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Chromium (Cr) is a heavy metal that poses a grave threat to the ecosystem including plants. Chromium is very harmful to plants due to its effects on many physiological and metabolic pathways culminating in a negative impact on plant's growth, development, and ability to take up nutrients. Plants have developed physiological, biochemical, and molecular ways of defense against Cr, such as by augmenting antioxidant potential to reduce reactive oxygen species (ROS). A number of genes have been discovered to play a significant role in the defense mechanisms of plants against Cr, for example, genes associated with the activation of phytochelatins, metallothioneins, and those of enzymes like glutathione-S-transferases. Along with this, a few miRNAs have been found to be associated in alleviating Cr stress and, to augment plant tolerance by controlling transcription factors, HSPs, and the expression of a few proteins and hormones. Defense pathway genes and miRNAs have been used for the generation of transgenic phytoremediator plants. Not only do the transgenic plants have a higher tolerance to Cr, but they also act as hyperaccumulators for Cr and have the potential to remediate other heavy metals. This article describes about environmental Cr contamination, Cr effects on plants, different genes and miRNAs involved in Cr stress mitigation and use of candidate genes, microRNAs for creating transgenic plant systems for phytoremediation, and the applications of CRISPR technology. It is expected that the integration of omics approach and advanced genomics will offer scope for more effective phytoremediation of Chromium in the coming years. [Display omitted] • Chromium adversely affects plant growth, development, and nutrient uptake. • MiRNAs regulate Chromium toxicity by metal chelation, ROS signaling, and transcription factors. • GSTs, MTs, and PCs play crucial roles in Chromium detoxification and tolerance in plants. • Transgenic plants with candidate genes improve Chromium accumulation and tolerance. [ABSTRACT FROM AUTHOR]

Metal contamination of the environment is a widespread problem threatening sustainable and safe crop production. Physio-biochemical and molecular mechanisms of plant responses to metal exposure have been studied to establish the best possible agronomical or biotechnological methods to tackle metal contamination. Metal stress tolerance is regulated by several molecular effectors among which microRNAs are one of the key master regulators of plant growth and stress responses in plants. MicroRNAs are known to coordinate multitude of plant responses to metal stress through antioxidant functions, root growth, hormonal signalling, transcription factors and metal transporters. The present review discusses integrative functions of microRNAs in the regulation of metal stress in plants, which will be useful for engineering stress tolerance traits for improved plant growth and productivity in metal stressed situations. • MicroRNAs are important regulatory elements in metal stress responses in plants. • MicroRNAs fine tune antioxidant defense machinery to counteract metal-induced oxidative stress. • The transporter expression is altered by microRNAs to reduce the accumulation of toxic metals. • Thiol metabolism is regulated by microRNAs for metal detoxification. [ABSTRACT FROM AUTHOR]

A field experiment was conducted in a combinatorial approach to evaluate the performance of five aquatic plants, singly and in all possible combinations of two plants, for As removal from 4 L of 2500 μg L −1 As in 30 days. Under As stress, Hydrilla showed an increase in growth rate (19%) in comparison to control, while other plants demonstrated a decline. Among different combinations, Ceratophyllum + Lemna , Hydrilla + Ceratophyllum and Hydrilla + Wolffia showed higher growth in As (92%, 43%, and 33%, respectively) than under control conditions. Total As removal (μg) in 30 days was found to be the maximum for Ceratophyllum + Lemna (4365) followed by Hydrilla + Ceratophyllum (3326) and Hydrilla + Wolffia (1896). In all combinations of plants, Hydrilla always contributed more than 50%. The study advocates the use of Hydrilla / Ceratophyllum as one plant of choice to be used in combination. It also proposes to screen for different combinations of two of more plants for better application of phytoremediation technology in field. [ABSTRACT FROM AUTHOR]

The present study analyzed the effects of individual microbes and their consortium (Priestia endophytica NDAS01F , Bacillus licheniformis NDSA24R, and P. flexa NDAS28R) either alone or in interaction with thiourea (TU) on growth and responses of rice plants subjected to As stress (50 mg kg−1 in soil) in a pot experiment. The bacteria used in the experiment were isolated from As contaminated fields of Nadia, West Bengal and showed significant As removal potential in in vitro experiment. The results revealed significant growth improvement, biomass accumulation, and decline in malondialdehyde levels in rice plants in bacterial and TU treatments as compared to control As treatment. The best results were observed in a bacterial consortium (B1-2-3), which induced a profound increase of 65%, 43%, 127% and 83% in root length, shoot length, leaf width and fresh weight, respectively. Sulfur metabolism and cell wall synthesis were stimulated upon bacterial and TU amendment in plants. The maximum reduction in As concentration was observed in B2 in roots (−55%) and in B1-2-3 in shoot (−83%). The combined treatment of B1-2-3 + TU proved to be less effective as compared to that of B1-2-3 in terms of As reduction and growth improvement. Hence, the usage of bacterial consortium obtained in the present work is a sustainable approach, which might find relevance in field conditions to achieve As reduction in rice grains and to attain higher growth of plants without the need for additional TU supplementation. [Display omitted] • Bacteria isolated from Nadia, West Bengal were used for consortium. • Bacterial consortium promoted growth of plants and reduced arsenic concentration. • Arsenic translocation from root to shoot was significantly decreased. • Bacterial consortium + thiourea did not result in synergistic effects on growth. • Bacterial consortium + thiourea did not cause additional arsenic reduction. [ABSTRACT FROM AUTHOR]

