Browsing by Author "Rama Shanker Dubey"

Now showing 1 - 20 of 31

Abiotic-stress tolerance in plants-system biology approach
(Elsevier, 2020) Poonam Pandey; Sarita Srivastava; Akhilesh Kumar Pandey; Rama Shanker Dubey
Abiotic stresses of the environment, such as soil salinity, drought, extreme temperatures (heat and cold), light, water supply, nutrient deficiency, excess levels of metals within the soil, negatively impact plant growth. Agriculture faces intolerable economic losses wherever stress-related alterations in plant development, growth, and productivity ultimately results in limited yield. Soil salinity and water scarcity (drought) problems exist in India, Argentina, China, the United States, Sudan, and many other countries in Western and Central Asia. Field crop estimation showed that almost all crops give best result only reaching 30% of the genetic potential for yield, but over 90% of global rural land area is considered affected globally by abiotic stresses during the growing season. Most common responses to abiotic stresses in plants include differential transcription of the many genes; production of stress-responsive genes leading to cellular metabolic changes; alteration in activity behavior of many enzymes; overproduction of several compatible metabolites such as amino acids, sugars, polyamines, phytochelatins, organic acids; increased synthesis of many enzymes and stress-specific proteins. These specific responses to stresses have served as basis to engineer crop plants suitable for cultivation in the stress-prone regions of the world. Generally, plants are affected by low and moderate levels of abiotic stresses, but when the intensity of stress increases, tolerance mechanism of plants start breaking down that might ultimately result into death of the plant. To satisfy the increasing demand of food of the developing and underdeveloped nations where abiotic stresses are severe constraints to crop productivity, development of stress-tolerant plants appear to be a propitious approach. Several biochemical, physiological, and metabolic strategies are developed in plants to combat such abiotic stresses. Often it is hard to foresee the complex signaling pathway that are activated or deactivated in response to various abiotic stresses. New biotechnological methods should be adopted by plant breeders to accelerate breeding program. Specifically, breeders must emphasize on increasing the tolerance of crops to abiotic stresses. Development of crop species with increasing yield below stress environment can be possible by the use of modern genetic engineering tools which help in selection across multiple traits and reduce cost and time. It is a big challenge to current agriculture biotechnology to fulfill increasing demand in food production due to constant increase in world population which may achieve 9 billion by 2050. Responses of crop plants in a systems biology manner will be helpful to build networks or models that will give better understanding of varied responses of crop plants to a dynamic environment which empowering us to outline the best engineering strategy for the development of enhanced abiotic-stress tolerant crop species. Systems biology is an imminent field in the area of plant science going for coordinating information from various high throughput “omics” platforms, for example, transcriptome, metabolome, proteome, and genomics to comprehend the regulatory structure and association of plant responses and their inherent components. They give new bits of knowledge and open new horizons for the better understanding of stresses and responses and also the improvement of plant responses and its resistance to stresses. Because of the vast-scale nature of these approaches, bioinformatics and computational approaches are highly connected with the above for either developing new data analytical methods, better visualization, or storage in sustainable online resources. Omic technologies have been used in substantial researches as a way to identify imperative intermediates controlling stress tolerance and as a tool to screen for variation in plants. The outcomes obtained by utilizing these approaches would then be able to be delivered using genetic transformation. © 2020 Elsevier Inc. All rights reserved.
