bayesian phylogeographic analyses of PVS using all available complete genome and coat protein (CP) gene sequences from 35 countries. Genome-based phylogenetic reconstruction identified four major phylogroups (I–IV), with Phylogroup I comprising only Colombian isolates and Phylogroup IV showing the broadest geographic distribution. In contrast, CP gene-based analyses revealed seven phylogroups (I–VII), including regionally restricted Phylogroups V (Colombia) and VI (Ecuador), and the globally dominant Phylogroup VII. A time-scaled Bayesian phylogenetic framework estimated a mean substitution rate of 3.11 × 10 -4 substitutions/site/year (95% HPD: 2.19 × 10 -4 –4.07 × 10 -4 ), and dated the most recent common ancestor (tMRCA) of PVS to approximately 1296 (95% HPD: 964–1578). Phylogeographic analysis based on CP gene sequences suggests that Ecuador is a likely center of origin for PVS, with intercontinental dissemination beginning in the 16th century and markedly accelerating during the 19th and 20th centuries. Iran and China were identified as major secondary hubs during this period, while Europe and the United States also contributed to global dissemination as important intercontinental transmission centers during the 20th and 21st centuries. Population genetic analyses indicated that South America retains the highest diversity, reinforcing its status as the center of origin, while the markedly lower diversity in Africa and Oceania suggests more recent introductions coupled with restricted gene flow. These data improve our understanding of PVS evolution, spread and population structure, supporting the development of effective monitoring and control strategies.