Published by De Gruyter

Volume 42 Issue 6

Issue of Zeitschrift für Naturforschung C

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Contents
Journal Overview

Open Access June 2, 2014

Herbicides Affecting Chloroplast Functions

Page range: 661-662

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Open Access June 2, 2014

The Role of Chirality in the Activity of Photosystem II Herbicides

Gary Gardner, James R. Sanborn

Page range: 663-669

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Abstract

Although significant differences in activity between optical isomers have been recognized in many types of pesticides, the role of stereoselectivity has not been fully characterized for one of the most important classes of commercial herbicides, those that inhibit photosynthetic electron transport. This report describes experiments in which optically active α-methylbenzylamine or sec-butylamine was used as starting material for the synthesis of optically active triazine and urea herbicides. The biological activities of the compounds were determined in two in vitro chloroplast assays - competition for specifically bound [ 14 C]atrazine and inhibition of photosystem II-medi- ated dye reduction - as well as in whole plant phytotoxicity. In both in vitro assays the (-)-isomer of the N-a-methylbenzyl triazine was about 15-fold more active than the (+)-isomer, and the racemate fell in between and was of about the same potency as atrazine. The same relative activities were also seen for in vivo phytotoxicity. The a-methylbenzyl urea derivatives were much less herbicidally active, but the in vitro assays were able to discriminate between the optical isomers. In both assays, the (-)-isomer of the urea was much more active than the (+)-isomer, with the racemate intermediate. Steric factors play a critical role in the degree of this chiral discrimination, since in both the corresponding triazines and ureas, the optically active molecules synthesized from the enantiomers of 2-butylamine showed only slight differences in activity. Saturation of the phenyl ring of the a-methylbenzyl triazines resulted in molecules which still showed substantial differences in activity related to chirality, further supporting the importance of steric factors, rather than electronic, in this chiral discrimination.

Open Access June 2, 2014

Cyanoacrylate Inhibitors of Photosynthetic Electron Transport in Atrazine Susceptible and Atrazine Resistant Brassica Chloroplasts

John N. Phillips, John L. Huppatz

Page range: 670-673

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Abstract

Comparison of the p/ 50 values for a series of cyanoacrylate derivatives in chloroplasts isolated from atrazinc susccptiblc (wild type) and atrazine resistant (mutant) Brassica napus biotvpes reveal that the degree and direction of discrimination can vary from being 200- fold more active against the wild type to 10-fold more active against the mutant. There appears to be a direct correlation between the level of inhibitory activity in thylakoids isolated from “susceptible” chloroplasts and the level of discrimination between “susceptible” and “resistant” chloroplasts - a correlation which can be improved by allowing for variations in molecular hydrophobicity. Studies with optically active ethoxyethyl-3-alkyl-2-cyano-3-α-methylbenzylamino acrylates suggest that there are specific receptor sites present in both “susceptible” and “resistant” chloroplasts for both the a-methylbenzyl chiral centre and the 3-alkyl moiety. There is a direct relationship between photosynthetic electron transport inhibitory activity and herbicidal activity of optical isomers.

Open Access June 2, 2014

Stereospecific Inhibitor Probes of the PS II Herbicide Binding Site

John L. Huppatz, John N. Phillips

Page range: 674-678

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Abstract

The influence of steric factors on the activity of 2-cyanoacrylic esters as inhibitors of the Hill reaction was examined. The spatial arrangement of the different groups in the inhibitor molecule was found to be an important factor in determining potency. The positioning of the phenyl ring in aralkylamino derivatives and the steric properties of the β-substituent are particularly significant in the interaction of molecules with the) hydrophobic domain of the receptor site. The difference in activity observed with optically active α-methylbenzylamino derivatives confirmed the importance of the orientation of the phenyl ring and indicated an interaction with a specific hydrophobic region.

Open Access June 2, 2014

Cyanoacrylate Inhibitors of the Hill Reaction IV. Binding Characteristics of the Hydrophobic Domain

John L. Huppatz, John N. Phillips

Page range: 679-683

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Abstract

Aryl- and aralkyl-amino derivatives of 2-cyanoacrylic esters were synthesized and assayed as inhibitors of the Hill reaction in isolated pea chloroplast fragments. Aryl- and aralkyl-amino 2-cyanoacrylates unsubstituted in the β-position were weak inhibitors but activity could be greatly enhanced by inclusion of a β-alkyl group with the increase in potency being dependent on the carbon chain length of the β-substituent. The magnitude of this effect appeared independent of the nature of the aryl- or aralkyl-amino function. Inclusion of a carbon chain between the phenyl and amino functions of phenylamino-2-cyano- acrylates produced a stepwise increase in activity with increasing chain length, indicating a prefer- red orientation for the phenyl ring within the hydrophobic binding domain.

Open Access June 2, 2014

Cyanoacrylate Inhibitors of the Hill Reaction V. The Effect of Chirality on Inhibitor Binding

John L. Huppatz, John N. Phillips

Page range: 684-689

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Abstract

Optically active α-methylbenzylamino 2-cyanoacrylic esters were synthesized and assayed as inhibitors of the Hill reaction in isolated pea chloroplast fragments. The 5-isomers were more potent inhibitors than the S-isomers with discriminations of from ten to greater than 100-fold being observed. A β-alkyl substituent in the cyanoacrylate molecule affected both the level of activity and the difference in activity between the isomers. An α,α-dimethylbenzylamino derivative was also active at about the same level as the corresponding α-methylbenzylamino racemate. This result could be explained in terms of the orientation of the phenyl ring in the receptor site. Replacement of the α-methylbenzylamino group by other α-alkyl and α-phenyl substituents had little effect on activity. However, an α-benzyl group was beneficial.

