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  • 1
    Electronic Resource
    Electronic Resource
    Origin and evolution of plasmids (1998)
    Springer
    Antonie van Leeuwenhoek 73 (1998), S. 117-126 
    Details
    ISSN: 1572-9699
    Keywords: riboplasmids ; encapsidation ; pseudovirions ; selfish plasmids ; replicons ; ribozyme ; Agrobacterium ; Rhizobium ; grapevines ; L-tartrate ; lignin ; methoxyphenols ; satellite viruses ; opines ; crown gall ; T-DNA ; origin of replication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies on the origin and evolution of plasmids may provide valuable insights on the promiscuous nature of DNA. The first examples of the selfish nature of nucleic acids are exemplified by primordial oligoribonucleotides which evolved into primitive replicons. The propagation of these molecules were likely patterned after the current viral RNA ribozymes, which have been recently shown to possess RNA synthesizing and template mediated polymerizing capabilities in the absence of proteins. The parasitic nature of nucleic acids is depicted by satellite nucleic acid molecules associated with viruses. The satellites of adenovirus and tobacco ringspot virus serve as established examples: they contain no open reading frames. Comparative analysis of the replication origins of virions and plasmids show them to be conserved, originating from the simplest autocatalytic replicon to highly complex and evolved plasmids, replicating by a rolling circle mechanism. The eventual association of proteins with nucleic acids provided added efficiency and protective advantages for molecular perpetuation. The promiscuous and selfish nature of plasmids is demonstrated by their ability to genetically engineer their host so that the host cell is best able to cope and survive in hostile environments. Survival of the host ensures survival of the plasmid. Sequestering of genes by plasmids occurs when the environmental conditions negatively affect the host. The sequestering mechanism is fundamental and forms the outreach mechanisms to generate and propagate macromolecules of increasing size when necessary for survival. The level of sophistication of plasmids increases with the addition of new genes such as those that allow the host to occupy a specific environment normally inhospitable to the host cell. The vast range of plasmid types which have obtained genes interchangeably reflect the levels of sophistication achieved by these macromolecules. The Ti plasmid in Agrobacterium tumefaciens and the pSym and accessory plasmids in Rhizobium illustrate the level of complexity attained by replicons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000652513822
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  • 2
    Electronic Resource
    Electronic Resource
    Transformation and regeneration of Lobelia erinus using Agrobacterium tumefaciens (1998)
    Springer
    Plant cell reports 18 (1998), S. 308-311 
    Details
    ISSN: 1432-203X
    Keywords: Key words Campanulaceae ; Lobelia erinus ; Transformation ; Agrobacterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A transformation/regeneration system was developed for the common garden Lobelia (Lobelia erinus). Using an Agrobacterium-based protocol, over 40 transformants have been generated with four different binary vectors. The explant source was hypocotyl-root sections from axenically grown seedlings. Stable transformation was demonstrated by Southern hybridization analysis, β-glucuronidase staining, and transmission of the T-DNA to progeny. This extends the ever-widening range of transformable plant species to the Campanulaceae and will allow molecular studies of development and physiology in this easily cultured and popular garden plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990050577
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  • 3
    Electronic Resource
    Electronic Resource
    Factors affecting soybean cotyledonary node transformation (1998)
    Springer
    Plant cell reports 18 (1998), S. 180-186 
    Details
    ISSN: 1432-203X
