Unravelling the halophyte Suaeda maritima as an efficient candidate for phytostabilization of cadmium and lead: Implications from physiological, ionomic, and metabolomic responses.

Cadmium (Cd) and lead (Pb) are among the most toxic heavy metals affecting human health and crop yield. Suaeda maritima (L.) Dumort is an obligate halophyte that is well adapted to saline soil. The inbuilt salinity tolerance mechanisms of halophytes help them to survive in heavy metal-contaminated rhizospheric soil. In the present study, growth and ionomic responses, reactive oxygen species (ROS) accumulation, modulations of phytochelatins, antioxidative defense, and metabolomic responses were studied in S. maritima imposed to Cd and Pb stresses with an aim to elucidate Cd and Pb tolerance mechanisms and phytoremediation potential of this halophyte. Our results showed a reduction of biomass in S. maritima, which may serve as an energy conservation strategy for survival under heavy metal stress. The increased accumulation of ROS with concomitant higher expression of various antioxidative enzymes suggests the efficient scavenging of ROS. The metabolite profiling revealed significant up-regulation of sugars, sugar alcohols, amino acids, polyphenols, and organic acids under Cd and Pb stresses suggesting their possible role in osmotic balance, ionic homeostasis, ROS scavenging, and signal transduction for stress tolerance. In S. maritima, the translocation factors (Tf) are <1 in both Cd and Pb treatments, which indicates that this halophyte has high phytostabilization potential for Cd and Pb in roots and through restricted translocation of heavy metal ions to the aboveground part. The findings of this study offer comprehensive information on Cd and Pb tolerance mechanisms in S. maritima and suggest that this halophyte can detoxify the HMs through physiological, ionic, antioxidative, and metabolic regulations.

Modulation of physio-biochemical and photosynthesis parameters by overexpressing SbPIP2 gene improved abiotic stress tolerance of transgenic tobacco.

The present study aims to explore the potential of a plasma-membrane localized PIP2-type aquaporin protein sourced from the halophyte Salicornia brachiata to alleviate salinity and water deficit stress tolerance in a model plant through transgenic intervention. Transgenic plants overexpressing SbPIP2 gene showed improved physio-biochemical parameters like increased osmolytes (proline, total sugar, and amino acids), antioxidants (polyphenols), pigments and membrane stability under salinity and drought stresses compared to control plants [wild type (WT) and vector control (VC) plants]. Multivariate statistical analysis showed that, under water and salinity stresses, osmolytes, antioxidants and pigments were correlated with SbPIP2-overexpressing (SbPIP2-OE) plants treated with salinity and water deficit stress, suggesting their involvement in stress tolerance. As aquaporins are also involved in CO2 transport, SbPIP2-OE plants showed enhanced photosynthesis performance than wild type upon salinity and drought stresses. Photosynthetic gas exchange (net CO2 assimilation rate, PSII efficiency, ETR, and non-photochemical quenching) were significantly higher in SbPIP2-OE plants compared to control plants (wild type and vector control plants) under both unstressed and stressed conditions. The higher quantum yield for reduction of end electron acceptors at the PSI acceptor side [Φ( R0 )] in SbPIP2-OE plants compared to control plants under abiotic stresses indicates a continued PSI functioning, leading to retained electron transport rate, higher carbon assimilation, and less ROS-mediated injuries. In conclusion, the SbPIP2 gene functionally validated in the present study could be a potential candidate for engineering abiotic stress resilience in important crops.

SOS1 tonoplast neo-localization and the RGG protein SALTY are important in the extreme salinity tolerance of Salicornia bigelovii.

The identification of genes involved in salinity tolerance has primarily focused on model plants and crops. However, plants naturally adapted to highly saline environments offer valuable insights into tolerance to extreme salinity. Salicornia plants grow in coastal salt marshes, stimulated by NaCl. To understand this tolerance, we generated genome sequences of two Salicornia species and analyzed the transcriptomic and proteomic responses of Salicornia bigelovii to NaCl. Subcellular membrane proteomes reveal that SbiSOS1, a homolog of the well-known SALT-OVERLY-SENSITIVE 1 (SOS1) protein, appears to localize to the tonoplast, consistent with subcellular localization assays in tobacco. This neo-localized protein can pump Na+ into the vacuole, preventing toxicity in the cytosol. We further identify 11 proteins of interest, of which SbiSALTY, substantially improves yeast growth on saline media. Structural characterization using NMR identified it as an intrinsically disordered protein, localizing to the endoplasmic reticulum in planta, where it can interact with ribosomes and RNA, stabilizing or protecting them during salt stress.

The novel chaperonin 10 like protein (SbCPN10L) from Salicornia brachiata (Roxb.) augment the heat stress tolerance in transgenic tobacco.

The heat stress is a significant environmental challenge and impede the plant growth, development and productivity. The characterization and utilization of novel genes for improving stress tolerance represents a paramount approach in crop breeding. In the present study, we report on cloning of a novel heat-induced chaperonin 10-like gene (SbCPN10L) from Salicornia brachiata and elucidation of its in-planta role in conferring the heat stress endurance. The transgenic tobacco over-expressing SbCPN10L gene exhibited enhanced growth attributes such as higher rate of seed germination, germination and vigor index at elevated (35 ± 1 °C) temperature (eT). The SbCPN10L tobacco exhibited greenish and healthy seedling growth under stress. Compared with control tobacco at eT, the transgenic tobacco had higher water contents, membrane stability index, stress tolerance index and photosynthetic pigments. Lower electrolyte leakage and less accumulation of malondialdehyde, hydrogen peroxide and reactive oxygen species indicated better heat stress tolerance in transgenic tobacco over-expressing SbCPN10L gene. Transgenic tobacco accumulated higher contents of sugars, starch, amino acids and polyphenols at eT. The negative solute potential observed in transgenic tobacco contributed to maintain water content and support improved growth under stress. The up-regulation of NtAPX, NtPOX and NtSOD in transgenic tobacco under stress indicated higher ROS scavenging ability and better physiological conditioning. The results recommend the SbCPN10L gene as a potential candidate gene with an ability to confer heat stress tolerance for climate resilient crops.

