Comparative biochemical and RAPD analysis in two varieties of rice (Oryza sativa) under arsenic stress by using various biomarkers

Deciphering the regulation of transporters and mitogen-activated protein kinase in arsenic and iron exposed rice

This study investigates the influence of arsenic (As) and iron (Fe) on the molecular aspects of rice plants. The mRNA-abundance of As (OsLsi, OsPHT, OsNRAMP1, OsABCC1) and Fe (OsIRT, OsNRAMP1, OsYSL, OsFRDL1, OsVIT2, OsSAMS1, OsNAS, OsNAAT1, OsDMAS1, OsTOM1, OsFER) related genes has been observed in 12-d old As and Fe impacted rice varieties. Analyses of phytosiderophores synthesis and Fe-uptake genes affirm the existence of specialized Fe-uptake strategies in rice with varieties PB-1 and Varsha favouring strategy I and II, respectively. Expression of OsNAS3, OsVIT2, OsFER and OsABCC1 indicated PB-1's tolerance towards Fe and As. Analysis of mitogen-activated protein kinase cascade members (OsMKK3, OsMKK4, OsMKK6, OsMPK3, OsMPK4, OsMPK7, and OsMPK14) revealed their importance in the fine adjustment of As/Fe in the rice system. A conditional network map was generated based on the gene expression pattern that unfolded the differential dynamics of both rice varieties. The mating based split ubiquitin system determined the interaction of OsIRT1 with OsMPK3, and OsLsi1 with both OsMPK3 and OsMPK4. In-silico tools also confirmed the binding affinities of OsARM1 with OsLsi1, OsMPK3 and OsMPK4, and of OsIDEF1/OsIRO2 with OsIRT1 and OsMPK3, supporting our hypothesis that OsARM1, OsIDEF1, OsIRO2 were active in the connections discovered by mbSUS.

The Molecular Mechanism of the Response of Rice to Arsenic Stress and Effective Strategies to Reduce the Accumulation of Arsenic in Grain

Rice (Oryza sativa L.) is the staple food for more than 50% of the world's population. Owing to its growth characteristics, rice has more than 10-fold the ability to enrich the carcinogen arsenic (As) than other crops, which seriously affects world food security. The consumption of rice is one of the primary ways for humans to intake As, and it endangers human health. Effective measures to control As pollution need to be studied and promoted. Currently, there have been many studies on reducing the accumulation of As in rice. They are generally divided into agronomic practices and biotechnological approaches, but simultaneously, the problem of using the same measures to obtain the opposite results may be due to the different species of As or soil environments. There is a lack of systematic discussion on measures to reduce As in rice based on its mechanism of action. Therefore, an in-depth understanding of the molecular mechanism of the accumulation of As in rice could result in accurate measures to reduce the content of As based on local conditions. Different species of As have different toxicity and metabolic pathways. This review comprehensively summarizes and reviews the molecular mechanisms of toxicity, absorption, transport and redistribution of different species of As in rice in recent years, and the agronomic measures to effectively reduce the accumulation of As in rice and the genetic resources that can be used to breed for rice that only accumulates low levels of As. The goal of this review is to provide theoretical support for the prevention and control of As pollution in rice, facilitate the creation of new types of germplasm aiming to develop without arsenic accumulation or within an acceptable limit to prevent the health consequences associated with heavy metal As as described here.

Iron reprogrammes the root system architecture by regulating OsWRKY71 in arsenic-stressed rice (Oryza sativa L.)

Iron (Fe) has been critically reported to act as a signal that can be interpreted to activate the molecular mechanisms involved in root developmental processes. Arsenic (As) is a well-known metalloid that restricts the growth and productivity of rice plants by altering their root architecture. Since root system architecture (RSA) under As stress targets WRKY transcription factors (TFs) and their interaction partners, the current investigation was carried out to better understand the Fe-dependent dynamics of RSA and its participation in this process. Here, we analyzed the effects of As and Fe (alone or in combination) exposed to hydroponically grown rice roots of 12-day-old plants. Our research showed that adding As to Fe changed how OsWRKY71 was expressed and improved the morphology and anatomy of the rice roots in Ratna and Lalat varieties. As + Fe treatment also manifested the biochemical parameters. OsWRKY71, revealed an up-regulation (Fe alone and As + Fe conditions) and down-regulation (As stress) in both varieties, in comparison to the controls. The improved root anatomy and root oxidizability indicated the enhanced capability of Lalat over the Ratna variety to induce OsWRKY71 for the better development of RSA during As + Fe treatment. Further, OsWRKY71 has revealed the presence of gibberellin-responsive cis-regulatory elements (GAREs) in its promoter region, indicating the involvement of OsWRKY71 in the gibberellin pathway. Molecular docking revealed that OsWRKY71 and SLR1 (DELLA protein) interact positively, which supports the hypothesis that Fe alters RSA by regulating OsWRKY71 through the gibberellin pathway in As-stressed rice.

Phytotoxicity and genotoxicity study of reactive red 141 dye on mung bean (Vigna radiata (L.) Wilczek) seedlings

BACKGROUND

Reactive Red (RR) 141 dye is widely used in various industrial applications, but its environmental impact remains a growing concern. In this study, the phytotoxic and genotoxic effects of RR 141 dye on mung bean seedlings (Vigna radiata (L.) Wilczek) were investigated, serving as a model for potential harm to plant systems.

METHODS AND RESULTS

Short-term (14 days) and long-term (60 days) experiments in paddy soil pot culture exposed mung bean seedlings to RR 141 dye. The dye delayed germination and hindered growth, significantly reducing germination percentage and seedling vigor index (SVI) at concentrations of 50 and 100 ml/L. In short-term exposure, plumule and radical lengths dose-dependently decreased, while long-term exposure affected plant length and grain weight, leaving pod-related parameters unaffected. To evaluate genotoxicity, high annealing temperature-random amplified polymorphic DNA (HAT-RAPD) analysis was employed with five RAPD primers having 58-75% GC content. It detected polymorphic band patterns, generating 116 bands (433 to 2857 bp) in plant leaves exposed to the dye. Polymorphisms indicated the appearance/disappearance of DNA bands in both concentrations, with decreased genomic template stability (GTS) values suggesting DNA damage and mutation.

CONCLUSION

These findings demonstrate that RR 141 dye has a significant impact on genomic template stability (GTS) and exhibits phytotoxic and genotoxic responses in mung bean seedlings. This research underscores the potential of RR 141 dye to act as a harmful agent within plant model systems, highlighting the need for further assessment of its environmental implications.

