Viroid RNAs of cadang-cadang disease of coconuts

Haseloff, J. V. svader; Mohamed, N. A.; Symons, Robert H.

doi:10.1038/299316a0

Cited by 157 publications

(71 citation statements)

References 29 publications

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“…Recently, a similar recombinant DNA, in which 11 nucleotides (GGATCCCCGGG) is terminally duplicated, was reported to have a fairly high level of infectivity (but less than that with dimeric inserts) (12). These results and the finding that the 14 nucleotide sequence is conserved in almost all the viroid RNAs (13,14) PSTV cDNA clone. pAV401 (I5) containing the full length of PSTV eDNA was a kind gift from Drs.…”

supporting

confidence: 71%

“…The 14 nucleotides sequence, GGAUCCCCGGGGAA, is strictly conserved in almost all viroids that have been sequenced so far (13,14). There are only a few exceptions: there is no such sequence in avocado sunblotch viroid (22), and the sequence is replaced in HSV (23) and in cucumber pale fruit viroid (24) by GGAGCCCCGGGGCA, which differs only in two nucleotides.…”

Section: Discussionmentioning

confidence: 99%

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The sequence in the potato spindle tuber viroid required for its cDNA to be infective: A putative processing site in viroid replication.

Hashimoto

Machida

1985

J. Gen. Appl. Microbiol.

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This paper describes the minimum length of the sequence required for the potato spindle tuber viroid (PSTV) cDNA cloned in plasmid or phage DNA vectors to be infective. To examine the infectivity, we cloned the BamHI fragments containing the full length of PSTV cDNA into the BamHI sites of pUC plasmids or double-stranded forms of M13mp phage DNA. When the BamHI monomeric unit was inserted into pUC8 or M13mp8 in a particular orientation, the 14 base pair sequence (GGATCCCCGGGGAA) of PSTV cDNA was directly duplicated at both of the insertion junctions. These recombinant DNAs were infectious to tomato plants at the same level as the recombinant containing a tandem dimer of cDNA. Insertion of the BamHI monomer into pUC 12 or M 13mp 10 created the direct repetition of the 11 base pair sequence (GGATCCCCGGG) at both of the insertion junctions. Infectivities of both the pUC 12 and the M 13mp 10 recombinants were tenfold lower than those of the pUC8 and the M 13mp8 recombinants. On the other hand, when the plasmids or the phage DNAs carried the BarHI monomer in the opposite orientation so as to create the terminal repetition of the 7 base pair sequence (GGGATCC), the infectivity was scarcely detected. We also constructed a recombinant DNA having the AIuI monomeric unit in either orientation, in which no terminal repetition was generated. This recombinant DNA showed no detectable infectivity. These results indicate that the cloned BamHI monomer having the direct repetition of the 14 base pair sequence at both the termini is able to express fully the infectivity, whereas the monomer having the shorter stretch of repetition shows only limited infectivity. Neither the sequences of vectors used nor the orientations of the cDNA sequence are crucial for infection by cloned cDNAs.

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supporting

confidence: 71%

Section: Discussionmentioning

confidence: 99%

The sequence in the potato spindle tuber viroid required for its cDNA to be infective: A putative processing site in viroid replication.

Hashimoto

Machida

1985

J. Gen. Appl. Microbiol.

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“…Furthermore, one of the critical loops for PSTVd trafficking has also been mapped to this domain (Zhong et al, 2008). Unlike the T L and T R domains, the P domain has not been associated with the contribution of the origin of new viroids (divergence) by molecular recombinant or rearrangement processes (Haseloff et al, 1982;Diener, 1983;Keese & Symons, 1985;Hammond et al, 1989;Szychowski et al, 2005;Darò s et al, 2006). Therefore, the functional role of…”

Section: Discussionmentioning

confidence: 99%

Effect of citrus hosts on the generation, maintenance and evolutionary fate of genetic variability of citrus exocortis viroid

