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Abstract
Overexpression of chimeric transgenes in plants can trigger post-transcriptional gene silencing that is dependent on epigenetic information and physiological conditions. The current view is that unproductive RNA serves as a crucial signal for gene silencing, although direct evidence is lacking for this theory. A signalling cascade then leads to strongly enhanced turnover of all RNAs that share a critical degree of sequence similarity. The molecular details of the mechanism are, however, insufficiently understood to explain the phenomenon completely and to comprehend its biological significance.
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27
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De Jaeger G, Buys E, Eeckhout D, Bruyns AM, De Neve M, De Wilde C, Gerats T, Van Montagu M, Fischer R, Depicker A. Use of phage display for isolation and characterization of single-chain variable fragments against dihydroflavonol 4-reductase from Petunia hybrida. FEBS Lett 1997; 403:116-22. [PMID: 9042949 DOI: 10.1016/s0014-5793(97)00025-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
To isolate specific single-chain variable (scFv) fragments against dihydroflavonol 4-reductase (DFR) from Petunia hybrida the phage display technology was used. DFR was overproduced in Escherichia coli, purified and used for immunization. From DFR-immunized mice, a phage display library was made starting from spleen mRNA using an optimized set of primers for V(H) and V(L) amplification. Several rounds of panning against recombinant DFR yielded five different scFv fragments, confirmed by subsequent DNA sequencing. They all specifically bound to recombinant DFR in ELISA and DFR in flower extracts on Western blot. These results show that phage display is a promising technology in plant molecular biology to obtain specific recombinant antibodies not only for ELISA and Western blot but also for in vivo applications in the long run.
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28
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De Neve M, De Buck S, Jacobs A, Van Montagu M, Depicker A. T-DNA integration patterns in co-transformed plant cells suggest that T-DNA repeats originate from co-integration of separate T-DNAs. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 1997; 11:15-29. [PMID: 9025300 DOI: 10.1046/j.1365-313x.1997.11010015.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Nicotiana protoplasts and Arabidopsis leaf discs or roots were co-cultivated with two Agrobacterium strains each carrying a different T-DNA. Co-transformed plants were selected and the integration of the different T-DNAs was analysed at the genetic and genomic level. Genetic analysis showed that the T-DNAs derived from different bacteria were frequently integrated at the same locus, independent of the plant species or transformation method used. Southern analysis revealed that 12 out of 27 Arabidopsis transformants contained the co-transferred T-DNAs linked to each other in all possible configurations but with a preference for those with at least one right border involved in linkage. Overall, our data support the hypothesis that ligation of separate T-DNAs is a dominant mechanism in formation of the frequently observed repeats of identical T-DNAs. We propose a scheme which could explain the formation of T-DNA repeats and the preferential involvement of right borders in T-DNA linkages.
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29
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Bruyns AM, De Jaeger G, De Neve M, De Wilde C, Van Montagu M, Depicker A. Bacterial and plant-produced scFv proteins have similar antigen-binding properties. FEBS Lett 1996; 386:5-10. [PMID: 8635602 DOI: 10.1016/0014-5793(96)00372-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A gene encoding a single-chain variable (scFv) antibody fragment was expressed as a cytoplasmic and endoplasmic reticulum-targeted protein in transgenic tobacco plants. In both cases, the scFv accumulated up to 0.01% of total soluble protein (TSP). The same scFv fragment was also produced in the periplasm of Escherichia coli. Measurement of the affinity by ELISA indicates that the affinity of the bacterially made scFv is about 80-fold lower than that of the parental Fab fragment. The results suggest that the affinity of the plant-produced scFv fragments is reduced to a similar extent, implying that all the plant-produced scFv fragments are antigen binding.
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Coppieters W, Van de Weghe A, Depicker A, Coppieters J, Peelman L, Van Zeveren A, Bouquet Y. Polymorphic CAC/T repetitive sequences in the pig genome 1. Anim Genet 1995; 26:327-30. [PMID: 7486250 DOI: 10.1111/j.1365-2052.1995.tb02667.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Three genomic clones were isolated from a size-selected pig DNA library by hybridization with a DNA-fingerprint probe. Analysis at the sequence level revealed that all three clones contain interrupted stretches of triplet repeats mainly composed of CAC and CAT triplets. Evaluation of the corresponding loci for polymorphism by Southern blot hybridization showed considerable length variation. For two loci the polymorphism was also demonstrated by polymerase chain reaction (PCR) amplification. The PiGMaP reference pedigree was typed for all three loci.
