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Robert W. Thornburg - One of the best experts on this subject based on the ideXlab platform.

  • Uridine 5′-Monophosphate Synthase Is Transcriptionally Regulated by Pyrimidine Levels in Nicotiana plumbaginifolia
    Plant Physiology, 1998
    Co-Authors: Djoko Santoso, Robert W. Thornburg
    Abstract:

    To understand the regulation and expression of pyrimidine biosynthesis in plants, we have examined the effect of the metabolic inhibitor 5-fluoroorotic acid (FOA) on uridine-5′-monophosphate synthase (UMPSase) expression in cell cultures of Nicotiana plumbaginifolia. UMPSase is the rate-limiting step of pyrimidine biosynthesis in plants. Addition of FOA causes an up-regulation of UMPSase enzyme activity in cell cultures after a lag phase of several days. Western-blot analysis demonstrated that the up-regulation in enzyme activity was caused by increased expression of the UMPSase protein. Northern-blot analysis demonstrated a higher level of UMPSase mRNA in the FOA-induced tissues than in control tissues. Run-on transcriptional assays showed that the UMPSase gene was transcriptionally activated after FOA treatment. The mechanism of toxicity of FOA is through thymine starvation. We found that addition of thymine abrogated the FOA-mediated up-regulation of UMPSase. In addition, methotrexate and aminopterin, which affect thymine levels by inhibiting dihydrofolate reductase, also up-regulate UMPSase in N. plumbaginifolia cells.

  • uridine 5 monophosphate synthase is transcriptionally regulated by pyrimidine levels in Nicotiana plumbaginifolia
    Plant Physiology, 1998
    Co-Authors: Djoko Santoso, Robert W. Thornburg
    Abstract:

    To understand the regulation and expression of pyrimidine biosynthesis in plants, we have examined the effect of the metabolic inhibitor 5-fluoroorotic acid (FOA) on uridine-5'-monophosphate synthase (UMPSase) expression in cell cultures of Nicotiana plumbaginifolia. UMPSase is the rate-limiting step of pyrimidine biosynthesis in plants. Addition of FOA causes an up-regulation of UMPSase enzyme activity in cell cultures after a lag phase of several days. Western-blot analysis demonstrated that the up-regulation in enzyme activity was caused by increased expression of the UMPSase protein. Northern-blot analysis demonstrated a higher level of UMPSase mRNA in the FOA-induced tissues than in control tissues. Run-on transcriptional assays showed that the UMPSase gene was transcriptionally activated after FOA treatment. The mechanism of toxicity of FOA is through thymine starvation. We found that addition of thymine abrogated the FOA-mediated up-regulation of UMPSase. In addition, methotrexate and aminopterin, which affect thymine levels by inhibiting dihydrofolate reductase, also up-regulate UMPSase in N. plumbaginifolia cells.

Djoko Santoso - One of the best experts on this subject based on the ideXlab platform.

  • Uridine 5′-Monophosphate Synthase Is Transcriptionally Regulated by Pyrimidine Levels in Nicotiana plumbaginifolia
    Plant Physiology, 1998
    Co-Authors: Djoko Santoso, Robert W. Thornburg
    Abstract:

    To understand the regulation and expression of pyrimidine biosynthesis in plants, we have examined the effect of the metabolic inhibitor 5-fluoroorotic acid (FOA) on uridine-5′-monophosphate synthase (UMPSase) expression in cell cultures of Nicotiana plumbaginifolia. UMPSase is the rate-limiting step of pyrimidine biosynthesis in plants. Addition of FOA causes an up-regulation of UMPSase enzyme activity in cell cultures after a lag phase of several days. Western-blot analysis demonstrated that the up-regulation in enzyme activity was caused by increased expression of the UMPSase protein. Northern-blot analysis demonstrated a higher level of UMPSase mRNA in the FOA-induced tissues than in control tissues. Run-on transcriptional assays showed that the UMPSase gene was transcriptionally activated after FOA treatment. The mechanism of toxicity of FOA is through thymine starvation. We found that addition of thymine abrogated the FOA-mediated up-regulation of UMPSase. In addition, methotrexate and aminopterin, which affect thymine levels by inhibiting dihydrofolate reductase, also up-regulate UMPSase in N. plumbaginifolia cells.

  • uridine 5 monophosphate synthase is transcriptionally regulated by pyrimidine levels in Nicotiana plumbaginifolia
    Plant Physiology, 1998
    Co-Authors: Djoko Santoso, Robert W. Thornburg
    Abstract:

    To understand the regulation and expression of pyrimidine biosynthesis in plants, we have examined the effect of the metabolic inhibitor 5-fluoroorotic acid (FOA) on uridine-5'-monophosphate synthase (UMPSase) expression in cell cultures of Nicotiana plumbaginifolia. UMPSase is the rate-limiting step of pyrimidine biosynthesis in plants. Addition of FOA causes an up-regulation of UMPSase enzyme activity in cell cultures after a lag phase of several days. Western-blot analysis demonstrated that the up-regulation in enzyme activity was caused by increased expression of the UMPSase protein. Northern-blot analysis demonstrated a higher level of UMPSase mRNA in the FOA-induced tissues than in control tissues. Run-on transcriptional assays showed that the UMPSase gene was transcriptionally activated after FOA treatment. The mechanism of toxicity of FOA is through thymine starvation. We found that addition of thymine abrogated the FOA-mediated up-regulation of UMPSase. In addition, methotrexate and aminopterin, which affect thymine levels by inhibiting dihydrofolate reductase, also up-regulate UMPSase in N. plumbaginifolia cells.