Arsenic exposure alters activity behaviour of key nitrogen assimilatory enzymes in growing rice plants
(2004) Ambuj Bhushan Jha; Rama Shanker Dubey
Rice seedlings when grown in sand cultures for 5-20 days under 25 and 50 μM As2O3 in the medium showed a marked decline in growth when compared to controls. Increased absorption of arsenic from the medium, against the concentration gradient was observed. Greater localization of absorbed arsenic was noted in roots than in shoots. Rice plants grown for 20 days with 50 μmol 1-1 arsenic in the medium accumulated upto 370 μmol arsenic kg-1 dry weight in roots. Increasing levels of As2O3 in situ caused a marked decline in the activities of the nitrate assimilatory enzymes nitrate reductase (NR), nitrite reductase (NiR) and glutamine synthetase (GS), whereas an increase in the activities of alanine and aspartate aminotransferases was observed. The activities of animating (NADH-GDH) and deaminating (NAD+-GDH) glutamate dehydrogenases increased at moderately toxic level (25 μM) of As 2O3 whereas a higher As level of 50 7mu;M was inhibitory to the enzymes. Addition of 1 M proline in the reaction medium caused significant restoration in As-led loss of NR and GS activities. NR and GS extracted from arsenic exposed seedlings showed higher Km values compared to the enzymes extracted from control-grown seedlings, whereas GDHs extracted from As-stressed seedlings showed a decrease in Km. Results suggest that inhibition in the activities of N assimilatory enzymes accompanied with decreased affinity of the enzymes towards their substrates would eventually lead to a marked suppression of N assimilation and impaired growth of rice seedlings in As polluted environment. © 2004 Kluwer Academic Publishers.
Azadirachta indica and Ocimum sanctum leaf extracts alleviate arsenic toxicity by reducing arsenic uptake and improving antioxidant system in rice seedlings
(Springer, 2020) Arti Gautam; Akhilesh Kumar Pandey; Rama Shanker Dubey
In the present study the potentials of aqueous extracts of the two plants, neem (Azadirachta indica) and Tulsi (Ocimum sanctum) were examined in alleviating arsenic toxicity in rice (Oryza sativa L.) plants grown in hydroponics. Seedlings of rice grown for 8 days in nutrient solution containing 50 μM sodium arsenite showed decline in growth, reduced biomass, altered membrane permeability and increased production of superoxide anion (O2 ·−), H2O2 and hydroxyl radicals (·OH). Increased lipid peroxidation marked by elevated TBARS (thiobarbituric acid reactive substances) level, increased protein carbonylation, alterated levels of ascorbate, glutathione and increased activities of enzymes SOD (superoxide dismutase), CAT (catalase), APX (ascorbate peroxidase) and GPX (glutathione peroxidase) were noted in the seedlings on As treatment. Exogenously added leaf aqueous extracts of Azadirachta indica (0.75 mg mL−1, w/v) and Ocimum sanctum (0.87 mg mL−1, w/v) in the growth medium considerably alleviated As toxicity effects in the seedlings, marked by reduced As uptake, restoration of membrane integrity, reduced production of ROS, lowering oxidative damage and restoring the levels of ascorbate, glutathione and activity levels of antioxidative enzymes. Arsenic uptake in the seedlings declined by 72.5% in roots and 72.8% in shoots, when A. indica extract was present in the As treatment medium whereas with O. sanctum extract, the uptake declined by 67.2% in roots and 70.01% in shoots. Results suggest that both A. indica and O. sanctum aqueous extracts have potentials to alleviate arsenic toxicity in rice plants and that A. indica can serve as better As toxicity alleviator compared to O. sanctum. © 2019, Prof. H.S. Srivastava Foundation for Science and Society.
Climate Change Impacts on Agriculture: Crop Productivity and Food Security
(CRC Press, 2023) Pratibha Singh; Shivani Singh; Rama Shanker Dubey
Climate change adversely affects agricultural productivity and food security across the world. Global warming due to increased greenhouse gases, increasing temperatures, has resulted in extremes of weather conditions, changing patterns of rainfall, flooding, heat wave, shortage of irrigation water, drought, salinity, loss of soil fertility, emergence of new pests and diseases, etc., which have adversely affected quantity and quality of food grain production. During the last 80 years, a consistent and substantial decline in the yield of major food and oil crops have been seen due to global warming. Climate change affects nutritional quality of foods, availability of nutrients within a food supply chain, and hence food security remains a great challenge due to climate change. To feed increasing global population strategies need to be adopted for sustainable production of foods. Climate-smart sustainable farming practices and improved technologies are needed to sustainably enhance agricultural productivity and to attain food security. © 2023 selection and editorial matter, M. H. Fulekar and Rama Shanker Dubey; individual chapters, the contributors.