Abstract: Thiourea (TU) has been found to enhance the stress tolerance of plants in our earlier field trials. In the present study, the TU mediated effect on the redox and antioxidant responses were studied in response to salinity (NaCl) stress in Indian mustard (Brassica juncea (L.) Czern.) seedlings. Biochemical analyses of reactive oxygen species (ROS) and lipid peroxidation revealed that TU supplementation to NaCl brought down their levels to near control values as compared to that of NaCl stress. These positive effects could be correlated to the significant increases in the 1,1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging activity, in the levels of reduced glutathione (GSH) and GSH/GSSG (reduced/oxidized glutathione) ratio and in the activities of superoxide dismutase (SOD; EC 1.1.5.1.1) and glutathione reductase (GR; EC 1.6.4.2) in NaCl+TU treatment as compared to that of NaCl treatment. Further, TU supplementation allowed plants to avoid an over-accumulation of pyridine nucleotides, to stimulate alternative pathways (through higher glycolate oxidase activity; EC 1.1.3.15) for channeling reducing equivalents and thus, to maintain the redox state to near control levels. These positive responses were also linked to an increased energy utilization (analyzed in terms of ATP/ADP ratio) and presumably to an early signaling of the stress through stimulated activity of ascorbate oxidase (EC 1.10.3.3), an important component of stress signaling. A significant reduction observed in the level of sodium ion (Na+) accumulation indicated that TU mediated tolerance is attributable to salt avoidance. Thus, the present study suggested that TU treatment regulated redox and antioxidant machinery to reduce the NaCl-induced oxidative stress. [Copyright &y& Elsevier]

Abstract: Sesuvium portulacastrum (L.) L., a facultative halophyte, is considered a suitable candidate for the phytoremediation of metals. An investigation of As accumulation and tolerance was conducted in Sesuvium plants upon exposure to As(V) (100–1000μM) for 30d. Plants demonstrated a good growth even after prolonged exposure (30d) to high As(V) concentrations (1000μM) and a significant As accumulation (155μgg−1 dry weight) with a bioaccumulation factor of more than ten at each concentration. The results of shoot and root dry weight, malondialdehyde accumulation, photosynthetic pigments, and total soluble proteins demonstrated that plants did not experience significant toxicity even at 1000μM As(V) after 30d. However, metabolites (total non-protein thiols and cysteine) and enzymes (serine acetyltransferase, cysteine synthase and γ-glutamylcysteine synthetase) of thiol metabolism, in general, remained either unaffected or showed slight decline. Hence, plants tolerated high As(V) concentrations without an involvement of thiol metabolism as a major component. Taken together, the results indicate that plants are potential As accumulator and may find application in the re-vegetation of As contaminated sites. [ABSTRACT FROM AUTHOR]

Abstract: The uranium (U) accumulation potential and ensuing biochemical responses were studied in Hydrilla verticillata (L.f.) Royle upon exposure to U (0, 20 and 100mgL−1). There was a concentration-duration dependent increase in U accumulation with the maximum being 78mgg−1 DW at 100mgL−1 U after 24h. Plants experienced an initial phase of the maximum toxicity (within 30min) followed by almost complete recovery after 24h. The recovery was attributed to an integrated modulation in the level of both enzymatic and molecular antioxidants (viz., guaiacol peroxidase, ascorbate peroxidase, catalase, proline, total phenolics) and also the constituents of thiol metabolism (viz., cysteine and glutathione). Thus, plants were found to be able to accumulate significant amount of U in a short time and to tolerate it efficiently. Hence, they may find application in U phytoremediation considering there accumulation ability, fast growth due to weed-like habit and world-wide distribution. [Copyright &y& Elsevier]