Open Access June 2, 2014

Herbicide and Quinone Binding to Chromatophores and Reaction Centers from Rhodobacter sphaeroides

Walter Oettmeier, Silvana Preuße

Page range: 690-692

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Abstract

Besides s-triazine and triazinone herbicides the chromone stigmatellin and tetrahalogen-substituted 1.4-benzoquinones are inhibitors of photosynthetic electron flow from reduced cytochrome c to ubiquinone-6 in isolated bacterial reaction centers. With isolated bacterial chromatophores binding experiments with radiolabeled herbicides can be performed in a similar way as with thylakoids from higher plants. Tetrahalogen-substituted 1.4-benzoquinones in a Michael type reaction can add onto nucleophilic groups in proteins. In bacterial reaction centers, a [ 14 C]tetra- bromo-1.4-benzoquinone (bromanil) exclusively binds to the H-subunit.

Open Access June 2, 2014

Irreversibly Binding Photosynthetic Electron Transport Inhibitors II. Halogen-Substituted 1,4-Naphthoquinones and Halogenmethyl-1,4-quinones

Walter Oettmeier, Ralf Dostatni, Hans-Joachim Santel

Page range: 693-697

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Abstract

Several halogen-substituted 1,4-naphthoquinones have been synthesized and found to be effective photosystem II inhibitors. Due to their properties as vinylogous acid halides they can react with nucleophiles under formation of a covalent linkage. In their presence other photosystem II herbicides show a decreased binding affinity. This decrease is dependent from the preincubation time. Halogenmethyl-1,4-quinones also turned out to be efficient photosystem II inhibitors and. in addition, possessed herbicidal in vivo activity. They function as “bioreductive alkylating agents” in a way that after reduction they can split off hydrogen halide under formation of a o-quinonemethide. This quinonemethide can react with nucleophilic groups in proteins.

Open Access June 2, 2014

Interaction of Halogenated 1,4-Benzoquinones with System II of Photosynthesis

Gernot Renger, Angela Kayed, Walter Oettmeier

Page range: 698-703

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Abstract

The interaction of halogenated p-benzoquinones with PS II has been analyzed by measurements of fluorescence induction curves and the average oxygen yield per flash in isolated class II chloroplasts. It was found: 1)The normalized area over the fluorescence induction curve in the presence of DCMU. A/F max , markedly increases if halogenated p-benzoquinones are added before DCMU. The effect is eliminated by DCMU addition prior to that of the quinones. 2)The extent of A/F max increases with increasing dark time between the additions of 2,3.5-tri- bromo-6-methyl-1,4-benzoquinone (TBTO) and DCMU. respectively. 3) Some of the halogenated p-benzoquinones were found to act as efficient electron acceptors under repetitive excitation at low flash frequency (2 Hz). In the case of TBTO and 2,3-di-chloro-5-t-butyl-1,4-benzoquinone (TBU 13) the sensitivity of the average oxygen yield per flash was shifted towards higher concentrations of DCMU. 4) Halogenated p-benzoquinones can also affect the stability of oxidizing redox equivalents in the water oxidizing enzyme system Y. This effect depends on the nature of the substituents. The present results are interpreted by the assumption of a covalent binding of halogenated p-benzoquinones in the vicinity of Q ᴀ . This binding is prevented by DCMU. The possibility of allosteric interaction between the donor and acceptor side of PS II is discussed.

Open Access June 2, 2014

Inhibition and Photoaffinity Labeling of Photosystem II by Thiazolyliden-ketonitriles

U. Bühmann, E. C. Herrmann, C. Kötter

Page range: 704-712

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Abstract

A new group of photosynthetic inhibitors is described. Thiazolyliden-ketonitriles are blocking electron flow at the acceptor side of photosystem II. They displace radioactive metribuzin from the membrane. Functional properties indicate that the new inhibitors share the binding site on the herbicide binding protein D-1 identical to that of the classical triazinone/urea-type inhibitors. However, fine details in the functional inhibition pattern, like lag in the inhibition and no loss of activity in tris-treated membranes, group them more specifically among the phenol-type family of photosystem II inhibitors. By photoaffinity labeling and immunoblotting it is shown that an azido- derivative of the thiazolyliden-ketonitriles tags the 32 kDa polypeptide subunit of photosystem II. This shows that also the phenol group inhibitors interact with the D-1 protein. MO calculations show that the predominant tautomeric form of the new ketonitrile inhibitors when bound to the membrane is the hydroxy-form, whereas cyanoacrylates with a comparable essential element are bound in the keto-form. As the first is a phenol-type, the second an urea- type inhibitor, this allows to define more clearly the essential chemical element in the phenol-type inhibitors responsible for effective binding to the D-1 protein, probably oriented in the binding niche towards histidine 215, rather than towards serine 264, as triazine/urea and the cyanoacrylate derivatives do.

Open Access June 2, 2014

Can Quantitative Structure Activity Analyses and Molecular Graphics Assist in Designing New Inhibitors of Photosystem II?

