Fungi harbor a vast diversity of mobile genetic elements (MGEs). Recently, novel fungal MGEs, tentatively referred to as 'ambiviruses,' were described. 'Ambiviruses' have single-stranded RNA genomes of about 4-5 kb in length that contain at least two open reading frames (ORFs) in non-overlapping ambisense orientation. Both ORFs are conserved among all currently known 'ambiviruses,' and one of them encodes a distinct viral RNA-directed RNA polymerase (RdRP), the hallmark gene of ribovirian kingdom Orthornavirae. However, 'ambivirus' genomes are circular and predicted to replicate via a rolling-circle mechanism. Their genomes are also predicted to form rod-like structures and contain ribozymes in various combinations in both sense and antisense orientations-features reminiscent of viroids, virusoids, ribozyvirian kolmiovirids, and yet-unclassified MGEs (such as 'epsilonviruses,' 'zetaviruses,' and some 'obelisks'). As a first step toward the formal classification of 'ambiviruses,' the International Committee on Taxonomy of Viruses (ICTV) recently approved the establishment of a novel ribovirian phylum, Ambiviricota, to accommodate an initial set of 20 members with well-annotated genome sequences.

• Klíčová slova
• Ambiviricota, Ascomycota, Basidiomycota, ICTV, International Committee on Taxonomy of Viruses, Riboviria, ambiviricot, ambivirus, deltavirus, fungi, fungus, hairpin, hammerhead, phylum, ribozyme, twister, viroid, virus classification, virus nomenclature, virus taxonomy,
• MeSH
• fylogeneze MeSH
• genom virový * MeSH
• houby genetika   virologie   MeSH
• mykoviry genetika   klasifikace   izolace a purifikace   MeSH
• otevřené čtecí rámce * MeSH
• RNA virová genetika   MeSH
• RNA-dependentní RNA-polymerasa genetika   MeSH
• RNA-viry genetika   klasifikace   MeSH
• viroidy * genetika   klasifikace   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• RNA virová MeSH
• RNA-dependentní RNA-polymerasa MeSH

Members of the family Pospiviroidae have single-stranded circular RNA genomes that adopt a rod-like or a quasi-rod-like conformation. These genomes contain a central conserved region that is involved in replication in the nucleus through an asymmetric RNA-RNA rolling-circle mechanism. Members of the family Pospiviroidae lack the hammerhead ribozymes that are typical of viroids classified in the family Avsunviroidae. The family Pospiviroidae includes the genera Apscaviroid, Cocadviroid, Coleviroid, Hostuviroid and Pospiviroid, with >25 species. This is a summary of the ICTV Report on the family Pospiviroidae, which is available at ictv.global/report/pospiviroidae.

• Klíčová slova
• ICTV Report, Pospiviroidae, taxonomy,
• MeSH
• genom virový MeSH
• kruhová RNA MeSH
• replikace viru * MeSH
• RNA katalytická genetika   MeSH
• RNA virová genetika   MeSH
• RNA genetika   MeSH
• viroidy klasifikace   genetika   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• hammerhead ribozyme MeSH Prohlížeč
• kruhová RNA MeSH
• RNA katalytická MeSH
• RNA virová MeSH
• RNA MeSH

Viroids are smallest known pathogen that consist of non-capsidated, single-stranded non-coding RNA replicons and they exploits host factors for their replication and propagation. The severe stunting disease caused by Citrus bark cracking viroid (CBCVd) is a serious threat, which spreads rapidly within hop gardens. In this study, we employed comprehensive transcriptome analyses to dissect host-viroid interactions and identify gene expression changes that are associated with disease development in hop. Our analysis revealed that CBCVd-infection resulted in the massive modulation of activity of over 2000 genes. Expression of genes associated with plant immune responses (protein kinase and mitogen-activated protein kinase), hypersensitive responses, phytohormone signaling pathways, photosynthesis, pigment metabolism, protein metabolism, sugar metabolism, and modification, and others were altered, which could be attributed to systemic symptom development upon CBCVd-infection in hop. In addition, genes encoding RNA-dependent RNA polymerase, pathogenesis-related protein, chitinase, as well as those related to basal defense responses were up-regulated. The expression levels of several genes identified from RNA sequencing analysis were confirmed by qRT-PCR. Our systematic comprehensive CBCVd-responsive transcriptome analysis provides a better understanding and insights into complex viroid-hop plant interaction. This information will assist further in the development of future measures for the prevention of CBCVd spread in hop fields.

• Klíčová slova
• Citrus bark cracking viroid, differentially expressed genes, hop, pathogen, transcriptome analysis, viroids,
• MeSH
• Humulus genetika   metabolismus   virologie   MeSH
• listy rostlin genetika   metabolismus   virologie   MeSH
• nemoci rostlin genetika   virologie   MeSH
• regulace genové exprese u rostlin MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• rostlinné viry genetika   izolace a purifikace   fyziologie   MeSH
• stanovení celkové genové exprese MeSH
• viroidy klasifikace   genetika   izolace a purifikace   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• rostlinné proteiny MeSH

Members of the family Avsunviroidae have a single-stranded circular RNA genome that adopts a rod-like or branched conformation and can form, in the strands of either polarity, hammerhead ribozymes involved in their replication in plastids through a symmetrical RNA-RNA rolling-circle mechanism. These viroids lack the central conserved region typical of members of the family Pospiviroidae. The family Avsunviroidae includes three genera, Avsunviroid, Pelamoviroid and Elaviroid, with a total of four species. This is a summary of the ICTV Report on the taxonomy of the family Avsunviroidae, which is available at http://www.ictv.global/report/avsunviroidae.

