Linear plasmidlike DNA in the plant pathogenic fungus Fusarium oxysporum f. sp. conglutinans

Kistler, H. Corby; Leong, Susan

doi:10.1128/jb.167.2.587-593.1986

Cited by 69 publications

(31 citation statements)

References 26 publications

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“…This indicated that the autonomous plasmids differ from the linear mitochondrial plasmid found in F. oxysporum from which pFT1 was partially derived. Mitochondrial plasmids band with the mitochondrial DNA fraction in the presence of bisbenzimide (14). The banding of the autonomous plasmids with nuclear DNA in CsCl-ethidium bromide gradients suggested that the plasmids were linear.…”

Section: Resultsmentioning

confidence: 97%

“…1) was constructed as follows: a 1.8-kilobase (kb) fragment from pFOXC2, the linear mitochondrial plasmid endogenous to F. oxysporum f. sp. raphani, was cloned into pUC12, producing pCK1 (14). A 2.4-kb SaiI fragment from pDH25 (6), which contains the bacterial hygromycin B phosphotransferase gene (hph) driven by the Aspergillus nidulans trpC promoter, was ligated into the single Sail site of pCK1.…”

Section: Resultsmentioning

confidence: 99%

“…Hybridizations were carried out under previously described conditions (14). To estimate the copy number of free plasmid in fungal cells, DNAs from fungal minipreps were hybridized to 32P-labeled pFTl (see Results) and compared with a dilution series of pFTl standards on the same filter.…”

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confidence: 99%

“…Large-scale nuclear and mitochondrial DNA isolations have been previously described (14). DNA "minipreps" from fungi were obtained from strains grown in 15 ml of PDB with 10 ,ug of hygromycin B per ml.…”

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confidence: 99%

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In vivo rearrangement of foreign DNA by Fusarium oxysporum produces linear self-replicating plasmids

1990

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Particular combinations of fungal strains and transformation vectors allow for fungal rearrangement of normally integrative plasmids, resulting in the creation of linear self-replicating plasmids in Fusarium oxysporum. The rearrangement results in the addition of fungal DNA, including telomere consensus sequences, to plasmid termini. The mechanism by which this rearrangement occurs is unclear, but it has similarities to extrachromosomal gene amplification. A DNA fragment which allows for linear autonomous replication upon reintroduction to the fungus was subcloned and sequenced. This DNA sequence contains the repeated telomeric sequence TTAGGG flanked by a region of twofold symmetry consisting primarily of pUC12 DNA. Isolation and identification of this sequence is the first step toward development of vectors that function as artificial chromosomes in filamentous fungi. This sequence was shown to promote autonomous replication and enhance transformation in several strains of F. oxysporum, Nectria haematococca, and Cryphonectria parasitica.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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In vivo rearrangement of foreign DNA by Fusarium oxysporum produces linear self-replicating plasmids

1990

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“…Plasmids pFOXC2 and pFOXC3 are 1.9-kb linear DNAs that reside in mitochondria of certain forma specialis of the fungal plant pathogen Fusarium oxysporum (17). The plasmids are classified as retroplasmids because they each encode a reverse transcriptase (RT) and replicate via an RNA intermediate (18,24).…”

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Relaxed Primer Specificity Associated with Reverse Transcriptases Encoded by the pFOXC Retroplasmids of Fusarium oxysporum

et al. 2004

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The pFOXC mitochondrial retroplasmids are small, autonomously replicating linear DNAs that have a telomere-like repeat of a 5-bp sequence at their termini. The plasmids are possible evolutionary precursors of the ribonucleoprotein complex telomerase, as they encode an active reverse transcriptase (RT) that is involved in plasmid replication. Using an in vitro system to study reverse transcription, we show that the pFOXC RT is capable of copying in vitro-synthesized RNAs by use of cDNA primers or extension of snapped-back RNA templates. The ability of the pFOXC RT to use base-paired primers distinguishes it from the closely related RTs encoded by the Mauriceville and Varkud mitochondrial retroplasmids of Neurospora spp. Reaction products are similar, but not identical, to those obtained with conventional RTs, and differences reflect the ability of the pFOXC RT to initiate cDNA synthesis with loosely associated primers. The pFOXC RT can also copy DNA templates and extend 3 mismatched DNA oligonucleotide primers. Analysis of pFOXC in vivo replication intermediates suggests that telomeric repeats are added during reverse transcription, and the ability to extend loosely associated primers could play a role in repeat formation by mechanisms similar to those associated with telomerase and certain non-long-terminal-repeat retrotransposons.Plasmids pFOXC2 and pFOXC3 are 1.9-kb linear DNAs that reside in mitochondria of certain forma specialis of the fungal plant pathogen Fusarium oxysporum (17). The plasmids are classified as retroplasmids because they each encode a reverse transcriptase (RT) and replicate via an RNA intermediate (18, 24). To date, retroplasmids have been found only in mitochondria of six species of filamentous fungi and fall into two groups, linear and circular, based on the structure of the plasmid DNA (1,3,7,14,20).Plasmids pFOXC2 and pFOXC3 have an interesting structure that is described as a "clothespin," as it includes a hairpin at one terminus and two to five copies of a pentameric repeat (5Ј-ATCTA) at the other terminus (24). This structure is unique among plasmids that have been identified thus far, yet it bears some resemblance to eukaryotic chromosomes that contain multiple copies of short DNA sequences at their termini. The association of genetic elements that have telomerelike repeats and replicate via reverse transcription suggests that the pFOXC plasmids may be contemporary descendants of primitive chromosomes and/or have a direct evolutionary relationship to telomerase, the ribonucleoprotein (RNP) complex that protects and maintains the ends of chromosomes. Phylogenetic analysis of the RT encoded by the pFOXC plasmids (pFOXC RT) indicates that it is most closely related to the RTs encoded by the Mauriceville and Varkud circular retroplasmids of Neurospora spp. (24). As a group, mitochondrial retroplasmids are deeply rooted within the RT phylogenetic tree and are thought to be ancestral to other retroelements, including telomerase RTs (TERTs) (9, 10). The ancestral nature of mitochondrial ...

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2006

The Fusarium Laboratory Manual

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Linear plasmidlike DNA in the plant pathogenic fungus Fusarium oxysporum f. sp. conglutinans

Cited by 69 publications

References 26 publications

In vivo rearrangement of foreign DNA by Fusarium oxysporum produces linear self-replicating plasmids

In vivo rearrangement of foreign DNA by Fusarium oxysporum produces linear self-replicating plasmids

Relaxed Primer Specificity Associated with Reverse Transcriptases Encoded by the pFOXC Retroplasmids of Fusarium oxysporum

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