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Duke SO, Pan Z, Bajsa-Hirschel J. Proving the Mode of Action of Phytotoxic Phytochemicals. PLANTS (BASEL, SWITZERLAND) 2020; 9:E1756. [PMID: 33322386 PMCID: PMC7763512 DOI: 10.3390/plants9121756] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 12/22/2022]
Abstract
Knowledge of the mode of action of an allelochemical can be valuable for several reasons, such as proving and elucidating the role of the compound in nature and evaluating its potential utility as a pesticide. However, discovery of the molecular target site of a natural phytotoxin can be challenging. Because of this, we know little about the molecular targets of relatively few allelochemicals. It is much simpler to describe the secondary effects of these compounds, and, as a result, there is much information about these effects, which usually tell us little about the mode of action. This review describes the many approaches to molecular target site discovery, with an attempt to point out the pitfalls of each approach. Clues from molecular structure, phenotypic effects, physiological effects, omics studies, genetic approaches, and use of artificial intelligence are discussed. All these approaches can be confounded if the phytotoxin has more than one molecular target at similar concentrations or is a prophytotoxin, requiring structural alteration to create an active compound. Unequivocal determination of the molecular target site requires proof of activity on the function of the target protein and proof that a resistant form of the target protein confers resistance to the target organism.
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Affiliation(s)
- Stephen O. Duke
- National Center for Natural Products Research, School of Pharmacy, University of Mississippi, Oxford, MS 38655, USA
| | - Zhiqiang Pan
- Natural Products Utilization Research Unit, Agricultural Research Service, United States Department of Agriculture, Oxford, MS 38655, USA; (Z.P.); (J.B.-H.)
| | - Joanna Bajsa-Hirschel
- Natural Products Utilization Research Unit, Agricultural Research Service, United States Department of Agriculture, Oxford, MS 38655, USA; (Z.P.); (J.B.-H.)
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Brown AE, Gilbert CW, Guy R, Arntzen CJ. Triazine herbicide resistance in the photosynthetic bacterium Rhodopseudomonas sphaeroides. Proc Natl Acad Sci U S A 2010; 81:6310-4. [PMID: 16593520 PMCID: PMC391913 DOI: 10.1073/pnas.81.20.6310] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The photoaffinity herbicide azidoatrazine (2-azido-4-ethylamino-6-isopropylamino-s-triazine) selectively labels the L subunit of the reaction center of the photosynthetic bacterium Rhodopseudomonas sphaeroides. Herbicide-resistant mutants retain the L subunit and have altered binding properties for methylthio- and chloro-substituted triazines as well as altered equilibrium constants for electron transfer between primary and secondary electron acceptors. We suggest that a subtle alteration in the L subunit is responsible for herbicide resistance and that the L subunit is the functional analog of the 32-kDa Q(B) protein of chloroplast membranes.
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Affiliation(s)
- A E Brown
- Department of Botany and Microbiology, Auburn University, Auburn, AL 36849
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Pfister K, Steinback KE, Gardner G, Arntzen CJ. Photoaffinity labeling of an herbicide receptor protein in chloroplast membranes. Proc Natl Acad Sci U S A 2010; 78:981-5. [PMID: 16592984 PMCID: PMC319929 DOI: 10.1073/pnas.78.2.981] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
2-Azido-4-ethylamino-6-isopropylamino-s-triazine (azido-atrazine) inhibits photosynthetic electron transport at a site identical to that affected by atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine). The latter is a well-characterized inhibitor of photosystem II reactions. Azido-atrazine was used as a photoaffinity label to identify the herbicide receptor protein; UV irradiation of chloroplast thylakoids in the presence of azido[(14)C]atrazine resulted in the covalent attachment of radioactive inhibitor to thylakoid membranes isolated from pea seedlings and from a triazine-susceptible biotype of the weed Amaranthus hybridus. No covalent binding of azido-atrazine was observed for thylakoid membranes isolated from a naturally occurring triazine-resistant biotype of A. hybridus. Analysis of thylakoid polypeptides from both the susceptible and resistant A. hybridus biotypes by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, followed by fluorography to locate (14)C label, demonstrated specific association of the azido[(14)C]atrazine with polypeptides of the 34- to 32-kilodalton size class in susceptible but not in resistant membranes.