Abstract: Ceratophyllum demersum L. is known to be a potential accumulator of arsenic (As), but mechanisms of As detoxification have not been investigated so far. In the present study, we analyzed the biochemical responses of Ceratophyllum plants to arsenate (AsV; 0–250μM) exposure to explore the underlying mechanisms of As detoxification. Plants efficiently tolerated As toxicity up to concentrations of 50μM AsV and durations of 4 d with no significant effect on growth by modulating various pathways in a coordinated and complementary manner and accumulated about 76μgAsg−1 dw. Significant increases were observed in the levels of various thiols including phytochelatins (PCs), the activities of enzymes of thiolic metabolism as well as arsenate reductase (AR). These primary responses probably enabled plants to detoxify at least some part of AsV through its reduction and subsequent complexation. The maximum proportion of As chelated by PCs was found to be about 30% (at 50μM AsV after 2 d). Simultaneously, a significant increase in the activities of antioxidant enzymes was observed and hence plants did not experience oxidative stress when exposed to 50μM AsV for 4 d. Exposure of plants to higher concentrations (250μM AsV) and/or for longer durations (7 d) resulted in a significant increase in the level of As (maximum 525μgg−1 dw at 250μM after 7 d) and an inverse relationship between As accumulation and various detoxification strategies was observed that lead to enhanced oxidative stress and hampered growth. [Copyright &y& Elsevier]

Arsenic toxicity has become a global concern owing to the ever-increasing contamination of water, soil and crops in many regions of the world. To limit the detrimental impact of arsenic compounds, efficient strategies such as phytoremediation are required. Suitable plants include arsenic hyperaccumulating ferns and aquatic plants that are capable of completing their life cycle in the presence of high levels of arsenic through the concerted action of arsenate reduction to arsenite, arsenite complexation, and vacuolar compartmentalization of complexed or inorganic arsenic. Tolerance can also be conferred by lowering arsenic uptake by suppression of phosphate transport activity, a major pathway for arsenate entry. In many unicellular organisms, arsenic tolerance is based on the active removal of cytosolic arsenite while limiting the uptake of arsenate. Recent molecular studies have revealed many of the gene products involved in these processes, providing the tools to improve crop species and to optimize phytoremediation; however, so far only single genes have been manipulated, which has limited progress. We will discuss recent advances and their potential applications, particularly in the context of multigenic engineering approaches. [Copyright &y& Elsevier]

Abstract: Copper, though essential, is potentially toxic heavy metal at supraoptimal level and has widespread contamination. The present investigation was carried out to study the responses induced by lower as well as higher doses of copper (0.1–25μM) in an aquatic macrophyte, Hydrilla verticillata (L.f.) Royle for a period of 1–7 days. The plants accumulated copper in high amount with a maximum of 770μgg−1 dw on day 7 at 25μM. Biomass and photosynthetic pigments showed less alteration up to 1μM while at higher concentrations, significant decline occurred. Malondialdehyde (MDA) content and electrical conductivity (EC) also showed sharp increase at higher concentrations indicating oxidative stress. In response to copper exposure, plants showed significant induction of proteins and enzymes like superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT) and glutathione reductase (GR), however, only up to moderate exposures. Total non-protein thiols (NP-SH) and cysteine levels increased significantly up to 5μM copper exposure while at 25μM, their level declined drastically. Reduced glutathione (GSH) showed decrease at all concentrations while oxidized glutathione (GSSG) simultaneously increased. Phytochelatins (PCs) were also induced significantly at studied concentrations of 1 and 5μM on day 4 in comparison to control. However, copper chelation depicted by PC-SH to copper ratio was found to be low (6.5% at 1μM and 2.4% at 5μM) suggesting that PCs play only a part in integrated mechanisms of copper homeostasis and detoxification. Tolerant response of plants to moderate copper exposures and high accumulation potential warrants their suitability for remediation of moderately copper polluted water bodies. [Copyright &y& Elsevier]

Abstract: Fruit ripening in climacteric fruit is triggered by ethylene and associated with the expression of hundreds of genes that influence various ripening related changes. We have used mRNA differential display to identify 22 ripening related genes in banana of which only two have previously been characterized in banana. Transcript analyses show that six genes are down-regulated and 16 up-regulated during the course of ripening with varied patterns of transcript accumulation. Treatment with 1-methylcyclopropene inhibits ripening and represses the expression of most of the up-regulated genes indicating that their expression is directly or indirectly governed by ethylene. The expression of most of the up- and down-regulated genes is specific to fruit and not observed in other tissues. Short time ethylene treatment of banana fruit reveals the induction of four up-regulated genes within 10–30min of ethylene treatment and the repression of two down-regulated genes within 30–60min of ethylene treatment. Sequence analyses reveal homology to genes that are involved in diverse processes such as gene regulation/signaling, defense, softening and other unknown functions. The studies have identified several candidate genes whose promoters could be used for isolation of specific cis elements involved in fruit specific expression as well as those responsible for ethylene induction and repression. [Copyright &y& Elsevier]

