Effect of Furostanol Glycosides from Dioscorea deltoidea on Redox State of Alfalfa Cells In Vitro

Russian Journal of Plant Physiology - The effect of exogenous furostanol glycosides (FG) on the activity of redox enzymes was investigated in suspension cell culture of alfalfa (Medicago sativa...     

Adaptogenic action of the complex of phenylpropanoids on Dioscorea deltoidea cell culture under abiotic stress

Biological activity of the extract from golden root (Rhodiola rosea L.) roots, containing the complex of phenylpropanoids (CPP), was studied on the cell culture of yam (Dioscorea deltoidea Wall) under normal conditions and abiotic stress. The high radical-binding capacity of CPP relative to anion- and hydroxyl-radicals was observed. Having a high level of antiradical protection, CPP at a high concentration(100 μM) exerted prooxidant effect, causing a decrease in D. deltoidea cell viability and a decrease in the activities of antioxidant enzymes: superoxide dismutase, guaiacol-dependent peroxidase, and catalase, with the exception of ascorbate peroxidase. At treatment with 100 μM CPP, oxidase (prooxidant) activity of peroxidase increased by three times. The low CPP concentration (2 μM) did not induce substantial changes in the activities of tested enzymes and also a substantial increase in the oxidase activity of peroxidase. Under conditions of oxidative stress induced by paraquat and high temperature, CPP manifested adaptogenic action, increasing cell viability; however, under hyperosmotic stress, it was not efficient. CPP was most efficient at a low concentration after cell pre-incubation with it for 5 days. In this case, the amount of primary and secondary POL products increased. Shortening pre-cultivation with CPP reduced its defensive effect.     

Sensitivity of antioxidant status of plant cells to furostanol glycosides

The present paper reports that in vitro plant objects (test tube plants and cell cultures), when subjected to furostanol glycosides (FG), underwent nonspecific reactions related to antioxidant status—decrease in peroxidation of lipids (POL) and increase in guaiacol-dependent peroxidase activity. The level of superoxide increased as early as after 5 min from contact with yam (Dioscorea deltoidea Wall) cells with FG. In this case, changes in POL processes and in activities of peroxidase and aldehyde-disposing emzymes were also observed. Upon a short-term cell exposure to FG, the levels of the primary POL products (conjugated dienes) increased, and that of the secondary POL products decreased compared to the control. These events were preceded by a rise in SOD activity and in an antioxidant activity of peroxidase along with a concurrent decrease in its oxidase (prooxidant) activity. The elevated activities of aldehyde-disposing enzymes aldehyde dehydrogenase and aldehyde reductase favored the reduction in the content of the secondary products of POL. Upon a long contact of FG with cells, the effect of FG was seen only at the initial and final phases of the culture growth cycle. Namely, FG diminished the POL level at the exponential growth phase and at the end of the cell degradation phase but had no effect at the stationary phase and the onset of the degradation phase. Therefore, the treatment with FG retarded the cell culture degradation and made the fall in cell viability not so dramatic by the end of the growth cycle. Actually, by the end of the degradation phase, the viability diminished down to 40% in the control but remained at 70% in the FG-treated counterpart.     

Characteristics of Eliciting Effects of Furostanol Glycosides on Cultured Yam Cells

To unravel mechanisms of elicitor action of furostanol glycosides (FGs), the formation of superoxide anion after the addition of FGs to a suspension culture of yam (Dioscorea deltoidea Wall. ex Griseb) cells was studied. The substantial increase in superoxide level, evaluated by nitroblue tetrazolium (NBT) reduction to formazan, was found at the exponential phase of cell growth. The involvement of NADPH oxidase in the superoxide generation was revealed by means of inhibitory analysis. Diphenyliodonium chloride (DPI), the inhibitor of NADPH oxidase, compromised the action of FGs. Meanwhile, the elimination of apoplastic peroxidase did not affect the accumulation of formazan, which suggests the involvement of NADPH oxidase but not peroxidase in the superoxide generation. In addition to NBT-test, the superoxide formation was judged by changes in activity of superoxide dismutase (SOD). Exogenous FGs activated the enzyme due to the increased production of superoxide anion. In this case, DPI decreased SOD activity that conforms to the NADPH oxidase involvement in the superoxide generation. The analysis of antioxidant activity of FGs by inhibition of radicals of 2,2-diphenyl-1-picrylhydrazyl showed that FGs are weak reductants in comparison with ascorbic acid. The results of the work allow for the suggestion that, supposing a weak reducing capacity of FGs, the special feature of their exogenous action on cultured yam cells is the increase in the level of superoxide anion radical mainly produced by NADPH oxidase.     

