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Viruses Mar 2023Hop latent viroid (HLVd) is the biggest concern for cannabis and hop growers worldwide. Although most HLVd-infected plants remain asymptomatic, research on hops has... (Review)
Review
Hop latent viroid (HLVd) is the biggest concern for cannabis and hop growers worldwide. Although most HLVd-infected plants remain asymptomatic, research on hops has demonstrated a decrease in both the α-bitter acid and terpene content of hop cones, which affects their economic value. The HLVd-associated "dudding" or "duds" disease of cannabis was first reported in 2019 in California. Since then, the disease has become widespread in cannabis-growing facilities across North America. Although severe yield loss associated with duds disease has been recorded, little scientific information is available to growers in order to contain HLVd. Consequently, this review aims to summarise all of the scientific information available on HLVd so as to be able to understand the effect of HLVd on yield loss, cannabinoid content, terpene profile, disease management and inform crop protection strategies.
Topics: Cannabis; Humulus; North America; Plant Diseases; Viroids; Carlavirus; Host Specificity
PubMed: 36992390
DOI: 10.3390/v15030681 -
Cell Feb 2023Viroids and viroid-like covalently closed circular (ccc) RNAs are minimal replicators that typically encode no proteins and hijack cellular enzymes for replication. The...
Viroids and viroid-like covalently closed circular (ccc) RNAs are minimal replicators that typically encode no proteins and hijack cellular enzymes for replication. The extent and diversity of viroid-like agents are poorly understood. We developed a computational pipeline to identify viroid-like cccRNAs and applied it to 5,131 metatranscriptomes and 1,344 plant transcriptomes. The search yielded 11,378 viroid-like cccRNAs spanning 4,409 species-level clusters, a 5-fold increase compared to the previously identified viroid-like elements. Within this diverse collection, we discovered numerous putative viroids, satellite RNAs, retrozymes, and ribozy-like viruses. Diverse ribozyme combinations and unusual ribozymes within the cccRNAs were identified. Self-cleaving ribozymes were identified in ambiviruses, some mito-like viruses and capsid-encoding satellite virus-like cccRNAs. The broad presence of viroid-like cccRNAs in diverse transcriptomes and ecosystems implies that their host range is far broader than currently known, and matches to CRISPR spacers suggest that some cccRNAs replicate in prokaryotes.
Topics: RNA, Circular; Viroids; RNA, Catalytic; RNA, Viral; Ecosystem; Plant Diseases
PubMed: 36696902
DOI: 10.1016/j.cell.2022.12.039 -
Current Opinion in Virology Apr 2021Viroids are single-stranded circular noncoding RNAs that infect plants. The noncoding nature indicates that viroids must harness their RNA genomes to redirect host... (Review)
Review
Viroids are single-stranded circular noncoding RNAs that infect plants. The noncoding nature indicates that viroids must harness their RNA genomes to redirect host machinery for infection. Therefore, the viroid model provides invaluable opportunities for delineating fundamental principles of RNA structure-function relationships and for dissecting the composition and mechanism of RNA-related cellular machinery. There are two viroid families, Pospiviroidae and Avsunviroidae. Members of both families replicate via the RNA-based rolling-circle mechanism with some variations. Viroid replication is generally divided into three steps: transcription, cleavage, and ligation. Decades of studies have uncovered numerous viroid RNA structures with a regulatory role in replication and multiple enzymes critical for the three replication steps. This review discusses these findings and highlights the latest discoveries. Future studies will continue to elucidate regulatory factors and mechanism of host machinery exploited by viroids and provide new insights into host-viroid interactions in the context of pathogenesis.
