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1Author    Nir Ohad3, Dekel Amir-Shapirab, Hiroyuki Koikec, Yorinao Inouec, Itzhak Ohadb, Joseph Hirschberg3Requires cookie*
 Title    Amino Acid Substitutions in the D 1 Protein of Photosystem II Affect Q b-Stabilization and Accelerate Turnover of D  
 Abstract    Isogenic strains of Synechococcus PCC 7942 were genetically engineered so that copy I of the gene psbA was mutated at specific sites. These mutations resulted in replacements of Ser 264 by Gly or Ala and of Phe 255 by Tyr or Leu in the D 1 protein. The mutants were resistant to herbicides inhibiting electron transfer in photosystem II. All mutants exhibited alterations in the stability of Q B' as demonstrated by a temperature downshift, to various extents, of the in vivo thermoluminescence emission. Measurements of the light-dependent turnover of D 1 showed a marked decrease in the 11 / 2 of this protein in the mutants as compared to wild-type, under low to medium light intensities. A correlation was found between the degree of pertur­ bation in the Q B" stability and the rate of acceleration in the turnover of D 1. These data pro­ vide a direct evidence for the overlapping binding sites for the plastoquinone B and herbicides in the D 1 protein. In addition these data indicate a close link between Q B" destabilization in reaction center II and the mechanism controlling the light-dependent turnover of D 1. Based on these results and previous work we suggest that destabilization of the semireduced quinone, facilitates a light-induced damage in D 1 which triggers its degradation. 
  Reference    Z. Naturforsch. 45c, 402—408 (1990); received November 21 1989 
  Published    1990 
  Keywords    Herbicide Resistance, Thermoluminescence, D 1 Turnover, Synechococcus PCC 7942 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0402.pdf 
 Identifier    ZNC-1990-45c-0402 
 Volume    45 
2Author    I. Sinning, J. Koepke, B. Schiller, H. MichelRequires cookie*
 Title    First Glance on the Three-Dimensional Structure of the Photosynthetic Reaction Center from a Herbicide-Resistant Rhodopseudomonas viridis Mutant  
 Abstract    A first model o f the three-dimensional structure o f the photosynthetic reaction center o f the mutant T1 (SerL223 —* ■ Ala, ArgL217 —* His) from Rhodopseudom onas viridis, resistant to ­ ward the triazine herbicide terbutryn (2-m ethylthio-4-ethylam ino-6-/-butylam ino-s-triazine), has been developed from X-ray data measured to a resolution o f 2.5 Ä. The secondary qui­ none, Q B, which in T 1 binds better than in the wild type, is present in the crystals. Both substi­ tuted residues are clearly visible in the difference fourier map. The replacement o f these two residues in the Q B site causes only minor changes in the overall structure o f the protein. 
  Reference    Z. Naturforsch. 45c, 455 (1990); received December 9 1989 
  Published    1990 
  Keywords    Three-Dimensional Structure, Herbicide Resistance, Terbutryn, Photosynthetic Reaction Center 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0455.pdf 
 Identifier    ZNC-1990-45c-0455 
 Volume    45 
3Author    Jack Farineaua, DanielleM. Laval-, ArtinbRequires cookie*
 Title    Characteristics of Thermoluminescence Bands of Euglena Cells Belonging to 2 Lines Presenting Different Degrees of Diuron-Resistance  
 Abstract    We have analysed the thermoluminescence (TL) properties of two lines o f Euglena exhibit­ ing two degrees of resistance to diuron, by a factor of 100 (Z R 25) and 1000 (Z R 250) respectively, as compared to wild type line (Z). In addition, the two ZR lines developped an identical resistance to atrazine since the I50 for this herbicide in each line was 75 times larger than in wild type. Special TL characteristics were evidenced in the two lines. Bands after 2 flashes (or more) showed a shift o f the peak maximum towards low temperature, the shift being the largest in the most DCM U-resistant cells. Similar results were obtained with isolated thylakoids, except that the TL bands appeared at a temperature higher than in corresponding cells. Oscillations in the amplitude of the bands in a flash sequence were largely damped in cells (and thylakoids), particularly in the most DCM U-resistant lines. The results are interpreted as indicating accumulation of Q a "Qb after flashes due to a decrease of the equilibrium constant for the reaction Q a ~Qb ^ QaQb~ accompanying the D CM U resistance. 