Wilfried Draber

Page range: 713-717

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Abstract

A calculation, based on various plausible assumptions, shows that under optimal conditions a rate of less than 10 g/ha of a potent photosynthesis inhibitor would be sufficient for good herbidical action. The possibility to achieve this by computer assisted drug design (CADD) is discussed. In order to provide some background, several methods of “classical” OSAR and the most frequently used parameters are discussed. Moreover, some aspects of molecular graphics are described. This powerful new CADD-method gives results that are qualitatively different from QSAR. It is not only intellectually demanding but also expensive with regard to hard- and software. In conclusion, one successful QSAR-based prediction of a herbicide is reviewed.

Open Access June 2, 2014

Interference by Herbicides with the Transmembrane Potential of Thylakoids

Donald E. Moreland, William P. Novitzky

Page range: 718-726

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Abstract

Interferences expressed by herbicides classified as inhibitory uncouplers were measured on the induction and maintenance of ΔpH and ΔΨ, the chemical and electrical components, respectively. of the proton motive force (pmf) generated by light-induced cyclic electron transport in spinach thylakoids. Maintenance of the pmf is required for the synthesis of ATP. The inhibitory uncouplers arc known to inhibit photophosphorylation, but the mechanisms involved remain to be identified. The dinoseb types (dinitrophenols. benzimidazoles. benzonitriles. bromophenoxim. perfluidone. thiadiazoles) of inhibitory uncouplers, most of which contain dissociable protons, were found to discharge ΔpΗ at low concentrations and to collapse ΔΨ at high concentrations. Collapse of ΔpΗ can be attributed to the protonophoric (proton shuttling) action of the herbicides. However, collapse of ΔΨ can be caused by alterations induced to the integrity and loss of semipermeability of the thylakoid membrane. As a result the membrane bccomes permeable to protons and other cations, and the electrical charges across the membrane are neutralized. The non-ionic dicryl types of inhibitory uncouplers (acylanilides. dinitroanilines. diphenylethcrs. bis-carbamates) collapsed ΔΨ at concentrations that were somewhat lower than those required for the collapse of ΔpΗ. These herbicides appear only to alter the integrity and permeability of the thylakoid membrane. Inhibition of photophosphorylation by the inhibitory uncouplcrs correlated with their ability to dissipate the pmf.

Open Access June 2, 2014

A Role of the Q_в Binding Protein in the Mechanism of Cyanobacterial Adaptation to Light Intensity?

Friederike Koenig

Page range: 727-732

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Abstract

Growth of the unicellular blue-green alga Anacystis nidulans in media containing sublethal concentrations of DCMU-type inhibitors of photosynthetic electron transport in strong white light gave rise to shade type appearance in this organism, as characterized by an increased ratio of phycocyanin to chlorophyll and reduced ratios, both, of carotenoids to chlorophyll and of total chlorophyll to P700. Shade type in Anacystis was caused neither by phenolic inhibitors tested nor by those known to bind to the cytochrome b 6 /f-complex. Surprisingly enough, the molar ratio of phycocyanin to chlorophyll in artificially shade adapted Anacystis 1 grown in strong white light in the presence of 10 -6 м atrazine, was found to increase with temperature for a given light intensity and with light intensity for a given temperature. Mutants of Anaeystis with a reduced binding capacity for DCMU-type herbicides due to an amino acid exchange in the 32 kDa Q в -binding polypeptide, also called D-1 protein, were ob- served to show shade type appearance in strong light, to respond very little to changes in light intensity and to show a reduced capability to further change their appearance to shade type by binding of competitors of Ob to the 32 kDa polypeptide. In Anaeystis a concentration of atrazine (10 -7 м), ten times lower than the one causing the highest rate of shade adaptation (10 -6 м), was shown to induce an optimum in cell density, which in turn resulted in an optimum in light-dependent O 2 evolution. Both factors together might be responsible for the so-called greening effect observed in higher plants treated with sublethal concentrations of DCMU-type inhibitors of photosynthetic electron transport.

Open Access June 2, 2014

The Topology of the 32 kDa Herbicide Binding Protein of Photosystem II in the Thylakoid Membrane

D. A. Kleier, T. A. Andrea, J. K. J. Hegedus, G. M. Gardner, B. Cohen

Page range: 733-738

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Abstract

The 32 kDa herbicide binding protein is a membrane bound protein which is implicated in the binding of many photosystem II herbicides as well as in the binding of the endogenous quinone OB which serves as the secondary electron acceptor on the reducing side of photosystem II. The topology of the 32 kDa protein has been predicted using a combination of hydrophobic moment analysis, membrane propensity analysis and empirical secondary structure predictions. Our model consists of five transmembrane helices. The loop connecting the fourth and fifth transmembrane helices is thought to form part of the herbicide binding site. Our analysis suggests that this loop also contains a helical segment which may seek the surface of the membrane by virtue of its relatively high hydrophobic moment. Our topology is compared with several others which have been proposed in the literature as well as with the topology of the L and M proteins of the bacterial reaction center of R. viridis. The significance of mutagenesis and photo-affinity labeling experiments is also discussed in terms of our model.