    Keywords: Key words Soybean ; SAAT (sonication assisted Agrobacterium-mediated transformation) ; Agrobacterium ; Transformation ; KYRT1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cotyledonary node transformation efficiency was evaluated using a sonication assisted Agrobacterium-mediated transformation (SAAT) protocol, three dissimilar A. tumefaciens strains, and explants derived from 28 diverse cultivars and/or genotypes of soybean [Glycine max (L.) Merr.]. The explants were evaluated at 10 and 45 days after co-cultivation for transformation with a binary vector containing both a GUS-intron gene and an NPTII selectable marker. The best overall strain of A. tumefaciens was determined to be KYRT1 based on stable GUS transformation of soybean cotyledonary node explants measured at the terminal 45 day evaluation point. SAAT did not increase stable transformation at 45 days post co-cultivation. SAAT was determined to significantly decrease shoot proliferation of some genotypes, but it is unclear what effect this may have on the recovery of transformed shoots. Significant differences were also detected between genotypes for transformation and shoot proliferation frequency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990050553
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  • 4
    Electronic Resource
    Electronic Resource
    Transgenic peppermint (Mentha×piperita L.) plants obtained by cocultivation with Agrobacterium tumefaciens (1998)
    Springer
    Plant cell reports 17 (1998), S. 165-171 
    Details
    ISSN: 1432-203X
    Keywords: Key words Peppermint ; Transformation ; Agrobacterium ; GUS ; Transgenic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The first transgenic peppermint (Mentha×piperita L. cultivar Black Mitcham) plants have been obtained by Agrobacterium-mediated transformation by cocultivation with morphogenically responsive leaf explants. Basal leaf explants with petioles, from leaves closest to the apex of in-vitro-culture-maintained shoots (5 cm), exhibited optimal shoot organogenetic responsiveness on medium supplemented with thidiazuron (8.4 µm). Shoot formation occurred at sites of excision on the leaf blade and petiole either directly from cells of the explant or via a primary callus. Analyses of transient GUS activity data indicated that DNA delivery by microprojectile bombardment was more effective than Agrobacterium infection. However, no transgenic plants were obtained from over 22,000 leaf explants after particle bombardment. Cocultivation of leaf explants with Agrobacterium strain EHA 105 and kanamycin selection produced transgenic plants. Greater transient and stable -glucuronidase (GUS) activities were detected in explants or propagules transformed with the construct where gusA was driven by the pBISN1 promoter rather than a CaMV 35S promoter. Eight plants were subsequently regenerated and verified as transgenic based on detection of the nptII transgene by PCR and Southern blot analyses. The Southern analyses indicated that the plants were derived from eight unique transformation events. All transgenic plants appeared morphologically normal. Analyses of GUS activities in leaves sampled from different portions of these transgenic plants, 10 months after transfer to the greenhouse, indicated that six out of the eight original regenerants were uniformly transformed, i.e., did not exhibit chimeric sectors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990050372
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  • 5
    Electronic Resource
    Electronic Resource
    Agrobacterium tumefaciens-mediated transformation of Eucalyptus camaldulensis and production of transgenic plants (1998)
    Springer
    Plant cell reports 17 (1998), S. 675-680 
    Details
    ISSN: 1432-203X
    Keywords: Key words Genetic transformation ; Agrobacterium ; Eucalyptus ; Regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An efficient system for Agrobacterium-mediated transformation of Eucalyptus camaldulensis and production of transgenic plants was developed. Transformation was accomplished by cocultivation of hypocotyl segments with Agrobacterium tumefaciens containing a binary Ti-plasmid vector harboring chimeric neomycin phosphotransferase and β-glucuronidase (GUS) genes. A modified Gamborg's B5 medium used in this study was effective for both callus induction and regeneration of transgenic shoots. This medium could also effectively maintain the organogenic capability of callus for more than a year. Culturing transgenic shoots in Murashige and Skoog medium supplemented with 0.1 mg ⋅ l–1 benzylaminopurine prior to root induction in rooting medium markedly increased the rootability of shoots that were recalcitrant to rooting. Histochemical assay revealed the expression of the GUS gene in leaf, stem, and root tissues of transgenic plants. Insertion of the GUS gene in the nuclear genome of transgenic plants was verified by genomic Southern hybridization analysis, further confirming the integration and expression of T-DNA in these plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990050464
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  • 6
    Electronic Resource
