Phytochelatin Synthesis Research Articles

Plants prioritize phytochelatin synthesis during cadmium exposure even under reduced sulfate uptake caused by the disruption of SULTR1;2

ABSTRACTGlutathione and phytochelatins are sulfur containing compounds playing an important role in cadmium (Cd) detoxification. We examined the Cd-induced changes in the percentage of sulfur containing compounds to total sulfur in wild-type and sulfate transporter 1;2 knockout mutant, sel1–10. Cd treatment increased the proportion of sulfate and thiols in the total sulfur content. Among the thiols analyzed, the proportion of cysteine and glutathione were decreased by the Cd treatment and that of the phytochelatins were increased. Although the total sulfur content in sel1–10 was decreased compared with that in wild-type, the percentages of individual thiol in the total thiol content were similarly maintained between sel1–10 and wild-type, suggesting that plants tightly controlled the balance of each thiol under Cd treatment.

The phytochelatin synthase gene in date palm (Phoenix dactylifera L.): Phylogeny, evolution and expression

We studied date palm phytochelatin synthase type I (PdPCS1), which catalyzes the cytosolic synthesis of phytochelatins (PCs), a heavy metal binding protein, in plant cells. The gene encoding PdPCS1 (Pdpcs) consists of 8 exons and 7 introns and encodes a protein of 528 amino acids. PCs gene history was studied using Notung phylogeny. During evolution, gene loss from several lineages was predicted including Proteobacteria, Bilateria and Brassicaceae. In addition, eleven gene duplication events appeared toward interior nodes of the reconciled tree and four gene duplication events appeared toward the external nodes. These latter sequences belong to species with a second copy of PCs suggesting that this gene evolved through subfunctionalization. Pdpcs1 gene expression was measured in seedling hypocotyls exposed to Cd, Cu and Cr using quantitative real-time polymerase chain reaction (qPCR). A Pdpcs1 overexpression was evidenced in P. dactylifera seedlings exposed to metals suggesting that 1-the Pdpcs1 gene is functional, 2-there is an implication of the enzyme in metal detoxification mechanisms. Additionally, the structure of PdPCS1 was predicted using its homologue from Nostoc (cyanobacterium, NsPCS) as a template in Discovery studio and PyMol software. These analyses allowed us to identify the phytochelatin synthase type I enzyme in date palm (PdPCS1) via recognition of key consensus amino acids involved in the catalytic mechanism, and to propose a hypothetical binding and catalytic site for an additional substrate binding cavity.

Diurnal changes of subcellular glutathione content in Arabidopsis thaliana

The aim of this study was to investigate diurnal changes of subcellular glutathione content in leaves of Arabidopsis thaliana by immunohistochemistry and quantitative transmission electron microscopy. The results revealed major diurnal changes in glutathione content. The highest content was found within 2 - 3 h of exposure to light (increase of 489 % in mitochondria, 318 % in plastids, 857 % in nuclei, 511 % in peroxisomes, and 900 % in the cytosol when compared to that during darkness), followed by a strong drop (49 % in mitochondria and the cytosol, 53 % in plastids, 68 % in nuclei, 38 % in peroxisomes) within the next 1 - 2 h. Glutathione content was 67 % lower in mitochondria, 76 % in plastids, 73 % in nuclei, 50 % in peroxisomes, and 68 % in the cytosol at the end of the light period which lasted for 8 h when compared to highest content. Lowest glutathione content was found in most cell compartments at the very end of the dark period. In context with previous studies it could be concluded that low glutathione content at the end of the dark period was caused by lack of glycine and cysteine due to lack of photorespiration and decreased sulfur uptake and assimilation during darkness. The rapid increase of glutathione content observed within 3 h of light was most probably caused by a strong increase in glutathione synthesis triggered by increased glycine and cysteine content. The strong drop of glutathione after that period was most probably due to elevated glutathione degradation rate or increased use of glutathione for phytochelatin synthesis.

