Triazine Resistance in Phalaris paradoxa: Physiological and Molecular Analyses

1987 ◽  
Vol 42 (7-8) ◽  
pp. 779-782 ◽  
Author(s):  
Mordechay Schönfeld ◽  
Tuvia Yaacoby ◽  
Adi Ben-Yehuda ◽  
Baruch Rubin ◽  
Joseph Hirschberg
Keyword(s):  
Electron Transport ◽  
Dry Weight ◽  
Resistant Mutant ◽  
Fluorescence Induction ◽  
Chlorophyll Fluorescence Induction ◽  
Single Mutation ◽  
Wild Type ◽  
Triazine Resistance ◽  
Herbicide Resistant ◽  
Isolated Chloroplasts

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 CO2 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 thyiakoid membrane 32 kDa Qв- protein. was found in the herbicide resistant mutant. The results indicate that triazine resistance is not necessarily linked to inferior photosynthetic and growth performance.

Triazine Resistance in Phalaris paradoxa: Physiological and Molecular Analyses

1987 ◽  
Vol 42 (6) ◽  
pp. 779-782
Author(s):  
Mordechay Schönfeld ◽  
Tuvia Yaacoby ◽  
Adi Ben-Yehuda ◽  
Baruch Rubin ◽  
Joseph Hirschberg
Keyword(s):  
Electron Transport ◽  
Dry Weight ◽  
Resistant Mutant ◽  
Fluorescence Induction ◽  
Chlorophyll Fluorescence Induction ◽  
Single Mutation ◽  
Wild Type ◽  
Triazine Resistance ◽  
Herbicide Resistant ◽  
Isolated Chloroplasts

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 CO2 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 Qв- protein. was found in the herbicide resistant mutant. The results indicate that triazine resistance is not necessarily linked to inferior photosynthetic and growth performance.

Effects of Atrazine, Cyanazine, and Procyazine on the Photochemical Reactions of Isolated Chloroplasts

Weed Science ◽  
1979 ◽  
Vol 27 (3) ◽  
pp. 300-308 ◽  
Author(s):  
P. E. Brewer ◽  
C. J. Arntzen ◽  
F. W. Slife
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Primary Electron ◽  
Fluorescence Induction ◽  
Photochemical Reactions ◽  
Time Dependent ◽  
Chlorophyll Fluorescence Induction ◽  
Transport Assay ◽  
Highly Hydrophobic ◽  
Isolated Chloroplasts

The effects of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], cyanazine {2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl] amino]-2-methylpropionitrile}, and procyazine {2-[[4-chloro-6-(cyclopropylamino)-1,3,5-triazine-2-yl] amino]-2-methylpropanenitrile} on the photochemical reactions of isolated pea (Pisum sativum L. ‘Progress #9 Dwarf’) chloroplasts were studied. Atrazine, cyanazine, and procyazine inhibited electron transport but did not uncouple photophosphorylation. The primary site of inhibition for all three herbicides was on the reducing side of photosystem II; the electron transfer step between the primary electron acceptor (Q) and the plastoquinone pool of the electron transport chain is suggested as the site of action of all three herbicides. The amount of inhibition of electron transport observed after addition of herbicide to isolated chloroplasts was time-dependent for cyanazine and procyazine but not for atrazine. This was apparently due to a slower partitioning of cyanazine and procyazine from the aqueous phase of the reaction solution into the highly hydrophobic environment within the chloroplast membrane. Treatment of the thylakoid membranes with detergent reduced the time-dependent inhibitory nature of cyanazine and procyazine, and the ability of atrazine to block electron transport. A photosystem II-dependent electron transport assay and a chlorophyll fluorescence induction assay were used to determine the inhibitory potentials of atrazine, cyanazine, and procyazine. After allowing for differences in the rate of membrane penetration, I50 values of approximately 2 × 10−7 M were determined for each of the three herbicides.