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Affiliation(s)
- K Pfister
- United States Department of Agriculture/Science and Education Administration/Agricultural Research, Department of Botany, University of Illinois, Urbana, Illinois 61801
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Astier C, Meyer I, Vernotte C, Etienne A. Photosystem II electron transfer in highly herbicide resistant mutants ofSynechocystis6714. FEBS Lett 2002. [DOI: 10.1016/0014-5793(86)81495-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Astier C, Boussac A, Etienne AL. Evidence for different binding sites on the 33-kDa protein for DCMU, atrazine and QB. FEBS Lett 2001. [DOI: 10.1016/0014-5793(84)80150-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Comparison of the decay of slow delayed luminescence in triazine-susceptible and -resistant biotypes of Erigeron canadensis L. FEBS Lett 2001. [DOI: 10.1016/0014-5793(86)80526-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Mattoo AK, Marder JB, Gressel J, Edelman M. Presence of the rapidly-labelled 32 000-dalton chloroplast membrane protein in triazine resistant biotypes. FEBS Lett 2001. [DOI: 10.1016/0014-5793(82)80515-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Hippler M, Redding K, Rochaix JD. Chlamydomonas genetics, a tool for the study of bioenergetic pathways. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1367:1-62. [PMID: 9784589 DOI: 10.1016/s0005-2728(98)00136-4] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- M Hippler
- Departments of Molecular Biology and Plant Biology, University of Geneva, 30 Quai Ernest Ansermet, 1211 Geneva-4, Switzerland
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Sinclair J, Hall CE. Photosynthetic energy storage in aquatic leaves measured by photothermal deflection. PHOTOSYNTHESIS RESEARCH 1995; 45:157-168. [PMID: 24301482 DOI: 10.1007/bf00032587] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/1995] [Accepted: 07/05/1995] [Indexed: 06/02/2023]
Abstract
In a study of photosynthetic energy storage efficiency (ES), the adaxial surface of the leaves of Vallisneria americana exhibited the highest ES values (22%) of the four aquatic plants examined. V. americana leaves have a dispersed structure and it was possible to measure the energy storage properties of the epidermal cells independently of the rest of the leaf. The abaxial epidermis had a higher value of ES at zero light fluence than the adaxial epidermis but ES in the abaxial epidermis declined much more rapidly with light fluence. Thus the abaxial epidermis is more suited to lower light fluences than the adaxial epidermis. ES declined as the pH rose from 4.0 to 8.0 at a constant dissolved inorganic carbon concentration. This paralleled the change from carbon dioxide to bicarbonate and suggests that these leaves utilise CO2 more efficiently than bicarbonate. ES increased by about 50% at pH 8.0 as leaf sections further from the leaf tip were examined which demonstrates that the older epidermal cells are less well able to use bicarbonate. Exposure to 30 min of a saturating light fluence caused the epidermal chloroplasts to move from the periclinal walls to the anticlinal walls. This decreased the photothermal signal by increasing the thermal diffusion distance and lowering the light fluence due to greater chloroplast shading. The latter effect increased ES. It appears that chloroplast movement could assist the epidermis to survive harmful light fluences.
