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Albert H, Dale EC, Lee E, Ow DW. Site-specific integration of DNA into wild-type and mutant lox sites placed in the plant genome. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 1995; 7:649-59. [PMID: 7742860 DOI: 10.1046/j.1365-313x.1995.7040649.x] [Citation(s) in RCA: 331] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The bacteriophage P1 Cre-lox site-specific recombination system has been used to integrate DNA specifically at lox sites previously placed in the tobacco genome. As integrated molecules flanked by wild-type lox sites can readily excise in the presence of Cre recombinase, screening for mutant lox sites that can resist excisional recombination was performed. In gene integration experiments, wild-type and mutant lox sites were used in conjunction with two strategies for abolishing post-integration Cre activity: (i) promoter displacement of a cre-expression construct present in the target genome; and (ii) transient expression of cre. When the promoter displacement strategy was used, integrant plants were recovered after transformation with constructs containing mutant lox sequences, but not with constructs containing wild-type lox sites. When cre was transiently expressed, integrant plants were obtained after transformation with either mutant or wild-type lox sites. DNA rearrangements at the target locus were less frequent when mutant lox sites were used. DNA integration at the genomic lox site was usually without additional insertions in the genome. Thus, the Cre-lox site-specific recombination system is useful for the single-copy integration of DNA into a chromosomal lox site.
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Ow DW, DE Wet JR, Helinski DR, Howell SH, Wood KV, Deluca M. Transient and Stable Expression of the Firefly Luciferase Gene in Plant Cells and Transgenic Plants. Science 1986; 234:856-9. [PMID: 17758108 DOI: 10.1126/science.234.4778.856] [Citation(s) in RCA: 312] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The luciferase gene from the firefly, Photinus pyralis, was used as a reporter of gene expression by light production in transfected plant cells and transgenic plants. A complementary DNA clone of the firefly luciferase gene under the control of a plant virus promoter (cauliflower mosaic virus 35S RNA promoter) was introduced into plant protoplast cells (Daucus carota) by electroporation and into plants (Nicotiana tabacum) by use of the Agrobacterium tumefaciens tumor-inducing plasmid. Extracts from electroporated cells (24 hours after the introduction of DNA) and from transgenic plants produce light when mixed with the substrates luciferin and adenosine triphosphate. Light produced by the action of luciferase was also detected in undisrupted leaves or cells in culture from transgenic plants incubated in luciferin and in whole transgenic plants "watered" with luciferin. Although light was detected in most organs in intact, transgenic plants (leaves, stems, and roots), the pattern of luminescence appeared to reflect both the organ-specific distribution of luciferase and the pathway for uptake of luciferin through the vasculature of the plant.
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Cunningham SD, Ow DW. Promises and Prospects of Phytoremediation. PLANT PHYSIOLOGY 1996; 110:715-719. [PMID: 12226213 PMCID: PMC157769 DOI: 10.1104/pp.110.3.715] [Citation(s) in RCA: 303] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
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Ortiz DF, Ruscitti T, McCue KF, Ow DW. Transport of metal-binding peptides by HMT1, a fission yeast ABC-type vacuolar membrane protein. J Biol Chem 1995; 270:4721-8. [PMID: 7876244 DOI: 10.1074/jbc.270.9.4721] [Citation(s) in RCA: 249] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The Schizosaccharomyces pombe hmt1 gene encodes an ABC (ATP-binding cassette)-type protein essential for Cd2+ tolerance. Immunoblot analysis of subcellular fractions indicates that the native HMT1 polypeptide is associated with the vacuolar membrane. Vacuolar membrane vesicles were purified from strains that hyperproduce, or are deficient in, the HMT1 protein. In vitro transport of radiolabeled substrates by these vesicles indicates that HMT1 is an ATP-dependent transporter of phytochelatins, the metal-chelating peptides involved in heavy metal tolerance of plants and certain fungi. Vacuolar vesicles containing HMT1 are capable of taking up both apo-phytochelatins and phytochelatin-Cd2+ complexes. HMT1 activity is sensitive to antibodies directed against this protein and to vanadate, but not to inhibitors affecting the vacuolar proton ATPase or ionophores that abolish the pH gradient across the vacuolar membrane. Vacuolar uptake of Cd2+ and of a glutathione conjugate were also observed, but are not attributable to HMT1. These studies highlight the importance of the yeast vacuole in detoxification of xenobiotics.