Fluorescence Induction Characteristics of Wild-Type and Herbicide-Resistant Strain of the Photosynthetic Bacterium Rhodobacter capsulatus

1990 ◽  
Vol 45 (5) ◽  
pp. 452-454 ◽  
Author(s):  
Gábor Horváth ◽  
Magdolna Droppa ◽  
Ágnes Puskás
Keyword(s):  
Rhodobacter Capsulatus ◽  
Photosynthetic Bacterium ◽  
Resistant Mutant ◽  
Fluorescence Induction ◽  
Natural Resistance ◽  
Wild Type ◽  
Triazine Herbicide ◽  
Herbicide Resistant ◽  
Resistant Mutants ◽  
Fast Rise

Fluorescence induction characteristics have been studied in wild-type and atrazine-resistant mutant of Rliodobacter capsulatus. Fluorescence induction was found to be a useful technique to monitor the altered electron transfer in the atrazine-resistant mutants as well as in the different membrane fractions of wild-type R. capsulatus. In both cases, the proportion of the fast rise of variable fluorescence was increased indicating the enhancement of QA. I`n the mutant strain, the I50 value of triazine herbicide terbutryn was increased by 100-fold whereas the natural resistance of R. capsulatus against diuron was abolished by the mutation.

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

1987 ◽  
Vol 42 (6) ◽  
pp. 670-673 ◽  
Author(s):  
John N. Phillips ◽  
John L. Huppatz
Keyword(s):  
Electron Transport ◽  
Inhibitory Activity ◽  
Photosynthetic Electron Transport ◽  
Resistant Mutant ◽  
Herbicidal Activity ◽  
Optical Isomers ◽  
Wild Type ◽  
Specific Receptor ◽  
Receptor Sites ◽  
Alkyl Moiety

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.

The Inhibition of Photosynthetic Electron Transport by DBMIB and its Restoration by p-Phenylenediamines; Studied by Means of Prompt and Delayed Chlorophyll Fluorescence of Green Algae

1974 ◽  
Vol 29 (11-12) ◽  
pp. 725-732 ◽  
Author(s):  
Robert Bauer ◽  
Mathijs J. G. Wijnands
Keyword(s):  
Chlorophyll Fluorescence ◽  
Electron Transport ◽  
Photosystem Ii ◽  
Photosynthetic Electron Transport ◽  
Primary Electron ◽  
Delayed Fluorescence ◽  
Fluorescence Induction ◽  
Chlorophyll Fluorescence Induction ◽  
Exchange Reactions ◽  
Redox Systems

Abstract The effect of the plastohydroquinone antagonist dibromothym oquinone (DBMIB) on photosynthetic electron transport reactions was studied in the presence and absence of p-phenylene-diamines by means of measurements of prompt and delayed chlorophyll fluorescence induction of the green alga Scenedesm us obliquus. Prompt and delayed chlorophyll fluorescence induction phenomena are valid indicators for the native presence of and cooperation between the two photosynthetic light reactions. Their kinetics reflect the balancing of electron exchange reactions in the chain of coupled redox-systems between the two photosystems upon sudden illumination. From distinct alterations of the short-term (sec) light induced changes in the yield of prom pt and delayed chlorophyll fluorescence it is concluded that DBMIB inhibits the photosynthetic electron transport in the chain of redox-systems between the two light reactions. There is evidence to show that upon illumination of DBMIB treated cells only the reduction of primary electron ac­ceptor pools of photosystem II (i. e. Q and PQ) is still possible. After their reduction the further electron transport through photosystem II is blocked. The addition of p-phenylenediamines to DBM IB-treated cells abolishes the typical DBMIB-affected prom pt and delayed fluorescence inhibition curves and the normal induction curves re­ appear qualitatively in all their important features. From these measurements it is suggested that the redox properties of p-phenylenediamines allow an electron transport bypass of the DBMIB inhibition site which results in a fully restored photosynthetic electron transport from water to NADP.

Activity of Photosystem II Herbicides Is Related with Their Residence Times at the D 1 Protein

1991 ◽  
Vol 46 (7-8) ◽  
pp. 575-578 ◽  
Author(s):  
J. Dirk Naber ◽  
Jack J. S. van Rensen
Keyword(s):  
Electron Transport ◽  
Release Kinetics ◽  
Chenopodium Album ◽  
Binding Kinetics ◽  
Residence Times ◽  
Binding Parameters ◽  
Reversible Binding ◽  
Triazine Resistance ◽  
Kinetics Of ◽  
Isolated Chloroplasts

