Sayak Banerjee, Amity University Kolkata
Viromics or viral metagenomics techniques have led to the characterization of many new plant viruses. This has been broadening our understanding of the evolution and ecology of plant viruses in nature. Generally, the knowledge regarding citrus viruses has been highly inclined towards virus pathology in cultivated orchards. Recently, scientists have used a metatranscriptomics technique for classifying the virus diversity in a wild citrus habitat in the Ailao Mountain region.
They had discovered collectively 44 virus isolates that could be categorized into species Citrus tristeza virusand putative species citrus associated ampelovirus 1, citrus associated ampelovirus 2, and citrus virus B within the family Closteroviridae. Three new citrus infecting closterovirids and various Closterovirus (CTV) isolates were discovered and characterized. This served as new insights towards the virus ecology in wild citrus plants and the genetic diversity of the family Closteroviridae.
Closteroviridae family of plant viruses:
Closteroviridae being the cause of novel or re-emerging diseases are major plant pathogens for citrus trees and other plants. They infect a broad range of agriculturally significant crops, resulting in severe economic damage. Nevertheless, its diversity in natural plant hosts remains unknown. The family of Closteroviridae includes four genera, namely Closterovirus (CTV), Crinivirus, Ampelovirus (CaAV-1 and CaAV-2), and Velarivirus. All of them have positive-sense single-stranded RNA genomes where Crinivirus are separately encapsulated with bi- or tripartite genomes, while others are not encapsulated, having monopartite genomes. Homologous recombination, the capture of foreign genes, and duplication of intragenomic sequences have given rise to the exceptional biological and molecular diversity of the family Closteroviridae.
The aphid-borne CTV is the only known citrus infecting closterovirids which causes seedling yellow, stem pitting, quick decline, and slow deterioration. These are all correlated to permanent chronic losses in commercial citrus production due to which numerous disease outbreaks have been taking place in the majority parts of the citrus-growing regions of the world. The application of viromics by researchers has enabled the identification and discovery of novel viruses. Their research has chiefly centered upon the host pathology and viral mechanisms. According to their study, within the long co-evolutionary period, these closterovirids have coexisted with other parasites like bacteria and fungi in the plant hosts which allow viruses to incorporate genes through Horizontal Gene Transfer (HGT) from diverse sources. Three horizontally obtained genes found in CaAV-1 and other closterovirids exhibited an inclination to their bacterial, fungal, and plant counterparts.
Citrus-infecting closterovirids:
Many viruses might have coevolved with the wild hosts over a long period thus making the latter natural reservoirs for viruses which could cause re-emerging diseases. These viral pathogens affect various agricultural and natural plants causing host diseases. Globalization has led to the transport of the monocultures to new areas and this is how the wild and cultivated citrus species come in contact via insect vectors or humans. Hence, CTV became prevalent and vicious for the citric industry.
Significance of the study:
This finding can serve as a warning regarding the existence of citrus-infecting closterovirids and might pose new troubles in citrus production. The scientists stated that further research should elaborate on their evolution and functions. Successive codivergence and cross-species transmission events might generate genes with undetectable similarity in the extent to closterovirids that have diverged independently. This enables the infection of multiple hosts or transmission by multiple insect vectors.
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Reference:
- Liu, Q., Zhang, S., Mei, S., Zhou, Y., Wang, J., Han, G.-Z., Chen, L., Zhou, C., & Cao, M. (2021). Viromics unveils extraordinary genetic diversity of the family Closteroviridae in wild citrus. PLOS Pathogens, 17(7), e1009751. https://doi.org/10.1371/journal.ppat.1009751
Author info:
Sayak Banerjee is a 3rd-year Biotechnology Student with a great interest in Immunology and Molecular genetics. He is a creative scientific writer in BIOXONE BIOSCIENCES with an inclination towards gaining knowledge regarding various sections of Biotechnology and emphasizing himself in various wet lab skills.
Previous publications:
- https://bioxone.in/news/worldnews/anaerobic-gut-fungi-make-way-for-novel-antibiotic-production/
- https://bioxone.in/news/worldnews/neutrophil-derived-nanovesicles-a-novel-drug-delivery-system/
- https://bioxone.in/news/worldnews/pig-to-human-heart-transplantation-a-solution-to-the-rarity-of-donor-organs/
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