Open Access June 2, 2014

The Use of HPLC for the Purification of the Q_в-Protein

Günter F. Wildner, Claudia Fiebig, Norbert Dedner, H. E. Meyer

Page range: 739-741

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Abstract

The Q в -protein is as a hydrophobic integral membrane protein firmly bound in the reaction center complex of photosystem II. A new method was developed to purify the SDS extracted protein using reversed-phase chromatography with two binary linear gradient systems. The identification of the Q в -protein was achieved by its rapidly labeling during photoassimilation of [ 35 S]sulfate and by its reaction with the photoaffinity label azido-[ 14 C]atrazine. Furtherm ore, antisera against the purified Q в -protein reacted with a single peak fraction, the second peak of the chrom atogram , which was identical with the labeled protein peak fraction.

Open Access June 2, 2014

The Three-Dimensional Structure of the Herbicide Binding Niche on the Reaction Center Polypeptides of Photosystem II

Achim Trebst

Page range: 742-750

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Abstract

The folding through the membrane of the plastoquinone and herbicide binding protein subunits of photosystem II and the topology of the binding niche for plastoquinone and herbicides is described. The model is based on the homology in amino acid sequence and folding prediction from the hydropathy analysis of the D-1 and D-2 subunits of photosystem II to the reaction center polypeptides L and M of the bacterial reaction center. It incorporates the amino acid changes in the D-1 polypeptide in herbicide tolerant plants and those indicated by chemical tagging to be involved in Q в binding. It proposes homologous amino acids in the D-1/D-2 polypeptides to those indicated by the X-ray structure of the bacterial reaction center to be involved in Fe-, quinone- and reaction center chlorophyll-binding. The different chemical compounds known to interfere with Q в function are grouped into two families depending on their orientation in the Q в binding niche.

Open Access June 2, 2014

Sequence Analysis of Mutants from Rhodopseudomonas viridis Resistant to the Herbicide Terbutryn

I. Sinning, H. Michel

Page range: 751-754

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Abstract

Several mutants resistant to terbutryn (2-thiom ethyl-4-ethylamino-6-t-butylamino-s-triazine) from the purple bacterium Rhodopseudom onas viridis have been isolated. The sequence analysis of that part of the DNA coding for the herbicide binding site in the photosynthetic reaction centre showed that only two genetically different mutant strains were obtained. The sequence data are discussed with respect to recent crystallographic results.

Open Access June 2, 2014

Expression of the psbA Gene in E. coli

Udo Johanningmeier

Page range: 755-757

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Abstract

A psbA gene fragment has been cloned into an expression vector in frame with the 3′ end of the beta-galactosidase gene. Expression of this construct in E. coli results in an overproduction of a hybrid protein consisting of part of the herbicide binding protein and beta-galactosidase. An antiserum raised against this fusion protein specifically detects a 34 kDa polypeptide within the complex mixture of spinach thylakoid membrane proteins.

Open Access June 2, 2014

Isolation and Characterization of Herbicide Resistant Mutants in the Cyanobacterium Synechococcus R2

Joseph Hirschberg, Nir Ohad, Iris Pecker, Ana Rahat

Page range: 758-761

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Abstract

A variety of mutants which are resistant to triazine - and urea - classes of herbicides have been isolated in the cyanobacterium Synechococcus R2. All the mutants that have been analyzed, show some cross-resistance to different herbicides suggesting that these herbicides share a common binding site in photosystem II. Three psbA genes have been identified in Synechococcus R2. The psbA-copy I gene was cloned from three mutants and used in DNA-mediated genetic transformation. It was found that in all three mutants this gene could transfer the mutation for herbicide resistance indicating that this gene codes for the herbicide resistant protein.

Open Access June 2, 2014

Site-Directed Mutations of Two Histidine Residues in the D2 Protein Inactivate and Destabilize Photosystem II in the Cyanobacterium Synechocystis 6803

Wim F. J. Vermaas, John G. K. Williams, Charles J. Arntzen

Page range: 762-768

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Abstract

Site-directed mutations were created in the cyanobacterium Synecliocystis 6803 to alter specific histidine residues of the photosystem II (PS II) D2 protein. In one mutant (tyr-197). the his-197 residue was replaced by tyrosine, in another mutant (asn-214). his-214 was changed into asparagine. The tyr-197 mutant did not show any low-temperature fluorescence attributable to PS II. but contained a PS II chlorophyll-protein. CP-47, in significant quantities. Another PS II chlorophyll-protein. CP-43, was absent, as was PS II-related herbicide binding. The asn-214 mutant showed a blue-shifted low-temperature fluorescence maximum around 682 nm. but did not have a significant amount of membrane-incorporated CP-43 or CP-47. Herbicide binding was also absent in this mutant. These data indicate a very important role of the his-197 and his-214 residues in the D2 protein, and are interpreted to support the hypothesis that the D2 protein and the M subunit from the photosynthetic reaction center of purple bacteria have analogous functions. According to this hypothesis, his-197 is involved in binding of P680, and his-214 forms ligands with Q ᴀ and Fe 2+ . In absence of a functional D2 protein, the PS II core complex appears to be destabilized as evidenced by loss of chlorophvll-proteins in the mutants.