Abstract The reversible binding kinetics of atrazine, diuron and ioxynil were measured via their binding and release parameters during steady state inhibition of electron transport. The parameters were determined in isolated chloroplasts of peas and of triazine-resistant and -susceptible bio­ types of Chenopodium album using a kinetic model. This model is based on the flash-induced oxygen evolution patterns of isolated broken chloroplasts. It was found that the binding parameters were always significantly higher in the case of an oxidized acceptor quinone complex as compared with a semi-reduced complex. Triazine resistance seems to originate from a significant increase of the release kinetics. The release parameters could be used to calculate the residence times of the herbicides at the D 1 protein. The values of these residence times were always much higher for the herbicides than for Q B; this explains the inhibition of electron transport. The only exception was the residence time of atrazine in the resistant biotype, where the value was close to that of Q B. It is concluded that the “on” kinetics of a compound to its binding environment at the D 1 protein are determined principally by the accessibility of the niche to the compound. The differences in activity between herbicides are mainly due to variations in the release kinetics.

A Chloroplast Photosystem 2 Reaction Resistant to Salicylaldoxime

1977 ◽  
Vol 32 (11-12) ◽  
pp. 968-972 ◽  
Author(s):  
G. F. W. Searle
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Electron Acceptor ◽  
Photosystem 2 ◽  
Electron Flow ◽  
Fluorescence Induction ◽  
Initial Slope ◽  
Chlorophyll Fluorescence Induction ◽  
Fluorescence Level ◽  
A Site

Abstract Photoreduction of the artificial electron acceptor, cytochrome c, by isolated spinach chloroplasts in the absence of added catalyst has been found to be resistant to inhibition by 10 mᴍ salicyl­ aldoxime. This contrasts with the pronounced inhibition of the photoreduction of both 2,6-dichloro-phenolindophenol and ferricyanide over a range of electron flow rates, and indicates an inhibition on the acceptor side rather than on the donor side of photosystem 2 (PS2). All photoreductions were susceptible to inhibition by 3-(3′,4′-dichlorophenyl)-1, 1-dimethyl urea (DCMU). Salicyl­ aldoxime (1 -10 mᴍ) inhibited electron flow from PS2 to P700, and also altered the chlorophyll fluorescence induction of dark-adapted chloroplasts. Salicylaldoxime concentrations up to 5 mM did not change the initial fluorescence level, F0 , or the initial slope, (dF/dt)0 , but lowered the final steady state fluorescence level, Fm , and the value of p0 [p0= (Fm - F0)/Fm] ; an effect similar to that seen on 1 mᴍ ferricyanide addition, thus indicating an induced oxidation of the fluorescence quencher, Q. Both DCMU and orthophenanthroline, which block electron transport directly after Q, caused an increase in (dF/dt)0 , F0 and Fm but left p0 unchanged. This contrasted with the effect of salicylaldoxime. It is proposed that salicylaldoxime inhibits electron transport from PS2 to photosystem 1, at a site which can probably be identified with the plastoquinone pool, by inducing a cyclic flow of electrons around PS2. Cytochrome c, under the conditions used, appears to be photoreduced at a site close to the secondary electron acceptor, R, of PS2.

scholarly journals Methyl Jasmonate Protects the PS II System by Maintaining the Stability of Chloroplast D1 Protein and Accelerating Enzymatic Antioxidants in Heat-Stressed Wheat Plants

Antioxidants ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1216
Author(s):  
Mehar Fatma ◽  
Noushina Iqbal ◽  
Zebus Sehar ◽  
Mohammed Nasser Alyemeni ◽  
Prashant Kaushik ◽  
...  
Keyword(s):  
Heat Stress ◽  
Chlorophyll Fluorescence ◽  
Electron Transport ◽  
Methyl Jasmonate ◽  
Reaction Center ◽  
D1 Protein ◽  
Fluorescence Induction ◽  
Chlorophyll Fluorescence Induction ◽  
Enzymatic Antioxidants ◽  
Ps Ii

