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Arsenic (As) is a major threat to the environment and human health due to its toxicity and carcinogenicity. Occurrence of alarming concentrations of As in water and soil leads to its bioaccumulation in crops which is a major health concern globally. Rice (Oryza sativa) is a staple food for a large population staying in As contaminated areas so, it is of utmost importance to reduce As levels in rice, especially grains. Amongst several strategies in practice, biotechnology may provide an effective option to reduce As accumulation in rice grains. Genetic engineering can be a viable approach to exploit potential genes playing roles in As metabolism pathway in plants. Besides, developing low As accumulating rice varieties through breeding is also an important area. Identifying genotypic variation in rice is a crucial step toward the development of a safe rice cultivar for growing in As-affected areas. Significant genotypic variation has been found in rice varieties for As accumulation in grains and that is attributable to differential expression of transporters, radial oxygen loss, and other regulators of As stress. This review provides recent updates on the research advances leading to transgenic and breeding approaches adopted to reduce As levels in rice, especially grains. Arsenic (As) contamination in water, soil, and crops is creating a difficult situation for the large population across the globe. Various efforts are being made to reduce As levels in rice as it is a staple crop. This review presents recent biotechnological advances toward the development of low As accumulating rice. The review shall be an important information resource for the readers on the topic. [ABSTRACT FROM AUTHOR]

Widespread distribution, toxicity and exposure through rice and rice-based food products make arsenic (As) contamination of environment a serious issue. This review discusses various strategies that can be utilised to tackle the As problem in rice, and the socioeconomic impacts of the As problem. The countries of south and south-east Asia are renowned as hotspots of As contamination owing to occurrence and enrichment of As in soil and groundwater via natural biogeochemical weathering of rocks and As-enriched sediment. The irrigation of rice is mostly applied through the use of contaminated groundwater leading to high As accumulation in rice grains. The intensification of research to address the problem of As in rice has been seen in the past two decades. It has been realised that appropriate irrigation water management, which acts as a major driver of As chemistry in soil and As uptake and transport in plants, can be an easy and affordable solution. Further, balanced supplement of various nutrient elements like selenium (Se), silicon (Si), sulfur (S), nitrogen (N), iron (Fe) and zinc (Zn) has been found to impart dual benefits in terms of reduced As toxicity as well as enhance the nutritional quality of rice grains. Several other agronomic and biotechnological approaches, processing, and cooking methods of rice were found to have profound impacts on rice As and its speciation from farms to table. [ABSTRACT FROM AUTHOR]

There are global concerns regarding heavy metals-induced pressure on soil ecosystem since past decades due to increasing urban, industrial and agricultural activities. Threat linked with heavy metals with respect to natural environment and humans is a function of their mobility and bioaccessibility. Zinc (Zn) is one of the most transportable and bioavailable heavy metals; hence, its excess levels in soil cause phytotoxicity and decrease yield and quality. Different physicochemical soil factors affect binding of Zn in soil. Moreover, phytoavailability of Zn is coupled with allocation of this element among various fractions of soil. Thus, comprehending the distribution of Zn among diverse soil fractions would assist in developing methods to safeguard human well-being and ecosystem against its lasting accumulation. Further, these soil fractions would impart comprehensive knowledge about chemical, biological and geological processes taking place in soil and in depth information regarding availability of Zn to plants. No doubt, Zn deficiency in plants is more widespread than Zn toxicity; still latter has been described in several regions of the world. Numerous strategies including use of beneficial microbes, mineral nutrients, phytohormones and other agents have been developed to alleviate Zn toxicity in plants. Present review focuses on different Zn forms present in soils and soil factors impacting its phytoavailability to explore a potential link between Zn and soil characteristics. Additionally, various Zn ameliorative approaches along with the prospects of genetic engineering in developing plants tolerant to Zn toxicity have been highlighted. • Zinc bioavailability in soil is influenced by several factors including pH and organic matter. • The toxicity of zinc to plants is dependent on its bioavailability in soil. • Phytohormones mitigate zinc toxicity by augmenting growth and antioxidant potential. • Microbes can ameliorate zinc toxicity plants through the improvement of elemental homeostasis. [ABSTRACT FROM AUTHOR]

SUMMARY: The Arabidopsis thaliana aldehyde oxidase 3 (AAO3) catalyzes the oxidation of abscisic aldehyde (ABal) to abscisic acid (ABA). Besides ABal, plants generate other aldehydes that can be toxic above a certain threshold. AAO3 knockout mutants (aao3) exhibited earlier senescence but equivalent relative water content compared with wild‐type (WT) during normal growth or upon application of UV‐C irradiation. Aldehyde profiling in leaves of 24‐day‐old plants revealed higher accumulation of acrolein, crotonaldehyde, 3Z‐hexenal, hexanal and acetaldehyde in aao3 mutants compared with WT leaves. Similarly, higher levels of acrolein, benzaldehyde, crotonaldehyde, propionaldehyde, trans‐2‐hexenal and acetaldehyde were accumulated in aao3 mutants upon UV‐C irradiation. Aldehydes application to plants hastened profuse senescence symptoms and higher accumulation of aldehydes, such as acrolein, benzaldehyde and 4‐hydroxy‐2‐nonenal, in aao3 mutant leaves as compared with WT. The senescence symptoms included greater decrease in chlorophyll content and increase in transcript expression of the early senescence marker genes, Senescence‐Related‐Gene1, Stay‐Green‐Protein2 as well as NAC‐LIKE, ACTIVATED‐BY AP3/P1. Notably, although aao3 had lower ABA content than WT, members of the ABA‐responding genes SnRKs were expressed at similar levels in aao3 and WT. Moreover, the other ABA‐deficient mutants [aba2 and 9‐cis‐poxycarotenoid dioxygenase3‐2 (nced3‐2), that has functional AAO3] exhibited similar aldehydes accumulation and chlorophyll content like WT under normal growth conditions or UV‐C irradiation. These results indicate that the absence of AAO3 oxidation activity and not the lower ABA and its associated function is responsible for the earlier senescence symptoms in aao3 mutant. Significance Statement: The current study demonstrates that AAO3, known to catalyze the last step of ABA biosynthesis by oxidizing ABal, is essential in preventing leaf damage by oxidizing toxic levels of aldehydes in rosette leaves. We provided credible evidences that premature senescence in this study was not because of low ABA content and its consequential function in aao3, but rather due to higher aldehyde accumulation, which is caused by AAO3 deficiency. [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]