Open Access June 2, 2014

Genetic Engineering of Herbicide Resistance: Saturation Mutagenesis of Isoleucine 229 of the Reaction Center L Subunit

Edward J. Bylina, Douglas C. Youvan

Page range: 769-774

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Abstract

Oligonucleotide-mediated mutagenesis has been used to change isoleucine 229 of the reaction center L subunit of Rhodopseudomonas capsulata to seventeen other amino acids. A system of deletion strains and complementing plasmids has been used to assay the effects of changing this residue, which forms part of the secondary quinone O в binding site. The reaction center is assembled in all seventeen mutants. Ten of the seventeen mutations (Gly, His, Tyr, Trp, Asn, Asp. Gin, Glu, Arg, and Lys) result in the loss of photosynthetic growth. The remaining seven mutations yield varying levels of photosynthetic growth (Ile, Val, Ala, Leu, Met>Thr, Cys, Ser). Six of these mutations lead to varying atrazine resistance (Met, Leu > Ser, Ala, Thr, Cys>Val, He). None of the mutations lead to atrazine sensitivity. These results suggest that hydrophobic residues of moderate size function best at this position. This set of mutations at isoleucine L229 include the first examples of mutants with null quinone function and the first examples of crystal- lography-based genetic engineering in the design of herbicide resistant reaction centers.

Open Access June 2, 2014

A Temporal Phase Mutation of Chlorophyll Fluorescence in Triazine-Resistant Brassica napus

Jack Dekker, Barbara Westfall

Page range: 775-778

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Abstract

The objectives of this study were to determine if there were variations in triazine-resistant and -susceptible Brassica napus leaf disc chlorophyll fluorescence (LCF) intensity in terms of: age of leaf on the plant and time of day. In growth room and field experiments triazine-susceptible B. napus cv. “Tower”, and triazine-resistant B. napus cv. OAC Triton” were used. Chlorophyll fluorescence intensity measurements were made 30 min after disc removal. In both environments, two periods of reduced photosynthetic efficiency occurred in the diurnal. The times that these periods occurred during the diurnal differed between biotvpes. A phase shift in LCF maxima between resistant and susceptible biotypes resulted in two periods, early and late in the light period of the diurnal, of increased LCF in resistant tissue. This differential pattern in LCF is support for the hypothesis that triazine resistance chloroplast alterations could imply an alteration in the temporal organization of chloroplast physiological function.

Open Access June 2, 2014

Triazine Resistance in Phalaris paradoxa: Physiological and Molecular Analyses

Mordechay Schönfeld, Tuvia Yaacoby, Adi Ben-Yehuda, Baruch Rubin, Joseph Hirschberg

Page range: 779-782

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Abstract

Triazine resistance in a mutant biotype of Phalaris paradoxa is accompanied by changes in the chlorophyll fluorescence induction curve, and by reduced quantum yield for electron transport, indicating altered photosystem II activity. However, light-saturated rates of electron transport in isolated chloroplasts, rates of CO 2 uptake in leaves and dry weight production of the triazine resistant biotype, are equal or superior to those of the wild type. A single mutation in the psbA gene, leading to a serine to glycine shift at position 264 of the thylakoid membrane 32 kDa Q в - protein. was found in the herbicide resistant mutant. The results indicate that triazine resistance is not necessarily linked to inferior photosynthetic and growth performance.

Open Access June 2, 2014

Photosynthetic Properties and Cross-Resistance to Some Urea Herbicides of Triazine-Resistant Conyza canadensis Cronq (L.)

E. Pölös, G. Laskay, Z. Szigeti, Sz. Pataki, E. Lehoczki

Page range: 783-793

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Abstract

A comparison of the photosynthetic activities, chloroplast ultrastructures and sensitivities to some urea herbicides of atrazine-resistant (R) and suspectible (S) biotypes of Conyza canadensis Cronq (L.) (horseweed) in the rosette stage showed that: I) The light-intensitv dependences of the rates of CO 2 reduction in intact leaves of the R and S plants are very similar. 2) The rate of the Hill reaction of the R chloroplasts at 25 0 C is 15 - 20% lower at all light intensities than that of the S chloroplasts. 3) The rates of the Hill reactions of the R and S chloroplasts exhibit different temperature-dependences. The activation energy for the S chloroplasts in the temperature range 10-40 0 C was found to be 15.3 kJ mol -1 . For the R chloroplasts. the discontinuity in the Arrhenius plot was found at around 20 °C: the activation energy was 20.1 kJ mol -1 at below 20 0 C. and decreased to 8.2 kJ mol -1 at higher temperatures. 4) The R plants have a better adaptive capacity than the S plants at low temperatures. 5) The chloroplast ultrastructure in the R plants was not reminiscent of that of plants grown under low light intensity. 6) The R biotype exhibited cross- resistance to chlorbromuron and metobromuron. and tolerance to linuron. The R and S biotypes, however, were equally sensitive to diuron. The results permitted conclusions on the properties of the triazine-resistance and urea cross-resistance.

Open Access June 2, 2014

Photosystem II Heterogeneity in Triazine-Resistant and Susceptible Biotypes of Chenopodium album

Jack J. S. van Rensen, Leon E. E M. Spätjens

Page range: 794-797

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Abstract

The heterogeneity of photosystem II with respect to α and β centers was investigated in triazine-resistant and susceptible biotypes of Chenopodium album . In both biotypes the light harvesting antenna sizes of photosystem II α centers was larger than those of β centers. In the resistant biotype the antenna size of the α centers was smaller than those in the susceptible one. There was not much difference in the antenna sizes of the β centers. The proportion of β centers was larger in the resistant biotype compared with the sensitive one.

