Domestic cooking effects on nutritional quality and phytochemical contents of zinc biofortified Lepidium sativum L. sprouts.

The impact of the common cooking practices on the nutritional value and the antioxidant contents of Lepidium sativum zinc biofortified sprouts was assessed in the present investigation. Garden cress sprouts showed an increase of dry matter, ash, proteins, carbohydrates, sodium, iron and zinc contents according to the applied cooking process. Antinutrient and pigment contents (chlorophylls, carotenoids and anthocyans) were diminished by applying various cooking treatments. A significant drop of total phenolic (25.57 - 60.87%) and total flavonoid contents (58.04 - 71.86%), catechin hydrate (81.90 - 96.15%), sinapic acid (62.44 - 84.79%), myricitin (97.62 - 99.12%) and rutin (52.83 - 83.41%) was detected in cooked plant material. Nevertheless, cooking practices raised the caffeic acid contents by 21.97 to 29.74% and boil and steam cooking increased the chlorogenic acid amounts by 1.89% and 9.28%, respectively. Microwaving favored an improvement of the antioxidant performances. Overall, Microwaving permitted good nutrients retention along with the best antioxidant performances.

Phytochemical investigation, antioxidant, anti-inflammatory and cytotoxic activities of Tunisian medicinal Tamarix africana Poir.

The current study aimed to evaluate Tunisian Tamarix africana Poir biological activities. In this study, novel biological activities of the shoot extracts related to their phenolics investigated. Secondary metabolite contents, antioxidant, anti-inflammatory and cytotoxic activities of four extracts (hexane, dichloromethane, methanol and water) were investigated. Antioxidant activities were assessed via in vitro and ex vivo assays. Besides, anticancer activity was investigated against human lung carcinoma (A-549) and colon adenocarcinoma (DLD-1) cells. The anti-inflammatory ability was evaluated via inhibition of LPS-induced NO production in RAW 264.7 macrophage cell lines. Methanol and water extracts displayed the highest antioxidant (IC50 = 3.3 and 4.3 µg/mL respectively), which are correlated activities correlated with phenolic contents. Hexane extract exhibited an important anti-inflammatory effect inhibiting NO ability by 100% at 80 µg/mL. Besides, T. africana extracts were found to be active against A-549 lung carcinoma cells with IC50 values ranging from 20 to 34 µg/mL. These results suggested that T. africana is considered as a potential source of readily accessible natural molecules with a promising effect on human health and diseases.

Improving environmental stress resilience in crops by genome editing: insights from extremophile plants.

In basic and applied sciences, genome editing has become an indispensable tool, especially the versatile and adaptable CRISPR/Cas9 system. Using CRISPR/Cas9 in plants has enabled modifications of many valuable traits, including environmental stress tolerance, an essential aspect when it comes to ensuring food security under climate change pressure. The CRISPR toolbox enables faster and more precise plant breeding by facilitating: multiplex gene editing, gene pyramiding, and de novo domestication. In this paper, we discuss the most recent advances in CRISPR/Cas9 and alternative CRISPR-based systems, along with the technical challenges that remain to be overcome. A revision of the latest proof-of-concept and functional characterization studies has indeed provided more insight into the quantitative traits affecting crop yield and stress tolerance. Additionally, we focus on the applications of CRISPR/Cas9 technology in regard to extremophile plants, due to their significance on: industrial, ecological and economic levels. These still unexplored genetic resources could provide the means to harden our crops against the threat of climate change, thus ensuring food security over the next century.

Priming seeds with salicylic acid modulates membrane integrity, antioxidant defense, and gene expression in Medicago sativa grown under iron deficiency and salinity.