  Reference    Z. Naturforsch. 50c, 86—9 (1995); received October 12/November 21 1994 
  Published    1995 
  Keywords    Diuron, Euglena, Herbicide-Resistance, Photosystem II, Thermoluminescence 
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 TEI-XML for    default:Reihe_C/50/ZNC-1995-50c-0086.pdf 
 Identifier    ZNC-1995-50c-0086 
 Volume    50 
4Author    Sophie Creuzet, TeresaM. Iranda, Jean-M Arc DucruetRequires cookie*
 Title    Comparison of Experimental and Calculated Hydrogen Bonding Properties of Some Urea and Triazine Inhibitors of Photosystem II  
 Abstract    Previous studies o f structure/activity relationships o f photosystem II inhibitors, including com parisons o f their inhibitory power in herbicide-resistant and susceptible chloroplasts, have led to predict the role o f hydrogen bonding, associated to hydrophobicity, in the binding onto the Qb site. The crystallographic structures o f bacterial reaction centers now allow these bonds to be identified. In order to be able to understand the binding o f various herbicides and the effects o f resistance mutations within the Q B site, a reliable estimation o f hydrogen bonding strengths is needed. We show here, by calculating interactions with model com pounds, con ­ trolled by physicochemical measurements, that the hydrogen bonding properties o f the C = X nucleophilic moiety present in most PS II inhibitors are different for triazines as compared to urea or amide derivatives. Semiempirical methods (AM 1) fail to reproduce the energies o f hy­ drogen bonds between a triazine ring nitrogen and a phenolic proton. An empirical method (SI BFA), designed to reproduce interaction energies, has been adapted with the aim o f calculat­ ing the binding energies o f various herbicides with models o f the Q B site. 
  Reference    Z. Naturforsch. 48c, 179 (1993); received November 12 1992 
  Published    1993 
  Keywords    Herbicide, Herbicide Resistance, Hydrogen Bonding, M olecular Calculation, Photosystem II 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0179.pdf 
 Identifier    ZNC-1993-48c-0179 
 Volume    48 
5Author    Jutta Thiem, Wolfgang BarzRequires cookie*
 Title    Photoautotrophic Chenopodium rubrum Cell Suspension Cultures Resistant against Photosynthesis-Inhibiting Herbicides I. Selection and Characterization  
 Abstract    For establishing metribuzin-resistant, photoautotrophic Chenopodium rubrum cell cul­ tures plated cells, callus cultures or suspension cultures were subjected to selection proce­ dures. The most effective procedure was the stepwise increase in the concentration of the herbicide from 0.01 ^im to 10 ^im in suspension cultures, which resulted in the isolation of eight different metribuzin-resistant photoautotrophic cell lines. Conjugation metabolism or a decrease in the uptake and translocation of the selective agent were not responsible for resist­ ance, which was stable in the absence of the inhibitor over numerous growth cycles. Meas­ urements of the photosynthetic electron transport, analyses of fluorescence induction kinetics and determination of the binding properties of 14C-labelled metribuzin to isolated thylakoids indicated that resistance of the cell lines is based on an alteration in the photosystem II her­ bicide-binding protein (D 1 protein). RFLP analysis of the psbA gene of the eight resistant cell lines demonstrated that none of them possess an amino acid exchange in position 264 of the D 1 protein leading to altered herbicide-binding properties. 