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Dale EC, Ow DW. Gene transfer with subsequent removal of the selection gene from the host genome. Proc Natl Acad Sci U S A 1991; 88:10558-62. [PMID: 1660141 PMCID: PMC52968 DOI: 10.1073/pnas.88.23.10558] [Citation(s) in RCA: 241] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
A general method of gene transfer that does not leave behind a selectable marker in the host genome is described. A luciferase gene was introduced into the tobacco genome by using the hygromycin phosphotransferase gene (hpt) as a linked selectable marker. Flanked by recombination sites from the bacteriophage P1 Cre/lox recombination system, the hpt gene was subsequently excised from the plant genome by the Cre recombinase. The Cre-catalyzed excision event in the plant genome was precise and conservative--i.e., without loss or alteration of nucleotides in the recombinant site. After removal of the Cre-encoding locus by genetic segregation, plants were obtained that had incorporated only the desired transgene. Gene transfer without the incorporation of antibiotic-resistance markers in the host genome should ease public concerns over the field release of transgenic organisms expressing such traits. Moreover, it would obviate the need for different selectable markers in subsequent rounds of gene transfer into the same host.
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Ortiz DF, Kreppel L, Speiser DM, Scheel G, McDonald G, Ow DW. Heavy metal tolerance in the fission yeast requires an ATP-binding cassette-type vacuolar membrane transporter. EMBO J 1992; 11:3491-9. [PMID: 1396551 PMCID: PMC556806 DOI: 10.1002/j.1460-2075.1992.tb05431.x] [Citation(s) in RCA: 213] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In response to heavy metal stress, plants and certain fungi, such as the fission yeast Schizosaccharomyces pombe, synthesize small metal-binding peptides known as phytochelatins. We have identified a cadmium sensitive S. pombe mutant deficient in the accumulation of a sulfide-containing phytochelatin-cadmium complex, and have isolated the gene, designated hmt1, that complements this mutant. The deduced protein sequence of the hmt1 gene product shares sequence identity with the family of ABC (ATP-binding cassette)-type transport proteins which includes the mammalian P-glycoproteins and CFTR, suggesting that the encoded product is an integral membrane protein. Analysis of fractionated fission yeast cell components indicates that the HMT1 polypeptide is associated with the vacuolar membrane. Additionally, fission yeast strains harboring an hmt1-expressing multicopy plasmid exhibit enhanced metal tolerance along with a higher intracellular level of cadmium, implying a relationship between HMT1 mediated transport and compartmentalization of heavy metals. This suggests that tissue-specific overproduction of a functional hmt1 product in transgenic plants might be a means to alter the tissue localization of these elements, such as for sequestering heavy metals away from consumable parts of crop plants.
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Day CD, Lee E, Kobayashi J, Holappa LD, Albert H, Ow DW. Transgene integration into the same chromosome location can produce alleles that express at a predictable level, or alleles that are differentially silenced. Genes Dev 2000; 14:2869-80. [PMID: 11090134 PMCID: PMC317066 DOI: 10.1101/gad.849600] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2000] [Accepted: 10/04/2000] [Indexed: 11/24/2022]
Abstract
In an effort to control the variability of transgene expression in plants, we used Cre-lox mediated recombination to insert a gus reporter gene precisely and reproducibly into different target loci. Each integrant line chosen for analysis harbors a single copy of the transgene at the designated target site. At any given target site, nearly half of the insertions give a full spatial pattern of transgene expression. The absolute level of expression, however, showed target site dependency that varied up to 10-fold. This substantiates the view that the chromosome position can affect the level of gene expression. An unexpected finding was that nearly half of the insertions at any given target site failed to give a full spatial pattern of transgene expression. These partial patterns of expression appear to be attributable to gene silencing, as low gus expression correlates with DNA methylation and low transcription. The methylation is specific for the newly integrated DNA. Methylation changes are not found outside of the newly inserted DNA. Both the full and the partial expression states are meiotically heritable. The silencing of the introduced transgenes may be a stochastic event that occurs during transformation.
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MESH Headings
- Alleles
- DNA Methylation
- DNA, Plant/genetics
- Gene Expression
- Gene Silencing
- Genes, Plant
- Genes, Reporter
- Genome, Plant
- Glucuronidase/genetics
- Meiosis
- Models, Genetic
- Mutagenesis, Insertional
- Plants, Toxic
- RNA, Messenger/genetics
- RNA, Plant/genetics
- Recombination, Genetic
- Tissue Distribution
- Nicotiana/genetics
- Transformation, Genetic
- Transgenes
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Srivastava V, Anderson OD, Ow DW. Single-copy transgenic wheat generated through the resolution of complex integration patterns. Proc Natl Acad Sci U S A 1999; 96:11117-21. [PMID: 10500139 PMCID: PMC17996 DOI: 10.1073/pnas.96.20.11117] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/1999] [Indexed: 01/14/2023] Open
Abstract
Genetic transformation of plants often results in multiple copies of the introduced DNA at a single locus. To ensure that only a single copy of a foreign gene resides in the plant genome, we used a strategy based on site-specific recombination. The transformation vector consists of a transgene flanked by recombination sites in an inverted orientation. Regardless of the number of copies integrated between the outermost transgenes, recombination between the outermost sites resolves the integrated molecules into a single copy. An example of this strategy has been demonstrated with wheat transformation, where four of four multiple-copy loci were resolved successfully into single-copy transgenes.
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Ow DW, Ausubel FM. Regulation of nitrogen metabolism genes by nifA gene product in Klebsiella pneumoniae. Nature 1983; 301:307-13. [PMID: 6337346 DOI: 10.1038/301307a0] [Citation(s) in RCA: 132] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The Klebsiella pneumoniae nifA gene product, which is known to activate expression of the nitrogen fixation (nif) structural genes, is shown here also to be able to substitute for the product of the gene glnG (ntrC) in the regulation of other nitrogen metabolism genes. An evolutionary relationship between the nifA and glnG genes is suggested.
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Ow DW, Jacobs JD, Howell SH. Functional regions of the cauliflower mosaic virus 35S RNA promoter determined by use of the firefly luciferase gene as a reporter of promoter activity. Proc Natl Acad Sci U S A 2010; 84:4870-4. [PMID: 16578811 PMCID: PMC305207 DOI: 10.1073/pnas.84.14.4870] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cauliflower mosaic virus (CaMV) 35S RNA promoter has been dissected and examined in a transient expression system using the firefly luciferase gene as a reporter of promoter activity. Deletion analysis has shown that the 35S RNA promoter is composed of at least three regions-distal, medial, and proximal-which are essential for activity. The distal region contains three smaller elements homologous to the simian virus 40 "core" enhancer element, the medial region possesses a CCAAT-like box, and the proximal region contains a TATA box. A DNA segment encompassing the distal region is capable of activating the CaMV 35S core promoter in an orientation-independent, but not position-independent, fashion. The distal region can also activate a heterologous weak promoter, the CaMV 19S RNA promoter, albeit not to the high levels of the 35S RNA promoter. Multimers of the distal region are able to activate the 35S RNA promoter core to even greater levels of expression than the native 35S promoter. These experiments demonstrate that elements outside the boundaries of the core promoter (composed of proximal and medial elements) are recognized in a plant cell transient expression system.
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Dale EC, Ow DW. Intra- and intermolecular site-specific recombination in plant cells mediated by bacteriophage P1 recombinase. Gene X 1990; 91:79-85. [PMID: 2205542 DOI: 10.1016/0378-1119(90)90165-n] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A site-specific recombination system has many potential uses for rearranging genetic material in higher eukaryotic cells: for example, the control of gene expression by deletion or inversion of DNA segments, the clustering of transgenic constructs via site-specific integration, and the generation of chromosomal translocations. In this report, we describe a first step towards the application of a site-specific recombination system in plant cells. By use of a transient assay, we demonstrate that the bacteriophage P1 cre gene can be expressed as a functional recombinase in tobacco cells. Upon expression in tobacco protoplasts, Cre recognizes its target sites, lox, and mediates reciprocal genetic crossovers at these sites. When the lox sites are present in cis to one another, and arranged in either direct or inverted orientations, we detect Cre/lox-specific deletion and inversion events, respectively. The placement of lox sites in trans resulted in the co-integration of the substrates by Cre-mediated intermolecular recombination. These results indicate that the Cre/lox site-specific recombination system might be further developed as an additional tool for manipulating DNA in plant cells. Applications relevant to the genetic engineering of higher plants are discussed.
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Sundaresan V, Jones JD, Ow DW, Ausubel FM. Klebsiella pneumoniae nifA product activates the Rhizobium meliloti nitrogenase promoter. Nature 1983; 301:728-32. [PMID: 6338395 DOI: 10.1038/301728a0] [Citation(s) in RCA: 101] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Bacteria in the genus Rhizobium normally fix nitrogen only when they interact with leguminous plants to produce on the roots a highly differentiated structure, the nodule, within which the bacteria differentiate into nitrogen-fixing bacteroids. By contrast, the enteric bacterium Klebsiella pneumoniae reduces nitrogen in a free-living state in conditions of low oxygen tension and deficiency of fixed nitrogen. In K. pneumoniae, the overall circuitry by which nitrogen-fixation (nif) genes are regulated has been elucidated. In response to ammonia starvation, the product of the glnG gene activates transcription of the nifLA operon; this activation is dependent on the product of glnF (ref. 4). The nifA gene product is in turn required for transcription of all the other nif genes, including the nifHDK operon which codes for the subunits of nitrogenase. In contrast, very little is known about the sequence of events involved in the regulated change in rhizobial nif gene expression associated with bacteroid differentiation. In the work described here, we identify the K. pneumoniae and Rhizobium meliloti nifHDK promoters by mapping the in vivo start points of transcription. By defining and comparing the DNA sequences of these two promoters, we find that they share an unexpected degree of homology. Further, by constructing fusions of each of the two promoters to the lacZ gene from Escherichia coli, we show that both promoters are activated by the product of the K. pneumoniae nifA gene.
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Qin M, Bayley C, Stockton T, Ow DW. Cre recombinase-mediated site-specific recombination between plant chromosomes. Proc Natl Acad Sci U S A 1994; 91:1706-10. [PMID: 8127869 PMCID: PMC43232 DOI: 10.1073/pnas.91.5.1706] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
We report the use of the bacteriophage P1 Cre-lox system for generating conservative site-specific recombination between tobacco chromosomes. Two constructs, one containing a promoterless hygromycin-resistance gene preceded by a lox site (lox-hpt) and the other containing a cauliflower mosaic virus 35S promoter linked to a lox sequence and the cre coding region (35S-lox-cre), were introduced separately into tobacco plants. Crosses between plants harboring either construct produced plants with the two constructs situated on different chromosomes. Plants with recombination events were identified by selecting for hygromycin resistance, a phenotype expressed upon recombination. Molecular analysis showed that these recombination events occurred specifically at the lox sites and resulted in the reciprocal exchange of flanking host DNA. Progenies of these plants showed 67-100% cotransmission of the new transgenes, 35S-lox-hpt and lox-cre, consistent with the preferential cosegregation of translocated chromosomes. These results illustrate that site-specific recombination systems can be useful tools for the large-scale manipulation of eukaryotic chromosomes in vivo.
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Abstract
A cadmium-hypersensitive mutant of the fission yeast Schizosaccharomyces pombe was found to accumulate abnormally high levels of sulfide. The gene required for normal regulation of sulfide levels, hmt2(+), was cloned by complementation of the cadmium-hypersensitive phenotype of the mutant. Cell fractionation and immunocytochemistry indicated that HMT2 protein is localized to mitochondria. Sequence analysis revealed homology between HMT2 and sulfide dehydrogenases from photosynthetic bacteria. HMT2 protein, produced in and purified from Escherichia coli, was soluble, bound FAD, and catalyzed the reduction of quinone (coenzyme Q2) by sulfide. HMT2 activity was also detected in isolated fission yeast mitochondria. We propose that HMT2 functions as a sulfide:quinone oxidoreductase. Homologous enzymes may be widespread in higher organisms, as sulfide-oxidizing activities have been described previously in animal mitochondria, and genes of unknown function, but with similarity to hmt2(+), are present in the genomes of flies, worms, rats, mice, and humans.