Topics: DNA-Directed RNA Polymerases; Host-Pathogen Interactions; Nucleotide Motifs; Plant Diseases; Plant Proteins; RNA, Viral; Transcription, Genetic; Viral Proteins; Viroids; Virus Replication
PubMed: 33460914
DOI: 10.1016/j.coviro.2020.12.004 -
Cells Feb 2022Studies on the ways in which viroids are transmitted are important for understanding their epidemiology and for developing effective control measures for viroid... (Review)
Review
Studies on the ways in which viroids are transmitted are important for understanding their epidemiology and for developing effective control measures for viroid diseases. Viroids may be spread via vegetative propagules, mechanical damage, seed, pollen, or biological vectors. Vegetative propagation is the most prevalent mode of spread at the global, national and local level while further dissemination can readily occur by mechanical transmission through crop handling with viroid-contaminated hands or pruning and harvesting tools. The current knowledge of seed and pollen transmission of viroids in different crops is described. Biological vectors shown to transmit viroids include certain insects, parasitic plants, and goats. Under laboratory conditions, viroids were also shown to replicate in and be transmitted by phytopathogenic ascomycete fungi; therefore, fungi possibly serve as biological vectors of viroids in nature. The term "mycoviroids or fungal viroids" has been introduced in order to denote these viroids. Experimentally, known sequence variants of viroids can be transmitted as recombinant infectious cDNA clones or transcripts. In this review, we endeavor to provide a comprehensive overview of the modes of viroid transmission under both natural and experimental situations. A special focus is the key findings which can be applied to the control of viroid diseases.
Topics: Plant Diseases; Plant Viruses; Plants; Pollen; Viroids
PubMed: 35203368
DOI: 10.3390/cells11040719 -
Cells Nov 2022Viroids are single-stranded, circular RNA molecules (234-406 nt) that infect a wide range of crop species and cause economic losses in agriculture worldwide. They are... (Review)
Review
Viroids are single-stranded, circular RNA molecules (234-406 nt) that infect a wide range of crop species and cause economic losses in agriculture worldwide. They are characterized by the existence of a population of sequence variants, attributed to the low fidelity of RNA polymerases involved in their transcription, resulting in high mutation rates. Therefore, these biological entities exist as . This feature allows them to replicate within a wide range of host plants, both monocots and dicots. Viroid hosts include economically important crops such as tomato, citrus, and fruit trees such as peach and avocado. Given the high risk of introducing viroids to viroid disease-free countries, these pathogens have been quarantined globally. As discussed herein, Mexico represents a geographical landscape of viroids linked to their origin and comprises considerable biodiversity. The biological features of viroid species endemic to Mexico are highlighted in this communication. In addition, we report the phylogenetic relationships among viroid and viroid strains, their economic impact, geographical distribution, and epidemiological features, including a broad host range and possible long-distance, seed, or insect-mediated transmission. In summary, this review could be helpful for a better understanding of the biology of viroid diseases and future programs on control of movement and spread to avoid economic losses in agricultural industries.
Topics: Viroids; Phylogeny; Mexico; Citrus; Solanum lycopersicum
PubMed: 36359881
DOI: 10.3390/cells11213487 -
Nature Communications May 2023Earth's life may have originated as self-replicating RNA, and it has been argued that RNA viruses and viroid-like elements are remnants of such pre-cellular RNA world....
Earth's life may have originated as self-replicating RNA, and it has been argued that RNA viruses and viroid-like elements are remnants of such pre-cellular RNA world. RNA viruses are defined by linear RNA genomes encoding an RNA-dependent RNA polymerase (RdRp), whereas viroid-like elements consist of small, single-stranded, circular RNA genomes that, in some cases, encode paired self-cleaving ribozymes. Here we show that the number of candidate viroid-like elements occurring in geographically and ecologically diverse niches is much higher than previously thought. We report that, amongst these circular genomes, fungal ambiviruses are viroid-like elements that undergo rolling circle replication and encode their own viral RdRp. Thus, ambiviruses are distinct infectious RNAs showing hybrid features of viroid-like RNAs and viruses. We also detected similar circular RNAs, containing active ribozymes and encoding RdRps, related to mitochondrial-like fungal viruses, highlighting fungi as an evolutionary hub for RNA viruses and viroid-like elements. Our findings point to a deep co-evolutionary history between RNA viruses and subviral elements and offer new perspectives in the origin and evolution of primordial infectious agents, and RNA life.
Topics: Viroids; RNA, Catalytic; RNA, Viral; Virus Replication; RNA; RNA Viruses; RNA-Dependent RNA Polymerase; Fungi
PubMed: 37147358
DOI: 10.1038/s41467-023-38301-2 -
Viruses Nov 2018In 2017, Hadidi et al. edited a voluminous monograph entitled "Viroids and Satellites", in which each known viroid and viroid-like satellite species was described in...