• Klíčová slova
• Avsunviroidae, ICTV, avocado sunblotch viroid, eggplant latent viroid, peach latent mosaic viroid, taxonomy, viroid,
• MeSH
• genom virový MeSH
• kruhová RNA MeSH
• replikace DNA MeSH
• replikace viru * MeSH
• RNA katalytická genetika   MeSH
• RNA virová genetika   MeSH
• RNA genetika   MeSH
• viroidy klasifikace   genetika   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• hammerhead ribozyme MeSH Prohlížeč
• kruhová RNA MeSH
• RNA katalytická MeSH
• RNA virová MeSH
• RNA MeSH

Parameters for biolistic transfer of viroid nucleic acids using a Helios Gene Gun device were assayed. The main achievement of this method is high efficiency of inoculation with linear monomeric viroid cDNAs and RNAs. This greatly facilitates the study of mutated sequence variants, viroid libraries and mixed populations. The lower limits for efficient inoculation of monomeric cDNA fragments with the sequence of potato spindle tuber viroid (PSTVd) and native PSTVd RNA as detected 21 days p.i. are in the range of 50 ng and 200 pg per tomato plant, respectively. At a higher dose, i.e. 2 ng of native RNA per plant, biolistic transfer causes drastic stunting compared to conventional mechanical inoculation, which points to higher PSTVd titers after the biolistic transfer. Infection is readily achieved with exact length monomeric RNA transcripts having 5'-triphosphate and 3'-OH termini in amounts ranging from 2 to 20 ng per plant, suggesting no need for any supplementary modifications of ends or RNA circularization. The biolistic transfer is efficient for viroid "thermomutants", which exhibit low or no infectivity with conventional mechanical inoculation with Carborundum. The biolistic inoculation is also efficient for two other members of the Pospiviroidae family, hop stunt and hop latent viroid.

• MeSH
• biolistika * MeSH
• dvouvláknová RNA analýza   MeSH
• nemoci rostlin virologie   MeSH
• RNA virová analýza   chemie   genetika   MeSH
• Solanum lycopersicum virologie   MeSH
• Solanum tuberosum virologie   MeSH
• viroidy klasifikace   genetika   růst a vývoj   patogenita   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• dvouvláknová RNA MeSH
• RNA virová MeSH

Thermal stress of PSTVd-infected Nicotiana benthamiana led to appearance of a broad PSTVd sequence distribution, where most of mutations accumulated in the left half of the viroid's secondary structure including the "pathogenicity" domain. A similar effect had been reported for hop latent viroid [Virology 287 (2001) 349]. The pool of viroid "thermomutants" progenies was transcribed into cDNA and used for biolistic inoculation of Raphanus sativa, where the PSTVd infection was detectable by reverse transcription and polymerase chain reaction (RT-PCR). Newly generated inoculum from R. sativa was used for biolistic transfer to Arabidopsis thaliana wild-type and silencing-deficient mutants bearing one of sde1, sde2, and sde3 locuses. Irrespective to A. thaliana silencing mutants, viroid levels in Brasicaceae species infected with mutated PSTVd variants were of approximately 300 times lower than it is expected for tomato. At the same time, no systemic infection of A. thaliana was achieved with the wild-type PSTVd. In Arabidopsis, a population of PSTVd, consisting of frequent and minor variants, was present and the sequence distribution differed from that of the original viroid "thermomutants"; that is, mutations were not predominantly restricted to the left half of viroid's secondary structure. At least 65% of viroid sequences from Arabidopsis library accumulated mutations in the upper conserved central region (UCCR). In addition, mutants having changes in "hairpin II" domain (C-->A transition at position 229) and in the conserved internal loop element in the left part of viroid structure (single insertion of G at position 39) were detected. All those mutants were inoculated biolistically to tomato and promoted infection especially after prolonged period of plant cultivation (50-80 days pi) when infection reached 70-90%. However, the sequence variants were unstable and reverted to the wild type and to other sequence variants stable in tomato. Our results demonstrate that heat stress-mediated production of viroid quasi-species could be of significance for viroid adaptations.

• MeSH
• Arabidopsis virologie   MeSH
• biolistika * MeSH
• genetická variace * MeSH
• molekulární sekvence - údaje MeSH
• mutace MeSH
• mutageneze MeSH
• nemoci rostlin virologie   MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• Raphanus virologie   MeSH
• reakce na tepelný šok MeSH
• sekvence nukleotidů MeSH
• sekvenční analýza DNA MeSH
• Solanum tuberosum virologie   MeSH
• tabák virologie   MeSH
• viroidy klasifikace   genetika   růst a vývoj   patogenita   MeSH
• vysoká teplota * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH