共查询到20条相似文献,搜索用时 15 毫秒
1.
Summary The mitochondria of isolate FS37 from Nectria haematococca mating population I (Fusarium solani f. sp. cucurbitae) contain two linear plasmids, pFSCI and pFSC2, of 9.2 and 8.3 kbp, respectively. Evidence for a protein blocking the 5 termini of these plasmids was obtained from exonuclease digestion experiments. A single protein band with an apparent Mr of 80 K was labeled when the DNA-protein complex of either plasmid was reacted with [125I] Bolton-Hunter reagent and then digested with DNase I. DNA sequence analysis of the termini of both plasmids revealed long inverted repeats of 1,211 by (pFSC1) and 1,027bp (pFSC2). No sequence similarity was found between the terminal inverted repeats (TIRs) of pFSC1 and pFSC2, nor was any similarity identified between the TIRs of the these plasmids and sequences of TIRs from other linear DNAs. A restriction fragment containing the TIR of pFSCI conferred autonomous replication when incorporated into an integrative transformation vector of Ustilago maydis. 相似文献
2.
Summary A linear DNA plasmid, designated pCF637, was isolated from the fungus Ceratocystis fimbriata Ell. & Halst. strain CF637. It has an apparent molecular weight of 5.3 × 106 daltons (8.2 kb). A restriction pattern of pCF637 using the enzymes AvaI, EcoRV and HpaII, was done. That pCF637 was sensitive to exonuclease III, but resistant to -exonuclease, suggest that there might be a protein associated with the 5 termini. The blocking action of the protein on -exonuclease was not eliminated by treatment with either pronase or proteinase K. The plasmid was also checked for homology with pFQ501, a linear plasmid found in strain CF560 of Ceratocystis fimbriata. By Southern hybridization under moderate stringency conditions, no homology was detected. The approximate copy number of the plasmid was estimated to be about 20–30 copies per cell by scanning, with a laser densitometer, a gel electrophoretic PolaroidTM negative. No function is known for these plasmids. 相似文献
3.
Mitochondrial RNA was isolated from the morel strain Morchella conica 3 harbouring the linear plasmid pMC3-2 and subjected to gel electrophoresis followed by a Northern analysis using cloned fragments of the plasmid pMC3-2 as probes. Hybridization was obtained only with central parts of pMC3-2 and specific bands of mtRNA. The hybridization bands (2.8 kb and 1.0 kb) correspond in size to the length of the two ORFs of pMC3-2 which were deduced from nucleotide-sequence data. Thus, both ORFs, one encoding a DNA polymerase and the other a yet unknown protein, are transcribed in the mitochondria of the plasmid-bearing Morchella conica strain. 相似文献
4.
Summary Crosses were set up, using the b2 locus of Ascobolus immersus, to detect and measure the restoration of the parental genotype of a chromatid from hetero-duplex. From the results it can be concluded that: (1) restoration occurs, and its frequency is comparable to the frequency of conversion; (2) the relative frequency of conversion and restoration on the two homologous chromatids is that expected if the disparity in conversion to mutant and to wild-type of the marker is caused by the decision whether to excise the mutant or wild-type chain. This decision is the same on both chromatids. However, when all data are pooled, a slight, but significant, excess of conversion over restoration is found. The cause of this in discussed; (3) the absence of an excess of restoration over conversion is taken to imply that, in this system, the length of heteroduplex formed in an event is continuous; (4) these findings support the interpretation of tetrads where a crossover is separated from conversion, that they arise by independent correction giving both conversion and restoration in a heteroduplex tract continuous with the crossover. 相似文献
5.
The molecular characterization of an additional DNA species (pAL2-1) which was identified previously in a long-lived extrachromosomal mutant (AL2) of Podospora anserina revealed that this element is a mitochondrial linear plasmid. pAL2-1 is absent from the corresponding wild-type strain, has a size of 8395 bp and contains perfect long terminal inverted repeats (TIRs) of 975 bp. Exonuclease digestion experiments indicated that proteins are covalently bound at the 5 termini of the plasmid. Two long, non-overlapping open reading frames, ORF1 (3,594 bp) and ORF2 (2847 bp), have been identified, which are located on opposite strands and potentially encode a DNA and an RNA polymerase, respectively. The ORF1-encoded polypeptide contains three conserved regions which may be responsible for a 3–5 exonuclease activity and the typical consensus sequences for DNA polymerases of the D type. In addition, an amino-acid sequence motif (YSRLRT), recently shown to be conserved in terminal proteins from various bacteriophages, has been identified in the amino-terminal part of the putative protein. According to these properties, this first linear plasmid identified in P. anserina shares all characteristics with invertrons, a group of linear mobile genetic elements. 相似文献
6.
Extrachromosomal DNA elements were found in field isolates of Rhizoctonia solani belonging to anastomosis groups (AG) 1–5. An isolate of AG-5 (Rh41) contains a 3.6-kbp plasmid (pRS188) which has a similar A+T content to mitochondrial DNA. pRS188 is linear and has knob structures at its ends, as revealed by electron microscopy. Exonuclease digestions show that the linear ends of pRS188 are protected, and remain protected even after proteinase K digestion. pRS188 does not hybridise to nuclear or mitochondrial DNAs of its host isolate (Rh41), to total DNAs of other plasmid-less AG-5 isolates, or to total DNA of plasmid-harbouring isolates belonging to different AGs. Cellular-fractionation experiments suggest that pRS188 is associated with mitochondria, but it remains undecided whether this occurs inside or outside of the organelles. The nucleotide sequence of about 60% of the plasmid has been determined, revealing no open reading frame longer than 91 amino acids, and no known gene or genetic element is detected in the sequence contigs of 300–1572 bp length. Similar studies were performed with the plasmid pRS104 present in an isolate of AG-4 (Rh36), the sequence of which exhibits essentially the same features as pRS188 except that its A+T content resembles that of nuclear DNA. Pathogenicity tests reveal that the isolates Rh41 and R36 are as virulent as the plasmid-less isolates of AG-4 and-5, indicating that the plasmids do not play any role in pathogenicity. 相似文献
7.
We have determined the complete nucleotide sequence of a linear mitochondrial plasmid from a natural isolate of a homothallic species ofGelasinospora. The plasmid genome is 8231 by long. It carries terminal inverted repeats of 1137 bp. Extending inwards from the terminal repeats are two long open reading frames coding for putative proteins with similarity to DNA and RNA polymerases. These are separated by a short intergenic region. The plasmid sequence shows remarkable similarity to that of theNeurospora intermedia senescence-plasmid kalilo. Overall the two plasmids have a similar genetic organization and are clearly homologous at the sequence level. The main differences are in the intergenic region and in the terminal repeats. 相似文献
8.
The gene structure and expression of the linear mitochondrial plasmids of the white-rot fungus Pleurotus ostreatus, pMLP1 and pMLP2, were analyzed. Cleavage by proteinase K and exonucleases indicated that the 5′ ends of pMLP1 and pMLP2
DNAs were associated with terminal proteins. Nucleotide sequencing of the entire pMLP1 DNA revealed that it consists of 9,879 bp
with terminal inverted repeat (TIR) sequences of 381 bp. The end sequence of TIR in pMLP1 is 3′-CCCCC-5′, similar to those
of Escherichia coli phage PRD1. The pMLP1 plasmid harbors two long open reading frames (ORF1 and ORF2) and at least one minor ORF (mORF1). The
deduced product of ORF1 is homologous to RNA polymerases of yeast mitochondria and several bacteriophages, whereas that of
ORF2 is homologous to the protein-primed DNA polymerases of family B type. The mORF1 encodes a highly basic protein, most
likely a TIR-binding protein, with no apparent sequence homology in the database. Expression of the predicted gene products
from pMLP1 in mitochondria was demonstrated by Western blot analysis using antibodies against various expressed regions of
pMLP1 ORFs. A plasmid-free strain, generated by curing with ethidium bromide, did not express any of these gene products.
Terminal proteins of 70 kDa (TP1) and 73 kDa (TP2) were identified from pMLP1 and pMLP2, respectively. Western blot analysis
indicated that TP1 was generated from the N-terminal half of the full-length product of ORF2 encoding a putative DNA polymerase.
Received: 9 February 2000 / Accepted: 18 July 2000 相似文献
9.
Monica Marcinko-Kuehn Xiao Yang Fons Debets David J. Jacobson Anthony J. F. Griffiths 《Current genetics》1994,26(4):336-343
Two Louisiana strains of Neurospora tetrasperma contain a linear plasmid (LA-kalDNA) with a restriction map identical to the Hawaiian Neurospora intermedia senescence plasmid, kalDNA, but with termini 100 nucleotide pairs shorter. One of these strains also bore a circular plasmid similar to the Hawaiian circular plasmid Hanalei-2. One species probably acquired both plasmids from the other by horizontal transfer, at a time sufficiently distant for sequence divergence to take place. Many LA-kalDNA-bearing derivative strains senesced, but this plasmid does not guarantee senescence. Furthermore, LA-kalDNA does not insert into mtDNA. One senescent strain showed no LA-kalDNA. The plasmids are effectively transmitted via the pseudohomothallic sexual cycle. Single mating-type derivatives transmit plasmids maternally. 相似文献
10.
The linear plasmid pMC3-2 from Morchella conica is structurally related to adenoviruses 总被引:4,自引:0,他引:4
Summary pMC3-2, one of two linear plasmids localised in the mitochondria of the ascomycete Morchella conica, was completely sequenced. It is 6044 bp in size, contains terminal inverted repeats of 713 and 710 bp length and two open reading frames, ORF1 and ORF2, spanning 2706 bp and 918 bp, respectively. ORF1 probably encodes a viral B-type DNA-polymerase. Concerning ORF2, no homology to any other published protein-or DNA-sequence could be detected. According to the structure of DNA-polymerases, linear plasmids can be grouped into two classes reflecting their localisation either in the cytoplasm or within the mitochondria. In general, the structure of plasmid pMC3-2, as well as of other linear plasmids from filamentous fungi, indicates a close relationship of these genetic elements to adenoviruses. 相似文献
11.
12.
Summary In one particular myxamoebal strain (NG7; mF+) of Physarum polycephalum, a linear mitochondrial plasmid (mF plasmid) which promotes mitochondrial fusion has been identified. A mating between mF- strains, that do not carry the mF plasmid, resulted in uniparental inheritance of the mtDNA. In matings between mF+ and mF- strains a recombination occurred between the mtDNA and the mF plasmid, and recombinant mtDNA was generated with the end of the mF plasmid as its ends. The DNA sequences of the recombination site in the mtDNA and the mF plasmid, and of the recombinant mtDNA, revealed that the mF plasmid had a 473-bp sequence that was identical to, but slightly shorter than, a 477-bp sequence of the mtDNA. This so-called identical sequence was found at the junction between unique sequences of the mF plasmid and the mtDNA in the recombinant mtDNA. Thus, the recombination between the mtDNA and the mF plasmid was due to reciprocal crossing-over at the identical sequence. 相似文献
13.
Summary
Pichia inositovora, strain NRRL Y-18709, which contains three linear double-stranded DNA plasmids, pPinl-1, pPinl-2 and pPinl-3, was cured of these plasmids both by growing the strain in the presence of 50 g/ml bisbenzimide, and by exposure to ultraviolet light. Both cured and uncured strains were tested for growth on a variety of carbon sources. No differences in growth response were detected, indicating no discernible involvement of the linear plasmids in the catabolism of these compounds. Culture supernatants of Pichia inositovora were shown to contain a substance larger than 100 kDa that is toxic to Saccharomyces cerevisiae, strain GS 1688. Toxin activity was optimal in YEPD assay plates containing 50 mM citrate buffer with a pH between 3.4 and 4.2. Culture supernatants from P. inositovora were also weakly active against Cephaloascus albidus, strain NRRL Y-18710, and Citeromyces matritensis, strain NRRL Y-18711. Concentrated supernatants from cured P. inositovora strains did not exhibit these activities, consistent with the hypothesis that this toxic activity is linear plasmid-encoded. Unlike the wellknown Kluyveromyces lactis system or the newly identified P. acaciae system, P. inositovora strains cured of their linear plasmids do not become detectably sensitive to toxin produced by the wild-type strain, suggesting a nonplasmid-encoded immunity function. 相似文献
14.
The mitochondria of Physarum polycephalum have a linear plasmid (mF) which promotes mitochondrial fusion. To determine the terminal structure of the mF plasmid, restriction fragments derived from its ends were cloned and sequenced. The sequences showed that the mF plasmid has three kinds of terminal inverted repeats (TIRs). The most characteristic feature is a 144-bp repeating unit which exists between a 205-bp TIR at the extreme ends of the plasmid and another 591-bp TIR. All of the clones showed at least one of these 144-bp repeating units. The GC content of the 205-bp TIR (49%) was higher than those of the other TIRs and of another sequenced region (23%). This TIR can form three thermodynamically-stable hairpin structures based on complex internal palindromic components. Moreover, in the right terminal region of the mF plasmid, there is an open reading frame (ORF) which covers the entire 591-bp TIR and most of one of the 144-bp repeating units. This ORF encodes a 547-amino-acid polypeptide, ORF-547, and shows extensive homology with the polymerization domain of the putative DNA polymerases of linear mitochondrial plasmids from other sources. 相似文献
15.
16.
Hurley S. Shepherd 《Current genetics》1992,21(2):169-172
Summary Three plasmids, with sizes of 7.0 kbp, 6.8 kbp, and 5.0 kbp and designated pAal-1, pAal-2 and pAal-3 respectively, have been found in a tentoxin-producing isolate of Alternaria alternata. Exonuclease digestions show these plasmids to be linear with blocked 5 ends. Plasmid pAal-1 does not hybridize to nuclear DNA, mitochondrial DNA, or double-stranded RNA from a mycovirus found in the isolate, but does hybridize weakly to a series of linear DNAs which are not visible on gels and may include pAal-2 and pAal-3. Cellular fractionation shows that, unlike other linear fungal plasmids, these plasmids are not localized in the mitochondria. Plasmids have not been found in other tentoxin-producing isolates and there is no evidence that these plasmids have any effect on the production of tentoxin. 相似文献
17.
Replicative plasmids generated through in-vivo recombination have been identified among transformants of the fungus Pleurotus ostreatus. In addition to sequences from a standard selection vector (pAN7-1), these recombinant plasmids contain recombined sequences of chromosomal origin conferring replicative potential upon the vector. One such recombined sequence, an 1148-bp insert into plasmid pP01, has been characterized. This sequence has been analyzed for secondary structural features as well as for consensus sites affiliated with origins of replication (ori) in other eukaryotic systems. The 1148-bp insert lacks an ORF and does not contain an acceptable match to the commonly identified 11-bp ars consensus sequence (A/TTTTATA/GTTTA/T) for autonomous replication in the yeast Saccharomyces cerevisiae. The analysis, however, revealed a cluster of three hairpin-loop-forming subsequences with individual G25°C free energy values of-7.6,-6.4 and-5.2 kcal mol-1. Also found were two 7-bp analogues to centromere-affiliated sequences recognized in other fungi, as well as several putative gyrase recognition sites comparable to the 9-bp S. cerevisiae/E. coli gyrase-binding consensus sequence. Sequences comparable to the ori of the yeast 2-m plasmid or to various sequences associated with ori of yeast/fungal mitochondrial DNAs (mtDNA) were not present in the 1148-bp insert. Replication of pP01 appears rather to involve a replication of chromosomal derivation devoid of an ars-type consensus. 相似文献
18.
Summary All isolates of Tilletia spp. investigated (five isolates of T. caries, including one from Japan, two isolates of T. laevis, and five isolates of T. controversa) contained a linear DNA plasmid ranging in size from 7.2 to 7.6 kb. All plasmids were highly homologous to each other as shown by DNA-DNA hybridization and comparison of restriction enzyme sites. Variability in the size of the plasmid was found to be due to differences within a central region of the plasmid. No homology between the plasmid and mitochondrial or nuclear DNA was found, but the mitochondrial origin of the plasmid was confirmed. 相似文献
19.
Summary To functionally characterize the genes encoded by the larger killer plasmid pGKL2 from Kluyveromyces lactis a previously developed in-vivo recombination system was exploited. An in-vitro modified version of the cytoplasmically expressible LEU2 gene cartridge (LEU2
*) flanked by appropriate pGKL2 segments was used to replace the central part of the ORF1 region of pGKL2. Transformation of a Leu- killer strain resulted in the expected disruption of ORF1 in the resident pGKL2. The Leu+ transformants obtained can be assigned to three classes. Class I carries both killer plasmids, pGKL1/2, and the recombinant pGKL2 derivative termed pRKL2. Class II and III additionally harbor palindrome and hairpin-like plasmids, respectively. Upon subculturing of class I transformants under selective pressure, segregation of the native pGKL2 and the recombinant pRKL2 eventually occurs resulting in total loss of pGKL2. No differences concerning killer and immunity phenotype between a pRKL2-harboring strain and the native pGKL2-carrying recipient could be detected. Thus pGKL2 ORF1 is dispensable for both expression of killer/immunity phenotypes and for the replication and maintenance of the K. lactis killer plasmids. 相似文献
20.
Summary Southern hybridization of the total DNA of Agrocybe aegerita with cloned mitochondrial (mt) probes revealed a sequence homology between two distant mitochondrial restriction fragments. From the mtDNA restriction map and the distribution of restriction sites on the cross-hybridizing mitochondrial fragments, two copies of a large inverted repeated sequence (IR) of 3 kbp were located on the mitochondrial genome. These IR sequences divided the 80 kbp mtDNA into two singlecopy regions of 24 kbp (SSC) and 50 kbp (LSC). For the first time in higher fungi, this IR sequence has been shown to be involved in an intramolecular homologous recombinational event. Such a rearrangement led to an inversion of the orientation of the two unique-copy regions, without any change in mtDNA complexity. The location of the recombinational event was compared with previously reported plant and fungal mitochondrial rearrangements and the potential role of the IR sequence was discussed. 相似文献