Comparative Evaluation of Cadmium Toxicity Effects on Growth, Photosynthetic and Oxidative Stress Parameters in Various Genotypes of Indica Rice (Oryza Sativa L.) Seedlings
(Indian Society of Agricultural Biochemists, 2022) Shivani Singh; Pratibha Singh; Rama Shanker Dubey
In hydroponics, experiments were performed to examine plant growth, oxidative stress parameters, and level of photosynthetic pigments in nine rice (Oryza sativa L.) genotypes collected from different locations in India, grown under 50 µM and 100 µM cadmium nitrate application. In all the rice genotypes, with an increase in Cd concentration in the growth medium, root and shoot growth as well as levels of Chl a, Chl b and carotenoids declined significantly compared to untreated seedlings. A significant elevation in the levels of H2O2 and lipid peroxidation was observed in the seedlings due to Cd treatment. The upland varieties of rice Sobhagi, Vandana and IDR-763 showed better growth performance, lesser H2O2 production and lesser oxidative damage due to Cd, compared to inland varieties. Results suggest that the rice cultivars Sobhagi, Vandana and IDR-763 appeared to be fairly tolerant to high Cd levels. © 2022, Indian Society of Agricultural Biochemists. All rights reserved.
Comprehensive analysis of regulatory elements of the promoters of rice sulfate transporter gene family and functional characterization of OsSul1;1 promoter under different metal stress
(Taylor and Francis Inc., 2015) Smita Kumar; Mehar Hasan Asif; Debasis Chakrabarty; Rudra Deo Tripathi; Rama Shanker Dubey; Prabodh Kumar Trivedi
Adverse environmental conditions including heavy metal stress impose severe effects on the plant growth and development limiting productivity and yield. Studies demonstrated that changes in genome-wide expression modulate various biochemical processes and molecular components in response to heavy metal stress in plants. Some of the key components involved in such a regulation are the transcription initiation machinery, nucleotide sequence of promoters and presence of cis-acting elements. Therefore, identification of the putative cis-acting DNA sequences involved in gene regulation and functional characterization of promoters are important steps in understanding response of plants to heavy metal stress. In this study, comprehensive analysis of the proximal promoters of members of rice sulfate transporter gene family which is an essential component of stress response has been carried out. Analysis suggests presence of various common stress related cis-acting elements in the promoters of members of this gene family. In addition, transcriptional regulation of the arsenic-responsive high affinity sulfate transporter, OsSul1;1, has been studied through development of Arabidopsis transgenic lines expressing reporter gene encoding b-glucuronidase under the control of OsSul1;1 promoter. Analysis of the transgenic lines suggests differential response of the OsSul1;1 promoter to various heavy metals as well as other abiotic stresses. © 2015 Taylor & Francis Group, LLC.
