Tentoxin does not cause chlorosis in greening mung bean leaves by inhibiting photophosphorylation

Duke, Stephen O.; Wickliff, James L.; Vaughn, Kevin C.; Paul, Rex N.

doi:10.1111/j.1399-3054.1982.tb04531.x

Cited by 36 publications

(18 citation statements)

References 44 publications

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“…Thus, the hypersensitivity of tentoxin-treated tissues is probably due to both reduced protection and increased effect of the herbicide on PPIX production. Protochlorophyll(ide) synthesis in tentoxintreated tissues is slower than in untreated tissues (10). Since, in the present study, we found increased PPIX synthesis in tentoxin-treated tissues, the tentoxin-impaired step in protochlorophyll(ide) synthesis is probably at a point in the Chl pathway after protoporphyrinogen oxidase.…”

Section: Discussionsupporting

confidence: 48%

Protoporphyrin IX Content Correlates with Activity of Photobleaching Herbicides

Becerril¹,

Duke²

1989

Plant Physiol.

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128

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Several laboratories have demonstrated recently that photobleaching herbicides such as acifluorfen and oxadiazon cause accumulation of protoporphyrin IX (PPIX), a photodynamic pigment capable of herbicidal activity. We investigated, in acifluorfen-treated tissues, the in vivo stability of PPIX, the kinefics of accumulation, and the correlation between concentration of PPIX and herbicidal damage. During a 20 hour dark period, PPIX levels rose from barely detectable concentrations to 1 to 2 nanomoles per 50 cucumber (Cucumis sativus L.) cotyledon discs treated with 10 micromolar acifluorfen. When placed in 500 micromoles per square meter per second PAR, PPIX levels decayed logarithmically, with an initial half-life of about 2.5 hours. PPIX levels at each time after exposure to light correlated positively with the cellular damage that occurred during the following 1 hour in both green and yellow (tentoxin-treated) cucumber cotyledon tissues. PPIX levels in discs incubated for 20 hours in darkness correlated positively with the acifluorfen concentration in which they were incubated. In cucumber, the level of herbicidal damage caused by several p-nitrodiphenyl ether herbicides, a p-chlorodiphenylether herbicide, and oxadiazon correlated positively with the amount of PPIX induced to accumulate by each of the herbicide treatments. Similar results were obtained with acifluorfen-treated pigweed and velvetleaf primary leaf tissues. In cucumber, PPIX levels increased within 15 and 30 minutes after exposure of discs to 10 micromolar acifluorfen in the dark and light, respectively. These data strengthen the view that PPIX is responsible for all or a major part of the photobleaching activity of acifluorfen and related herbicides.The cause of the photobleaching activity of NDPE2 herbicides has been a continuing mystery (1,20). Recent reports (8, 19, 21, 23-26, 30, 36) phyrin synthesis strongly inhibit the activity of the herbicide. PPIX presumably acts as a photodynamic pigment, generating singlet oxygen in the presence of light and molecular oxygen. The absorption spectrum of PPIX, with peaks in the blue, green, and red spectral regions, fits the published action spectra for these herbicides (11,12,31,32). Duke and Kenyon (7) argued that the toxic oxygen species in NDPE action is singlet oxygen and Haworth and Hess (15) recently demonstrated that singlet oxygen is the active toxic oxygen species in NDPE action. After dark incubation with the herbicide, the temperature independence of the light-induced photodestruction indicates that a photodynamic dye is responsible for the activity (17). If exposed to metabolic inhibitors, such as respiratory inhibitors, during the dark incubation period, the activity of NDPE herbicides is strongly reduced upon exposure to light (9, 22). Photobleaching NDPE, cyclic imide, and oxadiazole herbicides inhibit Chl synthesis (13,34,35). Furthermore, there is good evidence that photosynthetic light reactions are not required for activity of these herbicides (6, 9, 12, 15) or accumulation ...

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Section: Discussionsupporting

confidence: 48%

Protoporphyrin IX Content Correlates with Activity of Photobleaching Herbicides

Becerril¹,

Duke²

1989

Plant Physiol.

