The role of hydrogen peroxide in cadmium-inhibited root growth of rice seedlings (original) (raw)
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The growth and some physiological responses of rice to Cd toxicity as affected by nitrogen form
Plant Growth Regulation, 2008
A hydroponic experiment was conducted to examine the effect of Cd stress on anti-oxidative enzyme activities at heading stage, yield components, root exudation and Cd and N uptake of rice plants grew in different N source i.e. (NH4)2SO4, NH4NO3 and Ca(NO3)2. The results show that the effect of Cd stress on all measured parameters were N source dependent. Cd stress (1 μM) caused a remarkable reduction in grain yield and shoot biomass, an increase in root exudation, glutathione content, Cd concentration and catalase (CAT) and peroxidase (POD) activities of rice plants. In the plants under the control (without Cd addition) N source had no distinctive effect on the above measured parameters, but the differences among the three N forms in these parameters became significant when plants were exposed to Cd stress. Cd stress significantly increased POD and CAT activities, and gultathione content, with Ca(NO3)2-fed plants having the greatest POD and CAT activities and lowest glutathione content, and (NH4)2SO4-fed plants being just opposite. Moreover, organic acid exudation varied also with N form for the Cd-stressed plants. In comparison with other two N forms, (NH4)2SO4,-treated plants had higher grain yield, N concentration and lower Cd concentration in plants. The current results indicated that (NH4)2SO4 is a better fertilizer for use in Cd contaminated soil.
The present study was undertaken to investigate the regulatory role of exogenous application of calcium (Ca) in enhancing the antioxidant defense and glyoxalase systems in mitigating cadmium (Cd) stress in rice. Hydroponically grown fourteen-day-old rice (Oryza sativa L. cv. BRRI dhan29) seedlings were exposed to 0.25 and 0.5 mM CdCl2 alone and in combination with 2.5 mM CaCl2 for three days. Exposure to Cd caused chlorosis, leaf rolling symptoms, and growth inhibition. A higher concentration of Cd in the growth medium resulted in higher Cd accumulation, which induced oxidative stress through overproduction of reactive oxygen species (ROS) by disrupting the antioxidant defense system. Cadmium treatment increased the methylglyoxal (MG) level. Calcium supplementation in the Cd-treated growth medium reduced Cd uptake. Application of Ca also significantly increased the (ascorbate) AsA content, increased the activities of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) in the antioxidant system, and increased the glyoxalase I (Gly I) and glyoxalase II (Gly II) activities in the glyoxalase system in rice seedlings exposed to both levels of Cd. Exogenous Ca regulates the antioxidant defense and glyoxalase systems, which reverses overproduced ROS and detoxifies methylglyoxal, which in turn reduces Cd toxicity.
Protoplasma, 2014
The present study was undertaken to examine the possible roles of calcium (Ca 2+) and silica (Si) in protection against oxidative damage due to Cd 2+ toxicity in rice (Oryza sativa L.) seedlings grown in hydroponics. Rice seedlings raised for 12 days in hydroponics containing Cd(NO 3) 2 (75 μM) showed reduced growth; increase in the level of reactive oxygen species (ROS) (O 2 • − and H 2 O 2), thiobarbituric acid reactive substances (TBARSs) and protein carbonylation; and increase in the activity of antioxidant enzymessuperoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GPX) compared to untreated controls. Exogenously added Ca 2+ (2 mM) and Si (200 μM) significantly alleviated negative effect of Cd 2+ by restoration of growth of the seedlings, suppression of Cd 2+ uptake and restoration of root plasma membrane integrity. The levels of O 2 • − , H 2 O 2 , lipid peroxidation and protein carbonyls were much lower when Ca 2+ and Si were added in the growth medium along with Cd 2+ as compared to Cd-alone-treated seedlings. Ca 2+ and Si lowered Cd-induced increase in SOD, GPX and APX activities while they elevated Cd-induced decline in CAT activity. Using histochemical staining of O 2 • − and H 2 O 2 in leaf tissues, it was further confirmed that added Ca 2+ and Si suppressed Cd-induced accumulation of O 2 • − and H 2 O 2 in the leaves. The results suggest that exogenous application of Ca 2+ and Si appears to be advantageous for rice plants in alleviating Cd 2+ toxicity effects by reducing Cd 2+ uptake, decreasing ROS production and suppressing oxidative damage. The observations indicate that Ca 2+ and Si treatments can help in reducing Cd 2+ toxicity in rice plants.