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Affiliation(s)
- J Sinclair
- Biology Department, Carleton University, 1125 Colonel By Drive, K1S 5B6, Ottawa, Ontario, Canada
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Dekker JH, Burmester RG. Pleiotropy in Triazine-Resistant Brassica napus: Ontogenetic and Diurnal Influences on Photosynthesis. PLANT PHYSIOLOGY 1992; 100:2052-8. [PMID: 16653239 PMCID: PMC1075906 DOI: 10.1104/pp.100.4.2052] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Studies were conducted that supported the hypothesis that the mutation to the psbA plastid gene that confers S-triazine resistance (R) in Brassica napus also results in an altered diurnal pattern of photosynthetic carbon assimilation (A) relative to that of the susceptible (S) wild type, and that these patterns change over the ontogeny of a plant. Photosynthetic photon flux density, under closely controlled environmental conditions, was incrementally increased and decreased on either side of the midday maxima of 1150 to 1300 mumol quanta m(-2) s(-1). In all experiments, A approximately tracked the increasing and decreasing diurnal light levels. Younger (3- to 4-leaf) R plants had greater photosynthetic rates early and late in the diurnal light period, whereas those of S plants were greater during midday as well as during the photoperiod as a whole. These relative photosynthetic characteristics of R and S plants changed in several ways with ontogeny. As the plants aged during the vegetative phase of development, S plants gradually assimilated more carbon in the early, and then in the late, part of the day. At the end of the vegetative phase of development, R plant carbon assimilation was less relative to S plants at most times of the day, and was never greater. This relationship between the two biotypes dramatically changed with the onset of the reproductive phase (8(1/2) to 9(1/2) leaf) of plant development: R plants assimilated more carbon than S plants during all periods of the diurnal light period with the exception of the late part of the day. In addition to these differences in A, R plant stomatal function differed from that in S plants. R plant leaves were always cooler than S plant leaves under the same environmental and diurnal conditions. Correlated with this difference in leaf temperature were equal or greater total conductances to water vapor and intercellular CO(2) partial pressures in R compared to S leaves in most instances. These studies indicate a more complex pattern of photosynthetic carbon assimilation than previously observed. The photosynthetic superiority of one biotype relative to the other was a function of the time of day and the age of the plant. These studies also suggest that R plants may have an adaptive advantage over S plants in certain unfavorable ecological niches independent of the presence of S-triazine herbicides, such as cool, low-light environments early and late in the day, as well as late in the plants' development. This advantage could result in R biotypes appearing in populations of a species in greater numbers than plastidic mutation alone could cause.
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Affiliation(s)
- J H Dekker
- Department of Agronomy, Iowa State University, Ames, Iowa, 50011
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Dekker JH, Sharkey TD. Regulation of Photosynthesis in Triazine-Resistant and -Susceptible Brassica napus. PLANT PHYSIOLOGY 1992; 98:1069-73. [PMID: 16668728 PMCID: PMC1080309 DOI: 10.1104/pp.98.3.1069] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The response of photosynthetic carbon assimilation and chlorophyll fluorescence quenching to changes in intercellular CO(2) partial pressure (C(i)), O(2) partial pressure, and leaf temperature (15-35 degrees C) in triazine-resistant and -susceptible biotypes of Brassica napus were examined to determine the effects of the changes in the resistant biotype on the overall process of photosynthesis in intact leaves. Three categories of photosynthetic regulation were observed. The first category of photosynthetic response, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco)-limited photosynthesis, was observed at 15, 25, and 35 degrees C leaf temperatures with low C(i). When the carbon assimilation rate was Rubisco-limited, there was little difference between the resistant and susceptible biotypes, and Rubisco activity parameters were similar between the two biotypes. A second category, called feedback-limited photosynthesis, was evident at 15 and 25 degrees C above 300 microbars C(i). The third category, photosynthetic electron transport-limited photosynthesis, was evident at 25 and 35 degrees C at moderate to high CO(2). At low temperature, when the response curves of carbon assimilation to C(i) indicated little or no electron transport limitation, the carbon assimilation rate was similar in the resistant and susceptible biotypes. With increasing temperature, more electron transport-limited carbon assimilation was observed, and a greater difference between resistant and susceptible biotypes was observed. These observations reveal the increasing importance of photosynthetic electron transport in controlling the overall rate of photosynthesis in the resistant biotype as temperature increases. Photochemical quenching of chlorophyll fluorescence (q(P)) in the resistant biotype never exceeded 60%, and triazine resistance effects were more evident when the susceptible biotype had greater than 60% q(P), but not when it had less than 60% q(P).
