Irrigation of paddy fields to arsenic (As) containing groundwater leads to As accumulation in rice grains and causes serious health risk to the people worldwide. To reduce As intake via consumption ...of contaminated rice grain, identification of the mechanisms for As accumulation and detoxification in rice is a prerequisite. Herein, we report involvement of a member of rice NRAMP (Natural Resistance‐Associated Macrophage Protein) transporter, OsNRAMP1, in As, in addition to cadmium (Cd), accumulation through expression in yeast and Arabidopsis. Expression of OsNRAMP1 in yeast mutant (fet3fet4) rescued iron (Fe) uptake and exhibited enhanced accumulation of As and Cd. Expression of OsNRAMP1 in Arabidopsis provided tolerance with enhanced As and Cd accumulation in root and shoot. Cellular localization revealed that OsNRAMP1 resides on plasma membrane of endodermis and pericycle cells and may assist in xylem loading for root to shoot mobilization. This is the first report demonstrating role of NRAMP in xylem mediated loading and enhanced accumulation of As and Cd in plants. We propose that genetic modification of OsNRAMP1 in rice might be helpful in developing rice with low As and Cd content in grain and minimize the risk of food chain contamination to these toxic metals.
Arsenic (As) is a highly toxic environmental pollutant which accumulates in rice grain and causes chronic and epidemic effects on human health. We report role of rice NRAMP (Natural Resistance‐Associated Macrophage Protein) transporter, OsNRAMP1, in As, in addition to cadmium (Cd), accumulation through expression in yeast and Arabidopsis. Cellular localization revealed that OsNRAMP1 resides on plasma membrane of endodermis and pericycle cells and may assist in xylem loading for root to shoot mobilization. This is the first report demonstrating role of NRAMP in xylem mediated loading and enhanced accumulation of As and Cd in plants.
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.
•Arsenic affects plant growth and human health due to food chain contamination.•Omics can be an important tool to identify arsenic associated molecular networks.•Biotechnological interventions can modulate arsenic response in plants.•This review updates gene mining and approaches to develop altered arsenic response.
Fifteen fungal strains were isolated from arsenic contaminated (range 9.45–15.63
mg
kg
−
1
) agricultural soils from the state of West Bengal, India. Five fungal strains were belonged to the
...Aspergillus and
Trichoderma group each, however, remaining five were identified as the
Neocosmospora,
Sordaria,
Rhizopus,
Penicillium and sterile mycelial strain. All these fungal strains were cultivated on medium supplemented with 100, 500, 1000, 5000 and 10,000
mg
l
−
1
of sodium arsenate. After 30-day cultivation under laboratory conditions, radial growth of these strains was determined and compared with control. Toxicity and tolerance of these strains to arsenate were evaluated on the basis of tolerance index. Out of fifteen, only five fungal strains were found resistant and survived with tolerance index pattern as 0.956 (sterile mycelial strain)
>
0.311 (
Rhizopus sp.)
>
0.306 (
Neocosmospora sp.)
>
0.212 (
Penicillium sp.)
>
0.189 (
Aspergillus sp.) at 10,000
mg
l
−
1
of arsenate. The arsenic removal efficacy of ten fungal strains, tolerant to 5000
mg
l
−
1
arsenate, was also assayed under laboratory conditions for 21
days. All these strains were cultivated individually on mycological broth enriched with 10
mg
l
−
1
of arsenic. The initial and final pH of cultivating medium, fungal biomass and removal of arsenic by each fungal strain were evaluated. Fungal biomass of ten strains removed arsenic biologically from the medium which were ranged from 10.92 to 65.81% depending on fungal species. The flux of biovolatilized arsenic was determined indirectly by estimating the sum of arsenic content in fungal biomass and medium. The mean percent removal as flux of biovolatilized arsenic ranged from 3.71 to 29.86%. The most effective removal of arsenic was observed in the
Trichoderma sp., sterile mycelial strain,
Neocosmospora sp. and
Rhizopus sp. fungal strains. These fungal strains can be effectively used for the bioremediation of arsenic-contaminated agricultural soils.
► Biological removal of arsenic by different fungal strains. ► Fungal strains isolated from arsenic contaminated soils. ► Five fungal strains resistant at 10,000
mg
l
−
1
of arsenate. ► Flux of biovolatilized arsenic ranged from 3.71 to 29.86%. ► Fungal strains can be effectively used for the bioremediation of arsenic-contaminated agricultural soils.