Graphical abstract Highlights • Altered nitrogen supply influenced arsenic concentrations of rice seedlings. • High nitrogen supply improved plants performance under control conditions. • In presence of arsenic, high nitrogen supply negatively affected growth of plants. • Low nitrogen supply, in presence of arsenic, increased plants tolerance to arsenic. Abstract In the present study, the effects of nitrogen supply (low nitrogen: LN and high nitrogen: HN) on As stress (25 μM) responses of rice seedlings were monitored for 7 d. The mean length of primary, adventitious and lateral roots and number of adventitious and lateral roots were significantly improved in LN+As, while further reduced in HN+As, as compared to As alone treatment at 7 d. The LN+As treatment resulted in significant decline in As (848 μg g−1 DW) than that in As alone treatment (1434 μg g−1 DW) in roots but no significant effect was seen in shoot. In contrast, HN+As treatment showed significant increase in shoot As (6.86 μg g-1 DW) as compared to As alone treatment (3.43 μg g-1 DW). The level of nitrate was increased in roots but declined in shoots in As alone treatment. Surprisingly, no improvement in nitrate level was seen in HN+As as compared to that in As alone treatment in both root and shoot. The expression analysis of nitrate transporters (NRT2;1, NRT2;3a, NRT2;4) showed significant differences in expression patterns in As, LN+As and HN+As treatments. In conclusion, nitrogen supply had profound influences on responses of rice plants to As. [ABSTRACT FROM AUTHOR]

The nitrogen (N)-rich ureides allantoin and allantoate, which are products of purine catabolism, play a role in N delivery in Leguminosae. Here, we examined their role as an N source in nonlegume plants using Arabidopsis (Arabidopsis thaliana) plants mutated in XANTHINE DEHYDROGENASE1 (AtXDH1), a catalytic bottleneck in purine catabolism. Older leaves of the Atxdh1 mutant exhibited early senescence, lower soluble protein, and lower organic N levels as compared with wild-type older leaves when grown with 1 mm nitrate but were comparable to the wild type under 5 mm nitrate. Similar nitrate-dependent senescence phenotypes were evident in the older leaves of allantoinase (Ataln) and allantoate amidohydrolase (Ataah) mutants, which also are impaired in purine catabolism. Under low-nitrate conditions, xanthine accumulated in older leaves of Atxdh1, whereas allantoin accumulated in both older and younger leaves of Ataln but not in wild-type leaves, indicating the remobilization of xanthine-degraded products from older to younger leaves. Supporting this notion, ureide transporter expression was enhanced in older leaves of the wild type in low-nitrate as compared with high-nitrate conditions. Elevated transcripts and proteins of AtXDH and AtAAH were detected in low-nitrate-grown wild-type plants, indicating regulation at protein and transcript levels. The higher nitrate reductase activity in Atxdh1 leaves compared with wild-type leaves indicated a need for nitrate assimilation products. Together, these results indicate that the absence of remobilized purine-degraded N from older leaves of Atxdh1 caused senescence symptoms, a result of higher chloroplastic protein degradation in older leaves of low-nitrate-grown plants. [ABSTRACT FROM AUTHOR]

The present study was aimed to analyze the effects of external Zn supply on arsenic (As) toxicity inHydrilla verticillata(L.f.) Royle. The plants were exposed to arsenite (AsIII; 10 μM) with or without 50 and 100 μM Zn. The level of As accumulation (μg g−1dw) after 2 and 4 days was not significantly affected by Zn supply. The plants showed a significant stimulation of the thiol metabolism (nonprotein thiols, cysteine, glutathione-S-transferase activity) upon As(III) exposure in the presence of Zn as compared to As(III) alone treatment. Besides, they did not experience significant toxicity, measured in terms of hydrogen peroxide and malondialdehyde accumulation, which are the indicators of oxidative stress. The minus Zn plants suffered from oxidative stress probably due to insufficient increase in thiols to counteract the stress. Stress amelioration by Zn supply was also evident from antioxidant enzyme activities, which came close to control levels with increasing Zn supply as compared to the increase observed in As(III) alone treatment. Variable Zn supply also modulated the level of photosynthetic pigments and restored them to control levels. In conclusion, an improved supply of Zn to plants was found to augment their ability to withstand As toxicity through enhanced thiol metabolism. [ABSTRACT FROM AUTHOR]

