Protoporphyrinogen oxidase as a molecular target for diphenyl ether herbicides

Abstract

Diphenyl ether herbicides induce an accumulation of protoporphyrin IX in plant tissues. By analogy to human porphyria, the accumulation could be attributed to decreased (Mg or Fe)-chelatase or protoporphyrinogen oxidase activities. Possible effects of acifluorfen-methyl on these enzymes were investigated in isolated corn (maize, Zea mays) etioplasts, potato (Solanum tuberosum) and mouse mitochondria, and yeast mitochondrial membranes. Acifluorfen-methyl was strongly inhibitory to protoporphyrinogen oxidase activities whatever their origins [concn. causing 50% inhibition (IC50) = 4 nM for the corn etioplast enzyme]. By contrast, it was roughly 100,000 times less active on (Mg or Fe)-chelatase activities (IC50 = 80-100 microM). Our results lead us to propose protoporphyrinogen oxidase as a cellular target for diphenyl ether herbicides.

Biochemical and Physiological Changes in Rice Plants Due to the Application of Herbicides1

“…These compounds act through Biochemical and physiological changes in rice plants due to ... inhibition of common enzyme between the pathways of the chlorophyll and cytochromes synthesis, which results in the accumulation of intermediate tetrapyrrolic, paralyzing the formation of this pigment (Matringe et al, 1989).…”

Cellular Localization of Protoporphyrinogen-Oxidizing Activities of Etiolated Barley (Hordeum vulgare L.) Leaves (Relationship to Mechanism of Action of Protoporphyrinogen Oxidase-Inhibiting Herbicides)

“…Mitochondria do not have the enzymes to produce Protogen IX (Smith, 1988;Lee et al, 1991); however, mitochondria do have Protox (Jacobs and Jacobs, 1987;Matringe et al, 1989a). The only established source of Protogen IX in plant cells is the plastid.…”

“…A11 organellar Protox activities other than those of soybean root mitochondria (Jacobs et al, 1990) have been reported to be highly sensitive to Protox-inhibiting herbicides. These include cucumber, mustard, moming glory, barley, and maize etioplasts, as well as mitochondria from maize, potato, yeast, and mouse (Matringe et al, 1989a(Matringe et al, , 1989bCamadro et al, 1991;Sherman et ai., 1991aSherman et ai., , 1991b. Thus, it is highly probable that a11 organellar Protox activities are normally sensitive to these herbicides.…”

Efeitos da aplicação de herbicidas sobre a eficiência fotoquímica em plantas de soja convencional e geneticamente modificada

“…O aparecimento de sintomas de estresse nos primeiros dias após a aplicação dos herbicidas decorre, provavelmente, da aplicação do lactofen, o qual pertence à classe dos difeniléteres, que inibem a enzima protoporfirinogênio oxidase (PROTOX). Essa enzima converte o protoporfirinogênio-IX em protoporfirina-IX, a qual produz clorofila e citocromos a partir de reações com Mg e Fe, respectivamente (Matringe et al, 1989). A ação do herbicida acontece pela competição com a enzima PROTOX, impedindo a produção de protoporfirina-IX e resultando em acúmulo de protoporfirinogênio no cloroplasto.…”