Arsenic (As) is a ubiquitous environmental carcinogen that enters the human food chain mainly through rice grains. In the present study, we evaluated the potential of thiourea (TU; non-physiological reactive oxygen species scavenger) in mitigating the negative effects of arsenic (As) stress in indica rice variety IR64, with the overall aim to reduce grain As accumulation. At seedling stage, As + TU treatment induced the formation of more numerous and longer crown roots compared with As alone. The As accumulation in main root, crown root, lower leaf and upper leaf was significantly reduced to 0.1-, 0.14-, 0.16-, 0.14-fold, respectively in As + TU treated seedlings compared with those of As alone. This reduced As accumulation was also coincided with light-dependent suppression in the expression levels of aquaporins and photosynthesis-related genes in As + TU treated roots. In addition, the foliar-supplemented TU under As-stress maintained reducing redox conditions which decreased the rate of As accumulation in flag leaves and, eventually grain As by 0.53-fold compared with those of As treatment. The agronomic feasibility of TU was validated under naturally As contaminated sites of Nadia (West Bengal, India). The tiller numbers and crop productivity (kg seed/ha) of TU-sprayed plants were increased by 1.5- and 1.18-fold, respectively; while, grain As accumulation was reduced by 0.36-fold compared with those of water-sprayed control. Thus, this study established TU application as a sustainable solution for cultivating rice in As-contaminated field conditions. [Display omitted] • Crown root formation was activated as an adaptive mechanism under arsenic stress. • Thiourea supplementation reduced arsenic accumulation from root and leaves. • Thiourea downregulated aquaporins and photosynthesis related genes in roots. • Thiourea mediated changes coincided with increased salicylic acid accumulation. • Foliar-spray of thiourea enhanced yield and reduced grain arsenic accumulation. Thiourea supplementation downregulated aquaporins to restrict arsenic accumulation in seedlings. Foliar-applied thiourea enhanced yield and reduced grain arsenic accumulation. [ABSTRACT FROM AUTHOR]

Tonoplast Intrinsic Proteins (TIPs) are vital in transporting water and solutes across vacuolar membrane. The role of TIPs in the arsenic stress response is largely undefined. Rice shows sensitivity to the arsenite [As[III]] stress and its accumulation at high concentrations in grains poses severe health hazards. In this study, functional characterization of OsTIP1;2 from Oryza sativa indica cultivar Pusa Basmati-1 (PB-1) was done under the As[III] stress. Overexpression of OsTIP1;2 in PB-1 rice conferred tolerance to As[III] treatment measured in terms of enhanced shoot growth, biomass, and shoot/root ratio of overexpression (OE) lines compared to the wild-type (WT) plants. Moreover, seed priming with the IRW100 yeast cells (deficient in vacuolar membrane As[III] transporter YCF1) expressing OsTIP1;2 further increased As[III] stress tolerance of both WT and OE plants. The dithizone assay showed that WT plants accumulated high arsenic in shoots, while OE lines accumulated more arsenic in roots than shoots thereby limiting the translocation of arsenic to shoot. The activity of enzymatic and non-enzymatic antioxidants also increased in the OE lines on exposure to As[III]. The tissue-specific localization showed OsTIP1;2 promoter activity in root and root hairs, indicating its possible root-specific function. After As[III] treatment in hydroponic medium, the arsenic translocation factor (TF) for WT was around 0.8, while that of OE lines was around 0.2. Moreover, the arsenic content in the grains of OE lines reduced significantly compared to WT plants. [Display omitted] • The overexpression of OsTIP1;2 induced resilience in the rice plants against the As[III] stress. • Seed priming with OsTIP1;2 expressing IRW100 yeast increased As[III] tolerance of overexpressed (OE) lines of rice. • The overexpression of OsTIP1;2 reduced arsenic translocation factor (TF) in rice. • The overexpression of OsTIP1;2 reduced arsenic content in rice grains. [ABSTRACT FROM AUTHOR]

The SIN3 family of co-repressors is a family of highly conserved eukaryotic repressor proteins that regulates diverse functions in yeasts and animals but remains largely uncharacterized functionally even in plants like Arabidopsis. The sole SIN3 homologue in banana, MaSIN3, was identified as a 1408 amino acids, nuclear localized protein conserved to other SIN3s in the PAH, HID and HCR domains. Interestingly, MaSIN3 over-expression in Arabidopsis mimics a state of reduced ABA responses throughout plant development affecting growth processes such as germination, root growth, stomatal closure and water loss, flowering and senescence. The reduction in ABA responses is not due to reduced ABA levels but due to suppression of expression of several transcription factors mediating ABA responses. Transcript levels of negative regulators of germination ( ABI3, ABI5, PIL5 , RGL2 and RGL3 ) are reduced post-imbibition while those responsible for GA biosynthesis are up-regulated in transgenic MaSIN3 over-expressers. ABA-associated transcription factors are also down-regulated in response to ABA treatment. The HDAC inhibitors, SAHA and sodium butyrate, in combination with ABA differentially suppress germination in control and transgenic lines suggesting the recruitment by MaSIN3 of HDACs involved in suppression of ABA responses in different processes. The studies provide an insight into the ability of MaSIN3 to specifically affect a subset of developmental processes governed largely by ABA. [ABSTRACT FROM AUTHOR]