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31
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Ingelbrecht I, Van Houdt H, Van Montagu M, Depicker A. Posttranscriptional silencing of reporter transgenes in tobacco correlates with DNA methylation. Proc Natl Acad Sci U S A 1994; 91:10502-6. [PMID: 7937983 PMCID: PMC45049 DOI: 10.1073/pnas.91.22.10502] [Citation(s) in RCA: 155] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Endogenous plant genes or transgenes can be silenced on introduction of homologous gene sequences. Here we document a reporter gene-silencing event in Nicotiana tabacum that has a distinctive combination of features--i.e., (i) silencing occurs by a posttranscriptional process, (ii) silencing correlates with DNA methylation, and (iii) this de novo methylation is not restricted to cytosines located in the symmetrical motifs CG and CXG.
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32
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De Neve M, De Loose M, Jacobs A, Van Houdt H, Kaluza B, Weidle U, Van Montagu M, Depicker A. Assembly of an antibody and its derived antibody fragment in Nicotiana and Arabidopsis. Transgenic Res 1993; 2:227-37. [PMID: 8364605 DOI: 10.1007/bf01977353] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The yield and assembly of an IgG1 antibody and its derived F(ab) fragment were compared in Nicotiana and Arabidopsis. The results obtained showed a lot of interclonal variability. For 45% of the primary transgenic calluses, antigen-binding entities represented less than 0.1% of the total soluble protein (TSP). Only two of the 103 analysed transformants contained more than 1% of antigen-binding protein, with 1.26% being the highest yield. Analogous amounts of complete antibody and F(ab) accumulated in primary callus tissue. Moreover, yields were in the same range for both species as far as primary callus tissue is concerned. However, the accumulation of the F(ab) fragment in leaf tissue of regenerated plants differed significantly between Nicotiana and Arabidopsis. The F(ab) fragment accumulated to only 0.044% of TSP in Nicotiana leaves but up to 1.3% in Arabidopsis leaves. Furthermore, both species showed differences in the assembly pattern of the complete antibody. Whereas Arabidopsis contained primarily fully assembled antibodies of 150 kDa, Nicotiana showed an abundance of fragments in the 50 kDa range.
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33
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Coppieters W, Van de Weghe A, Peelman L, Depicker A, Van Zeveren A, Bouquet Y. Characterization of porcine polymorphic microsatellite loci. Anim Genet 1993; 24:163-70. [PMID: 8103299 DOI: 10.1111/j.1365-2052.1993.tb00281.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Twenty-seven (CA)n and two (GA)n microsatellite clones were isolated out of a size-selected genomic pig library. These were sequenced and the number of uninterrupted dinucleotides was found to range from 12 to 26. Flanking primers were chosen for 11 dinucleotide repeats and optimal conditions for polymerase chain reaction (PCR) amplifications were established. Different microsatellite loci were amplified simultaneously by combining primer sets. Related and unrelated pigs were screened for length polymorphisms of the different microsatellite loci. The polymorphic information content (PIC) of these loci ranged between 0.62 and 0.83. Segregation studies in pig reference families established Mendelian inheritance. Locus S0022 was found to be X-linked.
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34
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Breyne P, Gheysen G, Jacobs A, Van Montagu M, Depicker A. Effect of T-DNA configuration on transgene expression. MOLECULAR & GENERAL GENETICS : MGG 1992; 235:389-96. [PMID: 1465111 DOI: 10.1007/bf00279385] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
T-DNA vectors were constructed which carry a beta-glucuronidase (gusA) gene fused to the promoter of the nopaline synthase (nos) gene and the 3' end of the octopine synthase (ocs) gene. This reporter gene was cloned at different locations and orientations towards the right T-DNA border. For each construct, between 30 and 60 stably transformed calli were analysed for beta-glucuronidase activity. Depending on the T-DNA configuration, distinct populations of gusA-expressing calli were obtained. Placing the reporter gene in the middle of the T-DNA results in relatively low expression levels and a limited inter-transformant variability. Placing the gene with its promoter next to the right border led to an increase in both the mean activity and the variability level. With this construct, some of the calli expressed the gusA gene at levels four to five times higher than the mean. In all these series, at least 30% of the calli contained reporter gene activities that were less than half of the mean expression level. Separating the gusA gene from the right T-DNA border by an additional 3'-untranslated region, derived from the nos gene, resulted in an increase in the mean expression to a level almost four times higher than that of constructions carrying the reporter gene in the middle of the T-DNA. Moreover, the number of transformants with extremely low activities decreased by at least 50% and this resulted in significantly lower inter-transformant variability independently of the orientation of the reporter gene on the T-DNA.