Phytochelatin synthesis in response to Hg uptake in aquatic plants near a chlor-alkali factory

The effects of mercury (Hg) released from a chlor-alkali factory in aquatic plants along the Ebro River basin (NE Spain) were analysed considering the phytochelatins (PCn) and their isoforms content in these plants. These compounds were analyzed using HPLC with amperometric detection, and the macrophytes species Ceratophyllum demersum and Myriopyllum spicatum were collected in two sampling campaigns, autumn and spring, respectively. To correlate the PCn content in macrophytes with the Hg contamination, analysis of total Hg (THg) content in plants and suspended particulate matter, as well as the dissolved-bioavailable fraction of Hg in water measured by the diffusive gradient in thin film (DGT) technique were done. The results confirm the presence of PC2-Ala in extracts of C. demersum and PC2-desGly in M. spicatum, and the concentration of these thiol compounds depends clearly on the distance between the hot spot and the downstream sites: the higher the levels are, the closer the hot spot is. Since most of the Hg is hypothesized to be associated with SPM and transported downstream, our results of the DGT suggest that trace amounts of Hg in water can be released as free metal ions yielding a certain accumulation in plants (reaching the ppb level) that are enough for activation of induction of PCs. A few PCs species have been determined, at different seasons, indicating that they can be used as good indicators of the presence of bioavailable Hg in aquatic media throughout the year.

Phosphorus mediation of cadmium stress in two mangrove seedlings Avicennia marina and Kandelia obovata differing in cadmium accumulation

Mangrove ecosystems are vulnerable to environmental threats. In order to elucidate the effect of phosphorus (P) on cadmium (Cd) tolerance and physiological responses in mangroves under Cd stress, a mangrove specie with salt exclusion Kandelia obovata and a specie with salt secretion Avicennia marina were compared in a hydroponic experiment. The results showed that most Cd was accumulated in mangrove roots and that P addition induced Cd immobilisation in them. Cd stress significantly increased malonaldehyde content, whereas P significantly decreased malonaldehyde in mangroves. Phosphorus positively regulated the photosynthetic pigment, proline content and synthesis of non-protein thiols, glutathione and phytochelatins in the leaves under Cd stress conditions. The results suggest different adaptive strategies adopted by two mangroves in a complex environment and A. marina showed a stronger Cd tolerance than K. obovata. The study provides a theoretical basis for P mediated detoxification of Cd in mangrove plants.

Application of selective extraction and reverse phase chromatography with three detectors – PAD, FLD and ESI MS for characterization of platinum metabolites and identification of phytochelatins in Sinapis alba L. tissues

Several extraction procedures, with reagents having the potential to select different groups of compounds (water-soluble, polypeptide and polysaccharide complexes) were used to characterize platinum species in hydroponically cultivated plant white mustard (Sinapis alba L.). It was found, that 10% (roots) to 50% (leaves) of platinum species present in plants are soluble in water. Platinum is also bound to the hydrophobic proteins and polysaccharides in the cell walls. In plants exposed to the contaminant during the whole time of their cultivation, platinum was stronger bond to the matrix in comparison with plants exposed to platinum salt for the last week of their growth. To control the synthesis of phytochelatins in plants three different procedures were applied. Triple-step pulsed amperometry was used to detect selectively sulfur-containing compounds after their chromatographic separation. In the extract of mustard leaves together with other investigated thiol-compounds, phytochelatin containing two α-glutamylcysteine dipetide groups (PC2) was found. The presence of PC2 in plant extract was confirmed by HPLC FLD and ESI MS analysis after thiols derivatisation.

A role for APX1 gene in lead tolerance in Arabidopsis thaliana

Lead (Pb) is a dangerous and widespread metal pollutant. Numerous studies have been made in understanding heavy metal detoxification and tolerance in plants, however, relatively few are known about the mechanisms involved in Pb stress response. In this study, we provide evidence for a novel role of APX1 gene in Pb tolerance in Arabidopsis. KO-APX1 mutants apx1-3 and apx1-4 showed more resistant than wild type, and the APX1-complementary COM1 restored the growth state of wild type in Pb stress. The two KO-APX1 mutants showed reduced Pb accumulation, which was accompanied by the activation of metal transporters PDR12 and ATM3 genes expression. In addition, glutathione (GSH), phytochelatin (PC) synthesis and related gene GSH1, GSH2, PCS1 and PCS2 expression were also increased in apx1-3 plants subjected to Pb stress. The more improvements in antioxidant enzymes glutathione peroxidase (GPX) and catalase (CAT) activities were found in the mutant apx1-3. Taken together, our results suggest that APX1 gene knockout results in enhanced Pb tolerance mainly through activating the expression of the ATP-bind cassette (ABC)-type transporters and at least partially through GSH −dependent PC synthesis pathway by coordinated control of gene expression.