The presence of arsenic (As) and heavy metals in soil and water resources has serious impact on ecosystem as well as human health. In India, West Bengal (W.B.) is severely contaminated by higher levels of As in water, soil and growing plants/crops. The present study was designed to examine the remediation ability of indigenous plant species, growing naturally in the As contaminated Dakshin Panchpota village of Nadia district (W.B.). Soil and water samples, collected from the site, showed higher levels of arsenic and heavy metals. For the study, total twenty eight plants (eighteen terrestrial, ten aquatic) were collected from the contaminated area and among them ten terrestrial and seven aquatic plants showed bioaccumulation factor (BCF) > 1, suggesting their role in As remediation and site restoration. Althernanthera ficoides demonstrated highest accumulation as well as translocation of As (TF > 1) among all the terrestrial plants tested, showing its suitability for remediation of As contaminated soil. More As was recorded in shoots than the roots in Phyllanthus amarus and Cyanodon dactylon , showing their feasibility for phytoextraction purpose. Among aquatic plants, Eicchornia crassipes and Marsilea quadrifolia were found most effective for As remediation. Besides As, plants have also shown potential to tolerate and accumulate Fe, Zn, Cu and Cr in their tissues. Thus, the results of this study showed that the naturally growing plant species have potential to remediate As contaminated site in the presence of elevated concentrations of heavy metals and can play an important role in ecological restoration, however, care should be taken owing to medicinal properties possessed by some of the accumulators. • Demonstrated phytoremediation ability of indigenous plants (28) growing in the As contaminated area • Soil and water samples showed higher levels of arsenic and heavy metals than permissible limit • Ten terrestrial and seven aquatic plants showed bioaccumulation factor (BCF) > 1 • Phyllanthus amarus and Cyanodon dactylon showed feasibility for phytoextraction purpose • Among aquatic plants, Eicchornia crassipes and Marsilea quadrifolia were effective for As remediation [ABSTRACT FROM AUTHOR]

In the present study, the level of thiols and activity of related enzymes were investigated in coontail (Ceratophyllum demersum L.) plants to analyze their role in combating the stress caused upon exposure to cadmium (Cd; 0–10μM) for a duration up to 7d. Plants showed the maximum accumulation of 1293μgCdg−1 dw after 7d at 10μM. Significant increases in the level of total non-protein thiols (NP-SH) including phytochelatins (PCs) as well as upstream metabolites of the PC biosynthetic pathway, cysteine and glutathione (GSH) were observed. In addition, significant increases in the activities of cysteine synthase (CS), glutathione-S-transferase (GST), glutathione reductase (GR), as well as in vitro activation of phytochelatin synthase (PCS), were noticed in response to Cd. In conclusion, under Cd stress, plants adapted to a new metabolic equilibrium of thiols through coordinated synthesis and consumption to combat Cd toxicity and to accumulate it. [Copyright &y& Elsevier]

• TIP1;1, TIP1;2, TIP2;2, TIP3;1 , and TIP4;1 were cloned from Oryza sativa ssp. indica cultivar IR-64. • In silico analysis of the cloned genes strongly support their identity as member of TIPs. • Cloned TIPs showed differential regulation pattern in various tissues and abiotic stress response. Tonoplast Intrinsic Proteins (TIPs) constitute a significant class of the aquaporins. The TIPs control water trade among cytosolic and vacuolar compartments and can also transport glycerol, ammonia, urea, hydrogen peroxide, metals/metalloids, and so forth. Additionally, TIPs are engaged with different abiotic stress responses and developmental processes like leaf expansion, root elongation and seed germination. In this study, ten TIP genes in the rice genome were identified from Oryza sativa ssp indica. Among these, representative groups of TIP genes were cloned and sequenced whilst some TIP sequences showed stop codons in the coding region. The secondary structure analysis represented six conserved transmembrane helices along with the inter-helical regions having conserved motifs. The representative three-dimensional tetrameric design of protein sequence of TIP1;1 displayed key features like NPA motifs, aromatic/arginine (ar/R) selectivity filters, and Froger's residues. The vacuolar localization, transmembrane topological properties, and conserved motif analysis of the cloned genes altogether supported their identity as TIPs. An unrooted phylogenetic tree delineated the relatedness of TIPs from Oryza with different species and bunched them into five clades. The promoter analysis uncovered key regulons associated with administering abiotic stress responses. Gene expression studies showed that TIPs are differentially regulated under salt and drought stress at various time points in shoots and roots of rice. Also, the pattern of expression was found to be significantly variable in five different rice tissues. The heat-map based tissue and stress- specific expression analysis supported the experimental findings. In conclusion, the identification and transcript-level expression studies of TIPs significantly contribute towards the comprehension of their utilitarian significance in the abiotic stress response. [ABSTRACT FROM AUTHOR]