Open Access June 2, 2014

Structural and Physiological Comparisons of Triazine-Susceptible, -Resistant, and "Mixed" Biotypes of Poa

Kevin C. Vaughn, Jacques Gasquez

Page range: 798-802

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Abstract

Triazine-resistant (R) biotypes of several dicot weed biotypes have been shown to differ from triazine-susceptible (S) biotypes both structurally and biochemically. To this point, no R monocot has been examined, however. In this report, we examine the ultrastructure and physiology of three biotvpes of Poa annua L.: a S biotype, a R biotype, and a “mixed” (M) biotype that displays a level of resistance just slightly less than the R biotype, as well as a unique fluorescence in the so- called M region of the fluorescence induction curve. Like the dicots investigated previously, the R and M biotypes have larger grana stacks, and more light-harvesting chlorophyll alb protein than the S biotype. These are similar to the differences described between “shade-type” and “sun- type” chloroplasts although anatomical parameters, that normally vary between sun and shade type plants, do not appear to be different in the three biotypes. These data indicate that the structural and biochemical modifications of the chloroplast reported previously in R biotypes of dicots are also found in R biotypes of monocots and further indicate that these are natural consequences of the slower electron transport found in R biotypes.

Open Access June 2, 2014

Interconversion of Prenyl Pyrophosphates and Subsequent Reactions in the Presence of FMC 57020

Gerhard Sandmann, Peter Böger

Page range: 803-807

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Abstract

In vitro studies of the influence of FMC 57020 on terpenoid biosynthesis have shown that this herbicide acts at an early stage. It affects the conversion of isopentenyl pyrophosphate to geranylgeranyl pyrophosphate catalyzed by isopentenyl pyrophosphate isomerase and prenyl transferase. An inhibition of the carotenogenic enzymes phytoene desaturase, ζ-carotene desaturase, and lycopene cyclase could be excluded. Comparison of I 50 values for in vivo chlorophyll, carotenoid, ergosterol and gibberellin biosyn- thesis as well as in vitro formation of phytoene. phytol and kaurene in various autotrophic and heterotrophic organisms have shown that terpenoid biosynthesis in the chloroplast is much stronger affected than extraplastidic terpenoid formation.

Open Access June 2, 2014

Structure-Function-Relationship in Thylakoids Influenced by the Pyridazinone BAS 13–338 (SAN 9785)

Josef A. Graf, Reto J. Strasser, Ulrich Kull

Page range: 808-812

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Abstract

The pyridazinone BAS 13-338 (SAN 9785) inhibits the desaturation sequence leading to polyunsaturated fatty acids, mainly of glycolipids. Parallel to the inhibition of fatty acid desaturation in the presence of the pyridazinone, changes in energy-distribution parameters have been observed. These data indicate that the amount of polyunsaturated fatty acids in glycolipids is strongly correlated with excitation, trapping, grouping and dissipation, but not with spillover. Functional changes in energy distribution induced by BAS 13-338 are interpreted as a consequence of structural changes in the lipid matrix, which may imply a structure-function relationship between pigment protein complexes and the surrounding lipid environment in thylakoids.

Open Access June 2, 2014

A Non-Metabolic Model of Acifluorfen Activity

Stephen O. Duke, William H. Kenyon

Page range: 813-818

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Abstract

The para-nitro substituted diphenyl ether herbicides which cause rapid plant pigment photo- bleaching can be divided into two categories: 1. those that have a photosynthetic requirement for activity (e.g. oxyfluorfen) and 2. those that have no apparent metabolic requirement for activity (e.g. acifluorfen). A model is presented for the latter category, in which the diphenyl ether herbicide interacts with carotenoids and/or chlorophyllide in plastid membranes to form a complex which photochemically generates singlet oxygen or lipid-peroxidizing radicals.

Open Access June 2, 2014

Binding and Peroxidative Action of Oxyfluorfen in Sensitive and Tolerant Algal Species

R. Lambert, G. Sandmann, P. Böger

Page range: 819-823

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Abstract

Peroxidative activity of oxyfluorfen and binding of this nitrodiphenyl ether to cell fractions was investigated with the susceptible alga Scenedesrnus aeutus and the resistant alga Bumilleriopsis filiformis. Although a 10-fold higher concentration of oxyfluorfen was applied to Bumilleriopsis, the lag phase for initiation of peroxidative evolution of short-chain hydrocarbons from fatty acids was much longer than found with Seenedesmus. Oxyfluorfen was predominantly recovered after homogenization from the pellet which was separated into a lipid and a chloroform/methanol insoluble fraction. Parts of the oxyfluorfen which is present in the insoluble pellet fraction during the lag phase before the onset of peroxidation can be found in the lipid fraction when measurable peroxidative activities have started. This was observed with Seenedesmus as well as with Bumilleriopsis. During peroxidation initiated by oxyfluorfen acyl lipids are degradated as monitored by the disappearance of the plastidic sulfolipid. Analysis of bound fatty acids showed that they are targets for peroxidative reactions in acyl lipids. Destruction of polyunsaturated fatty acids was higher than for saturated ones.