The Arabidopsis (Arabidopsis thaliana) aldehyde oxidases are a multigene family of four oxidases (AAO1-AAO4) that oxidize a variety of aldehydes, among them abscisic aldehyde, which is oxidized to the phytohormone abscisic acid. Toxic aldehydes are generated in plants both under normal conditions and in response to stress. The detoxification of such aldehydes by oxidation is attributed to aldehyde dehydrogenases but never to aldehyde oxidases. The feasibility of the detoxification of aldehydes in siliques via oxidation by AAO4 was demonstrated, first, by its ability to efficiently oxidize an array of aromatic and aliphatic aldehydes, including the reactive carbonyl species (RCS) acrolein, hydroxyl-2-nonenal, and malondialdehyde. Next, exogenous application of several aldehydes to siliques in AAO4 knockout (KO) Arabidopsis plants induced severe tissue damage and enhanced malondialdehyde levels and senescence symptoms, but not in wild-type siliques. Furthermore, abiotic stresses such as dark and ultraviolet C irradiation caused an increase in endogenous RCS and higher expression levels of senescence marker genes, leading to premature senescence of KO siliques, whereas RCS and senescence marker levels in wild-type siliques were hardly affected. Finally, in naturally senesced KO siliques, higher endogenous RCS levels were associated with enhanced senescence molecular markers, chlorophyll degradation, and earlier seed shattering compared with the wild type. The aldehyde-dependent differential generation of superoxide and hydrogen peroxide by AAO4 and the induction of AAO4 expression by hydrogen peroxide shown here suggest a self-amplification mechanism for detoxifying additional reactive aldehydes produced during stress. Taken together, our results indicate that AAO4 plays a critical role in delaying senescence in siliques by catalyzing aldehyde detoxification. [ABSTRACT FROM AUTHOR]

Background and aim: Soil salinity is one of the major environmental obstacles that limit the crop productivity. A pot experiment was conducted with an aim to explore the ameliorative effects of exogenously applied 24-epibrassinolide (EBL) and sodium nitroprusside (SNP) in alone and/or combination against salinity stress in Brassica juncea (L.) cv. Varuna. Methods: Plants were grown in earthen pots and were exposed to 100 mM NaCl. Further, 30 days old plants were sprayed with 24-epibrassinolide (EBL, 10 M) and sodium nitroprusside (SNP, 100 μM) solutions in alone and/or combination. Plant growth indices, gas exchange parameters, chlorophyll fluorescence, nitrogen and proline metabolism, malondialdehyde, electrolytic leakage and ABA content were analyzed. Results: Salinity stress hampered the general plant growth, affected gas exchange parameters, chlorophyll fluorescence and nitrogen metabolism, showed increase in MDA, proline and ABA content while decreased electrolytic leakage and K/Na ratio. The endogenous levels of ABA revealed significant increase in salinity treatment (12.25 μg g FW) and approaching control value (4.31 μg g FW) in combined EBL and SNP treatment. Conclusion: The present findings demonstrated that EBL and SNP application could protect the plants against salinity stress suggesting the involvement of nitric oxide and brassinosteroids in salinity stress amelioration through impact on nitrogen, proline and ABA metabolism. [ABSTRACT FROM AUTHOR]

Arsenic (As) is a non-essential element whose entry into rice grains is an issue of public concern. The need, therefore, exists to understand the regulatory mechanisms of As accumulation and distribution patterns in plants. This study analyzed the effect of sulfur (S) supply on As accumulation and distribution in rice ( Oryza sativa L. var. IR64) plants. Nine day old seedlings were grown in 0.798 mM S (Normal S), 0.2 mM S (Low S) and 0.003 mM S (Zero S) for 7 days and then subjected to AsIII (20 μM) exposure for 7–15 days. The concentration of As varied significantly in different S treatments with a consistent trend of decrease in As concentration in depleted S supply treatments on both 7 days and 15 days. Arsenic concentration declined from 726 μg g − 1 DW to 537 μg g − 1 DW in roots and from 29 μg g − 1 DW to 8 μg g − 1 DW in shoots at 7 days, and from 1536 μg g − 1 DW to 1062 in roots and from 58 μg g − 1 DW to 16 μg g − 1 DW in shoots at 15 days, when S supply declined from normal to zero. The subcellular distribution of As was also found to vary with alteration in S supply and also differentially in shoot and root. In general, an up-regulation of sulfate transporters of groups 1 and 2 was observed while As transporters (Lsi1 and Lsi2) were down-regulated in response to As exposure to maintain sulfate and to regulate As levels. In spite of S depletion, an increase in cysteine, glutathione (GSH) and phytochelatin (PC) levels was observed upon As exposure. However, some negative impact of S depletion and As could be seen on the growth of plants. The study concluded that even in conditions of decreased S availability, plants continue to rely on thiol metabolism to tackle As levels and its toxicity effectively and altered subcellular distribution of As contributes only partially. [ABSTRACT FROM AUTHOR]

The present study evaluated uranium (U) removal ability and tolerance to low level nuclear waste (LLNW) of an aquatic weed Hydrilla verticillata . Plants were screened for growth in 10%–50% waste treatments up to 3 d. Treatments of 20% and 50% waste imposed increasing toxicity with duration assessed in terms of change in fresh weight and in the levels of photosynthetic pigments and thiobarbituric acid-reactive substances. U concentration, however, did not show a progressive increase and was about 42 μg g −1 dw from 20% to 50% waste at 3 d. This suggested that a saturation stage was reached with respect to U removal due to increasing toxicity. However, in another experiment with 10% waste and 10% waste+10 ppm U treatments, plants showed an increase in U concentration with the maximum level approaching 426 μg g −1 dw at 3 d without showing any toxicity as compared to that at 20% and 50% waste treatments. Hence, plants possessed significant potential to take up U and toxicity of LLNW limited their U removal ability. This implies that the use of Hydrilla plants for U removal from LLNW is feasible at low concentrations and would require repeated harvesting at short intervals. [ABSTRACT FROM AUTHOR]