Polyamine, 1,3-diaminopropane, regulates defence responses on growth, gas exchange, PSII photochemistry and antioxidant system in wheat under arsenic toxicity

The metalloid arsenic (As) is extremely hazardous to all living organisms, including plants. Pollution with As is very detrimental to the photosynthetic machinery, cell division, energy generation, and redox status. In order to cope with stress, the use of growth regulators such as polyamines (PA), which strengthen the antioxidant system of plants, has become widespread in recent years. PAs can modulate the plant growth through basic mechanisms common to all living organisms, such as membrane stabilization, free radical scavenging, deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and protein synthesis, enzyme activities and second messengers. However, the effect of 1,3- diaminopropane (Dap), which is a product of PA catabolism, is not clear enough in plants exposed to As toxicity. In the current study, the different concentrations of 1,3-diaminopropane (0.1, 0.5 and 1 mM Dap) were hydroponically treated to wheat (Triticum aestivum) under arsenic stress (100 μM As) and then relative growth rate (RGR), relative water content (RWC), proline content (Pro), gas exchange parameters, PSII photochemistry, chlorophyll fluorescence kinetics, antioxidant activity and lipid peroxidation were assessed. RGR, RWC, osmotic potential and Pro content decreased in As-applied plants. The inhibition of these parameters could be reversed by Dap treatments. Besides, Dap applications mitigated the As toxicity-induced suppression on chlorophyll fluorescence (Fv/Fm, Fv/Fo and Fo/Fm) and the performance of PSII photochemistry. As impaired the balance on antioxidant capacity by decreased activities of catalase (CAT), peroxidase (POX), glutathione peroxidase (GPX), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and the contents of ascorbate (AsA) and glutathione (GSH) and then lipid peroxidation (TBARS content) increased. In the presence of Dap under As stress, the plants exhibited an increase in superoxide dismutase (SOD), POX, and GPX. Dap treatments contributed to the maintenance of cellular redox state (AsA/DHA and GSH/GSSG) by regulating the activities/contents of enzyme/non-enzyme involved in the AsA-GSH cycle. After Dap applications against stress, ROS accumulation (H2O2 content) and lipid peroxidation (TBARS) were effectively reduced. The findings showed that by eliminating As-induced oxidative damage and protecting the biochemical processes of photosynthesis, Dap treatments have a substantial potential to give resistance to wheat.

Arsenic and cadmium induced macronutrient deficiencies trigger contrasting gene expression changes in rice

Arsenic (As) and cadmium (Cd), two major carcinogenic heavy metals, enters into human food chain by the consumption of rice or rice-based food products. Both As and Cd disturb plant-nutrient homeostasis and hence, reduces plant growth and crop productivity. In the present study, As/Cd modulated responses were studied in non-basmati (IR-64) and basmati (PB-1) rice varieties, at physiological, biochemical and transcriptional levels. At the seedling stage, PB-1 was found more sensitive than IR-64, in terms of root biomass; however, their shoot phenotype was comparable under As and Cd stress conditions. The ionomic data revealed significant nutrient deficiencies in As/Cd treated-roots. The principal component analysis identified NH₄⁺ as As-associated key macronutrient; while, NH₄⁺/NO₃^- and K⁺ was majorly associated with Cd mediated response, in both IR-64 and PB-1. Using a panel of 21 transporter gene expression, the extent of nutritional deficiency was ranked in the order of PB-1(As)<IR-64(As)<PB-1(Cd)<IR-64(Cd). A feed-forward model is proposed to explain nutrient deficiency induced de-regulation of gene expression, as observed under Cd-treated IR-64 plants, which was also validated at the level of sulphur metabolism related enzymes. Using urea supplementation, as nitrogen-fertilizer, significant mitigation was observed under As stress, as indicated by 1.018- and 0.794-fold increase in shoot biomass in IR-64 and PB-1, respectively compared to that of control. However, no significant amelioration was observed in response to supplementation of urea under Cd or potassium under As/Cd stress conditions. Thus, the study pinpointed the relative significance of various macronutrients in regulating As- and Cd-tolerance and will help in designing suitable strategies for mitigating As and/or Cd stress conditions.

Elimination of BBTV via a systemic in vitro electrotherapy approach

Banana bunchy top virus (BBTV) is the most destructive etiological agent limiting banana cultivation areas globally. This study attempted BBTV elimination by traditional shoot-tip culture (control) and alternative shoot-tip + electrotherapy (treated) techniques. Shoot-tip culture from Musa acuminata cv. 'Grand Naine' infected sources were exposed to 100 mA electric current for different time intervals (20-60 min). Virus indexing (via PCR) and genetic fidelity (by ISSR assay) from the cultures were tested, alongside the physio-biochemical parameters. Exposure of electric current for less than 50 min was ineffective for BBTV elimination. Still, a rise in the duration from 50 min or more led to eradicating the virus from some explants. Elimination of BBTV was complete from 100 % of explants exposed to 100 mA for 60 min, as confirmed by lack of BBTV detection even at six months after acclimatization. In the control treatment, the maximum efficiency of BBTV elimination was 28 % after eight subcultures. On the other hand, improved survival % was observed in the treated culture. Moreover, homogenous ISSR patterns were there between the treated and the mother plant and similar physio-biochemical activities were seen in electro-exposed cultures and healthy ones. Thus, the study reports complete BBTV-elimination from banana with international compliances, for the first time, via electrotherapy while maintaining genomic template and biochemical stability.

Uptake of hematite nanoparticles in maize and their role in cell cycle dynamics, PCNA expression and mitigation of cadmium stress

Cadmium toxicity is considered a major threat to several crops worldwide. Hematite nanoparticles (NPs), due to their small size and large specific surface area, could be applied as an adsorbent for toxic heavy metals in soil. Also, they serve as an efficient nano-fertilizer, promoting Fe availability and biomass production in plants, thus enabling Cd²⁺ -induced stress tolerance. The phytotoxicity of five different concentrations of hematite NPs, ranging from 500 to 8,000 mg·kg^-1 , and Cd²⁺ concentrations (110 or 130 mg·kg^-1 Cd²⁺ ) alone or combined with 500 mg·kg^-1 NPs was evaluated in maize. The changes in fresh weight, element analysis, cell cycle regulation, DNA banding patterns and proliferating cell nuclear antigen (PCNA) expression were used as biomarkers. The results revealed that increased fresh weight and fewest polymorphic DNA bands were detectable after treatment with 500 mg·kg^-1 NPs. However, at 8,000 mg·kg^-1 NPs, PCNA expression increased significantly, which resulted in cell cycle arrest at the G1/S checkpoint in roots. Significant reductions in fresh weight, altered nutrient profiles and cell cycle perturbations are considered symptoms of Cd²⁺ toxicity in maize. Conversely, amending 500 mg·kg^-1 NPs with 130 mg·kg^-1 Cd²⁺ increased fresh weight, Fe concentration and genomic template stability, while reducing Cd²⁺ uptake and PCNA1 expression. Overall, 8,000 mg·kg^-1 hematite NPs interfered with the cellular homeostatic balance of maize, resulting in a cascade of genotoxic events, leading to growth inhibition. Although 500 mg·kg^-1 hematite NPs alleviated Cd²⁺ -induced DNA damage to a certain extent, their impact on cell cycle progression requires further verification.