Open Access June 2, 2014

Counteraction of Paraquat Toxicity at the Chloroplast Level

Brad L. Upham, Kriton K. Hatzios

Page range: 824-828

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Abstract

Six pyridyl derivatives [benzylviologen, 2-anilinopyridine, 1,2-bis(4-pyridyl)ethane, 1,2-bis(4-pyridyl)ethylene, 2-benzoylpyridine, and 2-benzylaminopyridine] and five heme-iron derivatives [hemoglobin, hemin, hematin, ferritin, and ferrocene] were screened for their potential to counteract paraquat (1,1′-dimethyl-4.4′-bipyridinium ion) toxicity on pea (Pisum sativum L.) isolated chloroplasts. The H 2 O → methylviologen(MV)/O 2 and H 2 O → ferredoxin(Fd)/NADP + were two Hill reactions assayed with these compounds. Antagonists of paraquat toxicity should inhibit the first Hill reaction but not the latter. AU pyridyl derivatives examined did not inhibit the reaction H 2 O → MV/O 2 . Ferritin and ferrocene were also ineffective as inhibitors of this reaction. Hemoglobin inhibited the reaction H 2 O → MV/O 2 without inhibiting the reaction H 2 O → Fd/NADP + , providing protection to pea chloroplasts against paraquat. Hemin and hematin inhibited both Hill reactions examined. They also inhibited H 2 O → diaminodurene(DAD) ox and durohydro- quinone → MV/O 2 Hill reactions but not the dichlorophenol indophenol red → MV/O 2 and DAD red → MV/O 2 Hill reactions. These results suggest that hemin and hematin are inhibiting the photo- synthetic electron transport in the plastoquinone-pool region.

Open Access June 2, 2014

The Effects of Photosystem I Electron Acceptors on Leaf Discs

P. Camilleri, J. R. Bowyer, P. H. McNeil

Page range: 829-833

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Abstract

A leaf-disc chamber has been used to measure changes in photosynthesis by soybean leaf discs which have been supplied with photosystem I (PS I) electron acceptors via the transpiration stream. The uncharged heteropentalenes induce an inhibitory effect on CO 2 fixation which is dependent on the n-octanol-water partition coefficient of these molecules. Paraquat, which carries a di-positive charge, was ineffective under the same conditions and at a concentration of 10 -4 м. Cationic species such as K + , Ca 2+ and Mg 2+ greatly enhanced the effect of paraquat on CO 2 fixation while the presence of these ions did not affect inhibition by the heteropentalenes. Such differences between uncharged and charged PS I electron acceptors have been explained in terms of electrostatic interactions encountered by paraquat on its way to the site of action within the chloroplast, via the transpiration stream.

Open Access June 2, 2014

Use of Pyruvate-Phosphate Dikinase as a Target for Herbicide Design: Analysis of Inhibitor Specificity

Arthur L. Lawyer, Sarita R. Kelley, Judith I. Allen

Page range: 834-836

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Abstract

Pyruvate-phosphate dikinase (PPDK) was targeted for inhibitor design because of its central role in C 4 -type photosynthetic carbon metabolism and its relative absence in C 3 -type plants and organisms of the animal kingdom. Compounds were tested for their activities as reversible and irreversible inhibitors of PPDK isolated from maize. The relative activity of the test compounds against phosphoenolpvruvate carboxylase (PEPCase), isolated from wheat, was used as a measure of the specificity of the inhibitors for the targeted enzyme. PPDK. An ideal compound for successful herbicide design should be an inhibitor which is specific toward the targeted enzyme and either effectively inhibits enzyme activity at very low concentrations or inactivates the enzyme through an irreversible mechanism. Using results obtained with commercially purchased compounds. the discussion will emphasize the difficulty of obtaining specific inhibitors toward PPDK. Another report from this laboratory (A. L. Lawyer. S. R. Kelley, and J. I. Allen, in: Proc. Seventh Internat. Congr. Photosynth. (.I. Biggins, ed.). in press) emphasizes other results obtained from the targeting of PPDK for herbicide activity.

Open Access June 2, 2014

Chemical Control of Photorespiration: Steady-State Kinetic and Conformational Changes of Ribulose-1,5-bisphosphate Carboxylase/Oxygenase Obtained with O-p-Nitrophenylhydroxylamine

C. J. Van Assche, N. Reinier, B. Courtiade, A. Chancel, S. Huber

Page range: 837-844

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Abstract

Spinach RuBP carboxylase-oxygenase (Rubisco) purified from the commercially available enzyme, underwent kinetic changes when micromolar concentrations of O-p-nitrophenylhy- droxvlamine (NPHA) were applied on fully activated enzyme. Under steady-state conditions, a decrease of K m CO 2 was observed without changes in V max . Double reciprocal plots showed a competitive stimulation of carboxylase function. The substrate specificity factor k = V c K o /V o K c was increased from approximatively 15-20% upon treatment with NPHA, using both parallel and simultaneous determinations of RuBP-carboxylase and oxygenase activities. Such a limited change in partition between Rubisco functions actually resulted into an increase in CO 2 fixation of intact soybeans leaves treated with NPHA. arising from a substantial alleviation of O 2 -inhibition of photosynthesis. From spectrophotometric and sulfhydryl group titration data, evidence was accumulated for a conformational change of the native enzyme, induced by NPHA. bringing about an increased ratio of carboxylase to oxygenase activities. Direct interaction of NPHA with a cysteine residue of Rubisco near the catalytic site, appears as a candidate for such chemically-induced conformational modification.