Cultivar-Specific Oxidative Modification of Proteins, Proteolytic Activity and Alterations in Proteomes of Rice Seedlings to Simultaneous Water Deficit and Aluminum Toxicity
(Springer, 2022) Poonam Pandey; Rama Shanker Dubey
Water deficit (WD) and aluminum toxicity (Al) are two key constraints to crop production, especially in upland acid soils. We examined the combined effects of the two stresses in comparison to individual stresses in the seedlings of rice (Oryza sativa L.) cultivars with contrasting stress tolerance, on its antioxidant capacity, oxidative modification of proteins, status of proteolytic activity and proteomic alterations, when grown in sand cultures. Seedlings exposed to WD and Al-excess for 24–72 h showed growth reduction, increased protein carbonylation in the tissues and increased proteolysis. In WD/Al-sensitive cv. Malviya-36, the combined stresses caused more reduction in growth compared to the individual stresses. Immunoblot analysis of protein carbonyls from root/shoot extracts revealed increased oxidatively modified proteins due to WD and Al-excess. When exposed to either WD, Al-excess or combined stresses, cv. Malviya-36 seedlings showed increased proteolysis, more activity bands corresponding to proteolysis and more oxidized proteins than cv. Vandana (WD /Al-tolerant) seedlings. The antioxidant capacity appeared to be greater in cv. Vandana (tolerant) than cv. Malviya-36 (sensitive) measured by DPPH assay. Proteins from rice shoots, separated by 2DE, when analyzed by PDQuest, revealed nearly 200 clear spots, among which 55 were differentially abundant under individual and combined stresses. MALDI-TOF mass spectrometry of differentially abundant proteins revealed that many chloroplast and photosynthesis-related proteins were downregulated, 6 proteins disappeared and the expression of calmodulin and ABA/stress-induced proteins was specifically induced in the sensitive cultivar under combined stresses indicating that photosynthesis was affected in this cultivar under combined stresses. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Differential Expression of Rice Lambda Class GST Gene Family Members During Plant Growth, Development, and in Response to Stress Conditions
(2013) Smita Kumar; Mehar Hasan Asif; Debasis Chakrabarty; Rudra Deo Tripathi; Rama Shanker Dubey; Prabodh Kumar Trivedi
Glutathione S-transferases (GSTs; EC 2.5.1.18) are members of an isozyme family and catalyze the conjugation of the reduced tripeptide glutathione to a variety of hydrophobic and electrophilic substrates. Though members of different classes of the GST superfamily have been identified and characterized from many plant species including rice, no detailed information is available for the Lambda class gene family in rice. In this study, a genome-wide analysis was carried out to investigate expression patterns of three Lambda class GST members of rice including OsGSTL1, OsGSTL2 and OsGSTL3 in seedlings, at different growth and developmental stages as well as in response to various biotic and abiotic stresses. Expression analysis using microarray datasets and quantitative real-time reverse transcriptase polymerase chain reaction suggests that this gene family express differentially in various tissues, in response to hormones and during different biotic and abiotic stresses including heavy metals, cold, drought and salt stress. Massively Parallel Signature Sequencing (MPSS) analysis also showed differential expression of OsGSTLs during plant growth and development and under different stresses. Out of three members, maximum expression of OsGSTL2 was observed for the MPSS libraries in comparison to other members. We conclude that members of rice Lambda class GST family play an important role in plant growth and development and in combating different biotic and abiotic stresses. © 2012 Springer Science+Business Media New York.
Distinct defensive activity of phenolics and phenylpropanoid pathway genes in different cotton varieties toward chewing pests
(Taylor and Francis Inc., 2020) Garima Dixit; Alka Srivastava; Krishan Mohan Rai; Rama Shanker Dubey; Rakesh Srivastava; Praveen Chandra Verma
Identifying the maximum level of inherent defense against harmful insects in natural variation among wild lineages of crop plants may result in high yield tolerant varieties and reducing use of chemical insecticides. However, knowledge of natural cotton genotypes with high insect‐resistance is still indistinguishable at the biochemical or molecular level. In the present study, different cultivated Gossypium hirsutum varieties were evaluated for their inherent insect-tolerance against two major cottons chewing pests. The insect bio-assay identified two tolerant and one susceptible cotton varieties. The study demonstrates difference in phenolic acids, proanthocyanidin and tannin accumulation in tolerant and susceptible varieties. The post–infestation of chewing pests increases transcript level of the phenylpropanoid pathway genes were detected in tolerant varieties as compared to the susceptible varieties. Altogether, chewing pest-tolerance level in cotton varieties is the cumulative effect of enhanced phenylpropanoid pathway genes expression and secondary metabolite leading to defense responses to conventional host plant. © 2020, © 2020 Taylor & Francis Group, LLC.