  Reference    Z. Naturforsch. 49c, 186—194 (1994); received June 25/December 161993 
  Published    1994 
  Keywords    Herbicide Resistance, Selection Mechanism, Photoautotrophic Cell Culture, Chenopodium rubrum 
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 TEI-XML for    default:Reihe_C/49/ZNC-1994-49c-0186.pdf 
 Identifier    ZNC-1994-49c-0186 
 Volume    49 
6Author    M. Imoun, ElK. Aoua, Evelyne Duval, DanielleM. Laval-, ArtinRequires cookie*
 Title    Long-Term Effect of Diuron on Chlorophyllous Callus of Bromus erectus: Lipid Composition  
 Abstract    The selection o f plants resistant to photosynthetic herbicides is limited by the low rate o f success in obtaining a photosynthetic callus. An attempt was made to induce diuron tolerance with chlorophyllous tissue strains o f Bromus erectus: growth, chlorophyll contents and total fatty acids were studied during four months o f photoheterotrophic growth in the presence or absence o f 6 diuron. The presence o f the herbicide, which reduced the fresh weight by 40%, provoked increases in chlorophyll levels by 2-or 3-fold, and in galactolipids (especially D G D G) which were enriched in linolenic acid content. These results, closely related to already described characteristics o f herbicide-resistant material, suggest that callus o f Brom us erectus could constitute an interesting photosynthetic in vitro material. 
  Reference    Z. Naturforsch. 46c, 569—5 (1991); received January 11/M arch 25 1991 
  Published    1991 
  Keywords    Bromus erectus Chlorophyll Diuron A daptation, Glycerolipids, Herbicide Resistance, in vitro Cultures 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0569.pdf 
 Identifier    ZNC-1991-46c-0569 
 Volume    46 
7Author    Josef Vinnemeier, Wolfgang Dröge-Laser, ElfriedeK. Pistorius, Inge BroerRequires cookie*
 Title    Purification and Partial Characterization of the Streptomyces viridochromogenes TÜ494 Phosphinothricin-N-acetyltransferase Mediating Resistance to the Herbicide Phosphinothricin in Transgenic Plants  
 Abstract    A purification scheme for the enzyme phosphinothricin-N-acetyltransferase (PAT) origi­ nating from Streptomyces viridochrom ogenes {pat-gene product from Streptom yces virido­ chromogenes) and mediating herbicide resistance to transgenic plants was developed. The enzyme was isolated from a transformed and overproducing Escherichia coli strain. With a combination of ammonium sulfate fractionation, chromatography on D EAE-Sephadex A50-, Phenylsepharose-, Hydroxylapatite-and FPLC-Superose 12-columns it was possible to obtain PAT which was at least 90 % homogeneous on the basis of SDS-PAGE. The properties of the isolated PAT were compared with the properties of PAT from S. hygroscopicus (bar-gene product from S. hygroscopicus) previously isolated and characterisized by Botterman, J., Gossele, V., Thoen, C., Lauwereys, M. (1991), G ene 102, 33-37. Differences were observed in the molecular masses of the two native enzymes (PAT from S. viridochrom ogenes being a dimer of 40 kD and PAT from S. hygroscopicus being a m onomer of 21 kD), and in the tem perature sensitivity of the two enzymes (the PAT from S. viridochrom ogenes being slightly more tem perature stable than PAT from S. hygroscopicus). However, since the pat and the bar-gene are to 85 % homologous, substantial similarities exist between the two enzymes especially in the kinetic values and the substrate specificity. The isolated S. virido­ chromogenes PAT did not acetylate putative substrates present in the plant cell. Antibodies were raised against the isolated protein. This antiserum was able to detect PAT in transgenic plants and therefore is suitable to analyse the fate of the protein in such plants under various stress conditions. 