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MESH Headings
- Agrobacterium tumefaciens/enzymology
- Agrobacterium tumefaciens/genetics
- Amino Acid Oxidoreductases/genetics
- Analysis of Variance
- Cloning, Molecular
- Conjugation, Genetic
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- Gene Expression Regulation, Bacterial
- Gene Expression Regulation, Enzymologic
- Genes, Bacterial
- Genetic Vectors
- Glucuronidase/genetics
- Nucleic Acid Conformation
- Plants, Toxic
- Promoter Regions, Genetic
- Restriction Mapping
- Nicotiana
- Transcription, Genetic
- Transformation, Genetic
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35
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Hernalsteens JP, Van Vliet F, De Beuckeleer M, Depicker A, Engler G, Lemmers M, Holsters M, Van Montagu M, Schell J. The Agrobacterium tumefaciens Ti plasmid as a host vector system for introducing foreign DNA in plant cells. 1980. BIOTECHNOLOGY (READING, MASS.) 1992; 24:374-6. [PMID: 1422043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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36
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Herrera-Estrella L, Depicker A, Van Montagu M, Schell J. Expression of chimaeric genes transferred into plant cells using a Ti-plasmid-derived vector. 1983. BIOTECHNOLOGY (READING, MASS.) 1992; 24:377-81. [PMID: 1422044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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37
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Ingelbrecht I, Breyne P, Vancompernolle K, Jacobs A, Van Montagu M, Depicker A. Transcriptional interference in transgenic plants. Gene 1991; 109:239-42. [PMID: 1662656 DOI: 10.1016/0378-1119(91)90614-h] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
When a promoterless marker gene is transformed into the plant genome using the Agrobacterium vector system, on average 30% of the T-DNA inserts produce gene fusions. This suggests that the T-DNA is preferentially integrated into transcribed regions. Here, we proposed that this transcriptional activity is responsible for some of the variation in expression frequently observed among independent transformants. Using hybrid gene constructions, we show that transcriptional readthrough into a downstream gene with opposite orientation substantially reduces expression of this gene both in transient expression and in transgenic plants. Furthermore, a poly(A) signal/terminator can block readthrough and restore the expression of the gene. Finally, enzymatic analysis of calli suggests that less variation in neomycin phosphotransferase II synthesis is observed when the gene is separated from plant DNA by promoter and terminator elements.
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38
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De Loose M, Gheysen G, Tiré C, Gielen J, Villarroel R, Genetello C, Van Montagu M, Depicker A, Inzé D. The extensin signal peptide allows secretion of a heterologous protein from protoplasts. Gene 1991; 99:95-100. [PMID: 2022327 DOI: 10.1016/0378-1119(91)90038-d] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Extensins are hydroxyproline-rich glycoproteins which are amongst the most abundant proteins present in the cell wall of higher plants. Here, we describe the structural analysis of an extensin-encoding gene from Nicotiana plumbaginifolia. The encoded protein (46 kDa) has a highly repetitive structure and contains 37% proline, 18.1% tyrosine, 13.4% lysine, 8.1% serine and 7.1% histidine. The extensin-encoding sequence contains a typical signal peptide for translocation of the protein to the endoplasmic reticulum. By using chimeric genes consisting of different 5' parts of the extensin-encoding gene and the neomycin phosphotransferase II-encoding gene (nptII) as reporter gene, we show that the N-terminal part of extensin can mediate the secretion of NPTII from electroporated N. tabacum protoplasts.
