Effects of low chronic doses of ionizing radiation on antioxidant enzymes and G6PDH activities in Stipa capillata (Poaceae)

Abstract

Stipa capillata (Poaceae) seeds were harvested from a control area (displaying a gamma dose rate of 0.23 micro Sv h(-1)) (C plants) and from two contaminated areas (5.4 and 25 micro Sv h(-1)) on the Semipalatinsk nuclear test site (SNTS) in Kazakhstan. The plants were grown for 124 d in a greenhouse under controlled conditions and exposed to three different treatments: (0) control; (E) external gamma irradiation delivered by a sealed 137Cs source with a dose rate of 66 micro Sv h(-1); (E+I) E treatment combined with internal beta irradiation due to contamination by 134Cs and 85Sr via root uptake from the soil. The root uptake led to a contamination of 100 Bq g(-1) for 85Sr and 5 Bq g(-1) for 134Cs (of plant dry weight) as measured at harvest. The activity of SOD, APX, GR, POD, CAT, G6PDH, and MDHAR enzymes was measured in leaves. Under (0) treatment, all enzymes showed similar activities, except POD, which had higher activity in plants originating from contaminated areas. Treatment (E) induced an enhancement of POD, CAT, GR, SOD, and G6PDH activities in plants originating from contaminated areas. Only control plants showed any stimulation of APX activity. Treatment (E+I) had no significant effect on APX, GR, CAT, and POD activities, but MDHAR activity was significantly reduced while SOD and G6PDH activities were significantly increased. The increase occurred in plants from all origins for SOD, with a greater magnitude as a function of their origin, and it occurred only in plants from the more contaminated populations for G6PDH. This suggests that exposure to a low dose rate of ionizing radiation for almost a half century in the original environment of Stipa has led to natural selection of the most adapted genotypes characterized by an efficient induction of anti-oxidant enzyme activities, especially SOD and G6PDH, involved in plant protection against reactive oxygen species.

Gamma-ray Irradiation Induces Useful Morphological Variation in Bermudagrass

“…Similar results were reported with other species of Poaceae family (Busey, 1980;Krishna et al, 1984;Hase et al, 1999;Zaka et al, 2002). Results showed that gamma irradiation doses of 70 to 113 Gy were successful in creating bermudagrass mutants, concurring with earlier reports (Powel et al, 1974;Burton, 1985;Hanna et al, 1997b;Caetano-Anolles, 1999;Hanna and Elsner, 1999;Lu et al, 2009 Lu et al, (2009) and (Li et al, 2010), respectively.…”

Morphological and biochemical responses of Oryza sativa L. (cultivar MR219) to ion beam irradiation

“…Zaka et al (2002) demonstrated enhanced activities of peroxidase, catalase, superoxide dismutase, and other antioxidative enzymes in Stipa capillata upon treatment with an external γ irradiation.…”

“…By knowing that water radiolysis as the predominant effect of radiation in organisms which induces reactive oxygen species (ROS) formation, one can assume that plant enzymes that are involved in cell protection against oxidative stress will display similar responses under radiation stress as under other stress factors (Zaka et al, 2002). According to the research conducted by Zhang et al (2008), heavy ion obviously enhanced ROS, which is reflected by the increased production of O 2 and H 2 O 2 .…”

Identification of New Intrinsic Proteins in Arabidopsis Plasma Membrane Proteome

“…The PMassociated RPEase displays 75% identity with the cytosolic RPEase reported by Kopriva et al (100). Again, those are enzymes involved in oxidative stress responses at the membrane level in mammals, yeast, and also plants (101).…”