Reply to Serra et al.: Nucleotide substitutions in plant viroid genomes that multiply in phytopathogenic fungi

Wei, Shuang; Bian, Ruiling; Andika, Ida Bagus; Niu, Erbo; Liu, Qian; Kondō, Hideki; Liu, Yang; Zhou, Hongsheng; Pang, Tianxing; Lian, Ziqian; Liu, Xili; Wu, Yunfeng; Sun, Liying

doi:10.1073/pnas.2001670117

Cited by 12 publications

(8 citation statements)

References 8 publications

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“…graminearum , was determined by inverse RT-PCR in order to provide additional supporting evidence for viroid replication. This additional supporting evidence indicates that the viroid replicated and adapted in fungi and suggests that genome evolution or adaptation may occur during viroid replication in fungi [ 89 ].…”

Section: Vector Transmissionmentioning

confidence: 77%

“…It has been suggested that viroid replication in fungi should also be verified by other detection techniques [ 88 ]. The sequence analysis of the HSVd, which accumulated in F. graminearum , and of the ASBVd, which accumulated in C. parasitica , after eight fungal subcultures showed nucleotide-sequence substitutions, suggesting that these viroids were replicating in and adapting to the fungal hosts [ 89 ]. Nucleotide-sequence substitutions were single-site substitutions, except for two ASBVd mutants, with interchanges occurring between adenine/guanine or cytosine/uracil.…”

Section: Vector Transmissionmentioning

confidence: 99%

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Modes of Viroid Transmission

Hadidi

Sun

Randles

2022

Cells

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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.

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Section: Vector Transmissionmentioning

confidence: 77%

Section: Vector Transmissionmentioning

confidence: 99%

Modes of Viroid Transmission

Hadidi

Sun

Randles

2022

Cells

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“…Therefore, BdcRNAs may represent a novel class of autonomously replicating subviral agents which are not satellites but resemble plant viroids. In previous studies, avocado sunblotch viroid (ASBVd) was shown capable of infecting the unicellular fungus Saccharomyces cerevisiae with their dimeric/oligomeric cDNAs fused in an expression vector [3a] ; ASBVd, hop stunt viroid (HSVd), and iresine viroid-1 (IrVd-1) were respectively transfected with monomeric transcripts into three filamentous phytopathogenic fungi ( Cryphonectria parasitica, Valsa mali , and Fusarium graminearum ) These results support the notion that viroids could replicate in at least one of these three fungi [3e, 15] , although this study has stimulated some controversy since the major evidence for their replication in the fungi was derived by RT-PCR, and a reassessment (with a second detection technique, appropriate controls, and further experiments) is needed to support claims for infectivity in fungi [3e, 16] . No natural infections of fungi with viroids or viroid-like RNAs have been discovered in previous studies [17] and, to our knowledge, this is the first report of infectious viroid-like RNAs (or exogenous small circular RNAs) in a life kingdom (fungi) other than plants.…”

Section: Discussionmentioning

confidence: 57%

Novel Viroid-like RNAs Naturally Infect a Filamentous Fungus

Dong

et al. 2022

Preprint

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Viroids have been found to naturally infect only plants, resulting in big losses for some crops, but whether viroids or viroid-like RNAs naturally infect non-plant hosts remains unknown. Here we report the existence of a set of exogenous, single-stranded circular RNAs, ranging in size between 157-450 nucleotides (nt), isolated from the fungus Botryosphaeria dothidea and nominated Botryosphaeria dothidea circular RNAs (BdcRNAs). BdcRNA(s) replicate autonomously in the nucleus via a rolling-circle replication mechanism following symmetric pathways with distribution patterns depending on strand polarity and species. BdcRNAs can modulate to different degrees specific biological traits (e.g., alter morphology, decrease growth rate, attenuate virulence, and increase or decrease tolerance to osmotic stress and oxidative stress) of the host fungus by regulating related metabolic pathways. Overall, BdcRNA(s) have genome characteristics similar to those of viroids and exhibit pathogenic effects on the fungal hosts. These novel viroid-like RNAs infecting fungi are proposed to be termed as mycoviroids. BdcRNA(s) may be regarded as additional inhabitants at the frontier of life in terms of genomic complexity, and represent a new class of acellular entities endowed with regulatory functions, and novel epigenomic carriers of biological information.

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“…This disappearance could be caused by a defense mechanism against viroid, namely, the RNA silencing system. Viroids are the target of the RNA silencing system and become elicitors of the host defense system via RNA silencing (Cottilli et al, 2019;Wei et al, 2020). Thus, PSTVd could have been degraded by the silencing system, resulting in the elimination of PSTVd from P. infestans.…”

Section: Discussionmentioning

confidence: 99%

Transmission of potato spindle tuber viroid between <i>Phytophthora infestans</i> and host plants

et al. 2022

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Potato spindle tuber viroid (PSTVd) is a naked, circular, single-stranded RNA (356–363 nucleotides in length) which lacks any protein-coding sequences. It is an economically important pathogen and is classified as a high-risk plant quarantine disease. Moreover, it is known that PSTVd is mechanically transmitted by vegetative plant propagation through infected pollen, and by aphids. The aim of this study is to determine the possibility of viroid transmission by potato pathogen Phytophthora infestans (Mont.) de Bary. PSTVd-infected (strain VP87) potato cultivars Gala, Colomba, and Riviera were inoculated with P. infestans isolate PiVZR18, and in 7 days, after the appearance of symptoms, re-isolation of P. infestans on rye agar was conducted. RT-PCR diagnostics of PSTVd in a mixture of mycelia and sporangia were positive after 14 days of cultivation on rye agar. The PSTVd-infected P. infestans isolate PiVZR18v+ was used to inoculate the healthy, viroid-free plants of potato cv. Gala and tomato cv. Zagadka. After 60 days, an amplification fragment of PSTVd was detected in the tissues of one plant of tomato cv. Zagadka by RT-PCR with the primer set P3/P4, indicating successful transmission of PSTVd by P. infestans isolate PiVZR18v+. This result was confirmed by sequencing of the RT-PCR amplicon with primers P3/P4. The partial sequence of this amplicon was identical (99.5 %) to PSTVd strain VP87. RT-PCR showed the possibility of viroid stability in a pure culture of P. infestans isolate PiVZR18v+ after three consecutive passages on rye agar. PSTVd was not detected after the eighth passage on rye agar in P. infestans subculture. These results are initial evidence of potato viroid PSTVd being bidirectionally transferred between P. infestans and host plants.

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Reply to Serra et al.: Nucleotide substitutions in plant viroid genomes that multiply in phytopathogenic fungi

Cited by 12 publications

References 8 publications

Modes of Viroid Transmission

Modes of Viroid Transmission

Novel Viroid-like RNAs Naturally Infect a Filamentous Fungus

Transmission of potato spindle tuber viroid between <i>Phytophthora infestans</i> and host plants

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