Oxidative Stress Affects [alpha]- Tocopherol Content in Soybean Embryonic Axes upon Imbibition and following Germination

Abstract

The set of intracellular or extracellular conditions that leads to an increase in the steady-state concentration of reactive oxygen species such as superoxide radical (O2-), hydrogen peroxide (H202), hydroxyl radical (. OH), singlet oxygen ('O2), lipid hydroperoxides, or related species is termed oxidative stress (Chance et al., 1979). Physiologically, metabolic activity in conjunction with the structural organization of the cell is able to minimize adverse effects of oxidative stress. Susceptibility to oxidative stress is a function of the overall balance between the factors that increase oxidant generation and those substances that exhibit antioxidant capability.Tocopherols (with vitamin E activity) are critica1 antioxidants in eukaryotic organisms, ubiquitous in higher plants, and essential nutrients for animals (Tramontano et al., 1992). However, little is known about the endogenous content in plant tissues. aT (5,7,8-trimethyltocol) is the predominant tocopherol in vegetative tissue (Newton and Pennock, 1971; Hardy et al., 1991). Early studies in which two-dimensional chromatography was used showed that aT was predominant in young maize, wheat, barley, and peas and that other tocopherols appeared as the plant aged (Tramontano et al.,Supported by the Intemational Foundation for Science (Sweden), FundaciÓn Antorchas, and the University of Buenos Aires. S.P. and C.G.F. are Career Investigators from Consejo Nacional de Investigaciones Científicas y Técnicas de Ia República Argentina.* Corresponding author; fax 54-1-962-5341. 949 1992). It was reported that aT concentration increases with age in spruce seedlings (Franzen et al., 1991a(Franzen et al., , 1991b and in leaves of soybean and pinto beans (Tramontano et al., 1992).The content of flavonoids, which can also act as antioxidants (Fraga et al., 1987), increased in mesophyll cells of Vicia fuba incubated in the presence of methyl viologen (paraquat) (Takahama, 1989) Takahama et al., 1989) in the dark. It has been suggested that an increase in the steady-state concentrations of 02-and/or H202 in the cells is accompanied by increases in the leve1 of flavonoids, presumably due to the induction of their synthesis (Takahama et al., 1989).or H 2 0 2 (To study whether oxidative stress was able to affect antioxidant defenses, aT content was measured at the onset of germination of soybean embryonic axes. The effect of paraquat imbibition, increase in Fe concentration in the incubation medium, and aging were analyzed in terms of oxidative stress, assessed by a fluorescence technique (Bass et al., 1983; Szejda et al., 1984; Scott et al., 1988; LeBel et al., 1990) and aT content. MATERIALS AND METHODS Plant MaterialSoybean seeds (Glycine mux var Hood) were incubated for 2 to 48 h in the dark at 26OC over water-saturated filter paper. The composition of 1 L of the modified Steinberg nutrient solution (Tiffin, 1966) was: 51 mg of Ca, 6.6 mg of Mg, 59 mg of N, 3 mg of P, 44 mg of K, 5 mg of S, 0.13 mg of Mn, 0.07 mg of B, 0.04 mg of Zn, 0.01 mg of Cu, 0.01 mg of ...

Release of Reactive Oxygen Intermediates (Superoxide Radicals, Hydrogen Peroxide, and Hydroxyl Radicals) and Peroxidase in Germinating Radish Seeds Controlled by Light, Gibberellin, and Abscisic Acid

“…The polar, reactive DCFH liberated intracellularly, as well as the DCF produced in the reaction with ROI, remain trapped in the cytoplasm (Bass et al, 1983). The reaction can be inhibited by catalase and ⅐ OH scavengers, indicating that H 2 O 2 and ⅐ OH can participate in the oxidation of DCFH (Bass et al, 1983;Cathcart et al, 1983;Scott et al, 1988;Simontacchi et al, 1993). We have adapted this procedure for the in vivo measurement of extraprotoplasmic ROI by preparing the substrate DCFH from DCFH-diacetate with esterase in the reaction mixture before adding the plant material to be analyzed.…”

“…Much less attention has been paid to those physiological conditions where ROI are actively produced for serving a useful function within the seed or in its interaction with the environment. There are a few reports from work with soybean suggesting that seed germination is accompanied by a generation of ROI in the embryo axis as well as in the seed coat, which can be measured with suitable indicator reactions in situ or in the surrounding medium (Boveris et al, 1984;Puntarulo et al, 1988;1991;Simontacchi et al, 1993;Gidrol et al, 1994;Khan et al, 1996). As seed germination represents a developmental period most sensitive for pathogen infection, it is conceivable that ROI release in this stage plays an important role in protecting the emerging embryo against invasion by parasitic organisms.…”

Accumulation of tocopherols and tocotrienols during seed development of grape (Vitis vinifera L. cv. Albert Lavallée)

“…During the early stages of germination the concentration of tocopherol, mostly the α-form, increases in developing primary leaves of monocotyledonous grasses like Triticum vulgare L. [11], Triticum aestivum L., Hordeum vulgare L., Secale cereale L. and Oryza sativa L. (Horvath, unpublished results). In dicots like soybean and pinto beans, an initial increase in α-tocopherol levels seen at the onset of germination was found to be followed by a decline [23,32]. Immature chloroplasts isolated from 2-week-old Spinacia oleracea L. seedlings demonstrate a high tocopherol biosynthetic potential [29].…”

Rice MADS3 Regulates ROS Homeostasis during Late Anther Development

“…Tapetal PCD is initiated from stage 8 of anther development in rice , but whether ROS plays a role in tapetal development remains unknown. To examine whether changes in ROS levels are associated with the mutant phenotype in mads3-4, we measured ROS levels in both wild-type and mads3-4 anthers using 2',7'-dichlorofluorescin (DCFH), which can be oxidized by ROS to the highly fluorescent 2',7'-dichlorofluorescein (Simontacchi et al, 1993;Schopfer et al, 2001). Low ROS levels were observed in both wild-type and mads3-4 anthers before stage 8, while fluorescent levels increased in wild-type and mads3-4 anthers at stage 8 ( Figure 6A) and reached a higher level at stage 9.…”