•Microbial consortium of P. putida and C. vulgaris improved the growth and reduced arsenic induced oxidative stress in rice.•The consortium reduced the accumulation of arsenic and also improved the ...level of nutrient elements in rice.•Reduced arsenic in rice due to the consortium alleviated the requirement of thiols and antioxidant enzymes.
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 (O2−), hydrogen peroxide (H2O2) 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.
Arsenic (As) contamination in rice leads to yield decline and causes carcinogenic risk to human health. Although the role of nitric oxide (NO) in reducing As toxicity is known, NO-mediated genetic ...modulation in the plant during arsenic toxicity has not yet been established. We analyzed the key components of NO metabolism and the correlations between NO interaction and arsenic stress using rice as a relevant model plant. Illumina sequencing was used to investigate the NO-mediated genome-wide temporal transcriptomic modulation in rice root upon AsIII exposure during 12 days (d) of the growth period. Sodium nitroprusside (SNP) was used as NO donor. SNP supplementation resulted in marked decrease in ROS, cell death and As accumulation during AsIII stress. NO was found to modulate metal transporters particularly NIP, NRAMP, ABC and iron transporters, stress related genes such as CytP450, GSTs, GRXs, TFs, amino acid, hormone(s), signaling and secondary metabolism genes involved in As detoxification. We detected NO-mediated change in jasmonic acid (JA) content during AsIII stress. The study infers that NO reduces AsIII toxicity through modulating regulatory networks involved in As detoxification and JA biosynthesis.
Arsenic is commonly present in subsoil and is a carcinogen in humans. Rice takes up arsenic and it accumulates in different plant parts, including grains, at levels several-fold higher than the soil. ...In high arsenic regions, rice can contribute substantially to arsenic intake by the human population. Arsenic in rice grains is present in the carcinogenic inorganic or the relatively safer organic (methylated) form. A wide variation is noticed in different rice genotypes with respect to the proportion of arsenic in these forms in grains. Mechanisms involved in arsenic uptake, efflux from roots, loading into xylem, transport, partitioning, arsenate reduction, arsenic sequestration in vacuoles, volatilization from leaves, accumulation in grains etc. are poorly understood. Selection of cultivars accumulating low inorganic arsenic is an important trait to be used by breeders to develop rice varieties safer for cultivation in arsenic-contaminated regions. Systematic efforts have not been made to screen rice genotypes for mining the genes involved in arsenic uptake, transport and accumulation in grains. Identification of rice germplasm with varying arsenic uptake and partitioning, and development of mapping populations with contrasting grain arsenic, are required for association studies and QTL mapping for accelerating rice improvement. Efforts on gene expression profiling, deep transcriptome sequencing, high throughput metabolomics and phenotyping of contrasting arsenic accumulating lines need to be increased to develop strategies for design of safer rice varieties. Network research projects need to be developed along these approaches to accelerate the development of crop varieties safer for farming in arsenic-contaminated environments.
► Si addition significantly reduces As accumulation in rice. ► Si ameliorated As induced oxidative stress in both the cultivars. ► Si addition enhanced the level of antioxidant enzymes and their ...isozymes in rice during As(III) stress. ► Si addition reduced As phytotoxicity more significantly in tolerant rice than sensitive rice.
Arsenic (As) contamination of paddy rice in South and South-East Asia has raised much concern as rice is the subsidence diet for millions. Two contrasting rice (Oryza sativa L.) cultivars i.e. Triguna (As tolerant) and IET-4786 (As sensitive) were grown hydroponically to study the effect of silicon (Si) supplementation on As accumulation, growth, oxidative stress and antioxidative defence system in shoots during arsenite As(III) stress. Rice seedlings were exposed to three As(III) levels (0, 10 and 25μM) and three silicic acid levels (0, 0.5 and 1mM Si) in solution culture experiments. Addition of 1mM Si during As(III) exposure significantly lowers shoot As accumulation in both the cultivar, but more prominently in Triguna (P≤0.01) than IET-4786 (P≤0.05). However, addition of Si during As(III) stress had no significant effect on shoot length and dry weight (P<0.01) of both the cultivars, compared to their As(III) treated plants. In contrast to IET-4786 (P≤0.05), Triguna tolerated As induced oxidative stress through elevated level of cysteine, enhanced antioxidant enzymes activities and their isozymes. Upon Si supplementation lower conglomeration of oxidative stress parameters viz., superoxide and peroxide radicals, lipid peroxidation and electrolyte leakage coincides with increased antioxidants activities and enhanced level of thiols, more effectively in shoots of Triguna than IET-4786 during As(III) stress (P≤0.05). In conclusion, 1mM Si addition, significantly ameliorates As induced oxidative stress in Triguna cultivar by lowering the As accumulation and improving antioxidant and thiolic system compared to IET-4786, implying genotypic differences with Triguna being less susceptible to stress dependent membrane lipid peroxidation.