About this journal

Objective

A Journal of Biosciences: Zeitschrift für Naturforschung C (ZNC) is an international scientific journal and a community resource for the emerging field of natural and natural-like products.

The journal publishes original research on the isolation (including structure elucidation), bio-chemical synthesis and bioactivities of natural products, their biochemistry, pharmacology, biotechnology, and their biological activity and innovative developed computational methods for predicting the structure and/or function of natural products.

A Journal of Biosciences: Zeitschrift für Naturforschung C (ZNC) welcomes research papers in fields on the chemistry-biology boundary which address scientific ideas and approaches to generate and understand natural compounds on a molecular level and/or use them to stimulate and manipulate biological processes.

Topics

Bio-chemical synthesis and bioactivities of natural products
Isolation (including structure elucidation)
Biochemistry
Biotechnology
Pharmacology
Chemistry
Biology

Article formats

Original research articles, research notes, letters and review articles

Please have a look at the call for papers for two upcoming Special Issues:

Special Issue on CAZymes

Special Issue on Chitin Structures and Pathways as Targets for Biopesticides and Drugs

Volume 42 Issue 6

Issue of Zeitschrift für Naturforschung C

Herbicides Affecting Chloroplast Functions

The Role of Chirality in the Activity of Photosystem II Herbicides

Abstract

Cyanoacrylate Inhibitors of Photosynthetic Electron Transport in Atrazine Susceptible and Atrazine Resistant Brassica Chloroplasts

Abstract

Stereospecific Inhibitor Probes of the PS II Herbicide Binding Site

Abstract

Cyanoacrylate Inhibitors of the Hill Reaction IV. Binding Characteristics of the Hydrophobic Domain

Abstract

Cyanoacrylate Inhibitors of the Hill Reaction V. The Effect of Chirality on Inhibitor Binding

Abstract

Herbicide and Quinone Binding to Chromatophores and Reaction Centers from Rhodobacter sphaeroides

Abstract

Irreversibly Binding Photosynthetic Electron Transport Inhibitors II. Halogen-Substituted 1,4-Naphthoquinones and Halogenmethyl-1,4-quinones

Abstract

Interaction of Halogenated 1,4-Benzoquinones with System II of Photosynthesis

Abstract

Inhibition and Photoaffinity Labeling of Photosystem II by Thiazolyliden-ketonitriles

Abstract

Can Quantitative Structure Activity Analyses and Molecular Graphics Assist in Designing New Inhibitors of Photosystem II?

Abstract

Interference by Herbicides with the Transmembrane Potential of Thylakoids

Abstract

A Role of the Qв Binding Protein in the Mechanism of Cyanobacterial Adaptation to Light Intensity?

Abstract

The Topology of the 32 kDa Herbicide Binding Protein of Photosystem II in the Thylakoid Membrane

Abstract

The Use of HPLC for the Purification of the Qв-Protein

Abstract

The Three-Dimensional Structure of the Herbicide Binding Niche on the Reaction Center Polypeptides of Photosystem II

Abstract

Sequence Analysis of Mutants from Rhodopseudomonas viridis Resistant to the Herbicide Terbutryn

Abstract

Expression of the psbA Gene in E. coli

Abstract

Isolation and Characterization of Herbicide Resistant Mutants in the Cyanobacterium Synechococcus R2

Abstract

Site-Directed Mutations of Two Histidine Residues in the D2 Protein Inactivate and Destabilize Photosystem II in the Cyanobacterium Synechocystis 6803

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Genetic Engineering of Herbicide Resistance: Saturation Mutagenesis of Isoleucine 229 of the Reaction Center L Subunit

Abstract

A Temporal Phase Mutation of Chlorophyll Fluorescence in Triazine-Resistant Brassica napus

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Triazine Resistance in Phalaris paradoxa: Physiological and Molecular Analyses

Abstract

Photosynthetic Properties and Cross-Resistance to Some Urea Herbicides of Triazine-Resistant Conyza canadensis Cronq (L.)

Abstract

Photosystem II Heterogeneity in Triazine-Resistant and Susceptible Biotypes of Chenopodium album

Abstract

Structural and Physiological Comparisons of Triazine-Susceptible, -Resistant, and "Mixed" Biotypes of Poa

Abstract

Interconversion of Prenyl Pyrophosphates and Subsequent Reactions in the Presence of FMC 57020

Abstract

Structure-Function-Relationship in Thylakoids Influenced by the Pyridazinone BAS 13–338 (SAN 9785)

Abstract

A Non-Metabolic Model of Acifluorfen Activity

Abstract

Binding and Peroxidative Action of Oxyfluorfen in Sensitive and Tolerant Algal Species

Abstract

Counteraction of Paraquat Toxicity at the Chloroplast Level

Abstract

The Effects of Photosystem I Electron Acceptors on Leaf Discs

Abstract

Use of Pyruvate-Phosphate Dikinase as a Target for Herbicide Design: Analysis of Inhibitor Specificity

Abstract

Chemical Control of Photorespiration: Steady-State Kinetic and Conformational Changes of Ribulose-1,5-bisphosphate Carboxylase/Oxygenase Obtained with O-p-Nitrophenylhydroxylamine

Abstract

A Role of the Q_в Binding Protein in the Mechanism of Cyanobacterial Adaptation to Light Intensity?

The Use of HPLC for the Purification of the Q_в-Protein