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Bayley CC, Morgan M, Dale EC, Ow DW. Exchange of gene activity in transgenic plants catalyzed by the Cre-lox site-specific recombination system. PLANT MOLECULAR BIOLOGY 1992; 18:353-61. [PMID: 1310059 DOI: 10.1007/bf00034962] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
The Cre-lox site-specific recombination system of bacteriophage P1 was used to excise a firefly luciferase (luc) gene which had previously been incorporated into the tobacco genome. The excision event was due to site-specific DNA recombination between two lox sequences flanking the luc gene and was catalyzed by the Cre recombinase introduced by cross-fertilization. Recombination resulted in the fusion of a promoter with a distally located hygromycin phosphotransferase (hpt) coding sequence and the excision event was monitored as a phenotypic change from expression of luc to expression of hpt. The efficiency of recombination was estimated from the exchange of gene activity and confirmed by molecular analysis. The relevance to potential applications of site-specific deletion-fusion events for chromosome engineering are discussed.
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Thomason LC, Calendar R, Ow DW. Gene insertion and replacement in Schizosaccharomyces pombe mediated by the Streptomyces bacteriophage phiC31 site-specific recombination system. Mol Genet Genomics 2001; 265:1031-8. [PMID: 11523775 DOI: 10.1007/s004380100498] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The site-specific recombination system used by the Streptomyces bacteriophage phiC31 was tested in the fission yeast Schizosaccharomyces pombe. A target strain with the phage attachment site attP inserted at the leu1 locus was co-transformed with one plasmid containing the bacterial attachment site attB linked to a ura4+ marker, and a second plasmid expressing the phiC31 integrase gene. High-efficiency transformation to the Ura+ phenotype occurred when the integrase gene was expressed. Southern analysis revealed that the attB-ura4+ plasmid integrated into the chromosomal attP site. Sequence analysis showed that the attBxattP recombination was precise. In another approach, DNA with a ura4+ marker flanked by two attB sites in direct orientation was used to transform S. pombe cells bearing an attP duplication. The phiC31 integrase catalyzed two reciprocal cross-overs, resulting in a precise gene replacement. The site-specific insertions are stable, as no excision (the reverse reaction) was observed on maintenance of the integrase gene in the integrant lines. The irreversibility of the phiC31 site-specific recombination system sets it apart from other systems currently used in eukaryotic cells, which reverse readily. Deployment of the phiC31 recombination provides new opportunities for directing transgene and chromosome rearrangements in eukaryotic systems.
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Ow DW, Sundaresan V, Rothstein DM, Brown SE, Ausubel FM. Promoters regulated by the glnG (ntrC) and nifA gene products share a heptameric consensus sequence in the -15 region. Proc Natl Acad Sci U S A 1983; 80:2524-8. [PMID: 6133280 PMCID: PMC393858 DOI: 10.1073/pnas.80.9.2524] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
We have determined the nucleotide sequences of the Klebsiella pneumoniae nifL (regulation of N2 fixation genes) and the Escherichia coli glnA (glutamine synthetase) promoters. We compared these sequences with the published sequences of three other promoters that, like the nifL and glnA promoters, are activated by the general nitrogen regulators glnF (ntrA) and glnG (ntrC). The three promoters are the argTr (arginine transport) and dhuA (histidine transport) promoters of Salmonella typhimurium and the nifH (nitrogenase) promoter of Rhizobium meliloti. All five sequences (with at most one mismatch) contain the heptameric consensus sequence T-T-T-T-G-C-A. In the R. meliloti nifH and K. pneumoniae nifL promoters, in which the transcription initiation sites have been determined, the consensus sequence is situated in the -15 region. We recently reported that the K. pneumoniae nifA product, which activates nif genes, can substitute for the glnG (ntrC) product in activating promoters of several genes involved in nitrogen assimilation, including the nifL, the glnA, and the R. meliloti nifH promoters. It is likely that nifA also activates the S. typhimurium argTr and dhuA promoters. In contrast, the glnG product cannot substitute for the nifA product in the activation of the K. pneumoniae nifH (nitrogenase) promoter. Consistent with this latter observation, and supporting the conclusion that the T-T-T-T-G-C-A sequence is a regulatory site for glnG product activation, the K. pneumoniae nifH promoter (C-C-C-T-G-C-A) has only partial similarity with the T-T-T-T-G-C-A consensus sequence in the -15 region.