Exposure of plants to adverse environmental conditions reduces their growth and productivity. Currently, seed priming with phytohormones is considered one of the most reliable and cost-effective approaches that can help alleviate the toxic effects of environmental stress. In this context, the present study aims to investigate the effect of priming alfalfa seeds with salicylic acid (SA) on oxidative stress markers, including malonyldialdehyde, protein content, activities of antioxidant enzymes, and expression of genes encoding these enzymes in leaves and roots of alfalfa (Gabes ecotype) grown under saline stress, iron deficiency, or both. Our results showed that the application of salt stress and iron deficiency separately or simultaneously induces changes in the activities of antioxidant enzymes, but these are organ- and stress-dependent. The Gabes ecotype was able to increase the activities of these enzymes under salt stress to alleviate oxidative damage. Indeed, priming seeds with 100 µM SA significantly increases the enzymatic activities of APX, GPX, CAT, and SOD. Therefore, this concentration can be considered optimal for the induction of iron deficiency tolerance. Our results showed not only that Gabes ecotype was able to tolerate salt stress by maintaining high expression of the Fe-SOD isoform, but also that the pretreatment of seeds with 100 µM SA improved the tolerance of this ecotype to iron deficiency by stimulating Fe-SOD expression and inhibiting CAT and APXc.

Crithmum maritimum L. Volatile Compound's Diversity Through Tunisian Populations: Use of a Plant Organ-Based Statistical Approach for Chemotype Identification.

This work aimed to investigate the variability of the chemical composition of the aromatic halophyte Crithmum maritimum L. essential oils according to the geographical origin and separated organs, using a statistical approach based on the multiple analysis of variance and the Principal Component Analyses. One hundred twenty samples were collected from three distinct bioclimatic regions (10 samples×3 provenances×4 organs). Hydrodistillation of separated organs (roots, stems, leaves and flowers) yielded 0.13 to 1.75 % of the dry matter. Chemical investigation of the volatile compounds by Gas chromatography-mass spectrometry showed that C. maritimum essential oils were dominated by monoterpenes hydrocarbons, oxygenated monoterpenes, and phenylpropanoids varying, respectively, from 33.3 to 66.9, from 7.8 to 46.6 and from 4.5 to 57.2 % according to organs and localities. Statistical analyses identified three different chemotypes depending on the geographic origin as follow: γ-Terpinene-Thymol methyl ether / Dillapiole / Thymol methyl ether-Dillapiole.

The increase in O2 nodule-conductance under phosphorus deficiency varies among genotypes in Medicago truncatula.

The effect of phosphorus deficiency on plant growth, nodulation, and symbiotic nitrogen fixation as well as, the nodulated-roots oxygen consumption, nodule permeability and conductance to the oxygen diffusion of Medicago truncatula-Sinorhizobium meliloti symbiosis were studied. Three lines, namely TN6.18, originated from local populations, F83005.5 originated from Var (France) and Jemalong 6, a reference cultivar from Australia, were hydroponically grown in nutrient solution supplied with 5 µmol (P deficient) and 15 µmol (P sufficient: Control), under semi-controlled conditions in a glasshouse. A genotypic variation in tolerance to P deficiency was found: TN6.18 was the most tolerant line whereas F83005.5 was the most sensitive. The relative tolerance of TN6.18 was concomitant with the greater P requirement, the higher N2 fixation, the stimulation of nodule respiration and the less increases of conductance to the oxygen diffusion in nodules tissues. The higher P use efficiency for nodule growth and for symbiotic nitrogen fixation was detected in the tolerant line. Results suggest that the tolerance to P deficiency seems to depend on thehost plant ability to reallocate P from both leaves and roots to their nodules. P is needed in high energy demand conditions to maintain adequate nodule activity and prevent negative effects of the O2 excess on the nitrogenase.

Changes in organic compounds secreted by roots in two Poaceae species (Hordeum vulgare and Polypogon monspenliensis) subjected to iron deficiency.