Cytochrome P450s (CYPs) catalyse a wide variety of oxygenation/hydroxylation reactions that facilitate diverse metabolic functions in plants. Specific CYP families are essential for the biosynthesis of species-specialized metabolites. Therefore, we investigated the role of different CYPs related to secondary metabolism in Withania somnifera, a medicinally important plant of the Indian subcontinent. In this study, complete complementary DNAs (cDNAs) of four different CYP genes were isolated and christened as WSCYP93Id, WSCYP93Sm, WSCYP734B and WSCYP734R. These cDNAs encoded polypeptides comprising of 498, 496, 522 and 550 amino acid residues with their deduced molecular mass of 56.7, 56.9, 59.4 and 62.2 kDa, respectively. Phylogenetic study and molecular modelling analysis of the four cloned WSCYPs revealed their categorization into two CYP families (CYP83B1 and CYP734A1) belonging to CYP71 and CYP72 clans, respectively. BLASTp searches showed similarity of 75 and 56 %, respectively, between the two CYP members of CYP83B1 and CYP734A1 with major variances exhibited in their N-terminal regions. The two pairs of homologues exhibited differential expression profiles in the leaf tissues of selected chemotypes of W. somnifera as well as in response to treatments such as methyl jasmonate, wounding, light and auxin. Light and auxin regulated two pairs of WSCYP homologues in a developing seedling in an interesting differential manner. Their lesser resemblance and homology with other CYP sequences suggested these genes to be more specialized and distinct ones. The results on chemotype-specific expression patterns of the four genes strongly suggested their key/specialized involvement of the CYPs in the biosynthesis of chemotype-specific metabolites, though their further biochemical characterization would reveal the specificity in more detail. It is revealed that WSCYP93Id and WSCYP93Sm may be broadly involved in the oxygenation reactions in the plant and, thereby, control various pathways involving such metabolic reactions in the plant. As a representative experimental validation of this notion, WSCYP93Id was heterologouly expressed in Escherichia coli and catalytic capabilities of the recombinant WSCYP93Id protein were evaluated using withanolides as substrates. Optimized assays with some major withanolides (withanone, withaferin A and withanolide A) involving spectrophotometric as well as high-pressure liquid chromatography (HPLC)-based evaluation (product detection) of the reactions showed conversion of withaferin A to a hydroxylated product. The genes belonging to other CYP group are possibly involved in some specialised synthesis such as that of brassinosteroids. [ABSTRACT FROM AUTHOR]

Helianthus annuus is a potential metal accumulator plant, which can find application in cadmium (Cd) phytoremediation and provide economic gains in terms of oil yield. This study is focused on Cd accumulation analysis, physiological and biochemical responses of five varieties of H. annuus (DRSF-108, DRSF-113, LSFH-171, Phule Bhaskar and KBSH-44). Plantlets of all varieties were treated with various Cd concentrations (10, 50, 100, 300 and 500 mg kg−1) for 20, 40 and 60 days. DRSF-108 showed the maximum total Cd accumulation (430.52 mg kg−1) in whole plant while minimum accumulation was observed in KBSH-44 (150.66 mg kg−1) at 500 mg kg−1 Cd after 60 days. The highest level of proline and polyphenol in DRSF-108 were 27.206 µmol g−1 fw and 6.86 mg g−1 fw, respectively. Antioxidant enzymes (catalase, ascorbate peroxidase and glutathione reductase) also showed increased activity in response to Cd treatment. SEM-EDX analysis of potential accumulator genotype, DRSF-108, showed the distribution of intracellular Cd into plant tissues. Therefore, it is concluded that among five varieties, DRSF-108 was the most potential Cd accumulator and had a higher capacity for Cd tolerance compared to other varieties. Our findings may allow us to extend variety DRSF-108 for sustainable farming and Cd remediation. Phytoremediation of environmental contaminants is a promising strategy, however, the success depends on the use of suitable plants. Helianthus annuus is a good phytoremediator plant and the use of most promising genotype is desirable. This work evaluated five genotypes of H. annuus for cadmium accumulation and identified the best variety, DRSF-108 that can be used for cadmium remediation. The work shall pave way for field application of sunflower plants in cadmium remediation. [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]

MicroRNAs (miRNAs) constitute a novel mechanism of gene regulation affecting plant development, growth, and stress response. To study the role of miRNAs in arsenic (As) stress, microarray profiling of miRNAs was performed in Brassica juncea using a custom Phalanx Plant OneArray™ containing 381 unique miRNA probes representing 618 miRNAs from 22 plant species. miRNA microarray hybridization of roots exposed to As for 1h and 4h revealed that a total of 69 miRNAs belonging to 18 plant miRNA families had significantly altered expression. The As-responsive miRNAs also exhibited a time- and organ-dependent change in their expression. Putative target prediction for the miRNAs suggested that they regulate various developmental processes (e.g. miR156, miR169, and miR172), sulphur uptake, transport, and assimilation (miR395, miR838, and miR854), and hormonal biosynthesis and/or function (e.g. miR319, miR167, miR164, and miR159). Notable changes were observed in the level of auxins [indole-3-acetic acid (IAA), indole-3- butyric acid, and naphthalene acetic acid], jasmonates [jasmonic acid (JA) and methyl jasmonate], and abscisic acid. The exogenous supply of JA and IAA improved growth of plants under As stress and altered expression of miR167, miR319, and miR854, suggesting interplay of hormones and miRNAs in the regulation of As response. In conclusion, the present work demonstrates the role of miRNAs and associated mechanisms in the plant’s response towards As stress. [ABSTRACT FROM AUTHOR]