Michel Jacobs - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of UV damage at DNA level in Nicotiana plumbaginifolia protoplasts using single cell gel electrophoresis
    Plant Cell Tissue and Organ Culture, 2007
    Co-Authors: Yulheri Abas, Michel Jacobs, Nadia Touil, Micheline Kirsch-volders, Geert Angenon, Ivan Famelaer
    Abstract:

    The aim of the present study was to observe the induction and repair of single strand breaks (Ssbs) and double strand breaks (Dsbs) in mesophyll protoplasts of Nicotiana plumbaginifolia, irradiated with UV-C and cultured under light or dark conditions. DNA damage and repair was determined by the neutral and alkaline comet assay to reveal Dsbs and Ssbs respectively.

  • uv irradiation as a tool for obtaining asymmetric somatic hybrids between Nicotiana plumbaginifolia and lycopersicon esculentum
    Theoretical and Applied Genetics, 1997
    Co-Authors: M Vlahova, S Hinnisdaels, F Frulleux, M Claeys, A Atanassov, Michel Jacobs
    Abstract:

    UV-irradiated kanamycin-resistant Lycopersicon esculentum leaf protoplasts were fused with wild-type Nicotiana plumbaginifolia leaf protoplasts. Hybrid calli were recovered after selection in kanamycin-containing medium and subsequently regenerated. Cytological analysis of these regenerants showed that several (2–4) tomato chromosomes, or chromosome fragments, were present in addition to a polyploid Nicotiana genome complement. All lines tested had neomycin phosphotransferase (NPTII) activity and the presence of the kanamycin gene was shown by Southern blotting. In two cases a different hybridization profile for the kanamycin gene, compared to the tomato donor partner, was observed, suggesting the occurence of intergenomic recombination events. The hybrid nature of the regenerants was further confirmed by Southern-blotting experiments using either a ribosomal DNA sequence or a tomato-specific repeat as probes. The hybrids were partially fertile and some progeny could be obtained. Our results demonstrate that UV irradiation is a valuable alternative for asymmetric cell-hybridization experiments.

Chi-chang Chen - One of the best experts on this subject based on the ideXlab platform.

  • Two tandemly repeated telomere-associated sequences in Nicotiana plumbaginifolia.
    Chromosome Research, 1997
    Co-Authors: Chung-mong Chen, Yen-yu Kao, Chi-ting Wang, Chung-ju Wang, Chi-chang Chen
    Abstract:

    Two tandemly repeated telomere-associated sequences, NP3R and NP4R, have been isolated from Nicotiana plumbaginifolia. The length of a repeating unit for NP3R and NP4R is 165 and 180 nucleotides respectively. The abundance of NP3R, NP4R and telomeric repeats is, respectively, 8.4 × 104, 6 × 103 and 1.5 × 106 copies per haploid genome of N. plumbaginifolia. Fluorescence in situ hybridization revealed that NP3R is located at the ends and/or in interstitial regions of all 10 chromosomes and NP4R on the terminal regions of three chromosomes in the haploid genome of N. plumbaginifolia. Sequence homology search revealed that not only are NP3R and NP4R homologous to HRS60 and GRS, respectively, two tandem repeats isolated from N. tabacum, but that NP3R and NP4R are also related to each other, suggesting that they originated from a common ancestral sequence. The role of these repeated sequences in chromosome healing is discussed based on the observation that two to three copies of a telomere-similar sequence were present in each repeating unit of NP3R and NP4R.

  • A point mutation in the chloroplast rps12 gene from Nicotiana plumbaginifolia confers streptomycin resistance
    Plant Molecular Biology, 1993
    Co-Authors: Chen-mei Hsu, Chi-chang Chen, Wen-pei Yang, Yiu-kai Lai, Tsai-yun Lin
    Abstract:

    In an effort to understand the mechanism of streptomycin resistance in Nicotiana plumbaginifolia, we have sequenced the chloroplast rps12 gene, a potential molecular target. We report that a streptomycin-resistant mutant isolated from protoplast cultures of N. plumbaginifolia contains an A-to-G transition at nucleotide position 149 in exon 2 of the chloroplast rps12 gene. The detected point mutation predicts a substitution of arginine for lysine in a phylogenetically conserved region.