    Electronic Resource
    Activity of the CaMV 35S promoter in various parts of transgenic early flowering birch clones (1998)
    Springer
    Plant cell reports 18 (1998), S. 243-248 
    Details
    ISSN: 1432-203X
    Keywords: Key wordsBetula pendula ; Transformation ; Agrobacterium ; Gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Early flowering together with small size would be useful for various biotechnical or genetic studies on trees. We report here the selection and micropropagation of early flowering birch (Betula pendula) clones (BPM1–12) obtained from seeds of birches bred elsewhere for early flowering. Under conditions that accelerate flowering (a high CO2 level, strong and continuous illumination), the first male inflorescences emerged in 3–5 months, the trees then being 20–80 cm high. Transgenic lines (CaMV 35S-GUS INT) were produced through Agrobacterium-mediated gene transfer from BPM2, BPM5 and JR1/4 (a normally flowering birch). β-Glucuronidase (GUS) activities in the different lines, assayed 1–1.5 years after transformation, varied greatly. During further in vitro culture for 10 months, the activities decreased to 0.3–7% of the original values. GUS activities were detected in all organs studied, including the developing male inflorescences; the highest activity was in the roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990050564
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  • 7
    Electronic Resource
    Electronic Resource
    Transformation of arctic bramble (Rubus arcticus L.) by Agrobacterium tumefaciens (1998)
    Springer
    Plant cell reports 17 (1998), S. 822-826 
    Details
    ISSN: 1432-203X
    Keywords: Key words Rosaceae ; β-Glucuronidase ; Regeneration ; Agrobacterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Genetic transformation of arctic bramble (Rubus arcticus L.) was achieved utilizing a Ti-plasmid vector system of Agrobacterium tumefaciens. Internodal stem segments were inoculated with Agrobacterium strain EHA101 carrying a T-DNA with the CaMV 35 S promoter-gus-int marker gene from which β-glucuronidase (GUS) is expressed only in plants. Regenerants were produced on Murashige and Skoog medium. Growth of Agrobacterium was inhibited with cefotaxime. Kanamycin was used as the selective agent for the transformants. Regenerants were assayed by histochemical GUS staining, and by Southern analysis using a gus-int probe. Transgenic arctic bramble plants containing gus-int and expressing GUS were recovered. Expression has been stable for 3 years in micropropagation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990050491
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  • 8
    Electronic Resource
    Electronic Resource
    CaMV 35S promoter directs β-glucuronidase expression in the laticiferous system of transgenic Hevea brasiliensis (rubber tree) (1998)
    Springer
    Plant cell reports 17 (1998), S. 621-625 
    Details
    ISSN: 1432-203X
    Keywords: Key wordsHevea brasiliensis ; Agrobacterium ; CaMV 35S ; β-Glucuronidase ; Latex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hevea brasiliensis anther calli were genetically transformed using Agrobacterium GV2260 (p35SGUSINT) that harboured the β-glucuronidase (gus) and neomycin phosphotransferase (nptII) genes. β-Glucuronidase protein (GUS) was expressed in the leaves of kanamycin-resistant plants that were regnerated, and the presence of the gene was confirmed by Southern analysis. GUS was also observed to be expressed in the latex and more importantly in the serum fraction. Transverse sections of the leaf petiole from a transformed plant revealed GUS expression to be especially enhanced in the phloem and laticifers. GUS expression was subsequently detected in every one of 194 plants representing three successive vegetative cycles propagated from the original transformant. Transgenic Hevea could thus facilitate the continual production of foreign proteins expressed in the latex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002990050454
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  • 9
    Electronic Resource
    Electronic Resource
    Genetic transformation and regeneration of mature tissues of woody fruit plants bypassing the juvenile stage (1998)
    Springer
    Transgenic research 7 (1998), S. 51-59 
    Details
    ISSN: 1573-9368