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Affiliation(s)
- J H Dekker
- Department of Agronomy, Iowa State University, Ames, Iowa 50011
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Draber W, Kluth JF, Tietjen K, Trebst A. Herbizide in der Photosyntheseforschung. Angew Chem Int Ed Engl 1991. [DOI: 10.1002/ange.19911031210] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Ireland CR, Telfer A, Covello PS, Baker NR, Barber J. Studies on the limitations to photosynthesis in leaves of the atrazine-resistant mutant ofSenecio vulgaris L. PLANTA 1988; 173:459-467. [PMID: 24226682 DOI: 10.1007/bf00958958] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/1987] [Accepted: 08/27/1987] [Indexed: 06/02/2023]
Abstract
In leaves of an atrazine-resistant mutant ofSenecio vulgaris the quantum efficiency of CO2 assimilation was reduced by 21% compared to the atrazine-susceptible wild type, and at a light level twice that required to saturate photosynthesis in the wild type the CO2 fixation rate in the mutant was decreased by 15%. In leaves at steady-state photosynthesis there was a measurable increase in the reduction state of the photosystem II (PSII) primary quinone acceptor,Q A. Although this would lead to a decreased rate of PSII electron transport and may thus explain the decrease in quantum efficiency, this cannot account for the fall in the maximum rate of CO2 fixation. The atrazine-resistant mutant showed an appreciably longer photosynthetic induction time which indicates an effect on carbon metabolism; however, the response of CO2-fixation rate to intercellular CO2 concentration revealed no differences in carboxylation efficiency. There were also no differences in the ability to perform a State 1-State 2 transition between the atrazine-resistant and susceptible biotypes and no difference in the profiles of phosphorylated thylakoid polypeptides. It is concluded that the alteration of the redox equilibrium between PSII quinone electron acceptors in the atrazine-resistant biotype limits appreciably the photosynthetic efficiency in non-saturating light. Additionally, there is a further, as yet unidentified, limitation which decreases photosynthesis in the resistant mutant under light-saturating conditions.
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Affiliation(s)
- C R Ireland
- Department of Biology, University of Essex, CO4 3SQ, Colchester, Essex, UK
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Schönfeld M, Yaacoby T, Michael O, Rubin B. Triazine Resistance without Reduced Vigor in Phalaris paradoxa. PLANT PHYSIOLOGY 1987; 83:329-33. [PMID: 16665245 PMCID: PMC1056357 DOI: 10.1104/pp.83.2.329] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
A triazine-resistant (R) biotype of Phalaris paradoxa L. (hood canarygrass) was superior to a triazine-susceptible (S) biotype in seed-germinability and seedling emergence. It was equal or superior to the S-biotype in growth under noncompetitive conditions. Rates of CO(2) uptake by R-plants were similar to those of S-plants, except at very low photon flux densities, where S-plants exhibited higher rates of CO(2) uptake. Fluorescence induction curves of chloroplasts isolated from R-plants indicated an alteration in photosystem II. Analysis of the light dependence of electron transport shows a reduction in quantum yield (Q(y)) in R- compared to S-chloroplasts. The same analysis, however, shows for R-chloroplasts an increase in the light-saturated electron transport rate (V(max)). The increase in V(max) compensates for the reduction of Q(y) over a wide range of photon flux densities, which may explain the similarity between R- and S-biotypes in photosynthetic potential and growth.