The present experiment was designed to evaluate physico-chemical characteristics and phyto-genotoxicity of arsenic (As) contaminated soil collected from different sites of Lakhimpur, Uttar Pradesh (UP), India by employing Vicia faba L. The analyses included various biochemical as well as cyto-genotoxicity assays. The results showed that soil pH was slightly acidic to neutral in nature. The bulk density (1.18–1.23 gcm−3), particle density (2.51–2.59 gcm−3) and porosity (44–53%) varied in different places. The level of available nutrients, nitrogen, phosphorus and potassium was found to vary as 124–165 mgkg-1, 173–186 mgkg-1 and 48–98 mgkg-1, respectively. The maximum As levels were found in soil of Fulvareya (27.13 mgkg−1) and Atareya (24.12 mgkg−1), the level of As in water samples of these sites were 0.19 mgl−1and 0.21 mgl−1, respectively. Phytotoxicity of the As present in soils was evident through significant increases in stress metabolites, hydrogen peroxide (H 2 O 2), malondialdehyde (MDA) and carbonyl groups in root and shoot of V. faba. Cyto-genotoxic effects were also seen through reduced mitotic index (MI) and increased mitotic depression (MD), relative abnormality rate (RAR) as well as other chromosomal abnormalities along with micronuclei in root meristematic cells of V. faba. The phytotoxicity and cyto-genotoxicity assessment suggests the harmful soil properties that might affect biota. • Phyto-Genotoxicity of arsenic contaminated soil was assayed using Vicia faba L. • Phytotoxic markers showed increased oxidative stress like H 2 O 2 , MDA and carbonyl groups. • Genotoxic markers measured via induced frequency of various chromosomal anomalies. • Vicia faba L. can serve as a promising bioindicator for arsenic toxicity. [ABSTRACT FROM AUTHOR]

Highlights • The major source of arsenic exposure in human is rice and rice-based products. • Apart from rice, As levels in other important dietary sources has also been covered. • The level of As species (iAs/oAs) influences the associated As toxicity in food. • It is mandatory to set the regulatory limits of arsenic in food at earliest. Abstract Arsenic (As) is a carcinogenic element threatening the health of millions of people around the world. The sources for human exposure include drinking water, crops, processed food items, vegetables, mushrooms, animal products etc. The people at most risk are those living in hotspots of As contamination viz., Bangladesh and West Bengal, India. However, it has been found that rice growing in other uncontaminated regions like Australia can also contain high As levels. Further, rice import/export among various countries make the problem of global concern. The emergence of several reports of As in rice based food products including baby food from different parts of the world demonstrates that even the infants and toddlers are not spared. The variation in the levels of inorganic and organic As species in different food items influence the associated As toxicity. This review tries to present the available data on As levels in various dietary sources. [ABSTRACT FROM AUTHOR]

Abstract The rapid pace of industrial, agricultural and anthropogenic activities in the 20th century has resulted in contamination of heavy metals across the globe. Arsenic (As) is a ubiquitous, naturally occurring toxic metalloid, contaminating the soil and water and affecting human health in several countries. Several physicochemical methods exist for the cleanup of As contamination but these are expensive and disastrous to microbes and soil. Plant based remediation approaches are low cost and environmentally safe. Hence, extensive biochemical, molecular and genetic experiments have been conducted to understand plants’ responses to As stress and have led to the identification of potential genes. The available knowledge needs to be utilized to either reduce As accumulation in crop plants (rice) or to enhance As levels in shoots of hyperaccumulators (Pteris vittata). Gene manipulation using biotechnological tools can be an effective approach to exploit the potential genes (plasmamembrane and vacuolar transporters, glutathione and phytochelatin biosynthetic enzymes, etc.) playing pivotal roles in uptake, translocation, transformation, complexation, and compartmentalization of As in plants. The transgenic plants with increased tolerance to As and altered (increased/decreased) As accumulation have been developed. The need, however, exists to design plants with altered expression of two or more genes for harmonizing various events (like arsenate reduction, arsenite complexation, sequestration and translocation) so as to achieve desirable reduction (crop plants) or increase (phytoremediator plants) in As content. This review sheds light on transgenic approaches adopted to modulate As levels in plants and proposes future directions to achieve desirable results. Highlights • Arsenic is a toxic metalloid and a potential health hazard across the globe. • Arsenic stress responsive mechanisms and responsible crucial genes have been identified. • This review deals with the use of transgenic plants as an effective approach for arsenic removal. • The review also discusses the use of potential genes for lowering arsenic accumulation in crop plants. [ABSTRACT FROM AUTHOR]