In the present study, the effect of arsenate (AsV) exposure either alone or in combination with calcium (Ca) was investigated in callus cultures of Brassica juncea (L.) Czern. cv. Pusa Bold grown for a period up to 24 h. The AsV (250 μM) + Ca (10 mM) treatment resulted in a significantly higher level of As (464 μg g dry weight (DW)) than AsV without Ca (167 μg g DW) treatment at 24 h. Furthermore, AsV + Ca-treated calli had a higher percent of AsIII (24-47%) than calli subjected to AsV treatment (12-14%). Despite this, AsV + Ca-treated calli did not show any signs of hydrogen peroxide (HO) accumulation or cell death upon in vivo staining, while AsV-exposed calli had increased HO, shrinkage of cytoplasmic contents, and cell death. Thus, AsV treatment induced oxidative stress, which in turn elicited a response of antioxidant enzymes and metabolites as compared with control and AsV + Ca treatment. The positive effects of Ca supplementation were also correlated to an increase in thiolic constituents', viz., cysteine, reduced glutathione, and glutathione reductase in AsV + Ca than in AsV treatment. An analysis of selected signaling related genes, e.g., mitogen-activated protein kinases (MAPK3 and MAPK6) and jasmonate ZIM-domain (JAZ3) suggested that AsV and AsV + Ca followed variable pathways to sense and signal the As stress. In AsV-alone treatment, jasmonate signaling was seemingly activated, while MAPK3 was not involved. In contrast, AsV + Ca treatment appeared to specifically inhibit jasmonate signaling and activate MAPK3. In conclusion, Ca supplementation may hold promise for achieving increased As accumulation in plants without compromising their tolerance. [ABSTRACT FROM AUTHOR]

Arsenic (As) contamination of the environment has emerged as a serious problem. Consequently, there is an urge to understand plants’ responses to As. The analysis of various hypertolerant and hyperaccumulator plants and comparison of their responses with non-tolerant and nonaccumulators have provided valuable information about the mechanisms of As tolerance and detoxification. Therefore, we understand why most of the pteridophytes are able to hyperacumulate As, why it is difficult to find hyperaccumulators among angiosperms and why rice is able to translocate As to its grains more efficiently than any other cereal crop. This information can be employed to generate As hyperaccumulators in angiosperms and to develop safe cultivars of rice for human consumption through biotechnological approaches. Although measurable success, in terms of application in the field, has so far not been achieved, transgenic research has yielded promising results, which shed light on the approaches to be taken up in future endeavor. In this review, we discuss the mechanisms of As tolerance and detoxification in plants and transgenic research conducted. [ABSTRACT FROM PUBLISHER]

Arsenic (As) is a potential hazard to plants' health, however the mechanisms of its toxicity are yet to be properly understood. To determine the impact of redox state and energetic in stress imposition, plants of Hydrilla verticillata (L.f.) Royle, which are known to be potential accumulator of As, were exposed to 100 and 500 μM arsenate (AsV) for 4 to 96 h. Plants demonstrated significant As accumulation with the maximum being at 500 μM after 96 h (568 μg g dry weight, dw). The accumulation of As led to a significant increase in the level of reactive oxygen species, nitric oxide, carbonyl, malondialdehyde, and percentage of DNA degradation. In addition, the activity of pro-oxidant enzymes like NADPH oxidase and ascorbate oxidase also showed significant increases. These parameters collectively indicated oxidative stress, which in turn caused an increase in percentage of cell death. These negative effects were seemingly linked to an altered energetic and redox equilibrium [analyzed in terms of ATP/ADP, NADH/NAD, NADPH/NADP, reduced glutathione/oxidized glutathione, and ascorbate/dehydroascobate ratios]. Although there was significant increase in the levels of phytochelatins, the As chelating ligands, a large amount of As was presumably present as free ion particularly at 500 μM AsV, which supposedly produced toxic responses. In conclusion, the study demonstrated that the magnitude of disturbance to redox and energetic equilibrium of plants upon AsV exposure determines the extent of toxicity to plants. [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]

The present study was aimed to analyze the effects of variable S supply on arsenic (As) accumulation potential of Hydrilla verticillata (Lf.) Royle. Plants were exposed to either arsenate (AsV; 50 μM) or arsenite (AsIII; 5 μM) for 4 h and 1 day while S supply was varied as deficient (2 μM, -S), normal (1 mM, +S) and excess (2 mM, +HS). The level of As accumulation (μg g-1 dw) after 1 day was about 2-fold higher upon exposure to either AoV (30) or AsIII (50) in +HS plants than that being in +S(12 and 24) and -S (14 and 26) plants. The +HS plants showed a significant stimulation of the thiol metabolism upon As exposure. Besides, they did not experience significant toxicity, measured in terms of malondialdehyde accumulation; an indicator of oxidative stress. By contrast, -S plants suffered from oxidative stress probably due to negative impact to thiol metabolism. Variable S supply also modulated the activity of enzymes of glycine and serine biosynthesis indicating an interconnection between S and N metabolism. In conclusion, an improved supply of S to plants was found to augment their ability for As accumulation through stimulated thiol metabolism. [ABSTRACT FROM AUTHOR]

The mechanisms of perception of arsenic (As)-induced stress and ensuing tolerance in plants remain unresolved. To obtain an insight into these mechanisms, biochemical and transcriptional profiling of two contrasting genotypes of Brassica juncea was performed. After screening 14 varieties for As tolerance, one tolerant (TPM-1) and one sensitive (TM-4) variety were selected and exposed to arsenate [As(V)] and arsenite [As(III)] for 7 d and 15 d for biochemical analyses. The tolerant variety (TPM-1) demonstrated higher accumulation of As upon exposure to both 500 μM As(V) and 250 μM As(III) [49 μg g−1 and 37 μg g−1 dry weight (dw) after 15 d] as well as a better response of thiol metabolism as compared with the responses observed in the sensitive variety (TM-4). Transcriptional profiling of selected genes that are known to be responsive to sulphur depletion and/or metal(loid) stress was conducted in 15-d-old seedlings after 3 h and 6 h exposure to 250 μM As(III). The results showed an up-regulation of sulphate transporters and auxin and jasmonate biosynthesis pathway genes, whereas there was a down-regulation of ethylene biosynthesis and cytokinin-responsive genes in TPM-1 within 6 h of exposure to As(III). This suggested that perception of As-induced stress was presumably mediated through an integrated modulation in hormonal functioning that led to both short- and long-term adaptations to combat the stress. Such a coordinated response of hormones was not seen in the sensitive variety. In conclusion, an early perception of As-induced stress followed by coordinated responses of various pathways was responsible for As tolerance in TPM-1. [ABSTRACT FROM PUBLISHER]