Despite their economic and ecological interests, Poaceae are affected by the low availability of iron in calcareous soils. Several studies focused on the capacity of this family to secrete phytosiderophores and organic acids as a mechanism of tolerance to iron deficiency. This work aimed at studying the physiological responses of two Poaceae species; Hordeum vulgare (cultivated barley) and Polypogon monspenliensis (spontaneous species) to iron deficiency, and evaluate especially the release of phytosiderophores and organic acids. For this purpose, seedlings of these two species were cultivated in complete nutrient solution with or without iron. The biomass production, iron status, phytosiderophores and organic acids release by roots were studied. The results demonstrated that Polypogon monspenliensis was relatively more tolerant to iron deficiency than Hordeum vulgare. Polypogon monspenliensis had the ability to secrete a higher amount of phytosiderophores and organic acids, especially citric, acetic, oxalic and malic acids, compared to Hordeum vulgare. We propose this spontaneous species as a forage plant in calcareous soils and in intercropping systems with fruit trees to prevent iron chlorosis.

Nutraceutical Potential of Leaf Hydro-Ethanolic Extract of the Edible Halophyte Crithmum maritimum L.

Aromatic halophytes represent an exceptional source of natural bioactive compounds for the food industry. Crithmum maritimum L., also known as sea fennel, is a halophyte plant colonizing cliffs and coastal dunes along Mediterranean and Atlantic coasts. It is well known to produce essential oils and polyphenols endowed with antioxidant and biological effects. The present work reports the phytochemical profile, as well as antioxidant, antimicrobial and antimutagenic properties of C. maritimum leaf hydro-alcoholic extract. From LC-ESI-MS analysis, eighteen phenolic compounds were depicted in sea fennel extract and the amount of total phenolic content exceeds 3% DW. Accordingly, C. maritimum extract showed strong antioxidant activities, as evidenced by in vitro (DPPH, ORAC, FRAP) and ex vivo (CAA-RBC and hemolysis) assays. An important antimicrobial activity against pathogenic strains was found as well as a strong capacity to inhibit Staphylococcus aureus (ATCC 35556) biofilm formation. Sea fennel extracts showed a significant decrease of mutagenesis induced by hydrogen peroxide (H2O2) and menadione (ME) in Saccharomyces cerevisiae D7 strain. In conclusion, our results show that C. maritimum is an exceptional source of bioactive components and exert beneficial effects against oxidative or mutagenic mechanisms, and pathogenic bacteria, making it a potential functional food.

Investigation of Na+ and K+ Transport in Halophytes: Functional Analysis of the HmHKT2;1 Transporter from Hordeum maritimum and Expression under Saline Conditions.

Control of K+ and Na+ transport plays a central role in plant adaptation to salinity. In the halophyte Hordeum maritimum, we have characterized a transporter gene, named HmHKT2;1, whose homolog HvHKT2;1 in cultivated barley, Hordeum vulgare, was known to give rise to increased salt tolerance when overexpressed. The encoded protein is strictly identical in two H. maritimum ecotypes, from two biotopes (Tunisian sebkhas) affected by different levels of salinity. These two ecotypes were found to display distinctive responses to salt stress in terms of biomass production, Na+ contents, K+ contents and K+ absorption efficiency. Electrophysiological analysis of HmHKT2;1 in Xenopus oocytes revealed distinctive properties when compared with HvHKT2;1 and other transporters from the same group, especially a much higher affinity for both Na+ and K+, and an Na+-K+ symporter behavior in a very broad range of Na+ and K+ concentrations, due to reduced K+ blockage of the transport pathway. Domain swapping experiments identified the region including the fifth transmembrane segment and the adjacent extracellular loop as playing a major role in the determination of the affinity for Na+ and the level of K+ blockage in these HKT2;1 transporters. The analysis (quantitative reverse transcription-PCR; qRT-PCR) of HmHKT2;1 expression in the two ecotypes submitted to saline conditions revealed that the levels of HmHKT2;1 transcripts were maintained constant in the most salt-tolerant ecotype whereas they decreased in the less tolerant one. Both the unique functional properties of HmHKT2;1 and the regulation of the expression of the encoding gene could contribute to H. maritimum adaptation to salinity.