In the present study, arsenic (As) toxicity amelioration potential of a consortium of plant growth promoting rhizobacterium ( Pseudomonas putida ) and alga ( Chlorella vulgaris ) was evaluated during arsenate (AsV) exposure to rice ( Oryza sativa ) plants for 15 d. The consortium mediated amelioration of As toxicity was evident through improved growth of rice plants (root and shoot length and biomass) and reduced oxidative stress [as level of superoxide radicals (O 2 − ), hydrogen peroxide (H 2 O 2 ) and membrane damage]. The positive responses were attributable to a significant decline in As accumulation in root (94 mg kg −1 dw) and shoot (51 mg kg −1 dw) in consortium ( P. putida  +  C. vulgaris ) inoculated seedlings as compared to As alone exposed plants (156 and 98 mg kg −1 dw, respectively). There were also significant changes in the level of various nutrient elements (Mn, Fe, Co, Zn, Mo and Cu), thiols and in the activities of antioxidant and thiol metabolism enzymes in the consortium inoculated seedlings that allowed the plants to tolerate As stress effectively and achieve better growth. The study demonstrated that consortium of P. putida and C. vulgaris may alleviate As stress and improve growth of rice seedlings along with reduction in As levels. [ABSTRACT FROM AUTHOR]

The present study analysed the levels of potentially toxic elements along with physico-chemical properties of agricultural soil samples (n = 59) collected from fields situated along the path of river Ganga in the middle Gangetic floodplain in two districts, Ballia and Ghazipur. Arsenic (As), chromium (Cr), copper (Cu), nickel (Ni), zinc (Zn), lead (Pb), iron (Fe) and manganese (Mn) levels were analysed by Wavelength Dispersive-X-Ray Fluorescence Spectroscopy (WD-XRF) and the associated health risks along with diverse indices were calculated. The mean concentrations of As, Cu, Cr, Pb, Zn and Ni were found to be 15, 42, 85, 18, 87 and 47 mg kg−1, respectively in Ballia and 13, 31, 73, 22, 77 and 34 mg kg−1, respectively in Ghazipur. Physico-chemical properties like pH, ORP and organic matter were found to be 7.91, 209 and 1.20, respectively in Ballia and 8.51, 155 and 1.25, respectively in Ghazipur. The calculated health quotient (HQ) for all the elements was observed to be within the threshold value of one, however with few exemptions. Therefore, the present study showcases the contamination of potentially toxic elements in agricultural fields and possible health hazards for people. [Display omitted] • Agricultural soil were collected from middle Gangetic Basin in Uttar pradesh, India. • PTE's (As, Cr, Pb, Zn, Ni, and Cu) concentration were analysed by WD-XRF method. • Hazard quotient and Incremental lifetime cancer risk (ILCR) were analysed. [ABSTRACT FROM AUTHOR]

Metallothioneins (MTs) are diverse class of cysteine-rich proteins having metal-chelation properties. The role of MTs has been demonstrated in different abiotic stresses and MTs have been designated as biomolecular stress markers. Chickpea is an important legume crop supplying proteins to humans, as well as acting as great soil-binders along with nitrogen-fixation capability. The present research deals with the development of transgenic chickpea overexpressing metallothionein type-1 (CarMT1) gene for analyzing its role in stress tolerance against drought and heavy metals. The overexpression construct was designed using binary expression vector, pBI121 and transformed in chickpea desi cultivar, Pusa-362 for functional validation by using sonication-assisted Agrobacterium -mediated transformation. The results indicated high transcript levels under the drought (22-folds) and changes in physiological (photosynthesis rate, transpiration rate, stomatal conductance, water-use efficiency) and biochemical (antioxidant enzymes and compatible solutes) parameters suggesting stress-mitigating roles of CarMT1. The transgenic seeds were evaluated for heavy metal stress adaptation that resulted in better seed survival efficiency under different heavy metal stresses. The results indicated beneficial roles of MT gene in transgenic lines of chickpea in presence of different abiotic stresses, which could pave the way for multi-stress tolerant crop development. A schematic representation of working of MT gene in response to drought stress in transgenic chickpea plants. [Display omitted] • CarMT1 gene over-expressed in chickpea indicates drought and heavy metal stress enduring roles. • Transgenic plants were better in seed germination and root growth. • Physio-biochemical and molecular characterization reported stress adaptive roles. • Transgenic plants resulted up to 22-fold change in expression in comparison to control. [ABSTRACT FROM AUTHOR]