    Keywords: sweet orange ; Citrus ; woody ; transformation ; Agrobacterium ; mature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Regeneration and transformation systems from mature plant material of woody fruit species have to be achieved as a necessary requirement for the introduction of useful genes into specific cultivars and the rapid evaluation of resulting horticultural traits. We report here, for the first time, a procedure for genetic transformation and regeneration of mature tissues of woody plants that overcomes the long juvenile periods and high heterozygosity that are characteristic of most of these species. An improved regeneration frequency from mature explants was obtained by invigoration of the plant material through grafting of mature buds on juvenile seedlings. Co-cultivation of the explants in feederplates after inoculation with Agrobacterium tumefaciens resulted in enhanced transformation frequencies. Furthermore, in vitro shoot-tip grafting of the regenerated mature shoots on seedling rootstocks provided a rapid and efficient system for plant production. Citrus is the most extensivel y grown fruit crop worldwide and sweet orange (Citrus sinensis L. Osbeck) accounts for approximately 70% of the Citrus total production. Mature transgenic sweet orange plants have been obtained, which flowered and bore fruit in 14 months
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008855922283
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  • 10
    Electronic Resource
    Electronic Resource
    An efficient protocol for sugarcane (Saccharum spp. L.) transformation mediated by Agrobacterium tumefaciens (1998)
    Springer
    Transgenic research 7 (1998), S. 213-222 
    Details
    ISSN: 1573-9368
    Keywords: Saccharum ; Agrobacterium ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This is the first successful report of the recovery of morphologically normal transgenic sugarcane plants from co-cultivation of calluses with Agrobacterium tumefaciens. Transformation frequencies (total of transgenic plants/number of cell clusters) were between 9.4 × 10−3 and 1.15 × 10−2. In our experiments, both LBA4404 (pTOK233) and EHA101 (pMTCA3IG), carrying a super-binary vector or supervirulent strain, respectively, were successful for sugarcane transformation. We found that three main factors: (1) the use of young regenerable calluses as target explants; (2) induction and/or improvement of the A. tumefaciens virulence system with sugarcane cell cultures and (3) pre-induction of organogenesis or somatic-embryogenesis-like sexual embryos, seem to be crucial in order to increase the cells competence for T-DNA transfer process. Patterns generated by Southern hybridization confirmed that T-DNAs were randomly integrated into sugarcane genome without th e persistence of A. tumefaciens in the transgenic plants
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008845114531
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  • 11
    Electronic Resource
    Electronic Resource
    Agrobacterium tumefaciens-mediated transformation of cauliflower, Brassica oleracea var. botrytis (1998)
    Springer
    Molecular breeding 4 (1998), S. 531-541 
    Details
    ISSN: 1572-9788
    Keywords: Agrobacterium ; Brassica oleracea ; cauliflower ; regeneration ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We have developed an efficient and simpler method for genetic transformation and regeneration of cauliflower, Brassica oleracea var. botrytis plants. Explants from 4-day old seedlings were inoculated and cocultivated with Agrobacterium tumefaciens strain LBA4404 harbouring a binary vector with the neomycin phosphotransferase-II gene under the regulatory control of nopaline synthase promoter and terminator sequences, permitting transformed shoots to be selected on kanamycin containing medium. After three months rooted transformed plantlets were successfully transferred and grown under glasshouse conditions. Higher numbers of transformed plants were obtained from cotyledon than hypocotyl explants, presumably indicating cotyledons of cauliflower are more amenable to genetic transformation. Integration and expression of the introduced transgene were analysed by DNA gel blot and PCR analysis and NPT-II expression assay. Factors influencing transformation efficiency include explant age, concentration of bacterium used for infection, duration of infection and cocultivation with Agrobacterium. Transgenic plants of three commercial genotypes of cauliflower were produced using this method. We also show that introduction of antisense Bcp1 (pollen-specific gene) linked to a pollen-specific promoter (Lat52) resulted in the expected sterility of 50% pollen carrying this transgenic construct.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009658614579
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  • 12
    Electronic Resource
    Electronic Resource