Cadmium-induced changes in antioxidant enzyme activities in rice (Oryza sativa L. cv. Dongjin)
Journal of Plant Biology, 2002
We studied how the relationship between cadmium (Cd) toxicity and oxidative stress influenced the Brm~th, photo.. synthetic efficiency, lipid peroxidation, and activity of ntimddative enzymes in the roots and leaves of rice (Oryza sat/va L Don~in). Plants were exposed to Cd for 21 d. Both seedling growth and photosynthetic efficiency decreased 8radually with increasin 8 cadmium concentrations. Upid peroxi~ increased slowly in both roots and leaves, causing oxidative stress. However, each tissue type responded differentJy to Cd concentrations with regard to the induction/ inhibition of antioxidative enzymes. The acti~/of superoxide dismutase (SOD) increased in both roots and leaves. Ascorbate peroxidase (APX) activity increased in leaves treated with up to 0~5 I~l Cd, then decreased 8radually at higher concentrations. In contrast, APX activity in roots increased and remained constant between 0.25 and 25 pM Cd. Enhanced peroxidase (POD) activity was recorded for treatments with up to 25 ~ Cd, 8radually decreasing at higher concentrations in the leaves but remaining unchan~d in the roots. Catalase (CAT) activity increased in the roots, but decreased in the leaves, whereas the activity of 81utathione reductase (GR) was enhanced in both roots and leaves, where it remained elevated at higher Cd concentrations. These results susBest that.rice seedlinss tend to cope with free radicals bqmerated by Cd throush coordinated, enhanced activities of the antioxidative enzymes involved in detoxification.
Plant and Soil, 2010
Ascorbic acid (AsA) is the most abundant antioxidant in plants and plays a role in responding to oxidative stress. It has been shown that AsA plays a role in protecting against abiotic stresses. Rice seedlings stressed with 5 μM CdCl 2 showed typical Cd toxicity (chlorosis and increase in malondialdehyde content). Rice seedlings pretreated with heat shock at 45°C (HS) or H 2 O 2 under non-HS conditions resulted in the increase in ascorbic acid (AsA) content and the AsA/ dehydroascorbate ratio in rice leaves. Exogenous application of AsA or L-galactonone-1, 4-lactone (GalL), a biosynthetic precursor of AsA, under non-HS conditions, which resulted in an increase in AsA content in leaves, enhanced subsequent Cd tolerance of rice seedlings. Pretreatment with imidazole, an inhibitor of NADPH oxidase, under HS conditions significantly decreased H 2 O 2 and AsA contents in leaves and reduced subsequent Cd tolerance of rice seedlings. We also observed that pretreatment with lycorine, which is known to inhibit the conversion of GalL to AsA, significantly inhibited HS-induced AsA accumulation in leaves and reduced HS-induced protection against subsequent Cd stress of rice stress. It appears that HS-or H 2 O 2-induced protection against subsequent Cd stress of rice seedlings is mediated through AsA. The time-course analyses of HS in rice seedlings demonstrated that the accumulation of H 2 O 2 preceded the increase in AsA. Based on the data obtained in this study, it could be concluded that the early accumulation of H 2 O 2 during HS signals the increase in AsA content, which in turn protects rice seedlings from oxidative damage caused by Cd.
Plant Growth Regulation, 2010
Effect of Cd 2? toxicity and heat stress in sensitive rice cv. DR-92 and tolerant rice cv. Bh-1 grown in North East region of India were studied in sand cultures. Increasing levels of 0-500 lM Cd 2? alone and/or heat stress showed increased activities of superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase and glutathione reductase enzymes which were associated with induced oxidative stress and altered enzyme activities. The values for SOD and POD activities were always more in cv. DR-92 whereas CAT and GR activities were higher in cv. Bh-1 in roots and shoots under Cd 2? or heat stress alone in sensitive cv. DR-92. Upon imposition of a combination of Cd 2? ? heat the activities of SOD and POD decreased significantly in root/shoot of both the sensitive and tolerant rice varieties. A nine fold increase in GR activity under combination of heat ? 100 lM Cd 2? stress in shoots of cv. Bh-1 at day 15 was noted when compared to controls. The dual stress combination of Cd 2? ? heat did not alter catalase activity in vivo in both the rice varieties. Results suggest a time-specific and varietal distribution of the antioxidant enzymes in rice plants subjected to Cd 2? and/or heat stress. Tolerant cv. Bh-1 has better survival to combined stressors like Cd 2? and heat than sensitive rice cv. DR-92 and heat stress when given in combination with Cd 2? toxicity seem to mitigate the effect of Cd 2? stress alone in rice. The study indicates individual Cd 2? toxicity and heat stress and a combination of the two stresses to have separate implications on antioxidative defense mechanism in rice plants. Among enzymes of the defense apparatus ascorbate peroxidase and glutathione reductase appear to serve as an important component for better survival of rice plants under combination of Cd 2? ? heat stress.
