Pyrazole phenyl ether herbicides inhibit protoporphyrinogen oxidase

Sherman, Timothy D.; Duke, Mary V.; Clark, Robert D.; Sanders, Ernest F.; Matsumoto, Hiroshi; Duke, Stephen O.

doi:10.1016/0048-3575(91)90095-4

Cited by 37 publications

(22 citation statements)

References 37 publications

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“…Others (27,28) Proto IX accumulation in leaf discs in the dark (34). The results of the present study may not extrapolate to the field in every case; however, the relative herbicidal efficacy of acifluorfen that we found between species in the bioassays used in these studies are similar to those of whole plants.…”

Section: Relationship Between Proto IX Accumulation and Herbicidal Efsupporting

confidence: 59%

“…Accumulation of Proto IX is due to strong inhibition of Protox (1 1,12,21,22,32,34,36), resulting in uncontrolled oxidation of the enzymic substrate, protoporphyrinogen IX, to Proto IX outside the porphyrin pathway (12, 18) and to deregulation of the porphyrin pathway (16,20). Proto IX accumulation in plants treated with Protox-inhibiting herbicides is analogous to Proto IX accumulation in humans with a genetic defect in Protox, resulting in the disease variegate porphyria (4).…”

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confidence: 99%

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Physiological Basis for Differential Sensitivities of Plant Species to Protoporphyrinogen Oxidase-Inhibiting Herbicides

Sherman

Becerril²,

Matsumoto³

et al. 1991

Plant Physiol.

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With a leaf disc assay, 11 species were tested for effects of the herbicide acifluorfen on porphyrin accumulation in darkness and subsequent electrolyte leakage and photobleaching of chlorophyll after exposure to light. Protoporphyrin IX (Proto IX) was the only porphyrin that was substantially increased by the herbicide in any of the species. However, there was a wide range in the amount of Proto IX accumulation caused by 0.1 millimolar acifluorfen between species. Within species, there was a reduced effect of the herbicide in older tissues. Therefore, direct quantitative comparisons between species are difficult. Nevertheless, when data from different species and from tissues of different age within a species were plotted, there was a curvilinear relationship between the amount of Proto IX caused to accumulate during 20 hours of darkness and the amount of electrolyte leakage or chlorophyll photobleaching caused after 6 and 24 hours of light, respectively, following the dark period. Herbicidal damage plateaued at about 10 nanomoles of Proto IX per gram of fresh weight. Little difference was found between in vitro acifluorfen inhibition of protoporphyrinogen oxidase (Protox) of plastid preparations of mustard, cucumber, and moming glory, three species with large differences in their susceptibility at the tissue level. Mustard, a highly tolerant species, produced little Proto IX in response to the herbicide, despite having a highly susceptible Protox. Acifluorfen blocked carbon flow from 6-aminolevulinic acid to protochlorophyllide in mustard, indicating that it inhibits Protox in vivo. Increasing 5-aminolevulinic acid concentrations (33-333 micromolar) supplied to mustard with 0.1 millimolar acifluorfen increased Proto IX accumulation and herbicidal activity, demonstrating that mustard sensitivity to Proto IX was similar to other species. Differential susceptibility to acifluorfen of the species examined in this study appears to be due in large part to differences in Proto IX accumulation in response to the herbicide. In some cases, differences in Proto IX accumulation appear to be due to differences in activity of the porphyrin pathway. (12,18) and to deregulation of the porphyrin pathway (16,20). Proto IX accumulation in plants treated with Protox-inhibiting herbicides is analogous to Proto IX accumulation in humans with a genetic defect in Protox, resulting in the disease variegate porphyria (4). In the presence of light and molecular oxygen, singlet oxygen is generated by Proto IX, resulting in membrane lipid peroxidation (5).Considerable variation in susceptibility to these herbicides exists between plant species. Tolerance of soybeans to acifluorfen, a widely-used p-nitro-diphenyl ether herbicide, is due to metabolic detoxification of the herbicide (9). Acifluorfen was developed for use in soybeans. However, the mechanism of tolerance of other species to this herbicide is not understood. Tolerance could be related to the level of protection against photodynamic damage or to the effect of the herbic...