  • Restriction endonuclease analysis of chloroplast DNA from streptomycin-resistant mutants of Nicotiana plumbaginifolia.
    Genome, 1992
    Co-Authors: Yiu-kay Lai, Teng-yung Feng, Chi-chang Chen
    Abstract:

    Chloroplast DNA isolated from wild-type Nicotiana plumbaginifolia and 12 maternally inherited streptomycin-resistant mutants was digested with various restriction enzymes and the resultant patterns were compared. No gross structural alterations of the chloroplast genome were detected in any mutants; however, variant patterns owing to the gain or loss of a restriction site were found in three mutants, SR1007, SR1019, and SR1022. The variant patterns in SR1019 and SR1022 are identical and are the results of mutation in the psbG gene coding for a chloroplast membrane protein G, and that in SR1007 is due to mutation in the 16S rRNA gene. Inheritance of the variant patterns in mutants SR1007 and SR1019 was studied. The results showed that the variant patterns and streptomycin resistance were co-transmitted in reciprocal crosses.Key words: Nicotiana plumbaginifolia, streptomycin resistance, chloroplast DNA, restriction endonuclease analysis, 16S rRNA.

  • Mendelian inheritance of streptomycin resistance in Nicotiana plumbaginifolia
    Plant Cell Reports, 1991
    Co-Authors: Yen-yu Kao, Chiu-yueh Hung, Chi-chang Chen
    Abstract:

    In a previous study two haploid streptomycin-resistant clones of Nicotiana plumbaginifolia were isolated. The chromosome number of one of these clones has now been doubled through leaf-midvein culture and the resultant diploids were characterized genetically. Our results show that streptomycin resistance in this clone is conditioned by a recessive nuclear gene. Haploid protoplasts of this streptomycin-resistant mutant were selected for chlorate resistance. All clones obtained from the selection were deficient in nitrate reductase activity in addition to resistance to streptomycin. Genetic analysis of progeny of one of these clones revealed that the genes for streptomycin resistance and for the apoenzyme of nitrate reductase are unlinked.

Marc Boutry - One of the best experts on this subject based on the ideXlab platform.

  • Identification and characterization of a second plasma membrane H^+-ATPase gene subfamily in Nicotiana plumbaginifolia
    Plant Molecular Biology, 1993
    Co-Authors: Luc Moriau, Pierre Bogaerts, Jean-luc Jonniaux, Marc Boutry
    Abstract:

    A cDNA clone was isolated for a fourth pma gene encoding a putative plasma membrane H^+-ATPase of Nicotiana plumbaginifolia . The sequence of the predicted 952 residue PMA4 polypeptide was compared with those of other known plant PMAs, revealing a higher identity with the Arabidopsis thaliana proteins (86–89%) than with the other three N. plumbaginifolia PMA proteins (80–82%). This supports the view that there are two pma subfamilies which probably arose from a gene duplication predating the separation of the Dilleniidae and Asteridae plant subclasses. Measured pma4 transcript levels indicate that pma4 is similarly expressed in root, stem, leaf, and flower tissues, contrary to the pmal-3 subfamily whose members displayed differential expression according to the organ.

  • identification and characterization of a second plasma membrane h atpase gene subfamily in Nicotiana plumbaginifolia
    Plant Molecular Biology, 1993
    Co-Authors: Luc Moriau, Pierre Bogaerts, Jean-luc Jonniaux, Marc Boutry
    Abstract:

    A cDNA clone was isolated for a fourth pma gene encoding a putative plasma membrane H(+)-ATPase of Nicotiana plumbaginifolia. The sequence of the predicted 952 residue PMA4 polypeptide was compared with those of other known plant PMAs, revealing a higher identity with the Arabidopsis thaliana proteins (86-89%) than with the other three N. plumbaginifolia PMA proteins (80-82%). This supports the view that there are two pma subfamilies which probably arose from a gene duplication predating the separation of the Dilleniidae and Asteridae plant subclasses. Measured pma4 transcript levels indicate that pma4 is similarly expressed in root, stem, leaf, and flower tissues, contrary to the pmal-3 subfamily whose members displayed differential expression according to the organ.

  • Identification and characterization of a second plasma membrane H(+)-ATPase gene subfamily in Nicotiana plumbaginifolia.
    Plant Molecular Biology, 1993
    Co-Authors: Luc Moriau, Pierre Bogaerts, Jean-luc Jonniaux, Marc Boutry
    Abstract:

    A cDNA clone was isolated for a fourth pma gene encoding a putative plasma membrane H(+)-ATPase of Nicotiana plumbaginifolia. The sequence of the predicted 952 residue PMA4 polypeptide was compared with those of other known plant PMAs, revealing a higher identity with the Arabidopsis thaliana proteins (86-89%) than with the other three N. plumbaginifolia PMA proteins (80-82%). This supports the view that there are two pma subfamilies which probably arose from a gene duplication predating the separation of the Dilleniidae and Asteridae plant subclasses. Measured pma4 transcript levels indicate that pma4 is similarly expressed in root, stem, leaf, and flower tissues, contrary to the pmal-3 subfamily whose members displayed differential expression according to the organ.