Recent progress on the heavy metals ameliorating potential of engineered nanomaterials in rice paddy: a comprehensive outlook on global food safety with nanotoxicitiy issues

Soil contamination with toxic heavy metals (HMs) poses a serious threat to global food safety, soil ecosystem and human health. The rapid industrialization, urbanization and extensive application of agrochemicals on arable land have led to paddy soil pollution worldwide. Rice plants easily accumulate toxic HMs from contaminated agricultural soils, which ultimately accumulated in grains and enters the food chain. Although, physical and chemical remediation techniques have been used for the treatment of HMs-contaminated soils, however, they also have many drawbacks, such as toxicity, capital investment and environmental-associated hazards. Recently, engineered nanomaterials (ENMs) have gained substantial attention owing to their promising environmental remediation applications. Numerous studies have revealed the use of ENMs for reclamation of toxic HMs from contaminated environment. This review mainly focuses on HMs toxicity in paddy soils along with potential health risks to humans. It also provides a critical outlook on the recent advances and future perspectives of nanoremediation strategies. Additionally, we will also propose the interacting mechanism of HMs-ENMs to counteract metal-associated phytotoxicities in rice plants to achieve global food security and environmental safety.

Arsenic uptake and toxicity in wheat (Triticum aestivum L.): A review of multi-omics approaches to identify tolerance mechanisms

Arsenic (As) due to its widespread has become a primary concern for sustainable food production, especially in Southeast Asian countries. In that context, the present review presented a comprehensive detail of the available literature marking an assortment of As-induced impacts on wheat. The conclusive findings of past research suggest that As tends to grossly affect the germination, elongation, biomass, grain yield, and induce oxidative stress. Several human studies are suggestive of higher cancer risks (>1 × 10^-6) due to the ingestion of wheat grains. However, the body of proof is limited and the scarcity of information limited understanding about tolerance mechanism in wheat against As. Therefore, the paper provided a reference from tolerance mechanism based studies in other crops like rice and maize. The generated knowledge of arsenomics would pave the way for plant breeders to develop resistant varieties for As to ensure sustainable food production.

Main nitric oxide (NO) hallmarks to relieve arsenic stress in higher plants

Arsenic (As) is a toxic metalloid that adversely affects plant growth, and poses severe risks to human health. It induces disturbance to many physiological and metabolic pathways such as nutrient, water and redox imbalance, abnormal photosynthesis and ATP synthesis and loss of membrane integrity. Nitric oxide (NO) is a free radical molecule endogenously generated in plant cells which has signalling properties. Under As-stress, the endogenous NO metabolism is significantly affected in a clear connection with the metabolism of reactive oxygen species (ROS) triggering nitro-oxidative stress. However, the exogenous NO application provides beneficial effects under As-stress conditions which can relieve oxidative damages by stimulating the antioxidant systems, regulation of the expression of the transporter and other defence-related genes, modification of root cell wall composition or the biosynthesis of enriched sulfur compounds such phytochelatins (PCs). This review aims to provide up-to-date information on the key NO hallmarks to relieve As-stress in higher plants. Furthermore, it will be analyzed the diverse genetic engineering techniques to increase the endogenous NO content which could open new biotechnological applications, especially in crops under arsenic stress.

Plant Nitric Oxide Signaling under Drought Stress

Water deficit caused by drought is a significant threat to crop growth and production. Nitric oxide (NO), a water- and lipid-soluble free radical, plays an important role in cytoprotection. Apart from a few studies supporting the role of NO in drought responses, little is known about this pivotal molecular amendment in the regulation of abiotic stress signaling. In this review, we highlight the knowledge gaps in NO roles under drought stress and the technical challenges underlying NO detection and measurements, and we provide recommendations regarding potential avenues for future investigation. The modulation of NO production to alleviate abiotic stress disturbances in higher plants highlights the potential of genetic manipulation to influence NO metabolism as a tool with which plant fitness can be improved under adverse growth conditions.

Assessment of cyto- and genotoxic effects of Cesium-133 in Vicia faba using single-cell gel electrophoresis and random amplified polymorphic DNA assays

The aim of this study was to evaluate the ecotoxic effect of high concentration cesium (Cs) exposure on plant root growth and its toxicological mechanism. The radicle of broad bean (Vicia faba) was selected as experimental material. The cytotoxic and genotoxic effects of plants exposed to different Cs levels (0.19-1.5 mM) for 48 h were evaluated using scanning electron microscopy (SEM), X-ray fluorescence (XRF) analysis, single-cell gel electrophoresis (SCGE) and random amplified polymorphic DNA (RAPD) assays. The results showed that radicle elongation decreased clearly after 48 h of exposure treatment with different concentrations of Cs solution. The root cell structure was obviously damaged in the Cs treatment groups (0.19-1.5 mM). At a Cs concentration of 1.5 mM, the percentages of viable non-apoptotic cells, viable apoptotic cells, non-viable apoptotic cells, and non-viable cells were 40.09%, 20.67%, 28.73%, and 10.52%, respectively. SCGE showed DNA damage in radicle cells 48 h after Cs exposure. Compared with the control group, the percentage of tail DNA in Cs exposed group (0.38-1.5 mM) increased by 0.56-1.12 times (P < 0.05). RAPD results showed that the genomic stability of V. faba radicles decreased by 4.44%-15.56%. This study confirmed that high concentration Cs exposure had cytotoxicity and genotoxicity effects on plants.

Photosynthetic activity and RAPD profile of polyethylene glycol treated B. juncea L. under nitric oxide and abscisic acid application

The involvement of two extremely important signalling molecules, nitric oxide (NO) and abscisic acid (ABA) has been employed by plants to facilitate the adaptive/tolerate response during stressful conditions. However, the interactive role of exogenously applied NO and ABA is very less studied at physiological, biochemical and molecular levels. The present study therefore, evaluated the effects of individual and simultaneous addition of exogenous NO donor SNP (100μM) and ABA (10μM) on photosynthesis, Calvin-Benson cycle enzymes, S-assimilation enzymes, oxidative stress components, and genotoxicity in Brassica juncea cv. Varuna, exposed to polyethylene glycol (PEG)-induced drought stress. Results showed that a loss induced by PEG was significantly surpassed by the application of NO or/and ABA with PEG for chlorophyll content, net photosynthestic rate (Pn), internal CO₂ concentration (Ci), stomatal conductance (gs), transpiration rate (Tr), maximum photosystem II (PSII) efficiency (Fv/Fm), actual PSII efficiency (ΦPSII), intrinsic PSII efficiency (Fv´/ Fm´), photochemical quenching (qP), non-photochemical quenching (NPQ), electron transport chain (ETC), ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCo), glyceraldehyde-3-phosphate dehydrogenase (GapDH), phosphoribulokinase (PRK), ATP-sulfurylase (ATP-S), and serine acetyltransferase (SAT) activities. The genomic template stability (GTS) (measured as changes in RAPD profiles) was significantly affected and showed varying degrees of DNA polymorphism, highest in PEG and lowest in PEG + NO and PEG + NO + ABA. Furthermore, the changes in RAPD profiles showed consistent results when compared with various photosynthetic and oxidative parameters. Altogether, this study concluded that supplementation of individual NO and together with ABA was more effective than individual ABA in alleviating PEG-induced drought stress in B. juncea L. seedlings.

