Tamás Kőmíves

Enhanced Inducibility of Antioxidant Systems in a Nicotiana tabacum L. Biotype Results in Acifluorfen Resistance

Abstract Levels of non-protein thiols (mostly glutathione, GSH), ascorbic acid (AA), and activities of the enzymes ascorbate peroxidase (AP), glutathione reductase (GR) and GSH S-transferase (GST) were determined in cell-free leaf extracts of acifluorfen-resistant and -sensitive tobacco plants. These parameters were examined also in detached leaves of the above plants exposed to acifluorfen stress. In leaves of untreated plants the AA content was by 40% higher in the resist ant biotype as compared to the sensitive ones, but the levels of GSH, AP, GR, and GST did not differ significantly in the two biotypes. However, in the resistant leaves stressed by acifluorfen the activity of AP readily increased while in the sensitive leaves it did not change. The levels of GSH and the activities of GR and GST markedly increased in both biotypes after acifluorfen stress, but the induction in the resistant leaves was consistently stronger in each case. The AA contents were increased equally in both biotypes. These parameters were much less affected by paraquat stress. The only significant changes were observed at low concentrations of this herbicide (8 x 10-9 м): when the thiol content and the activity of GST increased in the resistant leaves. Enhanced inducibility of antioxidant systems seems to be involved in resistance of tobacco to acifluorfen stress.

Theoretical molecular descriptors relevant to the uptake of persistent organic pollutants from soil by zucchini. A QSAR study.

The uptake of persistent organic pollutants (POPs) from soil by plants allows the development of phytoremediation protocols to rehabilitate contaminated areas. The use of diverse theoretical descriptors has been reported in the literature for developing quantitative structure-activity relationship (QSAR) models for predicting the bioconcentration factors (BCFs) of POPs in different plants. In this paper an evaluation is given on the molecular properties of POPs in terms of theoretical molecular descriptors that are relevant to the uptake and accumulation of these persistent pollutants from soil by two zucchini varieties. Statistically significant and predictive linear regression models have been developed for the BCF values of 20 polychlorinated dibenzo-p-dioxins/dibenzofurans and 14 polyhalogenated biphenyls in two zucchini varieties based on retrospective data. The relevant parameters have been selected from a set of 1660 DRAGON, 150 VolSurf, and 11 quantum chemical descriptors. The two most significant regression models, containing VolSurf, DRAGON GETAWAY, and quantum chemical descriptors, displayed the following statistical parameters: (eq 3) n = 27, R(2) = 0.940, q(2) = 0.922, SE = 0.155, F = 392.1; (eq 4) n = 27, R(2) = 0.921, q(2) = 0.898, SE = 0.161, F = 140.4. Predictive capabilities of the equations have been validated by using external validation sets. The QSAR models proposed might contribute to the development of viable soil remediation strategies.

Effects of phenylamide pesticides on the GSH-conjugation system of Phytophthora spp. fungi.

Abstract Phytophthora cactorum, Ph. cambivora, Ph. cinnamomi, Ph. citricola, Ph. cryptogea, Ph. drechsleri, Ph. infestans, Ph. megasperma, Ph. parasitica, and Ph. syringae contain GSH-conjugation systems as indicated by the presence of active GST enzyme in addition to GSH. Basal levels of both GSH and GST in the thalli of Phytophthora strains studied did not correlate with either fungal sensitivity to phenylamides (acetochlor, butachlor, metolachlor, dimethachlor, propachlor, ofurace, CGA-29212, metalaxyl, RE-26745, benalaxyl, furalaxyl, LAB-149202) or their acquired resistance to metalaxyl. Thalli of Phytophthora strains from axenic cultures ex posed to sublethal concentrations of the above pesticides contained significantly higher levels of both GSH and GST than the untreated controls. This response was independent of the sensitivity and tolerance of the strains to phenylamides. When the responses of Phytophthora strains to phenylamide chemicals were compared by means of principal component analysis, four independent components were detected account ing for 88% of the total variation. Biological properties (basal and induced levels of GST and GSH, growth intensity, degree of acquired resistance to metalaxyl, sensitivity to propiconazole and to cis-and trans-tridemorph) of the strains contributed differently to this variation. It was concluded that, in contrast to plants, sensitivity or tolerance of Phytophthora species to phenylamide pesticides is not regulated by the efficiency of the GSH-conjugation system. In addition, our data clearly indicate that the acetanilide pesticides have multiple sites of action in the Phytophthora genus.

Chemistry and Structure-Activity Relationships of Herbicide Safeners

Abstract The discovery and commercial success of safeners against thiolcarbamate herbicide injury to corn has stimulated a rapid progress and opened new possibilities for further research and development in the last decade. Compounds with new chemistry, increased efficacy, and a broader selectivity spectrum were synthesized and developed for agricultural use. Structure-activity relationship studies helped to optimize their chemical properties and to understand their biological modes of action. Several examples indicate close similarity between chemical structures possessing herbicidal and safener properties. In some cases this differentiation may be marginal, as shown in crops pretreated with low herbicide doses leading to safening effects. In other examples, however, structural optima for safening and herbicidal efficacy can be clearly differentiated.

Phytoextraction Potential of Wild Type and 35S-GSHI Transgenic Poplar Trees (Populus × Canescens) for Environmental Pollutants Herbicide Paraquat, Salt Sodium, Zinc Sulfate and Nitric Oxide In Vitro

Phytoextraction potentials of two transgenic (TR) poplar (Populus × canescens) clones TRggs11 and TRlgl6 were compared with that of wild-type (WT) following exposure to paraquat, zinc sulfate, common salt and nitric oxide (NO), using a leaf-disc system incubated for 21 days on EDTA-containing nutritive WPM media in vitro. Glutathione (GSH) contents of leaf discs of TRlgl6 and TRggs11 showed increments to 296% and 190%, respectively, compared with WT. NO exposure led to a twofold GSH content in TRlgl6, which was coupled with a significantly increased sulfate uptake when exposed to 10−3 M ZnSO4. The highest mineral contents of Na, Zn, Mn, Cu, and Mo was observed in the TRggs11 clone. Salt-induced activity of catalase enzyme increased in both TR clones significantly compared with WT under NaCl (0.75% and 1.5%) exposure. The in silico sequence analyses of gsh1 genes revealed that P. × canadensis and Salix sachalinensis show the closest sequence similarity to that of P. × canescens, which predicted an active GSH production with high phytoextraction potentials of these species with indication for their use where P. × canescens can not be grown.