Protective responses of tolerant and sensitive wheat seedlings to systemic and local zearalenone application – Electron paramagnetic resonance studies

Abstract Background Mycotoxins are among the environmental stressors whose oxidative action is currently widely studied. The aim of this paper was to investigate the response of seedling leaves to zearalenone (ZEA) applied to the leaves (directly) and to the grains (indirectly) in tolerant and sensitive wheat cultivars. Results Biochemical analyses of antioxidant activity were performed for chloroplasts and showed a similar decrease in this activity irrespective of plant sensitivity and the way of ZEA application. On the other hand, higher amounts of superoxide radical (microscopic observations) were generated in the leaves of plants grown from the grains incubated in ZEA solution and in the sensitive cultivar. Electron paramagnetic resonance (EPR) studies showed that upon ZEA treatment greater numbers of Mn - aqua complexes were formed in the leaves of the tolerant wheat cultivar than in those of the sensitive one, whereas the degradation of Fe-protein complexes occurred independently of the cultivar sensitivity. Conclusion The changes in the quantity of stable, organic radicals formed by stabilizing reactive oxygen species on biochemical macromolecules, indicated greater potential for their generation in leaf tissues subjected to foliar ZEA treatment. This suggested an important role of these radical species in protective mechanisms mainly against direct toxin action. The way the defense mechanisms were activated depended on the method of the toxin application.

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Protective Reactions of Seedlings Against Systemic and Local Zearalenone Application to Tolerant and Sensitive Wheat Varieties – Epr Studies

10.21203/rs.3.rs-307893/v1 ◽

2021 ◽

Author(s):

Apolonia Sieprawska ◽

Maria Łabanowska ◽

Magdalena Kurdziel ◽

Maria Filek ◽

Magdalena Skórka ◽

...

Keyword(s):

Defense Mechanisms ◽

Protein Complexes ◽

Protective Mechanism ◽

Wheat Varieties ◽

Paramagnetic Resonance ◽

Fe Protein ◽

Plant Sensitivity ◽

Leaf Tissues ◽

Biochemical Analyses ◽

The Way

Abstract BACKGROUNDAmong the environmental stressors, which oxidative action is currently widely studied, are mycotoxins. The aim of presented studies was to investigate the response of leaves of seedlings to zearalenone (ZEN) applied directly to leaves and to grains (indirectly) of tolerant and sensitive wheat cultivars.RESULTS Biochemical analyses of antioxidative activity were performed for chloroplasts and showed the similar decrease of this activity independently of plant sensitivity and the way of ZEN application. On the other hand, higher amounts of superoxide radicals (microscopic observation) were formed in leaves of plants grown from grains incubated in solution of ZEN and in sensitive variety. Electron paramagnetic resonance (EPR) studies showed that upon ZEN treatment larger amount of Mn - aqua complexes was formed in leaves of tolerant wheat cultivar than in those of sensitive one whereas the degradation of Fe-protein complexes occurred independently of the sensitivity of plant varieties. CONCLUSIONThe changes in the quantity of organic stable radicals, which were formed by stabilizing reactive oxygen species on biochemical macromolecules, pointed to the higher ability to their generation in leaf tissues subjected to foliar ZEN treatment indicating the important role of these radical species in protective mechanism mainly against direct toxin action. The way of activation the defense mechanisms depended on the method of applications toxin.

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Electron-paramagnetic-resonance studies on nitrogenase of Klebsiella pneumoniae. Evidence for acetylene- and ethylene-nitrogenase transient complexes

Biochemical Journal ◽

10.1042/bj1730277 ◽

1978 ◽

Vol 173 (1) ◽

pp. 277-290 ◽

Cited By ~ 37

Author(s):

D J Lowe ◽

R R Eady ◽

R N F Thorneley

Keyword(s):

Electron Paramagnetic Resonance ◽

Klebsiella Pneumoniae ◽

Binding Site ◽

Dissociation Constants ◽

Paramagnetic Resonance ◽

Fe Protein ◽

Low Concentrations ◽

Direct Binding ◽

Electron Paramagnetic ◽

Single Binding Site

Klebsiella pneumoniae nitrogenase exhibited four new electron-paramagnetic-resonance signals during turnover at 10 degrees C, pH7.4, which were assigned to intermediates present in low concentrations in the steady state. 57Fe-substituted Mo–Fe protein showed that they arose from Fe–S clusters in the Mo–Fe protein of nitrogenase. The new signals are designated: Ic, g values at 4.67, 3.37 and approx. 2.0; VI, g values at 2.125, 2.000 and 2.000; VII, g values at 5.7 and 5.4; VIII, g values at 2.092, 1.974 and 1.933. The sharp axial signal VI arises from a Fe4S4 cluster at the −1 oxidation level. This signal was only detected in the presence of ethylene and provides the first evidence of an enzyme–product complex for nitrogenase. [13C]Acetylene and [13C]ethylene provided no evidence for direct binding of this substrate and product to the Fe–S clusters giving rise to these signals. The dependence of signal intensities on acetylene concentration indicated two types of binding site, with apparent dissociation constants K less than 16 micron and K approximately 13mM. A single binding site for ethylene (K=1.5mM) was detected. A scheme is proposed for the mechanism of reduction of acetylene to ethylene and inhibition of this reaction by CO.

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