Recovery aptitude of the halophyte Cakile maritima upon water deficit stress release is sustained by extensive modulation of the leaf proteome.

Among the most intriguing features characterizing extremophile plants is their ability to rapidly recover growth activity upon stress release. Here, we investigated the responses of the halophyte C. maritima to drought and recovery at both physiological and leaf proteome levels. Six week-old plants were either cultivated at 100% or at 25% field capacity. After 12 d of treatment, one lot of dehydrated plants was rewatered to 100% FC for 14 d (stress release). Drought stress impaired shoot hydration, photosynthetic activity and chlorophyll content compared to the control, resulting in severe plant growth restriction. This was concomitant with a marked increase in anthocyanin and proline concentrations. Upon stress release, C. maritima rapidly recovered with respect to all measured parameters. Two-dimensional gel-based proteome analysis of leaves revealed 84 protein spots with significantly changed volumes at the compared conditions: twenty-eight protein spots between normally watered plants and stressed plants but even 70 proteins between stressed and recovered plants. Proteins with higher abundance induced upon rewatering were mostly involved in photosynthesis, glycolytic pathway, TCA cycle, protein biosynthesis, and other metabolic pathways. Overall, C. maritima likely adopts a drought-avoidance strategy, involving efficient mechanisms specifically taking place upon stress release, leading to fast and strong recovery.

Phytochemical and Biological Activities in Limonium Species Collected in Different Biotopes of Tunisia.

A particular interest is nowadays given to natural antioxidants occurring in foods which can reduce the risk of several diseases through their protective effect. The genus Limonium is widely distributed in different salt regions of Tunisia and known in traditional medicine for the presence of highly effective viral and bacterial replication inhibitors. Limonium leaves have possible beneficial effects on human health for their antioxidant activities and free radical scavenging abilities. To exploit the potential of plants from extreme environments as new sources of natural antioxidants, we studied the extracts from leaves of eight Limonium species growing in extreme environments in Tunisia. Antioxidant molecules (polyphenols, flavonoids, flavonols, ascorbate, tocopherols), in vitro (DPPH, ORAC) and ex vivo antioxidant potential on human erythrocytes, antioxidant enzymes activities (superoxide dismutase, peroxidases, glutathione reductase) were evaluated to identify the species with the best antioxidant capacity. The results showed variability among the species considered in function of the environmental conditions of their natural biotopes, as for the antioxidants measured. In particular, L. vulgare from Oued Rane biotope, characterized by dryness and high temperatures, was the species with the highest enzymatic activity and antioxidant capacity, making it interesting as possible edible halophyte plant or as food complement.

High salinity impacts germination of the halophyte Cakile maritima but primes seeds for rapid germination upon stress release.

Seed germination recovery aptitude is an adaptive trait of overriding significance for the successful establishment and dispersal of extremophile plants in their native ecosystems. Cakile maritima is an annual halophyte frequent on Mediterranean coasts, which produces transiently dormant seeds under high salinity, that germinate fast when soil salinity is lowered by rainfall. Here, we report ecophysiological and proteomic data about (1) the effect of high salt (200 mM NaCl) on the early developmental stages (germination and seedling) and (2) the seed germination recovery capacity of this species. Upon salt exposure, seed germination was severely inhibited and delayed and seedling length was restricted. Interestingly, non-germinated seeds remained viable, showing high germination percentage and faster germination than the control seeds after their transfer onto distilled water. The plant phenotypic plasticity during germination was better highlighted by the proteomic data. Salt exposure triggered (1) a marked slower degradation of seed storage reserves and (2) a significant lower abundance of proteins involved in several biological processes (primary metabolism, energy, stress-response, folding and stability). Yet, these proteins showed strong increased abundance early after stress release, thereby sustaining the faster seed storage proteins mobilization under recovery conditions compared to the control. Overall, as part of the plant survival strategy, C. maritima seems to avoid germination and establishment under high salinity. However, this harsh condition may have a priming-like effect, boosting seed germination and vigor under post-stress conditions, sustained by active metabolic machinery.