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Affiliation(s)
- M Schönfeld
- Department of Agricultural Botany, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot 76100, Israel
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Bennoun P, Spierer-Herz M, Erickson J, Girard-Bascou J, Pierre Y, Delosme M, Rochaix JD. Characterization of photosystem II mutants of Chlamydomonas reinhardii lacking the psbA gene. PLANT MOLECULAR BIOLOGY 1986; 6:151-60. [PMID: 24307274 DOI: 10.1007/bf00021484] [Citation(s) in RCA: 99] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/1985] [Revised: 11/11/1985] [Accepted: 11/19/1985] [Indexed: 05/26/2023]
Abstract
We have examined 78 chloroplast mutants of Chlamydomonas reinhardii lacking photosystem II activity. Most of them are unable to synthesize the 32 Kdalton protein. Analysis of 22 of these mutants reveals that they have deleted both copies of the psbA gene (which codes for the 32 Kdalton protein) in their chloroplast genome. Although these mutants are able to synthesize and to integrate the other photosystem II polypeptides in the thylakoid membranes, they are unable to assemble a stable functional photosystem II complex. The 32 Kprotein appears therefore to play an important role not only in photosystem II function, but also in stabilizing this complex.
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Affiliation(s)
- P Bennoun
- Institut de Biologie Physico-chimique, 75005, Paris, France
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Holt JS, Goffner DP. Altered Leaf Structure and Function in Triazine-Resistant Common Groundsel (Senecio vulgaris). PLANT PHYSIOLOGY 1985; 79:699-705. [PMID: 16664476 PMCID: PMC1074955 DOI: 10.1104/pp.79.3.699] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Anatomical and physiological characteristics of leaves of triazinesusceptible and -resistant biotypes of common groundsel (Senecio vulgaris L.) were studied in order to explain the differences in light-saturated photosynthetic rates previously reported. Leaves were of uniform leaf plastochron index from greenhouse-grown plants. Susceptible plants had greater leaf fresh and dry weights and leaf areas, while resistant plants had greater specific leaf mass (mg fresh weight/cm(2)). Susceptible plants had greater amounts of total chlorophyll per unit leaf weight and a higher chlorophyll a/b ratio. Soluble protein in leaves was higher in susceptible chloroplasts on a weight and area basis, but similar to resistant chloroplasts on a unit chlorophyll basis. Activity of ribulose 1,5-bisphosphate carboxylase was higher in resistant plants on a fresh weight, leaf area, and milligram chlorophyll basis. Stomatal frequency, length, and arrangement were similar between biotypes, as were transpiration and conductance. Resistant leaves had less air space (v/v), more cells in palisade and spongy mesophyll, and a greater volume of palisade tissue than spongy, when compared to susceptible leaves. Differences in leaf structure and function between biotypes are probably due to a complex of developmental adaptations which may be only indirectly related to modified photosystem II in resistant plants. These results indicate that the consistently lower rates of net photosynthesis and yield in resistant plants cannot be explained solely on the basis of these leaf characteristics. Several possible mechanisms to account for reduced productivity are suggested.
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Affiliation(s)
- J S Holt
- Department of Botany and Plant Sciences, University of California, Riverside California 92521
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Galloway RE, Mets LJ. Atrazine, bromacil, and diuron resistance in chlamydomonas: a single non-mendelian genetic locus controls the structure of the thylakoid binding site. PLANT PHYSIOLOGY 1984; 74:469-74. [PMID: 16663446 PMCID: PMC1066710 DOI: 10.1104/pp.74.3.469] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
A series of Chlamydomonas reinhardii mutants were selected for resistance to the herbicides atrazine, bromacil, and diuron. Four of these have reduced herbicide binding to the thylakoid membranes and show the non-Mendelian inheritance pattern characteristic of chloroplast genes. These mutants show a variety of selective alterations in binding of the three herbicides. These changes account for the observed patterns of in vivo cross-resistance. Analyses of chloroplast gene recombination indicate that these four mutations are in the same gene. Overall, the results suggest that this gene codes for a protein component of the herbicide binding site. One of the mutants has slow phototrophic growth and altered electron transport as has been observed in atrazine-resistant higher plant varieties, but the others are normal in these respects. The slow growth characteristic of this mutant seems to be the consequence of the same mutation which confers herbicide resistance.The mutants isolated also include a large number which achieve resistance by some secondary mechanism. These are all nuclear gene mutations, and represent numerous loci. They also show a variety of patterns of cross-resistance, but the mechanisms behind them have not yet been investigated.