Polymerization Degree of Phytochelatin in Contaminated Soil Phytoremediation of Manganese in Hibiscus Sabdariffa Linn Var Sabdariffa

The aim of this study is to determine the usefulness of roselle (Hibiscus sabdariffa L. var sabdariffa), and its polymerization degree of phytochelatins (PCs) for contaminated soil Mn phytoremediation. Sorrel plants grow in three highly contaminated soils Mn (4μM, 6μM and 8μM) in control conditions. Roselle accumulates large amounts of Mn in the leaves in the various contaminated environments Mn. The removal rate of absorption in the higher Mn was observed in the medium 8μM Mn. In parallel, the middle 4μM Mn showed the lowest Mn extraction rate. Induced oxidative stress due to the Mn content, generates the highest level in ascorbate 8μM Mn. The medium 8μM Mn shows an induction of 9 to 16 times the amount of γ-glutamylcysteine and against a low induction of γ- glutamylcysteine in the medium 4μM Mn. Accordingly, the total content phytochelatin (PC) was 7-9 times higher 8μM Mn. In addition, PCs high polymerization degree were observed in 8μM Mn (PC4, PC6 and PC7), while PC2 and PC3 occurred in 4μM Mn and 6μM Mn only. The correlation analysis shows that 8μM Mn phytoremediation capacity is associated with the PCs synthesis and their polymerization degree is high.

Phytochelatin synthesis in Dunaliella salina induced by arsenite and arsenate under various phosphate regimes

This study investigated the dynamic variations in thiol compounds, including cysteine (Cys), glutathione (GSH), and phytochelatins (PCs), in Dunaliella salina samples exposed to arsenite [As(III)] and arsenate [As(V)] under various phosphate (PO43−) regimes. Our results showed that GSH was the major non-protein sulfhydryl compound in D. salina cells. As(III) and As(V) induced PC syntheses in D. salina. PC2, PC3, and PC4 were all found in algal cells; the PC concentrations decreased gradually while exposed to As for 3 d. The synthesis of PC2–3 was significantly affected by As(III) and As(V) concentrations in the cultures. More PCs were detected in the As(V)-treated algal cells compared with the As(III) treatment. PC levels increased with As(III)/As(V) amount in the medium, but remained stable after 112μgL−1 As(V) exposure. In contrast, significant (p<0.001) positive correlations were observed between PC synthesis and intracellular As(III) content or As accumulation in As(III)-treated algal cells during the 72-h exposure. PO43− had a significant influence on the PC synthesis in algal cells, irrespective of the As-treated species. Reductions in As uptake and subsequent PC synthesis by D. salina were observed as the PO43− concentration in the growth medium increased. L-Buthionine sulfoximine (BSO) differentially influenced PC synthesis in As-treated D. salina under different extracellular PO43− regimes. Overall, our data demonstrated that the production of GSH and PCs was affected by PO43− and that these thiols played an important role in As detoxification by D. salina.

Quantitative Relationship between Cadmium Uptake and the Kinetics of Phytochelatin Induction by Cadmium in a Marine Diatom.

Heavy metals activate the synthesis of phytochelatins (PCs), while the induced PCs might affect metal uptake via chelating intracellular free metals. However, the relationship of PCs to metal uptake is poorly understood. In this study, we examined the kinetics of cadmium (Cd) accumulation and the synthesis of PCs in a marine diatom, Thalassiosira weissflogii, under different irradiance levels. Irradiance alone could not change the concentrations of PCs in the Cd-free treatments, while higher irradiance accelerated the induction of intracellular PCs at the same [Cd2+] level. PC-SH (2 × PC2 + 3 × PC3 + 4 × PC4) was bound with Cd at a stoichiometric ratio of 2 to 49 in our short-term uptake experiments, indicating that PC induction is sufficient to serve as the first line of defense against Cd stress. A positive linear correlation between the induction rate of PCs and the Cd uptake rate was observed, while the ratio of the PC content to intracellular Cd varied greatly when the irradiance was increased several fold. Because metal uptake has been successfully used in predicting acute metal toxicity, our findings are helpful for understanding the role of PCs in metal detoxification and developing PCs as biomarkers for metal sensitivity.