Thiourea (TU) is a chemo-priming agent and non-physiological reactive oxygen species (ROS) scavenger whose application has been found to reduce As accumulation in rice grains along with improved growth and yield. The present field study explored TU-mediated mechanistic changes in silicon (Si) assimilation in root/shoot, biochemical and molecular mechanisms of arsenic (As) stress amelioration in rice cultivars. Gosai and Satabdi (IET-4786) rice cultivars were selected for field experiment at three different places; control field and two other As contaminated experimental fields (EF1 and EF2) in West Bengal, India. The average As reduction was observed to be 9.5% and 19.8% whereas the yield increment was 8.8% and 17.7% for gosai and satabdi, respectively among all the three experimental fields. The positive interrelation was also observed between improved internal ultrastructure anatomy and enhanced Si assimilation (36%–423%) upon TU application. The level of photosynthetic pigments was increased by 29.8%–99.2%. Further, activities of antioxidant enzymes were harmonically altered in TU supplemented plants. The expression of various As related transporter genes in flag leaf and developing grains (inflorescence) was changed in both the rice cultivars (gosai and satabdi). It was also presumably responsible for observed As reduction in grains. Thus, TU application was found to be an efficient and sustainable agronomic practice for amelioration of As toxicity in rice plants in As contaminated field conditions. [Display omitted] • Thiourea reduced 9.5% and 19.8% grain arsenic in gosai and satabdi respectively. • Thiourea improved pigment content and reduced oxidative stress in rice cultivars. • Thiourea improved ultrastructure anatomy by enhanced silica assimilation in rice. • Thiourea reduced As in rice cultivars through modulation in gene expressions. [ABSTRACT FROM AUTHOR]

The increasing industrialization and urbanization are also triggering environmental pollution, mostly unnoticed, in the case of soil pollution due to uncontrolled contamination by toxic elemental dispersion. The present study focused on this aspect and studied the clean-up of urban soil in a low-cost and eco-friendly way to restrict arsenic (As), lead (Pb) and mercury (Hg) contamination. Four potential ornamental plants, C atharanthus roseus (vinca) , Cosmos bipinnatus (cosmos) , Gomphrena globose (globosa) and Impatiens balsamina (balsamina) were used along with zero valent iron (ZVI) nanoparticles (Fe NPs) for remediation of the soil spiked with As (70 mg kg−1), Pb (600 mg kg−1) and Hg (15 mg kg−1) in a 60 d pot experiment. All plants were divided into four groups viz. control, spiked, spiked+20 mg kg−1 ZVI NP and spiked+50 mg kg−1 ZVI NP. FTIR and SEM were used for ZVI NP characterization. Soil and plant analyses and elemental assessments were done using ICP-MS, XRF and SEM. Among the four plants, cosmos showed the maximum accumulation of toxic elements (41.24 ± 0.022 mg kg−1 As, 139.15 ± 11.2 mg kg−1 Pb and 15.57 ± 0.27 mg kg−1 Hg) at 60 d. The application of ZVI NP at 20 mg kg−1 dosage was found to further augment plants' potential for metal(loid)s accumulation without negatively hampering their growth. Cosmos were observed to reduce soil As from 81.35 ± 1.34 mg kg−1 to 28.16 ± 1.38 mg kg−1 (65.38%), Pb from 1132.47 ± 4.66 to 516.09 ± 3.15 mg kg−1 (54.42%) and Hg from 17.35 ± 0.88 to 6.65 ± 0.4 mg kg−1 (61.67%) at 60 d in spiked + 20 mg kg−1 ZVI NP treatment. Balsamina was the most sensitive plant and showed the least metal(loid)s accumulation. In conclusion, three of these plants are potent enough to use together for a better and enhanced removal of toxic elements from the contaminated soil with cosmos to be the best amongst these in urban areas. [Display omitted] • Soil arsenic, lead and mercury contamination in urban areas is addressed. • Potential flowering plants were tested for phytoremoval of soil metal(loid)s. • The best, Cosmos bipinnatus, removed soil As (65.38%), Pb (54.42%) and Hg (61.67%). • Applied 20 ppm Fe nanoparticles assist plants in more efficient element removal. • Post-experimental soil was found having low bioavailability of selected elements. [ABSTRACT FROM AUTHOR]

Abstract: Recent breakthroughs in rice arsenic (As) research demonstrate that As accumulation significantly affects trace nutrients in rice grain. In the present study we analyzed the amino acid (AA) profile of sixteen rice genotypes differing in grain As accumulation, grown at three sites with different soil As concentrations, in ascending order, Chinsurah