In 2017, Hadidi et al. edited a voluminous monograph entitled "Viroids and Satellites", in which each known viroid and viroid-like satellite species was described in detail from many perspectives by more than 100 experts from 24 countries. In its 700+ pages, the book is a much needed detailed and reliable compendium of a subject, which, undoubtedly, is still little known by many potential readers. Because most users of the book may be expected to be practical plant pathologists, it appears essential that the book contain, in addition to the detailed viroid and satellite descriptions, one chapter, in which the basic molecular biology of viroids and satellites is described.
Topics: Books; History, 19th Century; History, 20th Century; Humans; Prions; Research; Viroids
PubMed: 30477079
DOI: 10.3390/v10120663 -
Virus Research May 2022Viroids are small (250-400 nucleotides), single-stranded, circular RNAs without protein-coding capacity that infect a large number of ornamental and crop plant species,... (Review)
Review
Viroids are small (250-400 nucleotides), single-stranded, circular RNAs without protein-coding capacity that infect a large number of ornamental and crop plant species, causing high economic losses worldwide. Strategies to control viroid diseases have included the use of naturally resistant cultivars in breeding programs, the superinfection exclusion with mild strains, the expression of ribonucleases, sense or antisense (catalytic) RNAs and, more recently, RNA interference (RNAi)-based tools. Here, I review the different RNAi strategies used to control viroid infections in plants, with particular focus on highly specific artificial small RNA (art-sRNA)-based tools such as artificial microRNAs and synthetic trans-acting small interfering RNAs. The advantages and future perspectives of art-sRNA-based RNAi for controlling viroid diseases are discussed.
Topics: Plant Breeding; Plant Diseases; RNA Interference; RNA, Small Interfering; RNA, Viral; Viroids
PubMed: 35263623
DOI: 10.1016/j.virusres.2022.198729 -
Viruses Apr 2024There has been substantial progress in the Mediterranean countries regarding research on viroids. Twenty-nine viroid species, all belonging to and genera, have been... (Review)
Review
There has been substantial progress in the Mediterranean countries regarding research on viroids. Twenty-nine viroid species, all belonging to and genera, have been detected in the Mediterranean Basin. Not only have detection methods, such as reverse transcription-quantitative polymerase chain reaction and next-generation sequencing, been used for viroid detection, along with molecular hybridization techniques allowing for rapid detection, identification, and characterization of known and novel viroids in these countries, but eradication measures have also been taken that allowed for the efficient elimination of certain viroids in a number of Mediterranean countries. The eradication measures were followed as recommended by the European and Mediterranean Plant Protection Organization, which is known by its abbreviation, EPPO. The Mediterranean Region has been a niche for viroids since ancient times due to the warm climate and the socio-cultural conditions that facilitate viroid transmission among different host plant species.
Topics: Viroids; Mediterranean Region; Plant Diseases; Plants; High-Throughput Nucleotide Sequencing
PubMed: 38675953
DOI: 10.3390/v16040612 -
Viruses Dec 2018Viroids are highly structured, single-stranded, non-protein-coding circular RNA pathogens. Some viroids are vertically transmitted through both viroid-infected ovule and... (Review)
Review
Viroids are highly structured, single-stranded, non-protein-coding circular RNA pathogens. Some viroids are vertically transmitted through both viroid-infected ovule and pollen. For example, potato spindle tuber viroid, a species that belongs to family, is delivered to the embryo through the ovule or pollen during the development of reproductive tissues before embryogenesis. In addition, some of are also horizontally transmitted by pollen. Tomato planta macho viroid in pollen infects to the ovary from pollen tube during pollen tube elongation and eventually causes systemic infection, resulting in the establishment of horizontal transmission. Furthermore, fertilization is not required to accomplish the horizontal transmission. In this review, we will overview the recent research progress in vertical and horizontal transmission of viroids, mainly by focusing on histopathological studies, and also discuss the impact of seed transmission on viroid dissemination and seed health.
Topics: Flowers; Solanum lycopersicum; Plant Diseases; Plant Viruses; Pollen; Pollination; RNA, Viral; Seeds; Viroids
PubMed: 30545048
DOI: 10.3390/v10120706