Drought induces oxidative stress and enhances the activities of antioxidant enzymes in growing rice seedlings
(2005) Pallavi Sharma; Rama Shanker Dubey
When rice seedlings grown for 10 and 20 days were subjected to in vitro drought stress of -0.5 and -2.0 MPa for 24 h, an increase in the concentration of superoxide anion (O2 .-), increased level of lipid peroxidation and a decrease in the concentration of total soluble protein and thiols was observed in stressed seedlings compared to controls. The concentration of H2O2 as well as ascorbic acid declined with imposition of drought stress, however glutathione (GSH) concentration declined only under severe drought stress. The activities of total superoxide dismutases (SODs) as well as ascorbate peroxidase (APX) showed consistent increases with increasing levels of drought stress, however catalase activity declined. Mild drought stressed plants had higher guaiacol peroxidase (GPX) and chloroplastic ascorbate peroxidase (c-APX) activity than control grown plants but the activity declined at the higher level of drought stress. The activities of enzymes involved in regeneration of ascorbate i.e. monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were higher in drought stressed plants compared to controls. Results suggest that drought stress induces oxidative stress in rice plants and that besides SOD, the enzymes of ascorbate-glutathione cycle, which have not been studied in detail earlier under stressful conditions, appear to function as important component of antioxidative defense system under drought stress. © Springer 2005.
Effect of arsenic toxicity on photosynthesis, oxidative stress and alleviation of toxicity with herbal extracts in growing rice seedlings
(Indian Society of Agricultural Biochemists, 2019) Arti Gautam; Akhilesh Kumar Pandey; Rama Shanker Dubey
When seedlings of an Indica rice cultivar Malaviya-36 were raised for 8 days in hydroponics in Yoshida nutrient solution containing 25 ìM NaAsO2, it was observed that arsenic treatment to the seedlings caused decline in plant height, fresh weight, relative water content, net photosynthetic rate, stomatal conductance, intracellular CO2 concentration and transpiration rate. The decline was greater with increase in the duration of As treatment. Arsenic t reated seedlings showed elevated levels of the reactive oxygen species superoxide radicals, H2 O2 and increased oxidative stress in the tissues. When aqueous extracts prepared from leaves of the two plants, Neem (Azadirachta indica) and Tulsi (Ocimum sanctum) were added in As containing growth medium, a marked alleviation of As toxicity was observed in relation to growth parameters, photosynthetic activities and extent of oxidative stress in the tissues. Results suggest that both A. indica and O. sanctum aqueous extracts have potential to alleviate arsenic toxicity in rice seedlings with A. indica extract showing greater efficacy than O. sanctum. © 2019, Indian Society of Agricultural Biochemists. All rights reserved.
Effect of chromium on protein oxidation, protease activity, photosynthetic parameters and alleviation of toxicity in growing rice seedlings
(Indian Society of Agricultural Biochemists, 2021) Akhilesh Kumar Pandey; Arti Gautam; Rama Shanker Dubey
Increasing concentration of Cr in soil and water creates a hazardous situation for agriculture across the world. The present study was aimed to examine the effect of toxic concentration of Cr on protein oxidation, protease activity and photosynthesis in rice at seedling stage. Protein oxidation was observed in terms of extent of protein thiolation and its carbonylation. Rice seedlings exposed to 100µM Cr for 8 days in hydroponics were marked by reduced growth, a significant elevation in non-protein thiols (NPTs), protein carbonyls and protease activity and decline in the level of protein thiols, photosynthesis rate (Ps), stomatal conductance (gs), intracellular CO2 concentration (Ci) and transpiration rate (E). When aqueous extract of the fruits of Phyllanthus emblica was added in the growth medium of Cr-stressed seedlings, a marked restoration in the growth of seedlings along with restoration of Cr-induced alterations was observed. Results indicate that P. emblica extract alleviates Cr-toxicity in rice by preventing oxidation of proteins and restoring photosynthetic activity. © 2021, Indian Society of Agricultural Biochemists. All rights reserved.