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39
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Herman L, Jacobs A, Van Montagu M, Depicker A. Plant chromosome/marker gene fusion assay for study of normal and truncated T-DNA integration events. MOLECULAR & GENERAL GENETICS : MGG 1990; 224:248-56. [PMID: 2177527 DOI: 10.1007/bf00271558] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
During Agrobacterium tumefaciens infection, the T-DNA flanked by 24 bp imperfect direct repeats is transferred and stably integrated into the plant chromosome at random positions. Here we measured the frequency with which a promoterless reporter gene is activated after insertion into the Nicotiana tabacum SR1 genome. When adjacent to the right or left T-DNA border sequences, at least 35% of the transformants express the marker gene, suggesting preferential T-DNA insertion (greater than 70%) in transcriptionally active regions of the plant genome. When the promoterless neomycin phosphotransferase II (nptII) gene is located internally in the T-DNA, the activation frequency drops to 1% since gene activation requires T-DNA truncation. These truncation events in the nptII upstream region occur independently of the nature of the upstream sequence and of the T-DNA length. Deletion of the right border region prevents the detection of activated marker genes. Therefore, T-DNA truncation probably occurs after synthesis of a normal T-DNA intermediate during the transfer and/or integration process. In the absence of border regions, expression of the nptII selectable marker directed by the nopaline synthase promoter was detected in 1 out of 10(5) regenerated calli, suggesting the possibility that any DNA sequence from the Ti plasmid can be transformed into the plant genome, albeit at a low frequency.
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40
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Gheysen G, Herman L, Breyne P, Gielen J, Van Montagu M, Depicker A. Cloning and sequence analysis of truncated T-DNA inserts from Nicotiana tabacum. Gene 1990; 94:155-63. [PMID: 1701747 DOI: 10.1016/0378-1119(90)90382-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Transgenic plants produced by Agrobacterium-mediated transformation usually have one or a few stable and intact T-DNA insertions. However, in a significant number of the transformants Southern blot analysis has revealed the occurrence of aberrant T-DNA insertions missing one or both ends. During the study of this phenomenon, we obtained KmR Nicotiana tabacum clones after cocultivation with an Agrobacterium strain containing a promoterless nptII gene located internally in the T-DNA. Expression of this nptII gene requires a break in the T-DNA region upstream from the nptII-coding sequence and insertion of the truncated T-DNA in a transcriptionally active plant DNA region. The most conspicuous result from Southern analyses on four such KmR plant clones is that they contain several T-DNAs truncated at other positions besides the upstream region of the nptII sequence. Four truncated T-DNA insertions have been cloned. Two insertions contain the nptII gene fused to plant expression signals and are missing the right part of the T-DNA. Another is missing the left T-DNA part and the last T-DNA is lacking both ends. Sequence analysis of the T-DNA::plant junctions has shown that the T-DNA breakpoints are randomly distributed and do not show obvious homologies to one another or to the border consensus sequence. S1-type mapping of the most strongly expressed plant genome::nptII fusion revealed a specific transcription start point and putative TATA and CAAT boxes in the upstream plant DNA region; the steady-state nptII mRNA in these plants is about 20 times more abundant than in transgenic Pnos-nptII plants.
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41
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Abstract
A region of 18 nucleotides surrounding the stop codon (the stop codon context) in 748 plant nuclear genes was analyzed. Non-randomness was found both upstream and downstream from the stop codon, suggesting that these sequences may help in ensuring efficient termination of translation. The UAG amber codon is the least-used stop codon and the bias in the nucleotide distribution 5' and 3' to the stop codon was more pronounced for the amber codon than for the other stop codons. This might indicate that the codon context affects termination more at UAG than at UGA or UAA stop codons.
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42
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Abstract
A new hypervariable tandem repeat was isolated from the pig genome and characterized by DNA sequence. The use of this DNA fragment as a probe in order to follow allelic segregation and DNA fingerprinting in pigs, horses and rabbits is documented.