Plant and Soil, 2010
The role of H 2 O 2 in salicylic acid (SA)induced protection of rice leaves against subsequent Cd toxicity was investigated. SA pretreatment resulted in an increase in the contents of endogenous SA, as judged by the expression of OsWRKY45 (a SA responsive gene), and H 2 O 2 in rice leaves. Diphenyleneiodonium (DPI) and imidazole (IMD), inhibitors of NADPH oxidase, prevented SA-increased H 2 O 2 production, suggesting that NADPH oxidase is a H 2 O 2-generating enzyme in SA-pretreated rice leaves. DPI and IMD also inhibited SA-increased activities of superoxide dismutase (SOD), ascorbate peroixdase (APX), and glutathione reductase (GR) activities, but had no effect on SA-increased catalase (CAT) activity. Moreover, SA-induced protection against subsequent Cd toxicity could also be prevented by DPI and IMD. The inhibitory effect of DPI and IMD on SA-induced protection against subsequent Cd toxicity could be reversed by exogenous H 2 O 2. All these results suggested that SAinduced protection against subsequent Cd toxicity is mediated through H 2 O 2. This conclusion is supported further by the observations that exogenous H 2 O 2 application resulted in an increase in SOD, APX, and GR activities, but not CAT activity and a protection against subsequent Cd toxicity of rice leaves.
Journal of Plant Physiology, 2012
While growing in the field, plants may encounter several different forms of abiotic stress simultaneously, rather than a single stress. In this study, we investigated the effects of calcium (Ca) deficiency on cadmium (Cd) toxicity in rice seedlings. Calcium deficiency alone decreased the length, fresh and dry weight, and the Ca concentration in shoots and roots. Also, the content of glutathione (GSH), the ratio of GSH/oxidized glutathione, and the activity of catalase were lower in Ca-deficient leaves compared to control leaves. Exogenous Cd caused a decrease in the contents of chlorophyll and protein, and induced oxidative stress. Based on these stress indicators, we found that Ca deficiency enhanced Cd toxicity in rice seedlings. Under exogenous Cd application, internal Cd concentrations were higher in Ca-deficient shoots and roots than in the respective controls. Moreover, we observed that Ca deficiency decreased heat-shock (HS) induced expression of HS protein genes Oshsp17.3, Oshsp17.7, and Oshsp18.0 in leaves thereby weakening the protection system and increasing Cd stress. In conclusion, Ca deficiency enhances Cd toxicity, and Ca may be required for HS response in rice seedlings.
Journal of Plant Physiology, 2012
Hydrogen peroxide (H 2 O 2) is considered a signal molecule inducing cellular stress. Both heat shock (HS) and Cd can increase H 2 O 2 content. We investigated the involvement of H 2 O 2 in HS-and Cd-mediated changes in the expression of ascorbate peroxidase (APX) and glutathione reductase (GR) in leaves of rice seedlings. HS treatment increased the content of H 2 O 2 before it increased activities of APX and GR in rice leaves. Moreover, HS-induced H 2 O 2 production and APX and GR activities could be counteracted by the NADPH oxidase inhibitors dipehenylene iodonium (DPI) and imidazole (IMD). HS-induced OsAPX2 gene expression was associated with HS-induced APX activity but was not regulated by H 2 O 2. Cd-increased H 2 O 2 content and APX and GR activities were lower with than without HS. Cd did not increase the expression of OsAPX and OsGR without HS treatment. Cd increased H 2 O 2 content by Cd before it increased APX and GR activities without HS. Treatment with DPI and IMD effectively inhibited Cd-induced H 2 O 2 production and APX and GR activities. Moreover, the effects of DPI and IMD could be rescued with H 2 O 2 treatment. H 2 O 2 may be involved in the regulation of HS-and Cd-increased APX and GR activities in leaves of rice seedlings.
Cadmium (Cd)-sensitive and -tolerant rice cultivars were used to study the role of reduced glutathione (GSH) in Cd-induced toxicity. Cd toxicity of rice seedlings was evaluated by the decrease in chlorophyll content and the increase in malondialehyde content in the second leaves. On treatment with 5 μM CdCl 2 for 6 days, the content of GSH decreased in the second leaves of Cd-sensitive cultivar (cv. Taichung Native 1; TN1) but not in the Cd-tolerant cultivar (cv. Tainung 67; TNG67). Moreover, Cd-reduced GSH content was prior to Cd-decreased chlorophyll content in the second leaves of TN1 seedlings. Pretreatment of TN1 seedlings with 1 mM GSH for 6 h resulted in an increase in the contents of GSH and ascorbate (AsA) and the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) in the second leaves of TN1 seedlings. Rice seedlings of TN1 pretreated with GSH were observed to reduce the subsequent Cd-induced toxicity. Exogenous application of the buthionine sulfoximine (BSO), a specific inhibitor of GSH biosynthesis, reduced the contents of GSH and AsA, the activities of GR and APX, and decreased Cd tolerance of TNG67 seedlings.