Expression of a rice Lambda class of glutathione S-transferase, OsGSTL2, in Arabidopsis provides tolerance to heavy metal and other abiotic stresses
(2013) Smita Kumar; Mehar Hasan Asif; Debasis Chakrabarty; Rudra Deo Tripathi; Rama Shanker Dubey; Prabodh Kumar Trivedi
Global industrial growth has contaminated the soil and water with many hazardous compounds, including heavy metals. These heavy metals are not only toxic to plants but also cause severe human health hazards when leach out into food chain. One of the approaches employed for the decontamination of environment includes identification and overexpression of genes involved in the detoxification mechanism of plants. Glutathione S-transferases (GSTs) are a superfamily of enzymes, principally known for their role in detoxification reactions. Different classes of GSTs have been used to develop plants with improved detoxification mechanism, but not much information is available for Lambda class of GSTs. Here, we studied expression of OsGSTLs in different rice genotypes under arsenic stress. The study suggests differential expression of these genes in arsenic sensitive and tolerant genotypes. Further, the role of one member of Lambda class OsGSTL2 was studied by expressing in heterologous system, Arabidopsis. Transgenic lines developed were analysed for their response to different abiotic stresses including heavy metals. Analysis suggests that OsGSTL2 provides tolerance for heavy metals and other abiotic stresses like cold, osmotic stress and salt. We conclude that OsGSTLs can be utilized for developing plant varieties tolerant to different abiotic stresses including heavy metals. © 2013 Elsevier B.V.
Failure of methanol detoxification in pests confers broad spectrum insect resistance in PME overexpressing transgenic cotton
(Elsevier Ireland Ltd, 2023) Alka Srivastava; Gourav Jain; Sushmita; Sateesh Chandra; Vinay Kalia; Santosh Kumar Upadhyay; Rama Shanker Dubey; Praveen Chandra Verma
Methanol is noxious to insect pests, but most plants do not make enough of it to shield themselves from encroaching insects. Methanol emission is known to increase in the instance of herbivory. In the current study, we showed that Aspergillus niger pectin methylesterase over-expression increases methanol emission and confers resistance to polyphagous insect pests on transgenic cotton plants by impeding the possible methanol detoxification pathways. Transgenic plants emitted ∼11 fold higher methanol displaying insect mortality of 96% and 93% in Helicoverpa armigera and Spodoptera litura, respectively. The larvae were unable to survive and finish their life cycle and the surviving larvae exhibited severe growth retardation. Insects try to detoxify methanol via catalase, carboxylesterase and cytochrome P450 monooxygenase enzymes, amongst which cytochrome P450 plays a major role in oxidizing methanol to formaldehyde and formaldehyde to formic acid, which is broken down into carbon dioxide and water. In our study, catalase and esterase enzymes were found to be upregulated, but cytochrome P450 monooxygenase levels were not much affected. Leaf disc assays and In-planta bioassays also showed 50–60% population reduction in the sap sucking pests, such as Bemisia tabaci and Phenacoccus solenopsis. These findings imply that elevated methanol emissions confer resistance in plants against chewing and sap-sucking pests by tampering the methanol detoxification pathways. Such mechanism will be useful in imparting expansive resistance against pests in plants. © 2023 Elsevier B.V.
Ferrous Chloride and Sodium Ascorbate Alleviate Pb Toxicity in Rice Seedlings my Modulating the Activity of Antioxidative Enzymes
(Indian Society of Agricultural Biochemists, 2021) Pratibha Singh; Shivani Singh; Rama Shanker Dubey
When seedlings of an Indica rice cultivar HUR-105 were raised for 8 days in hydroponics in Yoshida nutrient solution containing 800 μM Pb(NO3)2, it was observed that Pb treatment caused reduction in height and fresh weight, and increase in the activity of antioxidative enzymes such as superoxide dismutase, catalase and ascorbate peroxidase. The reduction in height and fresh weight was greater with increase in Pb treatment duration. Pb treated seedlings showed the elevated level of antioxidative enzymes activity at 8th day as compared to 4th day in the roots and shoots of the seedlings. When FeCl2 and sodium ascorbate were added in Pb containing growth medium, a noticeable alleviation of Pb toxicity was seen in correlation to growth parameters and antioxidative enzymes activity in both roots and shoots of rice seedlings. Results suggest that both FeCl2 and sodium ascorbate have high potential to alleviate Pb toxicity in rice seedlings. © 2021, Indian Society of Agricultural Biochemists. All rights reserved.