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Kahn M, Ow D, Sauer B, Rabinowitz A, Calendar R. Genetic analysis of bacteriophage P4 using P4-plasmid ColE1 hybrids. MOLECULAR & GENERAL GENETICS : MGG 1980; 177:399-412. [PMID: 6929401 DOI: 10.1007/bf00271478] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
A set of plasmids that contain fragments of the bacteriophage P4 genome has been constructed by deleting portions of a P4-ColE1 hybrid. A P4 genetic map has been established and related to the physical map by examining the ability of these plasmids to rescue various P4 mutations. The P4 virl mutation and P4 genes involved in DNA replication (alpha), activation of P2 helper genes (delta and epsilon), polarity suppression (psu) and head size determination (sid) have been mapped, as has the region responsible for synthesis of a nonessential P4 protein. One of the deleted plasmids contains only 5900 base pairs (52%) of P4 but will form plaques if additional DNA is added to increase its total size to near that of P4. This plasmid is also unique in that it will not form stable associations with P2 lysogens of E. coli which are recA+. P4 alpha mutants can be suppressed as a result of replication under control of the ColE1 part of the hybrid.
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Medberry SL, Dale E, Qin M, Ow DW. Intra-chromosomal rearrangements generated by Cre-lox site-specific recombination. Nucleic Acids Res 1995; 23:485-90. [PMID: 7885845 PMCID: PMC306701 DOI: 10.1093/nar/23.3.485] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Chromosomal rearrangements are useful genetic and breeding tools but are often difficult to detect and characterize. To more easily identify and define chromosome deletions and inversions, we have used the bacteriophage P1 Cre-lox site-specific recombination system to generate these events in plants. This involves three steps: (i) the introduction of two lox sites into one locus in a plant genome, including one site within a modified Ds transposon; (ii) Ac transposase-mediated transposition of the Ds-lox element to a new locus on the same chromosome; (iii) Cre-mediated site-specific recombination between the two lox sites that bracket a chromosome segment. We report the production of a deletion and three inversion events in tobacco. The utility of chromosomal segments bracketed by lox sites for targeted manipulation and cloning is discussed.
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Bayley C, Trolinder N, Ray C, Morgan M, Quisenberry JE, Ow DW. Engineering 2,4-D resistance into cotton. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 1992; 83:645-649. [PMID: 24202683 DOI: 10.1007/bf00226910] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/1991] [Accepted: 08/08/1991] [Indexed: 06/02/2023]
Abstract
To reduce damage by drift-levels of the herbicide 2,4-dichlorophenoxyacetic acid, we have engineered the 2,4-D resistance trait into cotton (Gossypium hirsutum L.). The 2,4-D monooxygenase gene tfdA from Alcaligenes eutrophus plasmid pJP5 was isolated, modified and expressed in transgenic tobacco and cotton plants. Analyses of the transgenic progeny showed stable transmission of the chimeric tfdA gene and production of active 2,4-D monooxygenase. Cotton plants obtained were tolerant to 3 times the field level of 2,4-D used for wheat, corn, sorghum and pasture crops.
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Sundaresan V, Ow DW, Ausubel FM. Activation of Klebsiella pneumoniae and Rhizobium meliloti nitrogenase promoters by gln (ntr) regulatory proteins. Proc Natl Acad Sci U S A 1983; 80:4030-4. [PMID: 6306658 PMCID: PMC394194 DOI: 10.1073/pnas.80.13.4030] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We have studied the expression, in different Escherichia coli gln (ntr) mutants, of fusions (constructed in vitro) of the nifHDK (nitrogenase) promoters from Klebsiella pneumoniae and Rhizobium meliloti to E. coli lacZ. Derepression of the K. pneumoniae nifH::lacZ fusion requires the glnF (ntrA) gene product in addition to the K. pneumoniae nifA gene product, indicating that regulation of the K. pneumoniae nif genes is more closely integrated with the overall nitrogen control system than previously demonstrated. Derepression of the R. meliloti nifH::lacZ fusion in E. coli by the K. pneumoniae nifA gene product (which we had previously shown) exhibits the same requirement for glnF. Derepression of the R. meliloti nifH::lacZ fusion, but not the K. pneumoniae nifH::lacZ fusion, can be mediated by the glnG (ntrC) gene product, suggesting that the gln regulatory genes might directly regulate the symbiotic nitrogen fixation genes in Rhizobium.