Facets of iron in arsenic exposed Oryza sativa varieties: A manifestation of plant's adjustment at morpho-biochemical and enzymatic levels☆

Rice consumption is one of the primary sources of arsenic (As) exposure as the grains contain relatively higher concentration of inorganic As. Abundant studies on the ability of iron (Fe) plaque in hampering As uptake by plants has been reported earlier. However, little is known about its role in the mitigation of As mediated oxidative damage in rice plants. The present study highlights the effect of As and Fe co-supplementation on growth response, oxidative stress, Fe uptake related enzymes and nutrient status in rice varieties. Eight different Indica rice varieties were screened and finally four varieties (Varsha, Jaya, PB-1 and IR-64) were selected for detailed investigations. Improved germination and chlorophyll/protein levels during As+Fe co-exposure indicate healthier plants than As(III) treated ones. Interestingly Fe was found act both as an antagonist and also as a synergist of As treatments. It acted by reducing As translocation and improving the nutritional levels and enhancing the oxidative stress. Fe uptake related enzymes (nitrite reductase and ferric chelate reductase) and phytosiderophores analysis revealed that Fe supplementation can reduce its deficiency in rice plants. Morpho-biochemical, oxidative stress and nutrient analysis symbolizes higher tolerance of PB-1 towards As, while Varsha being most sensitive, efficiently combated the As(III) stress in the presence of Fe.

Selenium amelioration of arsenic toxicity in rice shows genotypic variation: A transcriptomic and biochemical analysis

The toxic metalloid arsenic (As) is consumed mostly through contaminated rice. Therefore, reducing its accumulation and maintaining nutrient homeostasis in crop plants are imperative to ensure food safety. However, there is a dearth of information on the interrelationship between nutrient homeostasis and the regulatory mechanisms of arsenic-selenium (As-Se) interactive pathways responsible for stress tolerance. In the present study, experiments were conducted in hydroponically grown 12-day-old seedlings of rice (Oryza sativa L.) varieties (Pusa Basmati1 and IR64) treated with arsenite (AsIII) (150 μM), selenium (SeVI) (20 μM), and As + Se. It was observed that selenium supplementation ameliorated As toxicity by reducing its accumulation and retrieving As-induced nutrient deficiency. Significant decrease in As accumulation, H₂O₂ content, and fluorescent intensity of nitric oxide (NO), reactive oxygen species (ROS), and superoxide radical (O₂^.-) along with cell death with Se supplementation in both rice varieties demonstrated the protective role of Se as a probable ROS quencher. Addition of Se increased the enzyme activities of thiol metabolism and induced differential transcript accumulation patterns of sulfur-related genes. Nutrient level positively correlated with the differential expression pattern of NPK-related genes that play roles in metabolism and nutrient availability in both varieties. Though Pusa Basmati1 (PB1) showed higher tolerance to As, IR64 overcomes As toxicity more efficiently than PB1 in the presence of Se, which highlights that IR64 is a better performer in the presence of Se. Overall, this study provides novel insight into the role of Se in As-stressed rice genotypes through alteration of nutrient transporters and thiol-related genes.

Lead Tolerance and its Accumulation by a Tree Legume: Dalbergia sissoo DC

Dalbergia sissoo DC, a leguminous tropical timber tree has been investigated against the Pb toxicity; under the Pb-stress, plant's morphology, biochemical parameters and genomic template stability (GTS) screened in vitro. At the optimum Pb tolerance level (150 mg L^-1), plant's defense mechanism-superoxide dismutase, catalase, ascorbate peroxidases and proline could trigger to achieve optimum vegetative growth with minimum fluctuations of the GTS. Further, D. sissoo roots could accumulate 2399.8 ± 16 mg kg^-1 Pb. Scanning electron microscopy and energy dispersive X-ray spectrometer analysis also revealed the deposition of Pb in root tissues. In a 1 year pot experiment with Pb-contaminated soil, the plants exhibited normal growth, and Pb accumulation significantly enhanced by the amalgamation of citric acid in the soil. Thus, the tree may prove as a potential candidate for Pb phytostabilization.

Analysis and assessment of heavy metals in soils around the industrial areas in Mettur, Tamilnadu, India

Industrialization and extraction of natural resources have resulted in large-scale environmental contamination and pollution. We have collected the soil samples from five different industrial areas of Mettur (Chemplast Sanmar Limited, SIDCO-1, SIDCO-2, SIDCO-3, thermal power plant), Salem district, Tamil Nadu, India, and estimated the physical properties (pH, EC, and alkalinity), chemical properties (major and minor elements), and heavy metal analysis. Thermal power plant soil sample showed higher pH 5.01, EC 29.33 μmhos/cm compared with rest of the samples. Acidic nature of the soil samples near thermal power plant was due to the effect of ash disposal. The high electrical conductivity is due to the disposal of soluble electrolytes and deposition of dust particles released from Thermal Power Plant. Alkalinity of the SIDCO-2 soil (410 ppm) was higher than that of rest of the soil samples. Soil samples show higher concentrations of chloride (10,400 ppm) from thermal power plant when compared with soil sample collected from all 15 sample areas. It was found that heavy metal concentrations lie in the following ranges: Cu (3.780-86.360 ppm) > Pb (0.018-1.710 ppm) > As (0.053-0.342 ppm) in Mettur area. The maximum concentration of copper (Cu) found in SIDCO-1 (86.360 ppm) was due to electroplating industry, smelting and refining, mining, and biosolids. Maximum concentrations of arsenic (As) recorded (0.342 ppm) in thermal Power plant was due to ash disposal from the coal-fired thermal power plant. And maximum concentrations of lead (Pb) (1.710 ppm) in Chemplast area are due to the effluent discharge of manufacturing units like PVC resins, chlorochemicals, and piping systems in Chemplast which are main source of heavy metal pollutants. Therefore, major mining and smelting of metalliferous ores, burning of leaded gasoline, municipal sewage, industrial wastes enriched with Pb, and paints, which exceeded WHO (2011) and BIS (2003) recommended standard for lead (0.090 ppm) and arsenic (0.010 ppm). The geo-accumulation index (Igeo) study indicates that there is no significant contamination with lead and arsenic but there is a moderate contamination with copper (86.360 ppm). According to the calculated values of PLI, area 1 (0.061) has been contaminated high compared with other areas.

Arsenic-silicon priming of rice (Oryza sativa L.) seeds influence mineral nutrient uptake and biochemical responses through modulation of Lsi-1, Lsi-2, Lsi-6 and nutrient transporter genes

Silicon (Si) has attracted substantial attention because of its beneficial effect on plants during abiotic stress, including stress due to arsenic (As). We here report that priming rice seeds with As and Si together, helped the plant to sustain As stress for longer period. We examined Si induced tolerance against As in rice seedlings at short (7 d) and long (15 d) exposure periods under As^(III) and Si treatments since their germinating stage. Results showed that the expression of As^(III) transporter genes OsLsi1, OsLsi2 and OsLsi6 was more in As^(III) + Si treatment as compared to control and Si treatment, but lower than As^(III) alone treatments. The gene expression was maximum in shoot and root at 15 d over 7 d under both As^(III) and As^(III) + Si treatment, which ultimately leads to decreased accumulation of As in the presence of Si. Morphological characters, antioxidant capacity, oxidative stress marker (MDA), stress modulators (cysteine, proline), and enzymes related with ascorbate-glutathione cycle significantly altered during As^(III) + Si treatment at both exposure periods. Further, macro and micronutrient contents also improved with Si, and differentially regulated 12 key genes (NR, NiR, AMT, NR, GS, GOGAT, PT, PHT1, PHT2, APase, KAT1 and HAK10) related with NPK transport and utilization. Results highlight that Si priming of seeds along with As^(III) influences growth positively of As-stressed rice.