Inhibition of ribonuclease and protease activities in arsenic exposed rice seedlings: Role of proline as enzyme protectant
(Elsevier GmbH, 2006) Shruti Mishra; Rama Shanker Dubey
When seedlings of two rice (Oryza sativa L.) cvs. Malviya-36 and Pant-12 were raised under 25 and 50 μM As2O3 in the medium an increase in the level of RNA, proteins and proline accompanied with a decline in the level of free amino acid pool was observed under arsenic supplementation compared to controls. In situ As3+ treatment caused a marked inhibition in activities of ribonuclease (RNase, EC 3.1.27.1), protease and leucine aminopeptidase (LAP, EC 3.4.11.1) whereas the activity level of carboxypeptidase (EC 3.4.16.5) was enhanced. In vitro supply of As2O3 in the enzyme assay medium beyond 400 μM resulted in gradual inhibition of RNase and beyond 5 μM inhibition of LAP activities. Addition of 1 M proline in the assay medium significantly restored the loss in RNase activity due to in vitro arsenic treatment or due to osmotic stress created by incorporation of polyethylene glycol (PEG). Isoform pattern of RNase extracted from As3+-exposed seedlings showed a significant alteration compared to its pattern in unexposed seedlings. Results suggest that arsenic exposure impairs hydrolysis of RNA and proteins in rice seedlings due to inhibition of RNase and proteases activities and that proline accumulating under As3+ toxicity appears to serve as enzyme protectant. © 2005 Elsevier GmbH. All rights reserved.
Lead toxicity in plants
(Sociedade Brasileira de Fisiologia Vegetal, 2005) Pallavi Sharma; Rama Shanker Dubey
Contamination of soils by heavy metals is of widespread occurrence as a result of human, agricultural and industrial activities. Among heavy metals, lead is a potential pollutant that readily accumulates in soils and sediments. Although lead is not an essential element for plants, it gets easily absorbed and accumulated in different plant parts. Uptake of Pb in plants is regulated by pH, particle size and cation exchange capacity of the soils as well as by root exudation and other physico-chemical parameters. Excess Pb causes a number of toxicity symptoms in plants e.g. stunted growth, chlorosis and blackening of root system. Pb inhibits photosynthesis, upsets mineral nutrition and water balance, changes hormonal status and affects membrane structure and permeability. This review addresses various morphological, physiological and biochemical effects of Pb toxicity and also strategies adopted by plants for Pb-detoxification and developing tolerance to Pb. Mechanisms of Pb-detoxification include sequestration of Pb in the vacuole, phytochelatin synthesis and binding to glutathione and aminoacids etc. Pb tolerance is associated with the capacity of plants to restrict Pb to the cell walls, synthesis of osmolytes and activation of antioxidant defense system. Remediation of soils contaminated with Pb using phytoremediation and rhizofiltration technologies appear to have great potential for cleaning of Pb-contaminated soils.