Anthocyanins of Coloured Wheat Genotypes in Specific Response to SalStress.

The present study investigated the effect of salt stress on the development of adaptive responses and growth parameters of different coloured wheat genotypes. The different coloured wheat genotypes have revealed variation in the anthocyanin content, which may affect the development of adaptive responses under increasing salinity stress. In the early stage of treatment with salt at a lower NaCl concentration (100 mM), anthocyanins and proline accumulate, which shows rapid development of the stress reaction. A dose-dependent increase in flavonol content was observed for wheat genotypes with more intense purple-blue pigmentation after treatment with 150 mM and 200 mM NaCl. The content of Na⁺ and K⁺ obtained at different levels of salinity based on dry weight (DW) was more than 3 times greater than the control, with a significant increase of both ions under salt stress. Overall, our results demonstrated that coloured wheat genotypes with high anthocyanin content are able to maintain significantly higher dry matter production after salt stress treatment.

Effect of salinity on osmotic adjustment, proline accumulation and possible role of ornithine-δ-aminotransferase in proline biosynthesis in Cakile maritima.

The short time response to salt stress was studied in Cakile maritima. Plants were exposed to different salt concentrations (0, 100, 200 and 400 mM NaCl) and harvested after 4, 24, 72 and 168 h of treatment. Before harvesting plants, tissue hydration, osmotic potential, inorganic and organic solute contents, and ornithine-δ-aminotransferase activity were measured. Plants of C. maritima maintained turgor and tissue hydration at low osmotic potential mainly at 400 mM NaCl. The results showed that, in leaves and stems, Na+ content increased significantly after the first 4 h of treatment. However, in roots, the increase of Na+ content remained relatively unchanged with increasing salt. The K+ content decreased sharply at 200 and 400 mM NaCl with treatment duration. This decrease was more pronounced in roots. The content of proline and amino acids increased with increasing salinity and treatment duration. These results indicated that the accumulation of inorganic and organic compounds was a central adaptive mechanism by which C. maritima maintained intracellular ionic balance under saline conditions. However, their percentage contribution to total osmotic adjustment varies from organ to organ; for example, Na+ accumulation mainly contributes in osmotic adjustment of stem tissue (60%). Proline contribution to osmotic adjustment reached 36% in roots. In all organs, proline as well as δ-OAT activity increased with salt concentration and treatment duration. Under normal growth conditions, δ-OAT is mainly involved in the mobilization of nitrogen required for plant growth. However, the highly significant positive correlation between proline and δ-OAT activity under salt-stress conditions suggests that ornithine pathway contributed to proline synthesis.

Phospholipases Dζ1 and Dζ2 have distinct roles in growth and antioxidant systems in Arabidopsis thaliana responding to salt stress.

MAIN CONCLUSION: Phospholipases Dζ play different roles in Arabidopsis salt tolerance affecting the regulation of ion transport and antioxidant responses. Lipid signalling mediated by phospholipase D (PLD) plays essential roles in plant growth including stress and hormonal responses. Here we show that PLDζ1 and PLDζ2 have distinct effects on Arabidopsis responses to salinity. A transcriptome analysis of a double pldζ1pldζ2 mutant revealed a cluster of genes involved in abiotic and biotic stresses, such as the high salt-stress responsive genes DDF1 and RD29A. Another cluster of genes with a common expression pattern included ROS detoxification genes involved in electron transport and biotic and abiotic stress responses. Total superoxide dismutase (SOD) activity was induced early in the shoots and roots of all pldζ mutants exposed to mild or severe salinity with the highest SOD activity measured in pldζ2 at 14 days. Lipid peroxidation in shoots and roots was higher in the pldζ1 mutant upon salt treatment and pldζ1 accumulated H2O2 earlier than other genotypes in response to salt. Salinity caused less deleterious effects on K+ accumulation in shoots and roots of the pldζ2 mutant than of wild type, causing only a slight variation in Na+/K+ ratio. Relative growth rates of wild-type plants, pldζ1, pldζ2 and pldζ1pldζ2 mutants were similar in control conditions, but strongly affected by salt in WT and pldζ1. The efficiency of photosystem II, estimated by measuring the ratio of chlorophyll fluorescence (F v/F m ratio), was strongly decreased in pldζ1 under salt stress. In conclusion, PLDζ2 plays a key role in determining Arabidopsis sensitivity to salt stress allowing ion transport and antioxidant responses to be finely regulated.