The application of 10 µM methyl jasmonate (MeJA) for the protection of wheat (Triticum aestivum L.) photosystem II (PS II) against heat stress (HS) was studied. Heat stress was induced at 42 °C to established plants, which were then recovered at 25 °C and monitored during their growth for the study duration. Application of MeJA resulted in increased enzymatic antioxidant activity that reduced the content of hydrogen peroxide (H2O2) and thiobarbituric acid reactive substances (TBARS) and enhanced the photosynthetic efficiency. Exogenous MeJA had a beneficial effect on chlorophyll fluorescence under HS and enhanced the pigment system (PS) II system, as observed in a JIP-test, a new tool for chlorophyll fluorescence induction curve. Exogenous MeJA improved the quantum yield of electron transport (ETo/CS) as well as electron transport flux for each reaction center (ET0/RC). However, the specific energy fluxes per reaction center (RC), i.e., TR0/RC (trapping) and DI0/RC (dissipation), were reduced by MeJA. These results indicate that MeJA affects the efficiency of PS II by stabilizing the D1 protein, increasing its abundance, and enhancing the expression of the psbA and psbB genes under HS, which encode proteins of the PS II core RC complex. Thus, MeJA is a potential tool to protect PS II and D1 protein in wheat plants under HS and to accelerate the recovery of the photosynthetic capacity.

Chlorophyll fluorescence induction: an indicator of photosynthetic activity in marine algae undergoing desiccation

1978 ◽  
Vol 56 (21) ◽  
pp. 2787-2794 ◽  
Author(s):  
James Wiltens ◽  
Ulrich Schreiber ◽  
William Vidaver
Keyword(s):  
Chlorophyll Fluorescence ◽  
Electron Transport ◽  
Photosystem Ii ◽  
Water Content ◽  
High Tide ◽  
Net Photosynthesis ◽  
Fluorescence Induction ◽  
Chlorophyll Fluorescence Induction ◽  
Physiological Basis ◽  
Value Analysis

Algae of higher intertidal regions tend to be tolerant of extended periods of desiccation, while many lower tidal or subtidal species do not withstand even mild water loss. (Tidal regions can be characterized as high (regularly immersed at high tide and exposed at low tide), low (emergence only during minus tides (lower than mean low tide)), or subtidal (never exposed at low tide and extending to the maximum depth at which net photosynthesis can occur).) The ecological necessity for tolerance in frequently emerged species is obvious, but the physiological basis of it is not well understood. Changes of photosynthetic partial reactions upon desiccation and rehydration of tolerant and sensitive algae were studied by measurements of chlorophyll fluorescence induction kinetics (Kautsky effect). With progressive decrease in water content the gradual disappearance of the characteristic fluorescence transients was observed in both tolerant and sensitive species. The water content ranges where typical changes occurred were species dependent. Rehydration in tolerant plants resulted in rapid recovery from severe desiccation; there was no such recovery in sensitive plants when water content was decreased below a critical value. Analysis of the fluorescence changes upon desiccation and rehydration suggests: (1) electron transport between photosystem II and photosystem I, as well as H2O splitting are the partial reactions sensitive to desiccation; (2) in the resistant Porphyra sanjuanensis, intersystem electron transport is blocked at around 25% water content; (3) further desiccation leads to loss of water-splitting activity and eventually to the complete loss of variable fluorescence photosystem II reaction centers; and (4) on rehydration intersystem electron transport begins almost immediately while recovery of H2O splitting requires several minutes.

scholarly journals An Amino Acid Substitution in the QB-Protein Causes Herbicide Resistance without Impairing Electron Transport from QA to QB

1989 ◽  
Vol 44 (5-6) ◽  
pp. 431-434 ◽  
Author(s):  
Günter F. Wildner ◽  
Ursula Heisterkamp ◽  
Ulrich Bodner ◽  
Udo Johanmngmeier ◽  
Wolfgang Haehnel
Keyword(s):  
Amino Acid ◽  
Electron Transport ◽  
Sequence Analysis ◽  
Herbicide Resistance ◽  
Resistant Mutant ◽  
Structure And Function ◽  
Wild Type ◽  
Chlamydomonas Reinhardii ◽  
And Function ◽  
Kinetics Of

Abstract Structure and function of the QB-protein of a metribuzin resistant mutant of Chlamydomonas reinhardii were analyzed. The amino acid residue Leu-275 of the wild type protein is changed to Phe as was determined by RNA -sequence analysis. This mutation caused a 20-fold and 5-fold resistance to metribuzin and DCMU , respectively. No resistance to atrazine was observed. The kinetics of the electron transport from QA to OB was similar to that of the wild type (t1/2 = 0.4 ms).

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