Arsenic Uptake, Toxicity, Detoxification, and Speciation in Plants: Physiological, Biochemical, and Molecular Aspects

Environmental contamination with arsenic (As) is a global environmental, agricultural and health issue due to the highly toxic and carcinogenic nature of As. Exposure of plants to As, even at very low concentration, can cause many morphological, physiological, and biochemical changes. The recent research on As in the soil-plant system indicates that As toxicity to plants varies with its speciation in plants (e.g., arsenite, As(III); arsenate, As(V)), with the type of plant species, and with other soil factors controlling As accumulation in plants. Various plant species have different mechanisms of As(III) or As(V) uptake, toxicity, and detoxification. This review briefly describes the sources and global extent of As contamination and As speciation in soil. We discuss different mechanisms responsible for As(III) and As(V) uptake, toxicity, and detoxification in plants, at physiological, biochemical, and molecular levels. This review highlights the importance of the As-induced generation of reactive oxygen species (ROS), as well as their damaging impacts on plants at biochemical, genetic, and molecular levels. The role of different enzymatic (superoxide dismutase, catalase, glutathione reductase, and ascorbate peroxidase) and non-enzymatic (salicylic acid, proline, phytochelatins, glutathione, nitric oxide, and phosphorous) substances under As(III/V) stress have been delineated via conceptual models showing As translocation and toxicity pathways in plant species. Significantly, this review addresses the current, albeit partially understood, emerging aspects on (i) As-induced physiological, biochemical, and genotoxic mechanisms and responses in plants and (ii) the roles of different molecules in modulation of As-induced toxicities in plants. We also provide insight on some important research gaps that need to be filled to advance our scientific understanding in this area of research on As in soil-plant systems.

Genotoxic effects of olive oil wastewater on sunflower

The aim of this study is to determine in detail the genotoxic effects of Olive Oil Wastewater (OOWW) on sunflower. For this reason, different concentrations of OOWW (1/1,1/10,1/100) were applied as irrigation water to sunflowers at different times (3-day, 5-day, 10-day). In the plants taken during these times, RAPD-based genomic template stability (GTS) assays and gene expression (transcriptomic) levels of different free radical scavenging enzyme genes (SOD, CAT, SOD2, GST, GPX, APX), protein repair/chaperoning genes (HSP26, HSP70, HSP83), N metabolism gene (GS) and apoptotic genes (BAX, BCL2, BCLXL, CYT-C, XIAP) were compared to the those of the control (OOWW-free) group. As a result; The GTS rates seemed to be fairly lower than the control and therefore the OOWW was likely to cause significant damage to the DNA's nucleotide and genomic structure, and the GTS value increased inversely proportional when the OOWW concentration was reduced from 1/1 to 1/10, and after a 10-day application, it seemed to be partly healing. In transcriptomic analysis; all OOWW experiments caused a free radical threat, and especially in 5-day OOWW applications, this raised significantly almost all expressions of antioxidants, protein repair, N metabolism, and apoptotic genes. So, the damages of 5-day OOWW treatments were found to be relatively more than those of 3-day treatments. Regarding 10-day transcriptomic data; a partial repair was found. Additionally, it was determined that the values of B, F, Al, Mn, Ni, Cr, As, Se, Cd, Pb and total polyphenols were high in OOWW. Our findings were also supported by plant images and various heavy metals' and OOWW polyphenols' toxicity results. Our results pointed to key findings in OOWW genotoxicology.

Phosphate alleviates arsenate toxicity by altering expression of phosphate transporters in the tolerant barley genotypes

The contribution of the phosphate transporters (PHTs) in uptake of arsenate (As⁵⁺) and phosphate (P) is a widely recognized mechanism. Here we investigated how P regulates the uptake of As⁵⁺ and the subsequent effects on growth and relative expression of PHTs. The study was conducted on 3 barley genotypes differing in As tolerance (ZDB160, As-tolerant; ZDB115, moderately tolerant; ZDB475, As-sensitive) using a hydroponic experiment. There were 3 As⁵⁺ (0, 10 and 100µM) and 3P (0, 50 and 500µM) levels. The results showed that the negative effect of As stress on plant growth, photosynthesis and cell ultra-structure is As dose and barley genotype dependent, confirming the distinctly genotypic difference in As tolerance. As uptake and accumulation in plant tissues are closely associated with inhibited extent of growth and photosynthesis, with the tolerant genotype ZDB160 having lower As content than other two genotypes. The toxic effect caused by As stress could be alleviated by P addition, mainly due to reduced As uptake. Moreover, the tolerant genotype showed relatively lower expression PHTs than sensitive ones upon exposure to both As stress and P addition, suggesting regulation of PHTs expression is a major mechanism for relative uptake of As and P, in subsequence affecting As tolerance. Moreover, among 6 PHTs examined in this study, the expressions of PHT1.3, PHT1.4 and PHT1.6 showed the marked difference among the three barley genotypes in responses to As stress and P addition, indicating further research on the contribution of phosphate transporters to As and P uptake should be focused on these PHTs.

Genotoxic evaluation of newly synthesized iminothiazolidinones

The current study was designed to assess the potential toxicological effects of newly synthesized iminothiazolidinones by employing Ames Salmonella, Escherichia coli WP2, Zea mays seed germination, and random amplified polymorphic DNA (RAPD) assay systems. The bacterial tester strains S. typhimurium TA1535, TA1537, TA1538, TA98, TA100, and E. coli WP2 uvrA were chosen to test the direct gene mutation inducing capabilities of the test materials in prokaryotic systems and Z. mays seeds for determination of potential toxicological effects in eukaryotic systems. OPA-3 and OPA-6 primers were used in the RAPD analysis to determine genotoxic activities on the eukaryotic genomes. According to the results, none of the test materials showed significant mutagenic activity on the bacterial tester strains at the chosen concentrations. Additionally, none of the tested compounds showed inhibition of the germination of Z. mays seeds. In contrast, the RAPD analysis results were inconsistent with the bacterial reversion assays and the seed germination assay results. All test materials significantly changed the RAPD profiles for OPA-3; however, only compound 5 showed a significant change for OPA-6 when compared with the control groups. In conclusion, the newly synthesized iminothiazolidinone derivatives (C1-C5) were determined as potentially genotoxic compounds and they should be checked with multiple toxicology test systems before further studies to determine their actual use.