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Affiliation(s)
- R E Galloway
- Department of Biology, Washington University, St. Louis, Missouri 63130
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Barton JR, MacPeek WA, Cohen WS. Interaction of 2-n-heptyl-4-hydroxyquinoline-N-oxide with photosystem II in chloroplasts and subchloroplast particles. J Bioenerg Biomembr 1983; 15:93-104. [PMID: 18251099 DOI: 10.1007/bf00743222] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The effects of 2-n-heptyl-4-hydroxyquinoline-N-oxide on electron transport in thylakoids and oxygen-evolving photosystem II particles has been examined. Kinetic fluorescence studies reveal that the site of inhibition for alkyl derivatives of hydroxyquinoline-N-oxide (I50 approximately equal to 2 microM) is located between Q and plastoquinone. Studies with thylakoids isolated from atrazine-resistant pigweed plants indicate that the modification in the Q/B membrane complex that confers increased resistance to inhibition by atrazine also results in decreased sensitivity to inhibition by 2-n-heptyl-4-hydroxyquinoline-N-oxide (resistant/ sensitive ratio = 11). From the results of tetramethylphenylenediamine by-pass experiments, determinations of inhibitor sensitivity in trypsin-treated thylakoids and competitive displacement experiments made with [14C]metribuzin in thylakoids and photosystem II particles, it is suggested that 2-n-heptyl-4-hydroxyquinoline-N-oxide binds in a region of the Q/B complex that is distinct from the 3-(3,4-dichloro)-1,1-dimethyl urea and atrazine binding sites.
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Affiliation(s)
- J R Barton
- School of Biological Sciences, University of Kentucky, Lexington, Kentucky 40506, USA
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Galloway RE, Mets L. Non-Mendelian Inheritance of 3-(3,4-Dichlorophenyl)-1,1-dimethylurea-Resistant Thylakoid Membrane Properties in Chlamydomonas. PLANT PHYSIOLOGY 1982; 70:1673-7. [PMID: 16662742 PMCID: PMC1065953 DOI: 10.1104/pp.70.6.1673] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
A uniparentally inherited 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU)-resistant mutant of Chlamydomonas reinhardii, Dr2, which has a resistance mechanism of the type defined as ;primary,' has been isolated. In vitro Hill reactions catalyzed by isolated thylakoid membranes reveal a reduced apparent affinity of the thylakoids for DCMU. These changes in membrane properties quantitatively account for the resistance of mutant Dr2 to herbicide inhibition of growth. The properties of this mutant show that all of the Hill reaction-inhibiting DCMU binding sites are under identical genetic control. Mutant Dr2 is a useful new uniparental genetic marker, since it has a novel phenotype and it may be possible to identify its altered gene product. The low cross-resistance of Dr2 to atrazine suggests that there may be considerable flexibility in exploiting induced herbicide resistance of crop plants for improving herbicide specificity.Four mendelian mutants in at least three loci all have resistance mechanisms in the class we define as ;secondary.' They are as sensitive as wild type to in vitro inhibition of the Hill reaction, and must acquire resistance in vivo by preventing the active form of the herbicide from reaching the sensitive site.