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Section: Relationship Between Proto IX Accumulation and Herbicidal Efsupporting

confidence: 59%

mentioning

confidence: 99%

Physiological Basis for Differential Sensitivities of Plant Species to Protoporphyrinogen Oxidase-Inhibiting Herbicides

Sherman

Becerril²,

Matsumoto³

et al. 1991

Plant Physiol.

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“…Despite the inhibition of Protox by these compounds in intact plants, the product of the enzyme, Proto IX, accumulates (Sato et al, 1987b;Sandmann and Bö ger, 1988;Becerril and Duke, 1989;Sherman et al, 1991). The uniqueness and complexity of the mechanism of Protox inhibitors is illustrated in the accumulation of Proto IX.…”

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confidence: 99%

“…It is also known that Protox is the target enzyme of phthalimide compounds such as S23142 and diphenylether compounds such as AF (Sato et al, 1987b;Scalla et al, 1990;Varsano et al, 1990;Camadro et al, 1991;Duke et al, 1991;Matringe et al, 1992aMatringe et al, , 1992b. Despite the inhibition of Protox by these compounds in intact plants, the product of the enzyme, Proto IX, accumulates (Sato et al, 1987b;Sandmann and Bö ger, 1988;Becerril and Duke, 1989;Sherman et al, 1991).…”

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Molecular Characterization of Photomixotrophic Tobacco Cells Resistant to Protoporphyrinogen Oxidase-Inhibiting Herbicides

et al. 1998

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“…This may not occur in all species or in all tissues of a particular species. For example, we have found elevated PChlide levels in response to Protox inhibitors (diphenyl ethers and pyrazole-phenyl ethers) only in non-green cucumber cotyledons (18,24). PChlide is phototransformed to chlorophyllide, which is subsequently converted to chlorophyll ( Figure 1).…”

Section: Porphyrins That Accumulatementioning

confidence: 93%

Protoporphyrinogen Oxidase as the Optimal Herbicide Site in the Porphyrin Pathway

Duke

Ub²,

et al. 1994

Porphyric Pesticides

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Herbicide discovery efforts have yielded a large number of excellent herbicides that target the porphyrin pathway. Protoporphyrinogen oxidase (Protox) is the only molecular site inhibited by the commercially available members of this herbicide class. We hypothesize that this site of action is much better for herbicidal activity than other sites of the porphyrin pathway because of the location of herbicide-susceptible Protox within the cell (the plastid envelope and the mitochondrion), the existence of a herbicide-resistant form of the enzyme in the plasma membrane (which rapidly causes accumulation of protoporphyrin IX when plastid Protox is inhibited), and two chemical features of the substrate (its relatively low lipophilicity and its non-planar macrocycle). Although enzymes of the porphyrin pathway beyond Protox can be inhibited to cause the accumulation of phytotoxic levels of porphyrins, these sites do not share the unique properties of Protox. As a result, the number of active analogues that effectively inhibit these enzymes in vivo is much smaller than for Protox, and the amount of herbicide needed for effective herbicidal action is relatively higher.Thousands of herbicides have been patented that apparently exert their phytotoxicity through induced accumulation of phototoxic porphyrins (I, 2). All of those for which the molecular site of action is known are inhibitors of protoporphyrinogen oxidase (Protox), the last enzyme common to the synthesis of both chlorophyll and heme in green plants (J, 3-8). Theoretically, inhibition of any enzyme of the porphyrin pathway ( Figure 1; see Figure 1 of Chapter 1 for structures of intermediates) past porphobilinogen deaminase (uroporphyrinogen III cosynthase) would result in the accumulation of a photodynamic porphyrin. Sites in the 0097-6156/94/0559-0191$08.00/0

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Pyrazole phenyl ether herbicides inhibit protoporphyrinogen oxidase

Cited by 37 publications

References 37 publications

Physiological Basis for Differential Sensitivities of Plant Species to Protoporphyrinogen Oxidase-Inhibiting Herbicides

Physiological Basis for Differential Sensitivities of Plant Species to Protoporphyrinogen Oxidase-Inhibiting Herbicides

Molecular Characterization of Photomixotrophic Tobacco Cells Resistant to Protoporphyrinogen Oxidase-Inhibiting Herbicides

Protoporphyrinogen Oxidase as the Optimal Herbicide Site in the Porphyrin Pathway

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