Arsenic contamination of the environment is a serious problem threatening the health of millions of people exposed to arsenic (As) via drinking water and crops grown in contaminated areas. The remediation of As-contaminated soil and water bodies needs to be sustainable, low-cost and feasible to apply in the most affected low-to-middle income countries, like India and Bangladesh. Phytoremediation is an aesthetically appreciable and successful approach that can be used for As decontamination with use of the best approach(es) and the most promising plant(s). However, phytoremediation lacks the required speed and sometimes the stress caused by As could diminish plants' potential for remediation. To tackle these demerits, we need augment plants' potential with appropriate technological methods including microbial and nanoparticles applications and genetic modification of plants to alleviate the As stress and enhance As accumulation in phytoremediator plants. The present review discusses the As phytoremediation prospects of soil and water bodies and the usefulness of various plant systems in terms of high biomass, high As accumulation, bioenergy potential, and economic utility. The potential and prospects of assisted phytoremediation approaches are also presented. [ABSTRACT FROM AUTHOR]

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]

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 present study analysed time (0.5 h to 24 h) and tissue [roots, old leaves (OL) and young leaves (YL)] dependent nature of arsenic (As) accumulation and ensuing responses in two contrasting varieties of rice (Oryza sativa L.); Pooja (tolerant) and CO-50 (moderately sensitive). Arsenic accumulation was 5.4-, 4.7- and 7.3-fold higher at 24 h in roots, OL and YL, respectively of var. CO-50 than that in var. Pooja. Arsenic accumulation in YL depicted a delayed accumulation; at 2 h onwards in var. Pooja (0.23 µg g−1 dw) while at 1 h onwards in var. CO50 (0.26 µg g−1 dw). The responses of oxidative stress parameters, antioxidant enzymes, metabolites and ions were also found to be tissue- and time-dependent and depicted differential pattern in the two varieties. Among hormone, salicylic acid and abscisic acid showed variable response in var. Pooja and var. CO-50. Metabolite analysis depicted an involvement of various metabolites in As stress responses of two varieties. In conclusion, an early sensing of the As stress, proper coordination of hormones, biochemical responses, ionic and metabolic profiles allowed var. Pooja to resist As stress and reduce As accumulation more effectively as compared to that of var. CO-50. ga1 • T T Tracking As stress responses of contrasting tolerant (Pooja) and moderately sensitive (CO-50) rice varieties. • Arsenic accumulation was higher in CO-50 than in Pooja in root, OL and YL. • Root, OL and YL showed contrasting responses for hormones (SA, ABA, JA) and ions (K+, Ca2+). • Metabolite profiling showed significant up-regulation of phenolics and flavonoids in Pooja. [ABSTRACT FROM AUTHOR]

Nanotechnology is a rapidly developing discipline that has the potential to transform the way we approach problems in a variety of fields, including agriculture. The use of nanotechnology in sustainable agriculture has gained popularity in recent years. It has various applications in agriculture, such as the development of nanoscale materials and devices to boost agricultural productivity, enhance food quality and safety, improve the efficiency of water and nutrient usage, and reduce environmental pollution. Nanotechnology has proven to be very beneficial in this field, particularly in the development of nanoscale delivery systems for agrochemicals such as pesticides, fertilizers, and growth regulators. These nanoscale delivery technologies offer various benefits over conventional delivery systems, including better penetration and distribution, enhanced efficacy, and lower environmental impact. Encapsulating agrochemicals in nanoscale particles enables direct delivery to the targeted site in the plant, thereby reducing waste and minimizing off‐target effects. Plants are fundamental building blocks of all ecosystems and evaluating the interaction between nanoparticles (NPs) and plants is a crucial aspect of risk assessment. This critical review therefore aims to provide an overview of the latest advances regarding the positive and negative effects of nanotechnology in agriculture. It also explores potential future research directions focused on ensuring the safe utilization of NPs in this field, which could lead to sustainable development. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Selenium (Se) is an essential element for many animals including humans, prokaryotes and a few green algae. For plants, Se essentiality is yet to be demonstrated. Nevertheless, it is well recognized that Se is a beneficial element for plants. For all organisms, while, a narrow range of Se is beneficial, at elevated levels it becomes toxic. This is due to accumulation of various toxic inorganic and organic Se forms during Se metabolism as well as nonspecific replacement by Se of chemically similar sulfur (S) analogs. Interestingly, Se can act both as an antioxidant and a pro-oxidant. Hence, Se chemistry and metabolism play crucial roles in determining its effects at specific concentration in an organism. A lot of knowledge has been gained regarding Se metabolites, however, the functions of many of these metabolites are yet to be resolved. Other Se containing metabolites and proteins might yet be awaiting their identification. Future research in this direction would pave the way towards identification of Se as an essential element for plants too. This review discusses the various aspects of Se uptake and metabolism with a major focus on functions of Se-containing metabolites in plants. [ABSTRACT FROM AUTHOR]