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Ow DW, Xiong Y, Gu Q, Shen SC. Mutational analysis of the Klebsiella pneumoniae nitrogenase promoter: sequences essential for positive control by nifA and ntrC (glnG) products. J Bacteriol 1985; 161:868-74. [PMID: 3882668 PMCID: PMC214977 DOI: 10.1128/jb.161.3.868-874.1985] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
ntr (nitrogen regulated) and nif (nitrogen fixation) promoters are structurally similar to each other but bear no resemblance to canonic Escherichia coli promoters. ntr promoters are normally activated by the ntrC (glnG) product, but they can also be activated by the ntrC-related Klebsiella pneumoniae nifA product. In contrast, nif promoters of K. pneumoniae such as the nitrogenase (nifH) promoter can only be nifA activated. In this paper, we report the isolation and characterization of 28 mutants of the K. pneumoniae nifH promoter. Class A mutants no longer respond to nifA-mediated transcription, and class B mutants can now respond to ntrC-mediated activation. These two classes of mutants define sequences important to nifA- and ntrC-mediated transcription. Most surprising is that a single base change is sufficient to convert a nifA-activated promoter into an ntrC-activated one.
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Juang RH, McCue KF, Ow DW. Two purine biosynthetic enzymes that are required for cadmium tolerance in Schizosaccharomyces pombe utilize cysteine sulfinate in vitro. Arch Biochem Biophys 1993; 304:392-401. [PMID: 8346915 DOI: 10.1006/abbi.1993.1367] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In plants and in certain fungi, exposure to heavy metals induces the synthesis of metal-binding peptides commonly known as phytochelatins. With cadmium, phytochelatins can sequester the metal into a sulfide-containing complex. From genetic analysis of fission yeast mutants, we previously reported that two genes in purine biosynthesis, encoding adenylosuccinate synthetase and succinoaminoimidazole carboxamide ribonucleotide (SAICAR) synthetase, are required for the biogenesis of the phytochelatin-cadmium-sulfide complex in vivo. We suggested that a sulfur analog of aspartate, cysteine sulfinate, might be utilized by these enzymes and that the cysteine sulfinate-derived products would then become intermediates or carriers in a sulfur transfer pathway leading to the sulfide found within the metal chelate. In this paper, we report that partially purified adenylosuccinate synthetase and SAICAR synthetase are capable of utilizing cysteine sulfinate in vitro to form sulfur analog products. Adenylosuccinate lyase, however, fails to catalyze further conversion of these sulfur derivatives. These observations support the genetic data implicating a link among purine biosynthetic enzymes, sulfur metabolism, and cadmium tolerance.
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Abstract
The fission yeast Schizosaccharomyces pombe detoxifies cadmium by synthesizing phytochelatins, peptides of the structure (gamma-GluCys)nGly, which bind cadmium and mediate its sequestration into the vacuole. The fission yeast protein HMT2, a mitochondrial enzyme that can oxidize sulphide, appears to be essential for tolerance to multiple forms of stress, including exposure to cadmium. We found that the hmt2- mutant is unable to accumulate normal levels of phytochelatins in response to cadmium, although the cells possess a phytochelatin synthase that is active in vitro. Radioactive pulse-chase experiments demonstrated that the defect lies in two steps: the synthesis of phytochelations and the upregulation of glutathione production. Phytochelatins, once formed, are stable. hmt2- cells accumulate high levels of sulphide and, when exposed to cadmium, display bright fluorescent bodies consistent with cadmium sulphide. We propose that the precipitation of free cadmium blocks phytochelatin synthesis in vivo, by preventing upregulation of glutathione production and formation of the cadmium-glutathione thiolate required as a substrate by phytochelatin synthase. Thus, although sulphide is required for phytochelatin-mediated metal tolerance, aberrantly high sulphide levels can inhibit this pathway. Precise regulation of sulphur metabolism, mediated in part by HMT2, is essential for metal tolerance in fission yeast.
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