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128

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“…Control plastids and plastids recovering from a tentoxio-treatment always contain the nuclear-coded protein polyphenol oxidase (PPO), yet affected plastids totally lacked this enzyme activity Duke 1981a, 1982, andunpublished results). In single cells of plants recovering from tentoxin treatment, some plastids lack PPO, whereas recovered plastids in the same cell contain PPO (Vaughn and Duke 1982). Tentoxin has no in vitro affect on PPO activity, however (Vaughn and Duke 1981a).…”

Section: Introductionmentioning

confidence: 99%

Tentoxin stops the processing of polyphenol oxidase into an active protein

Vaughn

Duke

1984

Physiologia Plantarum

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Previous studies in our laboratory have indicated that polyphenol oxidase (PPO), as measured by its activity, is not present in tentoxin‐treated plants. In the present study, immunochemical techniques were used as a sensitive probe of tentoxin effects on PPO. Immunocytochemistry of PPO with peroxidase‐antiperoxidase labelling techniques, revealed that in control Vicia faba L. chloroplasts, PPO was associated mainly with the thylakoids. Cytochemical staining of PPO activity using DL‐dihydroxyphenylalanine (DOPA) as substrate was also localized only on the thylakoids in the control chloroplasts. In tentoxin‐treated plants all of the immunologically‐recognizable PPO accumulated at the plastid envelope although no PPO was detected by cytochemical methods. SDS polyacrylamide gels of extracts from control and tentoxin‐treated Vicia leaves were blotted onto nitrocellulose and reacted with rabbit anti‐PPO. Secondary labelling of the blots with goat‐antirabbit IgG labelled with peroxidase revealed a 40 kdalton protein in both extracts. However, only the PPO from the control extract had DOPA oxidase activity. These data suggest that PPO accumulates in the plastid envelope membranes in tentoxin‐affected cells and that PPO in these treated plants is not processed to an active protein.

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“…All rights reserved. Duke et al (1982) and Lax and Vaughn (1986) interpreted their own observations as indicating that chlorosis does not result from inhibition of ATP synthase; however, their case was never rigorously established. In the present study, the lack of correlation found between tentoxin-induced chlorosis and inhibition of ATP synthesis in the same tobacco seedlings clearly demonstrates that one is not the direct consequence of the other.…”

Section: Discussionmentioning

confidence: 97%

Involvement of Thylakoid Overenergization in Tentoxin-Induced Chlorosis in Nicotiana spp

et al. 1997

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The purpose of this work was to clarify the mechanism of tentoxin-induced chlorosis in Nicofiana spp. seedlings. We found that chlorosis does not correlate with the inhibition of chloroplast ATP synthesis in vivo, since it occurs at tentoxin concentrations far higher than that required for the inhibition of photophosphorylation measured in the same seedlings. However, tentoxin-induced chlorosis does correlate with in vivo overenergization of thylakoids. We show that tentoxin induces overenergization in intact plants and isolated thylakoids, probably via multiple interactions with ATP synthase. Furthermore, gramicidin D, a protonophore that relieves overenergization, also relieves chlorosis. Two lines of evidence suggest that reactive oxygen species may be involved in the process of chlorosis: ascorbate, a quencher of oxygen radicals, significantly protects against chlorosis, whereas transgenic Nicofiana spp. mutants overexpressing chloroplast superoxide dismutase are partially resistant to tentoxin-induced chlorosis. It is proposed that chlorosis in developing seedlings results from overenergization of thylakoids, which leads to the generation of oxygen radicals.

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Tentoxin does not cause chlorosis in greening mung bean leaves by inhibiting photophosphorylation

Cited by 36 publications

References 44 publications

Protoporphyrin IX Content Correlates with Activity of Photobleaching Herbicides

Protoporphyrin IX Content Correlates with Activity of Photobleaching Herbicides

Tentoxin stops the processing of polyphenol oxidase into an active protein

Involvement of Thylakoid Overenergization in Tentoxin-Induced Chlorosis in Nicotiana spp

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