Bernad

Duran-Vila

Elena

2009

Journal of General Virology

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Citrus exocortis viroid (CEVd) populations are composed of closely related haplotypes whose frequencies in the population result from the equilibrium between mutation, selection and genetic drift. The genetic diversity of CEVd populations infecting different citrus hosts was studied by comparing populations recovered from infected trifoliate orange and sour orange seedling trees after 10 years of evolution, with the ancestral population maintained for the same period in the original host, Etrog citron. Furthermore, populations isolated from these trifoliate orange and sour orange trees were transmitted back to Etrog citron plants and the evolution of their mutant spectra was studied. The results indicate that (i) the amount and composition of the within-plant genetic diversity generated varies between these two hosts and is markedly different from that which is characteristic of the original Etrog citron host and (ii) the genetic diversity found after transmitting back to Etrog citron is indistinguishable from that which is characteristic of the ancestral Etrog citron population, regardless of the citrus plant from which the evolved populations were isolated. The relationship between the CEVd populations from Etrog citron and trifoliate orange, both sensitive hosts, and those from sour orange, which is a tolerant host, is discussed. INTRODUCTIONViroids are small plant pathogens consisting of a naked single-stranded circular RNA molecule of 246-475 nt, that do not encode any proteins but are endowed with autonomous replication in their host plants. It is very likely that viroids have been co-evolving with their hosts since their origin, although many of them show a wide host range. The identification of viroids in wild and cultivated plants, as symptomless carriers, suggests that certain hosts may act as natural viroid reservoirs (Diener, 1995).Viroids are taxonomically classified into two families, Pospiviroidae and Avsunviroidae (Elena et al., 1991). These families mainly differ in three characteristics. First, all pospiviroidae present a central conserved region (CCR) in their rod-like secondary structure, whereas the avsunviroidae lack such a region. Second, the pospiviroidae rely on cellular factors to process their multimeric replication intermediates into unit-length molecules, while the avsunviroidae present hammerhead ribozyme structures that are able to self-cleave the multimeric forms. Third, the pospiviroidae replicate in the nucleus whereas the avsunviroidae replicate in the chloroplast (reviewed by Flores et al., 2005).Like most RNA and some DNA viruses, viroids replicate within their hosts as polymorphic populations composed of closely related sequence variants generally distributed around a predominant one. This polymorphic population structure arises as a result of (i) the high mutation rates inherent to the cellular DNA-dependent RNA polymerases involved in viroid replication subverted to replicate an RNA template and (ii) the diverse and fluctuating selective pressures imposed by the different ...

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“…On the other hand, the genesis of several viroids, including CLVd [31] and Australian grapevine viroid (AGVd, [52]), was proposed to result from recombination events between viroids belonging to species of different genera co-infecting the same host. Internal recombination events within the same viroid, generating terminal repeats, have also been reported for some nuclear-replicating viroids, such as coconut cadang-cadang viroid (CCCVd) and CEVd [14,32,57].…”

Section: Recombinant Viroidsmentioning

confidence: 99%

Current status of viroid taxonomy

Serio

Flores

Verhoeven³

et al. 2014

Arch Virol

161

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Viroids are the smallest autonomous infectious nucleic acids known so far. With a small circular RNA genome of about 250-400 nt, which apparently does not code for any protein, viroids replicate and move systemically in host plants. Since the discovery of the first viroid almost forty-five years ago, many different viroids have been isolated, characterized and, frequently, identified as the causal agents of plant diseases. The first viroid classification scheme was proposed in the early 1990s and adopted by the International Committee on Taxonomy of Viruses (ICTV) a few years later. Here, the current viroid taxonomy scheme and the criteria for viroid species demarcation are discussed, highlighting the main taxonomic questions currently under consideration by the ICTV Viroid Study Group. The impact of correct taxonomic annotation of viroid sequence variants is also addressed, taking into consideration the increasing application of nextgeneration sequencing and bioinformatics for known and previously unrecognized viroids.

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Viroid RNAs of cadang-cadang disease of coconuts

Cited by 157 publications

References 29 publications

The sequence in the potato spindle tuber viroid required for its cDNA to be infective: A putative processing site in viroid replication.

The sequence in the potato spindle tuber viroid required for its cDNA to be infective: A putative processing site in viroid replication.

Effect of citrus hosts on the generation, maintenance and evolutionary fate of genetic variability of citrus exocortis viroid

Current status of viroid taxonomy

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