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43
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Angenon G, Uotila J, Kurkela SA, Teeri TH, Botterman J, Van Montagu M, Depicker A. Expression of dicistronic transcriptional units in transgenic tobacco. Mol Cell Biol 1989; 9:5676-84. [PMID: 2479833 PMCID: PMC363739 DOI: 10.1128/mcb.9.12.5676-5684.1989] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We investigated whether the two cistrons of a dicistronic mRNA can be translated in plants to yield both gene products. The coding sequences of various reporter genes were combined in dicistronic units, and their expression was analyzed in stably transformed tobacco plants at the RNA and protein levels. The presence of an upstream cistron resulted in all cases in a drastically reduced expression of the downstream cistron. The translational efficiency of the gene located downstream in the dicistronic units was 500- to 1,500-fold lower than that in a monocistronic control; a 500-fold lower value was obtained with a dicistronic unit in which both cistrons were separated by 30 nucleotides, whereas a 1,500-fold lower value was obtained with a dicistronic unit in which the stop codon of the upstream cistron and the start codon of the downstream cistron overlapped. As a strategy to select indirectly for transformants with enhanced levels of expression of a gene which is by itself nonselectable, the gene of interest can be cloned upstream from a selectable marker in a dicistronic configuration. This strategy can be used provided that the amount of dicistronic mRNA is high. If, on the other hand, the expression of the dicistronic unit is too low, selection of the downstream cistron will primarily give clones with rearranged dicistronic units.
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44
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Teeri TH, Herrera-Estrella L, Depicker A, Van Montagu M, Palva ET. Identification of plant promoters in situ
by T-DNA-mediated transcriptional fusions to the npt
-II gene. EMBO J 1986; 5:1755-60. [PMID: 16453695 PMCID: PMC1167037 DOI: 10.1002/j.1460-2075.1986.tb04423.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We have constructed an Agrobacterium-mediated plant vector,pHTT88,which upon integration into the plant chromosomes can produce transcriptional fusions between upstream control elements in the plant genome and the gene for neomycin phosphotransferase II (npt-II). The vector is based on a juxtaposition of a T-DNA right border to the coding sequence of npt-II. Using this system it is possible to isolate kanamycin-resistant plant calli where the site of integration is suitably positioned downstream of plant transcription signals. We have demonstrated that the NPT-II activity of such tobacco transformants shows different tissue-specific patterns of regulation in the regenerated plants. Among eight transformants analyzed, we have isolated one gene fusion expressed only in roots and others expressed only in stem. The results demonstrate that a gene fusion vector can be used effectively in plants to identify and characterize regulatory elements.
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45
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Depicker A, Stachel S, Dhaese P, Zambryski P, Goodman HM. Nopaline synthase: transcript mapping and DNA sequence. JOURNAL OF MOLECULAR AND APPLIED GENETICS 1982; 1:561-573. [PMID: 7153689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The DNA sequence of the nopaline synthase gene (nos) from Agrobacterium tumefaciens Ti plasmid pTiT37 and adjacent regions up to the right border of the T-DNA was determined. The 5' and 3' termini of the polyadenylated nos mRNA, isolated from a T37 tobacco teratoma tumor line, were localized by S1 mapping. The final mRNA is unspliced, encoded by a region of about 1450 bp, and specifies an open reading frame of 413 amino acids. Potential transcriptional signals in the 5' flanking DNA, such as CATAAA ("TATA box") and GGTCACTAT ("CAT box"), bear close resemblance to other eukaryotic promoters. Two putative polyadenylation signals, AATAAA and AATAAT, are found about 135 and 50 bp from the 3' end, respectively. This study may provide information for the development of expression vectors for genes in plant cells; moreover, the structural gene can be used as an easy screenable marker.