Glutaredoxins (Grxs) are a family of small multifunctional proteins involved in various cellular functions, including redox regulation and protection under oxidative stress. Despite the high number ...of Grx genes in plant genomes (48 Grxs in rice), the biological functions and physiological roles of most of them remain unknown. Here, the functional characterization of the two arsenic-responsive rice Grx family proteins, OsGrx_C7 and OsGrx_C2.1 are reported. Over-expression of OsGrx_C7 and OsGrx_C2.1 in transgenic Arabidopsis thaliana conferred arsenic (As) tolerance as reflected by germination, root growth assay, and whole plant growth. Also, the transgenic expression of OsGrxs displayed significantly reduced As accumulation in A. thaliana seeds and shoot tissues compared to WT plants during both AsIII and AsV stress. Thus, OsGrx_C7 and OsGrx_C2.1 seem to be an important determinant of As-stress response in plants. OsGrx_C7 and OsGrx_C2.1 transgenic showed to maintain intracellular GSH pool and involved in lowering AsIII accumulation either by extrusion or reducing uptake by altering the transcript of A. thaliana AtNIPs. Overall, OsGrx_C7 and OsGrx_C2.1 may represent a Grx family protein involved in As stress response and may allow a better understanding of the As induced stress pathways and the design of strategies for the improvement of stress tolerance as well as decreased As content in crops.
Arsenic (As) contamination of water is a global concern and rice consumption is the biggest dietary exposure to human posing carcinogenic risks, predominantly in Asia. Sulfur (S) is involved in ...di-sulfide linkage in many proteins and plays crucial role in As detoxification. Present study explores role of variable S supply on rice leaf proteome, its inclination towards amino acids (AA) profile and non protein thiols under arsenite exposure. Analysis of 282 detected proteins on 2-DE gel revealed 113 differentially expressed proteins, out of which 80 were identified by MALDI-TOF-TOF. The identified proteins were mostly involved in glycolysis, TCA cycle, AA biosynthesis, photosynthesis, protein metabolism, stress and energy metabolism. Among these, glycolytic enzymes play a major role in AA biosynthesis that leads to change in AAs profiling. Proteins of glycolytic pathway, photosynthesis and energy metabolism were also validated by western blot analysis. Conclusively S supplementation reduced the As accumulation in shoot positively skewed thiol metabolism and glycolysis towards AA accumulation under AsIII stress.
World wide arsenic (As) contamination of rice has raised much concern as it is the staple crop for millions. Four most commonly cultivated rice cultivars, Triguna, IR-36, PNR-519 and IET-4786, of the ...West Bengal region were taken for a hydroponic study to examine the effect of arsenate (As
V) and arsenite (As
III) on growth response, expression of genes and antioxidants vis-à-vis As accumulation. The rice genotypes responded differentially under As
V and As
III stress in terms of gene expression and antioxidant defences. Some of the transporters were up-regulated in all rice cultivars at lower doses of As species, except IET-4786. Phytochelatin synthase, GST and γ-ECS showed considerable variation in their expression pattern in all genotypes, however in IET-4786 they were generally down-regulated in higher As
III stress. Similarly, most of antioxidants such as superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) increased significantly in Triguna, IR-36 and PNR-519 and decreased in IET-4786. Our study suggests that Triguna, IR-36 and PNR-519 are tolerant rice cultivars accumulating higher arsenic; however IET-4786 is susceptible to As-stress and accumulates less arsenic than other cultivars.
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