Malathion and dithane induce DNA damage in Vicia faba

The increasing use of pesticides such as malathion and dithane in agriculture causes environmental mutagenicity. However, their genotoxicity in edible crops is seldom assessed. In this study, the genotoxic potential of malathion and dithane was evaluated in the roots of Vicia faba L. All three concentrations (0.05, 0.1, and 0.2%) of malathion and dithane tested resulted in a significant decrease in root length and inhibited seed germination. Cytological observations showed that the mitotic frequency in the root meristematic cells decreased parallel to the increase in concentrations, and the increase in chromosome aberrations and micronuclei frequency was concentration dependent. Alkaline comet assay revealed significant onset of DNA damage at all tested concentrations. For the randomly amplified polymorphic (RAPD)-polymerase chain reaction (PCR) analyses, 10 random RAPD primers were found to produce 116 unique polymorphic RAPD band fragments of 223–3139 bp. Each primer generated 3–15 RAPD bands on an average. The percentage of polymorphic DNA fragments was higher in malathion-exposed plants than dithane ones. The changes in RAPD profiles included disappearance and/or appearance of DNA bands in malathion and dithane treatment. Hence, DNA damage observed by the cytogenetic endpoints and comet assay corroborated with RAPD-PCR analysis. A total of 15 new protein bands of molecular weight ranging 11.894–226.669 kDa were observed in roots of Vicia plants that were exposed to the pesticides. The number of new protein bands was higher in malathion-treated DNA samples than in dithane-treated ones. Based on the results, we conclude that the pesticides can alter genomic template stability and change protein profiles. Malathion was more genotoxic than dithane. Therefore, RAPD assays can be useful in determining genotoxicity of pesticides in V. faba and other crops along with other quantitative parameters.

Mercury induced oxidative stress, DNA damage, and activation of antioxidative system and Hsp70 induction in duckweed (Lemna minor)

Mercury uptake and its effects on physiology, biochemistry and genomic stability were investigated in Lemna minor after 2 and 6d of exposure to 0-30μM Hg. The accumulation of Hg increased in a concentration- and duration-dependent manner, and was positively correlated with the leaf damage. Oxidative stress after Hg exposure was evidenced in L. minor by a significant decrease in photosynthetic pigments, an increase in malondialdehyde and lipoxygenase activities (total enzyme activity and isoenzymes activity). Fronds of L. minor exposed to Hg showed an induction of peroxidase, catalase, and ascorbate peroxidase activities (total enzyme activity and some isoenzymes activities). Exposure of L. minor to Hg reduced the activity (total enzyme activity and some isoenzymes activities) of glutathione reductase, and superoxide dismutase. Exposure to Hg produced a transient increase in the content of glutathione and ascorbic acid. The content of dehydroascorbate and oxidized glutathione in L. minor were high during the entire exposure period. Exposure of L. minor to Hg also caused the accumulation of proline and soluble sugars. The amplification of new bands and the absence of normal DNA amplicons in treated plants in the random amplified polymorphic DNA (RAPD) profile indicated that genomic template stability (GTS) was affected by Hg treatment. The accumulation of Hsp70 indicated the occurrence of a heat shock response at all Hg concentrations. These results suggest that L. minor plants were able to cope with Hg toxicity through the activation of various mechanisms involving enzymatic and non-enzymatic antioxidants, up-regulation of proline, and induction of Hsp70.

Fusarium infection causes genotoxic disorders and antioxidant-based damages in Orobanche spp

This study aims to evaluate the toxic effects of Fusarium oxysporum on root parasitic weed, Orobanche spp. Comparative genetic and gene expression studies were conducted on uninfected and fungus-infected orobanches. In genetic studies, isolated total DNA was amplified by RAPD PCR. Fragment properties were analysed by GTS test. According to the results, the fragment properties of control and Fusarium infected (experimental) groups varied widely; and it has been observed that Fusarium has genotoxic effects on the DNA of orobanches. In gene expression studies, the expression levels of genes encoding enzymes or proteins were associated with ROS damage and toxic effects, therefore, gene expressions of Mn-superoxide dismutase (SOD), Zn-superoxide dismutase (=SOD2, mitochondrial), glutamine synthetase (GS), heat shock protein gene (HSP70), BAX, Caspase-3 and BCL2 were significantly higher in the experimental group. In the light of obtained data, it was concluded that F. oxysporum (1) caused heavy ROS damage in Orobanche (2) induced significant irrevocable genotoxic effects on the DNA of Orobanche, (3) degraded protein metabolism and synthesis, and finally (4) triggered apoptosis. The results of this study can be a ground for further research on reducing the toxic effects of Fusarium on agricultural products, so that advancements in bio-herbicide technology may provide a sustainable agricultural production.

Arsenic-induced genotoxic responses and their amelioration by diphenylene iodonium, 24-epibrassinolide and proline in Glycine max L

Presence of the toxic metalloid, "arsenic (As)" is ubiquitous in the environment especially in the soil and water. Its excess availability in the soil retards growth and metabolism of plants via (a) slowing down the cell division/elongation, (b) overproduction of reactive oxygen species (ROS), (c) modulation of antioxidant enzymes, and (d) alteration of DNA profile/genomic template stability (GTS). In the current study, diphenylene iodonium (DPI), 24-epibrassinolide (EBL) and proline (Pro) were used to analyze their roles in eliminating the adverse effects of As. Glycine max L. (variety JS 335) seeds were subjected to As (75 μM, Sodium arsenite was used as source of As), and in combination with DPI (10 μM), EBL (0.5 μM) or Pro (10 mM), for five consecutive days, and effects of these treatment combinations were analyzed on germination percentage, biomass, membrane stability, GTS and expressions of defensive genes. In addition, the levels of As, ROS, malondialdehyde, DNA content, oxidation, fragmentation, polymorphism, DNase activity, endogenous Pro and pyrroline-5-carboxylate synthetase activity were evaluated. The results indicated that the treatments of DPI, EBL or Pro are capable to alleviate detrimental effects of As, gauged from above variables, but with different magnitudes. Apropos As-stress mitigation, Pro was found to be the most effective under the confines of the study protocol. This study certainly provides new ideas for intensifying studies to unravel elusive central mechanism of amelioration involving use of DPI, EBL or Pro in plants with confirmed As-toxicity.

Arsenic affects the production of glucosinolate, thiol and phytochemical compounds: A comparison of two Brassica cultivars

Arsenic (As), a non-essential metalloid, severely affects the normal functioning of plants, animals and humans. Plants play a crucial role in metabolic, physiological and numerous detoxification mechanisms to cope up with As induced stress. This study aimed to examine the differential response in two Brassica juncea cultivars, Varuna and Pusa Jagannath (PJn) exposed to different doses of As (50, 150, 300 μM) for 48 h duration. Change in morphological traits, concentration of individual as well as total GSL, sulfur related thiol proteins, sulfur content, and phytochemicals were analyzed in both cultivars. Accumulation pattern of As showed dose dependent accumulation in both the cultivars, being more in PJn. Our finding revealed that both cultivars were tolerant at low concentrations of As, while at higher concentration Varuna excelled over PJn. The increased tolerance of Varuna cultivar exposed to 150 and 300 μM concentration of As, correlated with its increased thiol related proteins, sulfur content and phytochemicals, which serves as defence strategy in the plant against oxidative stress. Differential pattern of total as well as individual GSLs content was observed in both Varuna and PJn cultivars. Varuna cultivar showed higher level of total and aliphatic GSLs, which serves as defence compound with other detoxification machineries to combat As stress. Our findings provide foundation for developing metalloid tolerant crops by analyzing the role of different genes involved in GSL mechanism and signaling pathways in different organs of plant.