Metal toxicity in rice and strategies for improving stress tolerance
(Elsevier, 2018) Poonam Pandey; Rama Shanker Dubey
Rice (Oryza sativa) is a staple food for the majority of world population. Contamination of rice fields with various types of metals and metalloids causes a serious threat to the cultivation of this crop. Persistent nature and biomagnification potential of metals cause great concerns to the agricultural soils. High concentrations of metals in the soil environment suppress growth, alter metabolism of plants, cause stress and toxicity symptoms, ultimately leading to decreased productivity. To avoid the direct damaging effects of metals, plants have adopted some strategies like binding of metals with the cell wall, organic acids, sequestration of metals within the tissues, etc. Excessive levels of metals in the tissues cause increased production of reactive oxygen species (ROS) which cause oxidative damage to the cellular molecules. To combat oxidative damage due to ROS, plants trigger antioxidant defense mechanism leading to high activities of antioxidative enzymes, increased synthesis of non-enzymic antioxidants and synthesis of stress-related proteins. Overexpression of stress-related proteins and components of antioxidative defense mechanisms can serve as potential strategy for conferring metal stress tolerance in rice plants. Our ever-growing knowledge in the fields of metabolomics, transcriptomics, proteomics, etc., has immensely helped in characterizing the metabolites, transcription factors, and stress-associated proteins involved in metal tolerance of rice plants. © 2019 Elsevier Inc. All rights reserved.
Modulation of nitrate reductase activity in rice seedlings under aluminium toxicity and water stress: Role of osmolytes as enzyme protectant
(Elsevier GmbH, 2005) Pallavi Sharma; Rama Shanker Dubey
Nitrate reductase (NR) activity in the presence of Mg2+ (NR act) representing the non-phosphorylated NR state and the activity in the presence of EDTA (NR max) representing maximum NR activity was measured in roots and shoots of 15 d grown aluminium and water stressed rice seedlings to examine changes in NR activation state due to these stresses. Seedlings subjected to a moderate water stress level of -0.5 MPa for 24 h or grown in presence of 80 μM Al3+showed decreased level of NR max but resulted in higher NR act and NR activation state. However, seedlings grown in presence of a higher level of 160 μM Al3+ showed a decline in NR act as well as NR max. With a higher water stress level of -2.0 MPa a marked decline in the levels of both NR act and NR max was observed, whereas NR activation state remained almost unaltered with severe water stress. NR activity appeared to be sensitive to H2O2, PEG-6000, NaCl and various metal salts. Incorporation of these components in the enzyme assay medium led to decreased affinity of enzyme towards its substrate with increase in Km and decrease in Vmax values. Addition of each of the osmolytes i.e. 1 mol/L proline, 1 mol/L glycine betaine or 1 mol/L sucrose in the enzyme assay medium caused a considerable protection to the enzyme against the damaging effects of stressful components. An enhanced level of proline and glycine betaine was observed in Al-stressed seedlings and sucrose in Al as well as water stressed seedlings. Results suggest that Al toxicity and water stress decrease total amount of functional NR in rice seedlings and the osmolytes proline, glycine betaine and sucrose appear to have a direct protective action on enzyme NR under stressful conditions © 2005 Elsevier GmbH. All rights reserved.
Omics and biotechnology of arsenic stress and detoxification in plants: Current updates and prospective
(Elsevier Ltd, 2015) Smita Kumar; Rama Shanker Dubey; Rudra Deo Tripathi; Debasis Chakrabarty; Prabodh Kumar Trivedi
Arsenic (As), a naturally occurring metallic element, is a dreadful health hazard to millions of people across the globe. Arsenic is present in low amount in the environment and originates from anthropogenic impact and geogenic sources. The presence of As in groundwater used for irrigation is a worldwide problem as it affects crop productivity, accumulates to different tissues and contaminates food chain. The consumption of As contaminated water or food products leads to several diseases and even death. Recently, studies have been carried out to explore the biochemical and molecular mechanisms which contribute to As toxicity, accumulation, detoxification and tolerance acquisition in plants. This information has led to the development of the biotechnological tools for developing plants with modulated As tolerance and detoxification to safeguard cellular and genetic integrity as well as to minimize food chain contamination. This review aims to provide current updates about the biochemical and molecular networks involved in As uptake by plants and the recent developments in the area of functional genomics in terms of developing As tolerant and low As accumulating plants. © 2014 Elsevier Ltd.