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Affiliation(s)
- R E Galloway
- Department of Biology, Case Western Reserve University, Cleveland, Ohio 44106
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Burke JJ, Wilson RF, Swafford JR. Characterization of Chloroplasts Isolated from Triazine-Susceptible and Triazine-Resistant Biotypes of Brassica campestris L. PLANT PHYSIOLOGY 1982; 70:24-9. [PMID: 16662454 PMCID: PMC1067079 DOI: 10.1104/pp.70.1.24] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Chloroplasts isolated from triazine-susceptible and triazine-resistant biotypes of Brassica campestris L. were analyzed for lipid composition, ultrastructure, and relative quantum requirements of photosynthesis. In general, phospholipids, but not glycolipids in chloroplasts from the triazine-resistant biotype had a higher linolenic acid concentration and lower levels of oleic and linoleic fatty acids, than chloroplasts from triazine-susceptible plants. Chloroplasts from the triazine-resistant biotype had a 1.6-fold higher concentration of t-Delta3-hexadecenoic acid with a concomitantly lower palmitic acid concentration in phosphatidylglycerol. Phosphatidylglycerol previously has been hypothesized to be a boundary lipid for photosystem II. Chloroplasts from the triazine-resistant biotype had a lower chlorophyll a/b ratio and exhibited increased grana stacking. Light-saturation curves revealed that the relative quantum requirement for whole chain electron transport at limiting light intensities was lower for the susceptible biotype than for the triazine-resistant biotype. Although the level of the chlorophyll a/b light-harvesting complex associated with photosystem II was greater in resistant biotypes, the increased levels of the light-harvesting complex did not increase the photosynthetic efficiency enough to overcome the rate limitation that is inherited concomitantly with the modification of the Striazine binding site.
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Affiliation(s)
- J J Burke
- United States Department of Agriculture, Agricultural Research Service, North Carolina State University, Raleigh, North Carolina 27650
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Droppa M, Horváth G, Demeter S. Effect of Photosystem II Herbicides in Triazine Susceptible and Resistant Amaranthus retroflexusL. Biotypes Investigated by Thermoluminescence. ACTA ACUST UNITED AC 1981. [DOI: 10.1016/s0044-328x(81)80010-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Pillai P, John JB. Lipid composition of chloroplast membranes from weed biotypes differentially sensitive to triazine herbicides. PLANT PHYSIOLOGY 1981; 68:585-7. [PMID: 16661961 PMCID: PMC425943 DOI: 10.1104/pp.68.3.585] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Chloroplasts were isolated from triazine-sensitive and triazine-resistant biotypes of common groundsel (Senecio vulgaris L.), common lambsquarter (Chenopodium album L.), and redroot pigweed (Amaranthus retroflexus L.). Chloroplast lipids were extracted and analyzed for differences among sensitive and resistant biotypes. The distribution of lipid between major lipid classes differed in chloroplasts from resistant and susceptible biotypes. Chloroplasts from resistant biotypes contained higher proportions of monogalactosyl diglyceride and phosphatidyl ethanolamine and lower proportions of digalactosyl diglyceride and phosphatidyl choline than did chloroplasts from susceptible biotypes. Monogalactosyl diglyceride and phosphatidyl ethanolamine were also quantitatively higher in membranes of resistant versus susceptible biotypes. The major lipid classes of resistant chloroplast membranes contained lipids comparatively richer in unsaturated fatty acids with the exceptions of digalactosyl diglyceride from all three biotypes and phosphatidyl ethanolamine from common groundsel. Results correlated changes in triazine sensitivity with qualitative and quantitative differences in the lipid composition of chloroplast membranes.