    Investigation of Agrobacterium-mediated transformation of apple using green fluorescent protein: high transient expression and low stable transformation suggest that factors other than T-DNA transfer are rate-limiting (1998)
    Springer
    Plant molecular biology 37 (1998), S. 549-559 
    Details
    ISSN: 1573-5028
    Keywords: Agrobacterium ; apple ; GFP ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To investigate early events of Agrobacterium-mediated transformation of apple cultivars, a synthetic green fluorescent protein gene (SGFP) was used as a highly sensitive, vital reporter gene. Leaf explants from four apple cultivars (‘Delicious’, ‘Golden Delicious’, ‘Royal Gala’ and ‘Greensleeves’) were infected with Agrobacterium EHA101 harboring plasmid pDM96.0501. Fluorescence microscopy indicated that SGFP expression was first detected 48 h after infection and quantitative analysis revealed a high T-DNA transfer rate. Plant cells with stably incorporated T-DNA exhibited cell division and developed transgenic calli, followed by formation of transgenic shoots at low frequencies. The detection of SGFP expression with an epifluorescence stereomicroscope confirmed the effectiveness of SGFP as a reporter gene for detection of very early transformation events and for screening of putative transformants. The efficiency of the transformation and regeneration process decreased ca. 10000-fold from Agrobacterium infection to transgenic shoot regeneration, suggesting that factors other than Agrobacterium interaction and T-DNA transfer are rate-limiting steps in Agrobacterium-mediated transformation of apple.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006041313209
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  • 13
    Electronic Resource
    Electronic Resource
    The use of visual marker genes as cell-specific reporters of Agrobacterium-mediated T-DNA delivery to wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). (1998)
    Springer
    Euphytica 99 (1998), S. 17-25 
    Details
    ISSN: 1573-5060
    Keywords: Agrobacterium ; barley ; C1/Lc ; GFP ; GUS ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Transfer of T-DNA from Agrobacterium tumefaciens and A. rhizogenes to cells of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) is demonstrated following the inoculation of immature embryos and immature embryo-derived callus. Agrobacterium T-DNA vectors containing the C1/Lc anthocyanin-biosynthesis regulatory genes, the gusA gene or a synthetic green fluorescent protein gene (sgfp-S65T) were constructed from original binary vectors. The visual T-DNA markers were used as cell-autonomous reporters of early Agrobacterium-mediated transformation events in the wheat and barley cells. This localization of the transformed cells revealed a non-random distribution throughout each embryo and callus piece.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018303102488
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  • 14
    Electronic Resource
    Electronic Resource
    Cre/lox-mediated site-specific integration of Agrobacterium T-DNA in Arabidopsis thaliana by transient expression of cre (1998)
    Springer
    Plant molecular biology 38 (1998), S. 393-406 
    Details
    ISSN: 1573-5028
    Keywords: Agrobacterium ; Arabidopsis ; Cre/lox ; recombination ; site-specific integration ; T-DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Cre/lox system was used to obtain targeted integration of an Agrobacterium T-DNA at a lox site in the genome of Arabidopsis thaliana. Site-specific recombinants, and not random events, were preferentially selected by activation of a silent lox-neomycin phosphotransferase (nptII) target gene. To analyse the effectiveness of Agrobacterium-mediated transfer we used T-DNA vectors harbouring a single lox sequence (this vector had to circularize at the T-DNA left- and right-border sequences prior to site-specific integration) or two lox sequences (this vector allowed circularization at the lox sequences within the T-DNA either prior to or after random integration, followed by targeting of the circularized vector), respectively. Furthermore, to control the reversibility of the integration reaction, Cre recombinase was provided transiently by using a cotransformation approach. One precise stable integrant was found amongst the recombinant calli obtained after transformation with a double-lox T-DNA vector. The results indicate that Agrobacterium-mediated transformation can be used as a tool to obtain site-specific integration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006024500008
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