Stress-protective effect of phenylpropanoid complex on potato plants in vitro

In order to identify factors governing the maintenance of intracellular redox homeostasis, we investigated the effect of phenylpropanoid complex (PPC) isolated from the root extract of Golden root (Rhodiola rosea L.) on the plants of potato (Solanum tuberosum L.) in vitro. It was found that plant treatment with 100 μM PPC brought about a 23% decrease in peroxidase activity in the cells of potato plants and induced a reversible increase in the level of lipid peroxidation (POL) under oxidative stress caused by paraquat. In the presence of NADH known as an oxidase substrate of peroxidases (PO), a decrease in peroxidase activity was associated with switching peroxidase over to oxidase function. This effect was accompanied by a rise in the superoxide dismutase activity by 34% and identical POL elevation. After plant pretreatment with NADPH-oxidase inhibitor diphenylene iodinum, the stimulation of these processes upon the exposure to PPC decreased by 14 and 24%, respectively. This may point to the participation of a PO/NADPH-oxidase tandem in ROS generation. Along with a decrease in peroxidase function of PO, we also observed an opposite effect: in 3 h after the exposure to PPC, its activity rose, which depended on the ability of PPC to switch peroxidase from oxidative to reductive function and back. It was found that the observed effects of PPC comprise not only the respective modulation of antioxidant enzyme activity but also direct ROS quenching. The latter effect of PPC, detected by the rate of a decrease in the level of superoxide anion considerably exceeded the effect of individual antioxidants (salidroside and ascorbic acid), whose inhibitory activity was 5 times lower than the activity of PPC.     

Effect of exogenous steroid glycosides on cultured cells of potato under oxidative stress

Low doses of furostanol glycosides (FG) were shown to elevate the activity of peroxidases (guaiacol-dependent and ascorbate peroxidases) and reduce peroxidation of lipids (POL) below the control level in the cell culture of potato (Solanum tuberosum L.). Under oxidative stress (OS) induced by paraquat, FG protected the cell culture from injury with peroxidase activity being high and POL level lower as compared with the effect of paraquat alone. FG did not affect the activity of superoxide dismutase and catalase. Dynamics of the levels of chlorophyll (a + b) and carotenoids depended not only on the effect of FG and paraquat but on the composition of cell population as well. Greenish tissue contained more pigments and was more resistant to the herbicide action than whitish tissue was. Possible reasons for the elevation of resistance of the cultured cells treated with FG under OS are discussed as well as similarity and differences in the responses of cells to the effect of inducers.     

The Effect of Paraquat and Hypothermia on Norflurason-Resistant Mutants of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> and Derived Cell Cultures

A tolerance to paraquat (PQ) of plants and cell cultures of Arabidopsis thaliana mutants, nfz18 and nfz24, obtained by chemical mutagenesis and selected by their tolerance to norflurason was demonstrated. This tolerance to PQ was manifested in less active peroxidation of lipids (POL), which was assessed by the content of thiobarbituric acid-reactive substances, and in a less degree of plant and callus damages, which was accompanied by a higher activity of superoxide dismutase and other antioxidant enzymes. A capability of norflurason-tolerant mutants to cross-adaptation toward PQ and activation of antioxidant enzymes indicate a genetically determined activation of the antioxidant systems, resulting in improved mutant tolerance to these inducers of oxidative stress. The nfz24 mutant was much more sensitive to hypothermia than wild-type plants and nfz18 mutants, which was expressed in a higher level of POL in plants and calluses and in a more rapid decrease in the suspension cell viability of this mutant. A similarity in the responses of plants and derived heterotrophic cultures to PQ and hypothermia indicates that, in these A. thaliana mutants, adaptation to these types of stresses occurs mainly at the cellular level. Possible reasons of increased sensitivity to hypothermia of the nfz24 mutant, which was more tolerant to the inducers of oxidative stress, PQ and norflurason, are discussed.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 3, 2005, pp. 421–429.Original Russian Text Copyright © 2005 by Volkova, Burgutin, Soldatova, Ezhova, Lapshin.     

Stimulation of defense responses of in vitro potato plants by treatment with steroid glycosides under abiotic stresses

To elucidate the biological activity of furastanol glycosides (FG) as elicitors and their possible action mechanisms, antiradical properties of these compounds and their influence on in vitro potato (Solanum tuberosum L.) plants under abiotic stresses were studied. FG stimulated adaptive responses related to the activation of guaiacol-dependent peroxidase and suppression of lipid peroxidation (POL). Under normal conditions, in 30 min after plant treatment with 4.5 μM FG, the level of POL was decreased, activities of guaiacol- and ascorbate-dependent peroxidases increased, and activities of catalase and superoxide dismutase (SOD) remained unchanged. In 3 days after treatment with FG, POL was decreased by 20–60% in the leaves and by 50% in the roots. Under stress conditions (paraquat treatment for 11 days or hypothermia for 28 days), FG treatment reduced the level of POL by 20–40% as compared to the effects of stressors alone, which indicates FG elicitor properties. Antiradical properties of FG toward the hydroxyl radical were manifested in the reaction of deoxy-D-ribose destruction in water medium (without homogenate) within the concentration range from 4.5 to 65 μM; the effects toward the oxygen anion radical were insignificant. It is suggested that FG influence on generation of reactive oxygen species mediates the stimulation of potato plant defense responses to environmental factors.     

Activity of Respiratory Pathways in Cultured Yam Cells under the Influence of Furostanol Glycosides

Russian Journal of Plant Physiology - The role of furostanol glycosides (FGs) in the intensification of main metabolic processes in cultured yam (Dioscorea deltoidea Wall.) cells was shown. The...