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Affiliation(s)
- P Pillai
- Weed Science Laboratory, Beltsville Agricultural Research Center, Beltsville, Maryland 20705
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Holt JS, Stemler AJ, Radosevich SR. Differential Light Responses of Photosynthesis by Triazine-resistant and Triazine-susceptible Senecio vulgaris Biotypes. PLANT PHYSIOLOGY 1981; 67:744-8. [PMID: 16661747 PMCID: PMC425765 DOI: 10.1104/pp.67.4.744] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Studies were conducted to determine a physiological basis for competitive differences between Senecio vulgaris L. biotypes which are either resistant or susceptible to triazine herbicides. Net carbon fixation of intact leaves of mature plants was higher at all light intensities in the susceptible biotype than in the resistant biotype. Quantum yields measured under identical conditions for each biotype were 20% lower in the resistant than in the susceptible biotype. Oxygen evolution in continuous light measured in stroma-free chloroplasts was also higher at all light intensities in the susceptible biotype than in the resistant biotype. Oxygen evolution in response to flashing light was measured in stroma-free chloroplasts of both biotypes. The steady-state yield per flash of resistant chloroplasts was less than 20% that of susceptible chloroplasts. Susceptible chloroplasts displayed oscillations in oxygen yield per flash typically observed in normal chloroplasts, whereas the pattern of oscillations in resistant chloroplasts was noticeably damped. It is suggested that modification of the herbicide binding site which confers s-triazine resistance may also affect the oxidizing side of photosystem II, making photochemical electron transport much less efficient. This alteration has resulted in a lowered capacity for net carbon fixation and lower quantum yields in whole plants of the resistant type.
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Affiliation(s)
- J S Holt
- Department of Botany, University of California, Davis, California 95616
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Mattoo AK, Pick U, Hoffman-Falk H, Edelman M. The rapidly metabolized 32,000-dalton polypeptide of the chloroplast is the "proteinaceous shield" regulating photosystem II electron transport and mediating diuron herbicide sensitivity. Proc Natl Acad Sci U S A 1981; 78:1572-6. [PMID: 6940173 PMCID: PMC319173 DOI: 10.1073/pnas.78.3.1572] [Citation(s) in RCA: 149] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Mild trypsin treatment of Spirodela oligorrhiza thylakoid membranes leads to partial digestion of the rapidly metabolized, surface-exposed, 32,000-dalton protein. Under these conditions, photoreduction of ferricyanide becomes insensitive to diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], an inhibitor of photosystem II electron transport. Preincubation of thylakoids with diuron leads to a conformational change in the 32,000-dalton protein, modifying its trypsin digestion and preventing expression of diuron insensitivity. Finally, light affects the susceptibility of the 32,000-dalton protein to digestion by trypsin. In other experiments, thylakoids specifically depleted in the 32,000-dalton protein were found to be deficient in electron transport at the reducing side of photosystem II but not at the oxidizing side or in photosystem I activities. Thus, the rapidly metabolized 32,000-dalton thylakoid protein in Spirodela chloroplasts fulfills the requirements of the hypothesized "proteinaceous shield" [Renger, G. (1976) Biochim. Biophys. Acta 440, 287-300] regulating electron flow through photosystem II and mediating diuron sensitivity.
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Böger P, Sandmann G, Miller R. Herbicide resistance in a mutant of the microalga Bumilleriopsis filiformis. PHOTOSYNTHESIS RESEARCH 1981; 2:61-74. [PMID: 24470157 DOI: 10.1007/bf00036166] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/1981] [Indexed: 06/03/2023]
Abstract
A DCMU* (diuron)-resistant algal mutant was selected and characterized. Chlorophyll content, growth, and photosystem-I activity are as in the wild-type. Growth in liquid medium with 3 μM DCMU present is half of the control. Apparently only the herbicide-binding site is affected within the redox chain. In contrast to the wild-type, trypsin treatment of isolated chloroplast material completely abolishes photosynthetic electron transport inhibition by DCMU or atrazine.DCMU resistance of chloroplasts is accompanies by tolerance to triazinones and phenylpyridazinones, but not to symmetric triazines. Sensitivity to diphenylethers, DBMIB or o-phenanthroline is not altered.Data on this algal mutant combined with those from triazine-resistant mutants of higher plants give direct evidence of overlapping binding sites at a (hypothetical) binding protein located at the reducing side of photosytem II.
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Affiliation(s)
- P Böger
- Lehrstuhl für Physiologie und Biochemie der Pflanzen, Universität Konstanz, D-7750, Konstanz, West Germany
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