Phytochelatin synthesis and responses of antioxidants during arsenic stress in Nasturtium officinale

The induction of thiols including glutathione and phytochelatins as well as the activities of antioxidant enzymes namely superoxide dismutase isoenzymes and those enzymes involved in the ascorbate-glutathione cycle in watercress plants under arsenic stress were investigated. Arsenic concentrations and tissue type-dependent response to arsenic were assessed. Plant was capable of accumulating large amounts of arsenic in the shoots. Superoxide dismutase isoenzymes activity and phytochelatin level was higher in shoots than in roots. In roots, ascorbate levels increased significantly, while no relationship was found between ascorbate contents and arsenic tolerance in shoots. Treatment with arsenic resulted in a remarkable increase in glutathione content of roots at all of the arsenic concentrations, while in shoots, glutathione content increased by lower levels of arsenic. Differences were noted in both roots and shoots for enzymes involved in the ascorbate-glutathione cycle. These results suggest that, the strategy of tolerance to arsenic toxicity in roots of watercress plants is different from that of shoots.

Phytochelatin Synthesis Promotes Leaf Zn Accumulation of Arabidopsis thaliana Plants Grown in Soil with Adequate Zn Supply and is Essential for Survival on Zn-Contaminated Soil.

Phytochelatin (PC) synthesis is essential for the detoxification of non-essential metals such as cadmium (Cd). In vitro experiments with Arabidopsis thaliana seedlings had indicated a contribution to zinc (Zn) tolerance as well. We addressed the physiological role of PC synthesis in Zn homeostasis of plants under more natural conditions. Growth responses, PC accumulation and leaf ionomes of wild-type and AtPCS1 mutant plants cultivated in different soils representing adequate Zn supply, Zn deficiency and Zn excess were analyzed. Growth on Zn-contaminated soil triggers PC synthesis and is strongly impaired in PC-deficient mutants. In fact, the contribution of AtPCS1 to tolerating Zn excess is comparable with that of the major Zn tolerance factor MTP1. For plants supplied with a normal level of Zn, a significant reduction in leaf Zn accumulation of AtPCS1 mutants was detected. In contrast, AtPCS1 mutants grown under Zn-limited conditions showed wild-type levels of Zn accumulation, suggesting the operation of distinct Zn translocation pathways. Contrasting phenotypes of the tested AtPCS1 mutant alleles upon growth in Zn- or Cd-contaminated soil indicated differential activation of PC synthesis by these metals. Experiments with truncated versions identified a part of the AtPCS1 protein required for the activation by Zn but not by Cd.

Amending the seedling bed of eggplant with biochar can further immobilize Cd in contaminated soils

Untreated municipal sewage is a potential source of Cd but has been used for irrigating vegetables in many countries in recent years. In growing vegetables and fruits in greenhouses, seedling breeding method is generally used in which the seedlings are transplanted into soils together with their seedling culture. Biochar has been increasingly used to amend soils contaminated by heavy metals, but there are few studies on the effectiveness of different ways of applying the biochar. In this paper, we investigated the efficacy of immobilizing Cd by amending eggplant seedling bed with biochar before transplanting them to biochar-amended soil contaminated by Cd. The results showed that, in comparison with traditional seedling method (without adding biochar), amending the seedling bed by biochar not only had a positive effect on plant growth and production, but further reduced the Cd concentration in the roots, shoots and the fruits by 12.2%, 12.5% and 18.5%, respectively. Furthermore, it increased the pH in rhizosphere to 8.83, reduced the exchangeable Cd concentration in soil by 28.6%, and decreased the Cd bio-accumulation factor from 0.36 to 0.32. Phytochelatin synthesis could be induced when plants are exposed to Cd and it has been used in the literature as a biomarker for evaluating metal toxicity. Our results showed that the seedling culture amended with biochar reduced phytochelatin synthesis in both roots and shoots. It can therefore be concluded that amending the eggplant seedlings bed with biochar can further enhance the effectiveness of remediating Cd contamination in soil after transplanting the plants into soil also amended with biochar. Capsule abstractWe found a new method to further immobilize Cd in contaminated soils by amending the seedling bed with biochar.

Editorial: Ethylene's Role in Plant Mineral Nutrition.

Editorial: Ethylene's Role in Plant Mineral Nutrition.

The PSE1 gene modulates lead tolerance in Arabidopsis.