Impact of silicon on Indian mustard (Brassica juncea L.) root traits by regulating growth parameters, cellular antioxidants and stress modulators under arsenic stress

Arsenic (As) is an emerging pollutant causing inhibition in growth and development of plants resulting into phytotoxicity. On the other hand, silicon (Si) has been suggested as a modulator in abiotic and biotic stresses that, enhances plant's physiological adaptations in response to several stresses including heavy metal stress. In this study, we used roots of hydroponically grown 14 day old seedlings of Brassica juncea var. Varuna treated with 150 μM As, 1.5 mM Si and both in combination for 96 h duration. Application of Si modulated the effect of As by improving morphological traits of root along with the development of both primary and lateral roots. Changes observed in root traits showed positive correlation with As induced cell death, accumulation of reactive oxygen species (ROS), nitric oxide (NO) and intracellular superoxide radicals (O2(-)). Addition of 1.5 mM Si during As stress increased accumulation of As in roots. Mineral nutrient analysis was done using energy-dispersive X-ray fluorescence (EDXRF) technique and positively correlated with increased cysteine, proline, MDA, H2O2 and activity of antioxidant enzymes (SOD, CAT and APX). The results obtained from the above biochemical approaches support the protective and active role of Si in the regulation of As stress through the changes in root developmental process.

Genotoxicity assessment of pesticides on terrestrial snail embryos by analysis of random amplified polymorphic DNA profiles

The study explores the relevance of coupling Random Amplified Polymorphic DNA (RAPD) and a High-Resolution capillary electrophoresis System (HRS) method for assessing the genotoxic potential of the wide variety commercial formulations of pesticides. Using this technique, the genotoxic potential of a glyphosate-based herbicide (Roundup Flash(®) (RU)) and two fungicide formulations based on tebuconazole and copper (Corail(®) and Bordeaux mixture (BM), respectively) was evaluated on terrestrial snail embryos. Clutches of Cantareus aspersus were exposed during their entire embryonic development to a range of concentration around the EC50 values (based on hatching success) for each compound tested. Three primers were used for the RAPD amplifications of pesticides samples. RAPD-HRS revealed concentration-dependent modifications in profiles generated with the three primers in RU(®)-exposed embryos from 30 mg/L glyphosate. For Corail(®)-exposed embryos, only two of the three primers were able to show alterations in profiles from 0.05 mg/L tebuconazole. For BM-exposed embryos, no signs of genotoxicity were observed. All changes observed in amplification profiles have been detected at concentrations lower than the recommended doses for vineyard field applications. Our study demonstrates the efficiency of coupling RAPD and HRS to efficiently screen the effect of pesticide formulations on DNA.

Measuring the damage of heavy metal cadmium in rice seedlings by SRAP analysis combined with physiological and biochemical parameters

BACKGROUND

Cadmium (Cd) is one of the most poisonous pollutants, and Cd pollution has become the limiting factor of rice production and quality improvement. Therefore it is of significant importance to monitor Cd toxicity by the detection of Cd contamination in rice with biomarkers. In the present study, sequence-related amplified polymorphism (SRAP) and physiological and biochemical methods were applied to determine the toxicological effects of Cd stress on rice.

RESULTS

With increasing Cd concentration and duration, the content of chlorophyll in the two rice varieties W7 and M63 decreased and that of malondialdehyde increased. This tendency was more apparent in M63. The antioxidant enzymes superoxide dismutase and peroxidase both increased significantly compared with controls. SRAP polymerase chain reaction results indicated significant differences between Cd treatments and controls in terms of SRAP profile, as well as genotypic differences. The genomic template stability (GTS) decreased with increasing Cd concentration and duration. Under the same treatment conditions, the GTS of W7 was higher than that of M63. Comparison analysis revealed that the changes in physiological and biochemical parameters of rice seedlings under Cd stress had a good correlation with the changes in SRAP profile. Furthermore, the changes in SRAP profile showed enhanced sensitivity in the roots of rice seedlings.

CONCLUSION

The SRAP profile and physiological and biochemical parameters could act as appropriate biomarkers for the measurement of Cd contamination during rice production.

Selenium and auxin mitigates arsenic stress in rice (Oryza sativa L.) by combining the role of stress indicators, modulators and genotoxicity assay

Arsenic (As) is known to disrupt the biological function in plants by inhibiting their growth and developmental process, while selenium (Se) is an essential micronutrient within the appropriate amount. Phytohormone auxin on the other hand is an established growth regulator and plays a significant role in stress management. Present study is designed to see the effect of Se and auxin on morphological and biochemical characteristics and, on the genotoxicity in rice plants under As stress. The observations indicated that seedlings supplemented only with As showed inhibition in the growth parameters, however, co-application of Se and auxin improved growth of rice seedlings, level of stress indicators, (chlorophyll, protein, MDA content) and modulators (cysteine, proline) as compared the individual treatment of As. Genomic template stability calculated through changes in RAPD profile showed consistent results when compared with the indicator and modulator parameters. Altered DNA profile showed varying degrees of polymorphism, highest in roots of As treated seedlings and lowest in roots of Se+auxin and As+Se treated seedlings. Altogether, this study conclude that application of Se and auxin alone or in combination were more effective in lowering the As induced stress in rice.

The determination of physiological and DNA changes in seedlings of maize (Zea mays L.) seeds exposed to the waters of the Gediz River and copper heavy metal stress

In this study, the effects of the heavy metal-polluted waters of the Gediz River, which flow into the Aegean Sea, and different concentrations of copper (Cu) solutions on maize (Zea mays L.) seedlings are investigated with physiological parameters and random amplified polymorphic DNA (RAPD) assay. Results displayed physiologically a significant difference in root and stem length between the control seedlings and the seedlings grown with the waters of the Gediz River. Also, the certain ascending concentrations of copper solution (80, 160, 320, 640, and 1280 ppm) caused a significant decrease in root and stem length of seedlings compared to the control seedlings. As a result of the waters of the Gediz River and copper solution treatment, the changes occurred in RAPD profiles of seedlings observed as variations like increment and/or loss of bands compared with the control seedlings. And these changes were reflected as a decrease in genomic template stability (GTS, changes in RAPD profile) derived by genotoxicity. RAPD band profiles and GTS values showed consistent results with physiological parameter. In conclusion, the study revealed the environmental risk and negative effect of waters of the Gediz River on maize seedlings and the suitability of RAPD assay for the detection of environmental toxicology.

Mercury heavy-metal-induced physiochemical changes and genotoxic alterations in water hyacinths [Eichhornia crassipes (Mart.)]