In the present study, the effects of zinc oxide nanoparticles (ZnO NPs) on rice (Oryza sativa L. cv. PB1509) plant growth were assessed in hydroponics (5, 10, 25, 50 mg L-1) and soil microcosm (5, 10, 25 50 mg kg-1) experiments. In both hydroponics and soil experiments, Zinc (Zn) accumulation in plant parts (roots, shoots and grains) was found to increase with increasing doses of ZnO NPs. Grains accumulated 29 mg kg-1 Zn at 50 mg kg-1 ZnO NPs in the soil experiment. In the hydroponics experiment, growth and photosynthetic pigments were induced by ZnO NPs up to 10 mg L-1, while higher doses of 25 and 50 mg L-1 were toxic to plant growth. Antioxidant enzyme activities (SOD, CAT, APX and GPX) were mostly increased or unaffected by all ZnO NPs doses. In soil experiments, acid and alkaline phosphatase activities were increased at 5 mg kg-1 followed by a declining trend. However, a significant decrease occurred only at 50 mg kg-1. Urease activity in soil was significantly increased at all doses of ZnO NPs, while the activity of dehydrogenase did not show any significant change up to 25 mg kg-1. The length of plants and photosynthetic pigments did not show much toxicity except root length beyond 10 mg kg-1; however, the biomass of plants including grains was significantly lower than control beyond 5 mg kg-1 dose. The activity of antioxidant enzymes (GPX, APX and CAT) showed a significant increase at all doses of ZnO NPs. The DTPA extractable Zn concentration in the soil was significantly elevated with increasing exposure concentrations of ZnO NPs. Based on hydroponics and soil experiments, this study suggests a dose of up to 10 mg L-1 or 10 mg kg-1 would be an appropriate dose for augmenting the growth of rice plants and Zn accumulation, and this can be practically utilized for rice plants growing in submerged conditions. [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]

Salicornia and Sarcocornia are almost identical halophytes whose edible succulent shoots hold promise for commercial production in saline water. Enhanced sulfur nutrition may be beneficial to crops naturally grown on high sulfate. However, little is known about sulfate nutrition in halophytes. Here we show that Salicornia europaea (ecotype RN) exhibits a significant increase in biomass and organic-S accumulation in response to supplemental sulfate, whereas Sarcocornia fruticosa (ecotype VM) does not, instead exhibiting increased sulfate accumulation. We investigated the role of two pathways on organic-S and biomass accumulation in Salicornia and Sarcoconia: the sulfate reductive pathway that generates Cys and l-Cys desulfhydrase that degrades Cys to H2S, NH3, and pyruvate. The major function of O-acetyl-Ser-(thiol) lyase (OAS-TL; EC 2.5.1.47) is the formation of l-Cys, but our study shows that the OAS-TL A and OAS-TL B of both halophytes are enzymes that also degrade l-Cys to H2S. This activity was significantly higher in Sarcocornia than in Salicornia, especially upon sulfate supplementation. The activity of the sulfate reductive pathway key enzyme, adenosine 5'-phosphosulfate reductase (APR, EC 1.8.99.2), was significantly higher in Salicornia than in Sarcocornia. These results suggest that the low organic-S level in Sarcocornia is the result of high l-Cys degradation rate by OAS-TLs, whereas the greater organic-S and biomass accumulation in Salicornia is the result of higher APR activity and low l-Cys degradation rate, resulting in higher net Cys biosynthesis. These results present an initial road map for halophyte growers to attain better growth rates and nutritional value of Salicornia and Sarcocornia. [ABSTRACT FROM AUTHOR]

Unexpected bioaccumulation and biomagnification of heavy metal(loid)s (HMs) in the environment have become a predicament for all living organisms, including plants. The presence of these HMs in the plant system raised the level of reactive oxygen species (ROS) and remodeled several vital cellular biomolecules. These lead to several morphological, physiological, metabolic, and molecular aberrations in plants ranging from chlorosis of leaves to the lipid peroxidation of membranes, and degradation of proteins and nucleic acid including the modulation of the enzymatic system, which ultimately affects the plant growth and productivity. Plants are equipped with several mechanisms to counteract the HMs toxicity. Among them, seed priming (SP) technology has been widely tested with the use of several inorganic chemicals, plant growth regulators (PGRs), gasotransmitters, nanoparticles, living organisms, and plant leaf extracts. The use of these compounds has the potential to alleviate the HMs toxicity through the strengthening of the antioxidant defense system, generation of low molecular weight metallothionein's (MTs), and phytochelatins (PCs), and improving seedling vigor during early growth stages. This review presents an account of the sources, uptake and transport, and phytotoxic effects of HMs with special attention to different mechanism/s, occurring to mitigate the HMs toxicity in plants employing SP technology. Novelty statement: To the best of our knowledge, this review has delineated the consequences of HMs on the crucial plant processes, which ultimately affect plant growth and development. This review also compiled the up to dated information on phytotoxicity of HMs through the use of SP technology, this review discussed how different types of SP approaches help in diminishing the concentration HMs in plant systems. Also, we depicted mechanisms, represent how HMs transport and their actions on cellular levels, and emphasized, how diverse SP technology effectiveness in the mitigation of plants' phytotoxicity in unique ways. [ABSTRACT FROM AUTHOR]

The present study was planned to delineate the role of antioxidants and different functional groups ofRicinus communisandBrassica junceain the tolerance mechanisms toward cadmium (Cd) for phytoremediation. Application of Cd caused a reduction in dry biomass of 53.84% and 26.58% in root and 45.33% and 33.84% in shoots ofB. junceaandR. communis, respectively. Antioxidant enzymes, namely superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase and glutathione-S-transferase, and metabolites (proline) increased in both the species due to Cd exposure. The metal caused substantial changes in the functional groups present in the roots and leaves of the plants. A number of new peaks appeared in the Cd-treated plants, which indicate the production of the compounds responsible for the metal tolerance of these plants.R. communishas been found to possess a good antioxidant defense system against Cd stress and may be used for the phytoremediation of metal-contaminated soils in place of edible crops, which enhance the risk of contaminating the food chain. It has been observed thatR. communisaccumulated 213.39 and 335.68 mg Cd in roots and shoots, respectively, whereasB. junceaaccumulated 28.19 and 310.15 mg Cd in the roots and shoots, respectively. [ABSTRACT FROM AUTHOR]