Lead (Pb) is a dangerous heavy metal contaminant with high toxicity to plants. However, the regulatory mechanism of plant Pb tolerance is poorly understood. Here, we showed that the PSE1 gene confers Pb tolerance in Arabidopsis. A novel Pb-sensitive mutant pse1-1 (Pb-sensitive1) was isolated by screening T-DNA insertion mutants. PSE1 encodes an unknown protein with an NC domain and was localized in the cytoplasm. PSE1 was induced by Pb stress, and the pse1-1 loss-of-function mutant showed enhanced Pb sensitivity; overexpression of PSE1 resulted in increased Pb tolerance. PSE1-overexpressing plants showed increased Pb accumulation, which was accompanied by the activation of phytochelatin (PC) synthesis and related gene expression. In contrast, the pse1-1 mutant showed reduced Pb accumulation, which was associated with decreased PC synthesis and related gene expression. In addition, the expression of PDR12 was also increased in PSE1-overexpressing plants subjected to Pb stress. Our results suggest that PSE1 regulates Pb tolerance mainly through glutathione-dependent PC synthesis by activating the expression of the genes involved in PC synthesis and at least partially through activating the expression of the ABC transporter PDR12/ABCG40.

Arsenate (AsV) stress response in maize (Zea mays L.)

The present study assesses the impact of arsenate (AsV) stress on maize (Zea mays L.) seedlings. Three different levels of AsV stress (25, 50 and 100μM Na2HAsO4·7H2O) were imposed and seedling growth performances were studied at 2d and 4d of experiment. Arsenate induced modulation of antioxidant enzymes of ascorbate-glutathione cycle along with antioxidant molecules (glutathione and ascorbate) were monitored. Dose and time dependent decline in shoot biomass along with yellowing and drying of leaf tips were observed in AsV treated seedlings. Comparatively high phytochelatin synthesis in roots appears to restrict arsenic translocation from root to aboveground tissues as evident from low arsenic concentration in leaves as compared to roots. Increased uptake of Evans blue by AsV stressed roots indicates loss of root cells viability. Histochamical staining with NBT and DAB revealed dark blue and brown spots respectively on the leaves under AsV stress, which indicated oxidative burst. CM-H2DCFDA and DHE staining of AsV stressed roots further indicated enhanced formation of ROS. Western blot and real-time qRT-PCR analyses revealed high GR expression at protein and transcript levels respectively in presence of high AsV concentration. However, increased GR activity coupled with high GSH/GSSG ratio and enhanced GST activity does not seem to prevent cells from oxidative damages, as evident from high MDA level in leaves of 50 and 100μM AsV stressed seedlings. Marked decrease in DHAR and MDAR render the stressed cells in futile recycling of ascorbate pool which might contribute to increased susceptibility towards high AsV dose.

Brassinosteroids and Response of Plants to Heavy Metals Action.

Brassinosteroids (BRs) are a widespread group of plant hormones. These phytohormones play a crucial role in the regulation of growth and development of various plant species, and they demonstrate high biological activity. BRs are considered to demonstrate protective activity in the plants exposed to various stresses. Due to rapid industrialization and urbanization, heavy metals have become one of the most important plant stressors. In plants, accumulation of heavy metals beyond the critical levels leads to oxidative stress. However, BRs may inhibit the degradation of lipids, resulted from the overproduction of reactive oxygen species under stress conditions, and increase the activity of antioxidants. They also have the ability to promote phytochelatins synthesis.

Research on Root Responses to Pb and Zn Combined Stress of Carex putuoshan.

