A. tumefaciens-mediated transient expression as a tool for antigen production for cucurbit yellow stunting disorder virus

Mechanistic Investigation of Green Fluorescent Protein Acquiring Energy for Emitting Light: A Theoretical Study

Green fluorescent protein (GFP) is famous for noninvasively observing the internal biological processes of cells and organisms, revolutionizing the field of cell biology. GFP was first discovered in jellyfish Aequorea victoria (AV). The GFP bioluminescence (BL) in AV can be divided into three stages: the first singlet excited state coelenteramide (S1-CTD) is formed in aequorin; GFP acquires energy from S1-CTD via an energy transfer (ET) process; and GFP emits green light. The first and final stages have been well studied, whereas the detailed mechanism of the second stage remains unclear, with only sporadic experimental evidence. The purpose of this study is to clarify how GFP acquires energy before emitting green light in AV. Through protein-protein docking, molecular dynamics simulations, and combined quantum mechanics and molecular mechanics calculations, we demonstrate that the ET process occurs via the Förster resonance energy transfer (FRET) mechanism. The calculated FRET rate is faster than the radiative and nonradiative decay ones of S1-CTD, which means the ET process can occur efficiently. Additionally, the calculated fluorescence quantum yield explains the experimentally observed BL enhancement after the ET. This is the first theoretical report on the ET mechanism in BL. This study not only clearly interprets how GFP acquires energy for emitting light but also helps to understand the ET mechanism in other bioluminescent systems and sheds new light on bioluminescence resonance energy transfer.

Development of diagnostic tools and discovery of two novel Indian citrus ringspot virus species: insights into global mandarivirus phylogeography

Emerging viral pathogens, Indian citrus ringspot virus (ICRSV) and Citrus yellow vein clearing virus (CYVCV), pose significant threats to global citrus production, a cornerstone of agriculture and trade. The rapid transboundary spread of CYVCV underscores the urgent need for effective diagnostic tools. To tackle this issue, we developed a novel RT-PCR assay capable of simultaneously detecting ICRSV and CYVCV with high sensitivity and specificity in a single reaction. This assay, targeting conserved genomic regions, provides a cost-effective, reliable, and scalable diagnostic solution. Field validation across 49 citrus samples revealed infection rates of 61.22% for ICRSV and 24.48% for CYVCV, with notable co-infections, highlighting its precision and utility. Phylogenetic analyses uncovered substantial genetic diversity, delineating two ICRSV species (ICRSV-A and ICRSV-B) and eight geographically clustered CYVCV clades, reflecting trade-driven and environmental dispersal patterns. These findings emphasize the need for region-specific diagnostics and tailored management strategies. By addressing critical diagnostic gaps, this assay enables early detection and intervention, reducing economic losses and enhancing efforts to control emerging citrus pathogens. Additionally, it provides a foundation for future epidemiological research and contributes to the sustainability of global citrus production.

High incidence of citrus tristeza virus in mandarin (Citrus reticulata) in North-East states of India

Khasi mandarin is one of the most remunerative crop in North Eastern Hills region of India playing a very critical role in the socio-economic upliftment of the people. The orchards of this region were found to express the typical symptoms of citrus tristeza virus (CTV). An extensive survey of the Khasi mandarin orchard for six North Eastern states of India namely Arunachal Pradesh, Meghalaya, Assam, Nagaland, Sikkim and Tripura, was carried out to establish the identity of these viruses using ELISA and PCR/RT-PCR techniques. Out of 300 Khasi mandarin tree samples collected from the six states, 172 were found to be positive for CTV infection by DAS-ELISA indicating 57.33% overall CTV disease incidence. Results revealed presence of CTV in all the surveyed states showing a maximum incidence of 66.00% in Arunachal Pradesh followed by 62.00% in Assam, 60.00% in Meghalaya and Nagaland, 54.00% in Sikkim and 42.33% in Tripura. Higher CTV concentration was recorded in the age group > 15 years (69.09%) followed by 10-15 (57%) and 5-10 years (43.33%). However, this study, to the best of our knowledge, is the first report for the detection of CTV in Khasi mandarin from Arunachal Pradesh, Nagaland and Tripura and also the first authentic survey of overall disease incidence of CTV Khasi mandarins from the six major mandarin growing North Eastern states of India.

Development of multiplex polymerase chain reaction assay for simultaneous detection of clostero-, badna- and mandari-viruses along with huanglongbing bacterium in citrus trees

Citrus trees harbor a large number of viral and bacterial pathogens. Citrus yellow vein clearing virus (CYVCV), Indian citrus ringspot virus (ICRSV), Citrus yellow mosaic virus (CYMV), Citrus tristeza virus (CTV) and a bacterium, Candidatus Liberibacter asiaticus (CLa) associated with huanglongbing (HLB) disease, the most prevalent pathogens in citrus orchards of different regions in India and are responsible for debilitating citriculture. For detection of these viral and bacterial pathogens a quick, sensitive and cost effective detection method is required. With this objective a multiplex polymerase chain reaction (mPCR) assay was developed for simultaneous detection of four viruses and a bacterium in citrus. Several sets of primers were designed for each virus based on the retrieved reference sequences from the GenBank. A primer pair published previously was used for greening bacterium. Each pair of primers was evaluated for their sensitivity and differentiation by simplex and mPCR. The constant amplified products were identified on the basis of molecular size in mPCR and were compared with standard PCR. The amplicons were cloned and results were confirmed with sequencing analysis. The mPCR assay was validated using naturally infected field samples for one or more citrus viruses and the huanglongbing bacterium. The mPCR assay developed here will aid in the production of virus free planting materials and rapid indexing for certification of citrus budwood programme.

Whitefly-transmitted criniviruses of cucurbits: current status and future prospects

In the past decade, crinviruses have gained interest due to their rapid widespread and destructive nature for cucurbit cultivation. Several members of the genus Crinivirus are considered emerging viruses. Currently, four criniviruses: Beet pseudo-yellows virus, Cucurbit chlorotic yellows virus, Cucurbit yellow stunting disorder virus and Lettuce infectious yellows virus have been reported to infect field- or greenhouse- grown cucurbits. Apart from their cucurbit hosts, criniviruses infect other cash crops and weeds. Criniviruses are exclusively transmitted by whiteflies. The virion titer and the vector genus or species complex are predominant factors affecting virus transmission. These criniviruses maintain genetic stability with limited intra-species variability. They share similar core genome structure and replication strategies with some variations in the non-core proteins and downstream replication processes. Management of the diseases induced by criniviruses relies on integrated disease management strategies and on resistant varieties, when available. This review will cover their epidemiology, molecular biology, detection and management.