  Reference    Z. Naturforsch. 50c, 796—805 (1995); received August 16 1995 
  Published    1995 
  Keywords    Biosafety, Herbicide Resistance, Nicotiana tabacum, Phosphinothricin-A'-acetyltransferase (PAT), Transgenic Plants 
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 TEI-XML for    default:Reihe_C/50/ZNC-1995-50c-0796.pdf 
 Identifier    ZNC-1995-50c-0796 
 Volume    50 
8Author    Britta Förster3, PeterB. Heifetz0, Anita Lardansd, JohnE. Boyntona, NicholasW. GillhambRequires cookie*
 Title    Herbicide Resistance and Growth of D1 Ala25i Mutants in Chlamydomonas  
 Abstract    We elucidated the effects of substituting seven amino acids for Ala at residue 251 of the Chlam ydom onas reinhardtii D1 protein on herbicide resistance and photoautotrophic growth. A la25i has been suggested to play a key role in the structural integrity and function of the stromal loop between transmembrane helices IV and V of D1 and has previously been shown to affect resistance to "classical" PSII specific herbicides. Sensitive and rapid microtiter assays were employed to compare herbicide resistance and photoautotrophic growth in the various mutants. Substitution of Ala25i by Ile, Leu or Val conferred resistance to the PSII herbicides atrazine, bromacil and metribuzin but not to DCMU, and impaired photoautotrophic growth in high and low light. Compared to an otherwise isogenic wildtype strain, the lie and Val mutants exhibited nearly identical levels of herbicide resistance and reduced growth while the Leu mutant had even slower growth and higher levels of herbicide resistance. In contrast Cys, Pro, Ser and Gly mutants were phenotypically indistinguishable from wildtype in terms of herbicide sensitivity and photoautotrophic doubling times. Collectively the seven A la251 mutations differed markedly from an Ala mutant (dr-1) at the well characterized Ser264 D1 residue in terms of herbicide resistance and photoautotrophic growth. 
  Reference    Z. Naturforsch. 52c, 654—664 (1997); received June ll/Ju ly 2 1997 
  Published    1997 
  Keywords    D1 Protein, Site-Directed Chloroplast Mutations, Herbicide Resistance, Photoautotrophic Growth, Microtiter Assay 
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 TEI-XML for    default:Reihe_C/52/ZNC-1997-52c-0654.pdf 
 Identifier    ZNC-1997-52c-0654 
 Volume    52 
9Author    Z. NaturforschRequires cookie*
 Title    Kinetics of Electron Transfer between Q A and Q B in Wild Type and Herbicide-Resistant Mutants of Chlamydomonas reinhardtii  
 Abstract    A n ton y R . C ro fts*, Irene B aroli, D avid K ra m e r, and Shinichi T a o k a Biophysics Division and *D epartm ent o f M icrobiology, University o f Illinois at U rbana-Cham paign, U rb ana, We have investigated the electron transfer kinetics for reduction o f plastoquinone by photo­ system II in six m utant strains o f Chlamydomonas reinhardtii by following the decay o f the high fluorescence state after flash activation, and com pared the separate reactions of the two-electron gate with those o f a wild type strain. By analysis o f the electron transfer kinetics, and separate measurement o f the equilibrium constant for stabilization o f the bound semiquinone after one flash, we have been able to deconvolute the contributions o f rate constants and equi­ librium constants for plastoquinone binding and electron transfer to the overall process. Two mutations, S 264 A and A 251 V, led to a marked slowing o f kinetics for reduction of plastoqui­ none to the bound semiquinone. In S 2 6 4 A , the second electron transfer was also slower, but was normal in A 2 5 1 V. In m utant G 2 5 6 D , the electron transfer kinetics were normal after the first flash, but slowed after the second. In mutants L 2 5 7 F , V 2 1 9 I, and F 2 5 5 Y , the electron transfer kinetics after both flashes were similar to those in wild type. We discuss the results in terms of a model which provides a description o f the mechanism o f the two-electron gate in terms of measured kinetic and equilibrium constants, and we give values for these parameters in all strains tested. 
  Reference    Z. Naturforsch. 48c, 259 (1993); received December 10 1992 
  Published    1993 
  Keywords    Electron Transfer, Kinetics, Tw o-Electron G ate, Herbicide Resistance, Photosystem II 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0259.pdf 
 Identifier    ZNC-1993-48c-0259 
 Volume    48