Effect of O-methylated and glucuronosylated flavonoids from Tamarix gallica on α-glucosidase inhibitory activity: structure-activity relationship and synergistic potential.

O-Methylated and glucuronosylated flavonoids were isolated from Tamarix gallica as α-glucosidase inhibitors. Structure-activity relationship of these flavonoids suggests that catechol moiety and glucuronic acid at C-3 are factors in the increase in α-glucosidase inhibitory activity. Furthermore, rhamnetin, tamarixetin, rhamnazin, KGlcA, KGlcA-Me, QGlcA, and QGlcA-Me exhibit synergistic potential when applied with a very low concentration of acarbose to α-glucosidase from rat intestine.

Proteomic and functional analysis of proline dehydrogenase 1 link proline catabolism to mitochondrial electron transport in Arabidopsis thaliana.

Proline accumulates in many plant species in response to environmental stresses. Upon relief from stress, proline is rapidly oxidized in mitochondria by proline dehydrogenase (ProDH) and then by pyrroline-5-carboxylate dehydrogenase (P5CDH). Two ProDH genes have been identified in the genome of the model plant Arabidopsis thaliana To gain a better understanding of ProDH1 functions in mitochondria, proteomic analysis was performed. ProDH1 polypeptides were identified in Arabidopsis mitochondria by immunoblotting gels after 2D blue native (BN)-SDS/PAGE, probing them with an anti-ProDH antibody and analysing protein spots by MS. The 2D gels showed that ProDH1 forms part of a low-molecular-mass (70-140 kDa) complex in the mitochondrial membrane. To evaluate the contribution of each isoform to proline oxidation, mitochondria were isolated from wild-type (WT) and prodh1, prodh2, prodh1prodh2 and p5cdh mutants. ProDH activity was high for genotypes in which ProDH, most likely ProDH1, was strongly induced by proline. Respiratory measurements indicate that ProDH1 has a role in oxidizing excess proline and transferring electrons to the respiratory chain.

High salinity helps the halophyte Sesuvium portulacastrum in defense against Cd toxicity by maintaining redox balance and photosynthesis.