Mercury heavy metal pollution has become an important environmental problem worldwide. Accumulation of mercury ions by plants may disrupt many cellular functions and block normal growth and development. To assess mercury heavy metal toxicity, we performed an experiment focusing on the responses of Eichhornia crassipes to mercury-induced oxidative stress. E. crassipes seedlings were exposed to varying concentrations of mercury to investigate the level of mercury ions accumulation, changes in growth patterns, antioxidant defense mechanisms, and DNA damage under hydroponics system. Results showed that plant growth rate was significantly inhibited (52 %) at 50 mg/L treatment. Accumulation of mercury ion level were 1.99 mg/g dry weight, 1.74 mg/g dry weight, and 1.39 mg/g dry weight in root, leaf, and petiole tissues, respectively. There was a decreasing trend for chlorophyll a, b, and carotenoids with increasing the concentration of mercury ions. Both the ascorbate peroxidase and malondialdehyde contents showed increased trend in leaves and roots up to 30 mg/L mercury treatment and slightly decreased at the higher concentrations. There was a positive correlation between heavy metal dose and superoxide dismutase, catalase, and peroxidase antioxidative enzyme activities which could be used as biomarkers to monitor pollution in E. crassipes. Due to heavy metal stress, some of the normal DNA bands were disappeared and additional bands were amplified compared to the control in the random amplified polymorphic DNA (RAPD) profile. Random amplified polymorphic DNA results indicated that genomic template stability was significantly affected by mercury heavy metal treatment. We concluded that DNA changes determined by random amplified polymorphic DNA assay evolved a useful molecular marker for detection of genotoxic effects of mercury heavy metal contamination in plant species.

Determination of genotoxic effects of fipronil in Vicia faba using random amplified polymorphic DNA analysis

This study was undertaken to appreciate genotoxic potential of fipronil herbicides in the roots of Vicia faba seedlings. Fipronil was clearly dose dependent on root growth inhibitors, total soluble protein, and random amplified polymorphic DNA (RAPD) assays. Increase in concentration of fipronil resulted in decreased amount of root length and increased level of protein. For the RAPD analyses, 15 RAPD primers were found to produce unique polymorphic band patterns and were subsequently used to produce a total of 110 bands of 45–1250 bp. Each primer generated 4–11 RAPD bands across 15 primers. The changes occurring in RAPD profiles following fipronil treatment included variation becoming evident as disappearance and/or appearance of DNA bands compared with the normal seedlings. These results indicated that genomic template stability was significantly affected at the above fipronil concentration. This study further confirmed that the RAPD assays are useful in determining potential genotoxicity of fipronil.

miRNA plays a role in the antagonistic effect of selenium on arsenic stress in rice seedlings

We report that miRNA plays an important role in the selenium mediated antagonistic effect on arsenic stress in rice seedlings.

Effect of lead on phytotoxicity, growth, biochemical alterations and its role on genomic template stability in Sesbania grandiflora: a potential plant for phytoremediation

The present study was aimed at evaluating phytotoxicity of various concentrations of lead nitrate (0, 100, 200, 400, 600, 800 and 1000mgL(-1)) in Sesbania grandiflora. The seedling growth was significantly affected (46%) at 1000mgL(-1) lead (Pb) treatment. Accumulation of Pb content was high in root (118mgg(-1) dry weight) than in shoot (23mgg(-1) dry weight). The level of photosynthetic pigment contents was gradually increased with increasing concentrations of Pb. Malondialdehyde (MDA) content increased in both the leaves as well as roots at 600mgL(-1) Pb treatment and decreased at higher concentrations. The activity of antioxidative enzymes such as superoxide dismutase and peroxidase were positively correlated with Pb treatment while catalase and ascorbate peroxidase activities increased up to 600mgL(-1) Pb treatment and then slightly decreased at higher concentrations. Isozyme banding pattern revealed the appearance of additional isoforms of superoxide dismutase and peroxidase in Pb treated leaf tissues. Isozyme band intensity was more consistent with the respective changes in antioxidative enzyme activities. Random amplified polymorphic DNA results indicated that genomic template stability (GTS) was significantly affected based on Pb concentrations. The present results suggest that higher concentrations of Pb enhanced the oxidative damage by over production of ROS in S. grandiflora that had potential tolerance mechanism to Pb as evidenced by increased level of photosynthetic pigments, MDA content, and the level of antioxidative enzymes. Retention of high levels of Pb in root indicated that S. grandiflora has potential for phytoextracting heavy metals by rhizofiltration.

Arsenate induced differential response in rice genotypes

To study the differential response in two rice genotypes (PB1 and IR-64), hydroponically grown 14 days old plants were exposed to 50, 150 and 300µM As(V) for 24 and 96h. Accumulation of As was not significantly higher in PB1 variety except at higher concentration (300μM) and duration (96h), but up regulation of gene transcripts were higher as compared to IR-64. Inhibition in seed germination, root-shoot length, chlorophyll and protein content was observed in both varieties with increasing concentration and exposure time. PB1 variety was found more capable to detoxify As(V) through induction of antioxidant defense system and other stress related parameters (cysteine, proline content). SDS-PAGE and semi quantitative RT-PCR analysis showed significant changes in protein profile and gene expression analysis. The results suggests that various studied parameters and transcripts accumulation showed a combinatorial type of tolerance mechanism in PB1 variety to provide better protection against As(V) stress.

Exposure of Brassica juncea (L) to arsenic species in hydroponic medium: comparative analysis in accumulation and biochemical and transcriptional alterations

Arsenic (As) contamination in the environment has attracted considerable attention worldwide. The objective of the present study was to see the comparative effect of As species As(III) and As(V) on accumulation, biochemical responses, and gene expression analysis in Brassica juncea var. Pusa Jaganath (PJn). Hydroponically grown 14-day-old seedlings of B. juncea were treated with different concentrations of As(III) and As(V). Accumulation of total As increased with increasing concentration of both As species and exposure time, mainly in roots. Reduction in seed germination, root-shoot length, chlorophyll, and protein content were observed with increasing concentration and exposure time of both As species, being more in As(III)-treated leaves. PJn variety showed that antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)) and stress-related parameters (cysteine, proline, and malondialdehyde (MDA)) were stimulated and allows plant to tolerate both As species. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis in leaves showed significant changes in protein profile with more stringent effect with As(III) stress. Semiquantitative RT-PCR analysis showed regulation in expression of phytochelatin synthase (PCS), metallothionine-2 (MT-2), glutathione reductase (GR), and glutathione synthetase (GS) genes under both As(III) and As(V) stresses. Results suggested that accumulation and inhibition on physiological parameters differ according to the As species, while molecular and biochemical parameters showed a combinatorial type of tolerance mechanism against As(III) and As(V) stresses.

Coupling of random amplified polymorphic DNA profiles analysis and high resolution capillary electrophoresis system for the assessment of chemical genotoxicity

Cadmium (Cd) can be toxic to terrestrial snails, but few data are available about its genotoxic effects on early life stages (ELS). The aim of this study was to investigate the genotoxic potential of Cd in embryos of Helix aspersa using a new approach that couples Random Amplified Polymorphic DNA (RAPD) and a high-resolution capillary electrophoresis system (HRS). Clutches of H. aspersa were exposed to Cd solutions (2, 4, and 6 mg/L) from the beginning of their embryonic development. In addition to a dose-dependent effect of Cd on hatching rate, DNA fragmentation was observed in embryos that were exposed to 6 mg Cd/L. The analysis of RAPD products with HRS showed differences between the profiles of exposed and nonexposed embryos, starting at 2 mg Cd/L. In comparison to the profiles of the control samples, all profiles from the exposed snails exhibited an additional 270 bp DNA fragment and lacked a 450 bp DNA fragment. These profile modifications are related to the genotoxic effect of Cd on the ELS of H. aspersa . Our study demonstrates the efficacy of coupling RAPD and HRS for a rapid and efficient screening of the effects of chemicals on DNA.