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46
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Engler G, Depicker A, Maenhaut R, Villarroel R, Van Montagu M, Schell J. Physical mapping of DNA base sequence homologies between an octopine and a nopaline Ti plasmid of Agrobacterium tumefaciens. J Mol Biol 1981; 152:183-208. [PMID: 6276566 DOI: 10.1016/0022-2836(81)90239-4] [Citation(s) in RCA: 136] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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47
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Lemmers M, De Beuckeleer M, Holsters M, Zambryski P, Depicker A, Hernalsteens JP, Van Montagu M, Schell J. Internal organization, boundaries and integration of Ti-plasmid DNA in nopaline grown gall tumours. J Mol Biol 1980; 144:353-76. [PMID: 7253020 DOI: 10.1016/0022-2836(80)90095-9] [Citation(s) in RCA: 173] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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48
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Van Montagu M, Holsters M, Zambryski P, Hernalsteens JP, Depicker A, De Beuckeleer M, Engler G, Lemmers M, Willmitzer L, Schell J. The interaction of Agrobacterium Ti-plasmid DNA and plant cells. PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON. SERIES B, BIOLOGICAL SCIENCES 1980; 210:351-65. [PMID: 6109298 DOI: 10.1098/rspb.1980.0139] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The tumour-inducing plasmids of Agrobacterium tumefaciens (Ti-plasmids) reveal several interesting properties. They are catabolic plasmids, which, instead of rendering Agrobacterium strains capable of catabolizing compounds found in Nature, force a plant to synthesize these catabolites (denoted 'opines'). This situation is obtained by insertion of a segment of the Ti-plasmid (the T-DNA) into the plant nucleus, where T-DNA genes become expressed and intervene in the biosynthesis of these opines. Cells containing the T-DNA behave as neoplasms (crown gall cells). Southern blotting shows that the insertion process responsible for T-DNA transfer probably recognizes special sequences on the T-DNA since the length of the T-DNA segment observed in different, independently isolated tumour lines was found to be similar. For the nopaline Ti-plasmids both left-hand and right-hand borders were found to be constant. For the octopine plasmid the left border was constant and at least two classes of right-hand borders were found. Upon redifferentiation of the transformed plant cells, the T-DNA was found to be conserved in all somatic cells examined. However, small deletions at the border fragments of the T-DNA have been observed. The exact arrangement and copy number of the T-DNA in a nucleus is still under study, but genomic cloning has already revealed that an interspersed tandem arrangement is dominant in nopaline tumours. Clones containing both the right border of one T-DNA and the left border of the neighbouring tandem T-DNA were isolated. In order to identify the different T-plasmid encoded functions an extensive use was made of transposon insertion mutagenesis. When an antibiotic resistance transposon was inserted into the non-essential regions of the T-DNA, a linked transfer to the plant DNA of the transposon together with the T-DNA was observed. This indicates that Ti-plasmids are possible vectors for genetic engineering in plants. A strategy is described for insertion of any cloned DNA segment into the T-DNA.
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49
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Zambryski P, Holsters M, Kruger K, Depicker A, Schell J, Van Montagu M, Goodman HM. Tumor DNA structure in plant cells transformed by A. tumefaciens. Science 1980; 209:1385-91. [PMID: 6251546 DOI: 10.1126/science.6251546] [Citation(s) in RCA: 190] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Crown gall tumors are induced in plants by infection with the soil bacterium Agrobacterium tumefaciens. Because the tumor induction involves transfer of a portion of the tumor-inducing (Ti) plasmid DNA from the bacterium to the plant cells, this system is of interest for the study of genetic exchange as well as tumor induction. The boundaries of the transferred DNA (T-DNA) have been cloned from transformed plant cells of tobacco. Detailed mapping with restriction enzymes and nucleotide sequence analysis of two independent clones were used to study the molecular structure of the ends of the T-DNA. One clone contains the two ends of the T-DNA joined together; the other contains one end of the T-DNA joined to repetitive plant DNA sequences. These studies provide direct evidence that the T-DNA can be integrated into the plant genome. In addition, the data suggest that in the plant, T-DNA can be tandemly repeated. Sequence analysis of the junction of crown gall clone 1 reveals several direct repeats as well as an inverted repeat; these structures may be involved in the transfer of the DNA from Agrobacterium to plant cells.
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50
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Depicker A, De Block M, Inzé D, Van Montagu M, Schell J. IS-like element IS8 in RP4 plasmid and its involvement in cointegration. Gene X 1980; 10:329-38. [PMID: 6253354 DOI: 10.1016/0378-1119(80)90153-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The structure of the cointegrate plasmids formed by fusion of RP4 and the tumour-inducing plasmid (pTi) of Agrobacterium tumefaciens was analyzed. In all of the nine independently isolated pTi::RP4 cointegrates, the integration occurred at the same site on the RP4 genome. Moreover, a 1.2 Md (1750 bp) RP4 sequence (IS8) was directly repeated at both junction sites of the two replicons. The insertion of RP4 generated deletions, starting from the IS8 sequence and extending into the Ti part of the cointegrate. Dissociation of the cointegrates resulted in wild-type RP4 and Ti-plasmids with the IS8 sequence inserted at the original RP4 insertion site. The processes of integration and dissociation and the genetic properties of the cointegrates indicate that the IS8 sequence has unique characteristics defining a new insertion sequence.
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