Pb hyper-accumulated Carex putuoshan was taken as experimental material and subjected to combined stress of Pb and Zn. The differential expression of proteins in their roots were analyzed by Proteomic Approach. The protein that was directly involved in the cellular defense under the Pb and Zn combined stress was separated, and expression of those genes was analyzed with Carex Evergold as control. The results were obtained by MALDI-TOF/MS analysis. After applying Pb and Zn combined stress, the expression of 9 protein spots (including 7 different proteins, 2 identical proteins, 1 unknown protein) in Carex putuoshan root was found to be significantly up-regulated. Five proteins were obtained from the 9 proteins related to carbohydrate metabolism, including malate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, frutose-1,6-bisphosphate aldolase, enolase, and 6- phosphogluconate dehydrogenase. Two proteins were related to protein biosynthesis, including isoflavone reductase and phytochelatin synthase (PCS). From these proteins, the most important protein is PCS, which is a key enzyme in the synthesis of phytochelatins (PCs) and plays an important role in chelation. It is directly involved in cellular defense under Pb and Zn stress. After Pb and Zn combined stress, the CpPCS in Carex putuoshan was cloned. The full length of cDNA is 1461 bps, and it encodes 486 amino acids with molecular weight of 53.86 kD and pI value of 6.12. Two typical phytochelatin synthase subfamily domains constitute CpPCS protein, which includes three adjacent Cys-Cys elements in the C-terminal region. Phylogenetic analysis of PCS proteins from different species showed that it had the closest relationship with the Oryza sativa and Triticum aestivum. Real-time quantitative PCR analysis indicated that CpPCS and CePCS (Carex Evergold) genes were expressed in the root. The CpPCS and CePCS genes were up-regulated by Pb and Zn treatments. The expression of CpPCS was higher than that of CePCS under the same condition. The study found that CpPCS expression was increased by Pb and Zn stress in the Carex putuoshan enrichment process of Pb, which lead to high expression of PCS protein. CpPCS improved the accumulation ability and resistance of Carex putuoshan to heavy metals with the expression level of glucose metabolism related proteins increasing after Pb and Zn stress.

Increased lead and cadmium tolerance of Typha angustifolia from Huaihe River is associated with enhanced phytochelatin synthesis and improved antioxidative capacity

ABSTRACTHeavy metal contamination of water is an increasing environmental problem worldwide, and the use of aquatic plants for phytoremediation of heavy metal pollution has become an important subject of research. One key to successful phytoremediation is the identification of plants that are efficient at sequestering heavy metals. In this study, we examined the growth and heavy metal accumulation of Typha angustifolia and compared growth characteristics and tolerance mechanisms in plants from the Huaihe and Chaohu Rivers irrigated with different concentrations of lead (Pb) and cadmium (Cd). T. angustifolia from Huaihe River showed enhanced tolerance and accumulation of Pb and Cd and had greater biomass and more vigorous growth than the ecotype from Chaohu River. In addition, higher phytochelatin (PC) content and significantly higher superoxide dismutase and catalase activities were detected in T. angustifolia from Huaihe River than in T. angustifolia from Chaohu River. These findings suggest that high Pb and Cd accumulation and tolerance in T. angustifolia from Chaohu River is associated with its higher PC synthesis and better antioxidative capacity, and that the Huaihe ecotype of T. angustifolia might also be an efficient species for phytoremediation of Pb and Cd in water contaminated by heavy metals.

Biochemical and molecular responses underlying differential arsenic tolerance in rice (Oryza sativa L.)

The arsenic (As) is a toxic element causing major health concern worldwide. Arsenate stress caused no significant reduction in growth parameters and shoot electrolyte leakage but showed increased root arsenate reductase activity along with relatively lower root As content and shoot translocation rate in As-tolerant BRRI 33 than in As-sensitive BRRI 51. It indicates that As inhibition and tolerance mechanisms are driven by root responses. Interestingly, As stress showed consistent decrease in phosphate content and expression of phosphate transporters (OsPT8, OsPT4, OsPHO1;2) under both high and low phosphate conditions in roots of BRRI 33, suggesting that limiting phosphate transport mainly mediated by OsPHO1;2 directs less As accumulation in BRRI 33. Further, BRRI 33 showed simultaneous increase in OsPCS1 (phytochelatin synthase) expression and phytochelatins (PCs) content in roots under As exposure supporting the hypothesis that root As sequestration acts as ‘firewall system’ in limiting As translocation in shoots. Furthermore, increased CAT, POD, SOD, GR, along with elevated glutathione, methionine, cysteine and proline suggests that strong antioxidant defense plays integral part to As tolerance in BRRI 33. Again, BRRI 33 self-grafts and plants having BRRI 33 rootstock combined with BRRI 51 scion had no adverse effect on morphological parameters but showed reduced As translocation rate, increased root arsenate reductase activity, shoot PC synthesis and root OsPHO1;2 expression due to As stress. It confirms that signal driving As tolerance mechanisms is generated in the roots. These findings can be implemented for As detoxification and As-free transgenic rice production for health safety.