MAIN CONCLUSION: NaCl alleviates Cd toxicity in Sesvium portulacastrum by maintaining plant water status and redox balance, protecting chloroplasts structure and inducing some potential Cd (2+) chelators as GSH and proline. It has been demonstrated that NaCl alleviates Cd-induced growth inhibition in the halophyte Sesuvium portulacastrum. However, the processes that mediate this effect are still unclear. In this work we combined physiological, biochemical and ultrastructural studies to highlight the effects of salt on the redox balance and photosynthesis in Cd-stressed plants. Seedlings were exposed to different Cd concentrations (0, 25 and 50 µM Cd) combined with low (0.09 mM) (LS), or high (200 mM) NaCl (HS) in hydroponic culture. Plant-water relations, photosynthesis rate, leaf gas exchange, chlorophyll fluorescence, chloroplast ultrastructure, and proline and glutathione concentrations were analyzed after 1 month of treatment. In addition, the endogenous levels of stress-related hormones were determined in plants subjected to 25 µM Cd combined with both NaCl concentrations. In plants with low salt supply (LS), Cd reduced growth, induced plant dehydration, disrupted chloroplast structure and functioning, decreased net CO2 assimilation rate (A) and transpiration rate (E), inhibited the maximum potential quantum efficiency (Fv/Fm) and the quantum yield efficiency (Φ PSII) of PSII, and enhanced the non-photochemical quenching (NPQ). The addition of 200 mM NaCl (HS) to the Cd-containing medium culture significantly mitigated Cd phytotoxicity. Hence, even at similar internal Cd concentrations, HS-Cd plants were less affected by Cd than LS-Cd ones. Hence, 200 mM NaCl significantly alleviates Cd-induced toxicity symptoms, growth inhibition, and photosynthesis disturbances. The cell ultrastructure was better preserved in HS-Cd plants but affected in LS-Cd plants. The HS-Cd plants showed also higher concentrations of reduced glutathione (GSH), proline and jasmonic acid (JA) than the LS-Cd plants. However, under LS-Cd conditions, plants maintained higher concentration of salicylic acid (SA) and abscisic acid (ABA) than the HS-Cd ones. We conclude that in S. portulacastrum alleviation of Cd toxicity by NaCl is related to the modification of GSH and proline contents as well as stress hormone levels thus protecting redox balance and photosynthesis.

New Sulphated Flavonoids from Tamarix africana and Biological Activities of Its Polar Extract.

The phytochemical investigation of Tamarix africana Poir. (Tamaricaceae) shoot polar extract afforded three new sulphated flavonoids, (2S,4R)-5,7,4'-trihydroxyflavan-4-ol 5,7-disulphate (1), (2S)-5,7,4'-trihydroxyflavan 7-O-sulphate (2), and (2S)-naringenin 4'-O-sulphate (3), together with ten known compounds. Their structures were determined by spectroscopic methods including 1D and 2D NMR analysis and HRMS. Biological activities of the polar extract of T. africana shoots related to its phenolic content were also investigated. A high total phenolic content (151.1 mg GAE/g) was found in the methanol shoot extract, which exhibits strong antioxidant activities using the oxygen radical absorbance capacity method and a skin cell-based assay. Moreover, the shoot extract showed significant anti-inflammatory activity, reducing nitric oxide release by 53.5 % at 160 µg/mL in lipopolysaccharide-stimulated RAW 264.7 macrophages. Finally, T. africana shoot extract inhibited the growth of A-549 lung carcinoma cells, with an IC50 value of 34 µg/mL.

Implication of citrate, malate and histidine in the accumulation and transport of nickel in Mesembryanthemum crystallinum and Brassica juncea.

Citrate, malate and histidine have been involved in many processes including metal tolerance and accumulation in plants. These molecules have been frequently reported to be the potential nickel chelators, which most likely facilitate metal transport through xylem. In this context, we assess here, the relationship between organics acids and histidine content and nickel accumulation in Mesembryanthemum crystallinum and Brassica juncea grown in hydroponic media added with 25, 50 and 100 µM NiCl2. Results showed that M. crystallinum is relatively more tolerant to Ni toxicity than B. juncea. For both species, xylem transport rate of Ni increased with increasing Ni supply. A positive correlation was established between nickel and citrate concentrations in the xylem sap. In the shoot of B. juncea, citric and malic acids concentrations were significantly higher than in the shoot of M. crystallinum. Also, the shoots and roots of B. juncea accumulated much more histidine. In contrast, a higher root citrate concentration was observed in M. crystallinum. These findings suggest a specific involvement of malic and citric acid in Ni translocation and accumulation in M. crystallinum and B. juncea. The high citrate and histidine accumulation especially at 100µM NiCl2, in the roots of M. crystallinum might be among the important factors associated with the tolerance of this halophyte to toxic Ni levels.