Ureides, the degraded products of purine catabolism in Arabidopsis , have been shown to act as antioxidant and nitrogen sources. Herein we elucidate purine degraded metabolites as a carbon source using the Arabidopsis Atxdh1 , Ataln , and Ataah knockout (KO) mutants vis-à-vis wild-type (WT) plants. Plants were grown under short-day conditions on agar plates containing half-strength MS medium with or without 1% sucrose. Notably, the absence of sucrose led to diminished biomass accumulation in both shoot and root tissues of the Atxdh1 , Ataln, and Ataah mutants, while no such effect was observed in WT plants. Moreover, the application of sucrose resulted in a reduction of purine degradation metabolite levels, specifically xanthine and allantoin, predominantly within the roots of WT plants. Remarkably, an increase in proteins associated with the purine degradation pathway was observed in WT plants in the presence of sucrose. Lower glyoxylate levels in the roots but not in the shoot of the Atxdh1 mutant in comparison to WT, were observed under sucrose limitation, and improved by sucrose application in root, indicating that purine degradation provided glyoxylate in the root. Furthermore, the deficit of purine-degraded metabolites in the roots of mutants subjected to carbon starvation was partially mitigated through allantoin application. Collectively, these findings signify that under conditions of sucrose limitation and short-day growth, purines are primarily remobilized within the root system to augment the availability of ureides, serving as an additional carbon (as well as nitrogen) source to support plant growth. • Ureides support Arabidopsis growth during carbon starvation. • Purine degradation mutants reduce biomass under carbon starvation. • Root-centric purine degradation in carbon stressed WT. • Ureides enhances biomass in WT and Atxdh1 mutant. [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]

The roles of cytosolic O-acetylserine-(thiol)-lyase A (OASTLA), chloroplastic OASTLB, and mitochondrial OASTLC in plant selenate resistance were studied in Arabidopsis. Impairment in OASTLA and OASTLB resulted in reduced biomass, chlorophyll and soluble protein content compared with selenate-treated OASTLC-impaired and wild-type plants. The generally lower total selenium (Se), protein-Se, organic-sulfur and protein-sulfur (S) content in oastlA and oastlB compared with wild-type and oastlC leaves indicated that Se accumulation was not the main cause for the stress symptoms in these mutants. Notably, the application of selenate positively induced S-starvation markers and the OASTLs, followed by increased sulfite reductase, sulfite oxidase activities, and increased sulfite and sulfide concentrations. Taken together, our results indicate a futile anabolic S-starvation response that resulted in lower glutathione and increased oxidative stress symptoms in oastlA and oastlB mutants. In-gel assays of l -cysteine and l -seleno-cysteine, desulfhydrase activities revealed that two of the three OASTL activity bands in each of the oastl single mutants were enhanced in response to selenate, whereas the impaired proteins exhibited a missing activity band. The absence of differently migrated activity bands in each of the three oastl mutants indicates that these OASTLs are major components of desulfhydrase activity, degrading l -cysteine and l -seleno-cysteine in Arabidopsis. [ABSTRACT FROM AUTHOR]

Drought, a major abiotic limiting factor, could be modulated with in-built reprogramming of plants at molecular level by regulating the activity of plant developmental processes, stress endurance and adaptation. The transgenic Arabidopsis thaliana over-expressing metallothionein 1 (MT1) gene of desi chickpea (Cicer arietinum L.) was subjected to transcriptome analysis. We evaluated drought tolerance of 7 days old plants of Arabidopsis thaliana in both wild-type (WT) as well as transgenic plants and performed transcriptome analysis. Our analysis revealed 24,737 transcripts representing 24,594 genes out of which 5,816 were differentially expressed genes (DEGs) under drought conditions and 841 genes were common in both genotypes. A total of 1251 DEGs in WT and 2099 in MT1 were identified in comparison with control. Out of the significant DEGs, 432 and 944 were upregulated, whereas 819 and 1155 were downregulated in WT and MT1 plants, respectively. The physiological and molecular parameters involving germination assay, root length measurements under different stress treatments and quantitative expression analysis of transgenic plants in comparison to wild-type were found to be enhanced. CarMT1 plants also demonstrated modulation of various other stress-responsive genes that reprogrammed themselves for stress adaptation. Amongst various drought-responsive genes, 24 DEGs showed similar quantitative expression as obtained through RNA sequencing data. Hence, these modulatory genes could be used as a genetic tool for understanding and delineating the mechanisms for fine-tuning of stress responses in crop plants. [ABSTRACT FROM AUTHOR]

Purine degradation products have been shown to play roles in plant response to stresses such as drought, salinity, extended dark, nitrogen deficiency, and pathogen infection. In this study, we used Arabidopsis wild-type (WT) and an Atxdh1 -knockout mutant defective in xanthine dehydrogenase1 (XDH1) to examine the role of degraded purine metabolites in the responses to wounding or UV-C stress applied to the middle leaves of the plant. Wounding or UV-C stress in the mutant resulted in lower fresh-weight, increased senescence symptoms, and increased cell death compared to WT plants. In addition, WT plants exhibited lower levels of oxidative stress indicators, reactive oxygen species, and malondialdehyde in their leaves than the mutant. Notably, transcripts and proteins functioning in the purine degradation pathway were regulated in such a way that it led to enhanced ureide levels in WT leaves 24h after applying the UV-C or wound stress. However, different remobilization of the accumulated ureides was observed after 72h of stress. In plants treated with UV-C, the concentration of allantoin was highest in young leaves, whereas in wounded plants it was lowest in these leaves and instead accumulated mainly in the middle leaves that had been wounded. These results indicated that in WT plants treated with UV-C, ureides were remobilized from the lower older and damaged leaves to support young leaf growth during the recovery period from stress. After wounding, however, whilst some ureides were remobilized to the young leaves, more remained in the wounded middle leaves to function as antioxidants and/or healing agents. [ABSTRACT FROM AUTHOR]