Regulation of chromium translocation to shoot and physiological, metabolomic, and ionomic adjustments confer chromium stress tolerance in the halophyte Suaeda maritima.

Chromium (Cr) is a highly toxic element adversely affecting the environment, cultivable lands, and human populations. The present study investigated the effects of Cr (VI) (100-400 µM) on plant morphology and growth, photosynthetic pigments, organic osmolytes, ionomics, and metabolomic dynamics of the halophyte Suaeda maritima to decipher the Cr tolerance mechanisms. Cr exposure reduced the growth and biomass in S. maritima. The photosynthetic pigments content significantly declined at higher Cr concentrations (400 µM). However, at lower Cr concentrations (100-300 µM), the photosynthetic pigments remained unaffected or increased. The results suggest that a high concentration of Cr exposure might have adverse effects on PS II in S. maritima. The enhanced uptake of Na+ in S. maritima imposed to Cr stress indicates that Na+ might have a pivotal role in osmotic adjustment, thereby maintaining water status under Cr stress. The proline content was significantly upregulated in Cr-treated plants suggesting its role in maintaining osmotic balance and scavenging ROS. The metabolomic analysis of control and 400 µM Cr treated plants led to the identification of 62 metabolites. The fold chain analysis indicated the upregulation of several metabolites, including phytohormones (SA and GA3), polyphenols (cinnamic acid, sinapic acid, coumaric acid, vanillic acid, and syringic acid), and amino acids (alanine, leucine, proline, methionine, and cysteine) under Cr stress. The upregulation of these metabolites suggests the enhanced metal chelation and sequestration in vacuoles, reducing oxidative stress by scavenging ROS and promoting photosynthesis by maintaining the chloroplast membrane structure and photosynthetic pigments. Furthermore, in S. maritima, Cr tolerance index (Ti) was more than 60% in all the treatments, and Cr bio-concentration factor (BCF) and translocation factor (Tf) values were all greater than 1.0, which clearly indicates the Cr-hyperaccumulator characteristics of this halophyte.

Perennial halophyte Salicornia neei Lag.: Cell wall composition and functional properties of its biopolymers.

Salicornia neei halophyte extends in Argentina seashores. To envisage potential applications, cell wall sequential extraction performed on dry plant yielded 1.1, 2.4, 0.3 and 0.9% of pectin fractions respectively extracted by room temperature water, 90 °C-water, CDTA and Na2CO3. They contained 21-33% uronic acids (UA) with low degree of methylation and 0.5-1.2 M ratios of neutral sugars to UA. High arabinose level suggests that long arabinan side-chains maintain cell wall flexibility in water deficit. Fractions also contained 10-36% of proteins. The KOH-soluble fractions (4.3%) were mainly arabinoxylans. At 2.0% w/v, pectin fractions developed "weak gel"-type networks with Ca2+, while arabinoxylans generated "dilute solutions". Cellulose (28%) and lignin (45.1%) were the main biopolymers in the final residue, which showed low water swelling capacity (3.6 mL/g) due to lignin, increasing when arabinoxylans were also present. Phenolics (9.8%) were mainly water-extractable. Salicornia is a source of biopolymers and antioxidants potentially useful for food applications.

Unraveling salt responsive metabolites and metabolic pathways using non-targeted metabolomics approach and elucidation of salt tolerance mechanisms in the xero-halophyte Haloxylon salicornicum.

Haloxylon salicornicum is a xero-halophyte growing in saline and arid regions of the world. Metabolite profiling was carried out in shoot of both control and salinity treated (400 mM NaCl) samples by GC-QTOF-MS and HPLC-DAD analysis to decipher the salinity tolerance mechanism in this xero-halophyte. The present study investigates the alteration in metabolite profile of H. salicornicum that support the salinity tolerance of the plant. The metabolomic analysis of H. salicornicum shoot identified 56 metabolites, of which 47 metabolites were significantly changed in response to salinity. These metabolites were mainly included in the category of amino acids, organic acids, amines, sugar alcohols, sugars, fatty acids, alkaloids, and phytohormones. In response to salinity, most of the amino acids were down-regulated except alanine, phenylalanine, lysine, and tyramine, which were up-regulated in H. salicornicum. In contrast to amino acids, most sugars and organic acids were up-regulated in response to salinity. Correlation and pathway enrichment analysis identified important biological pathways playing significant roles in conferring salt tolerance of H. salicornicum. These biological pathways include amino sugar and nucleotide sugar metabolism, citrate cycle (TCA cycle), starch and sucrose metabolism, phenylalanine metabolism, cysteine, methionine, glycine, serine, and threonine metabolism, etc. The data presented here suggest that the modulations of various metabolic pathways facilitate H. salicornicum to survive and grow optimally even under high salinity condition. This study offers comprehensive information on metabolic adaptations and overall salt tolerance mechanisms in H. salicornicum. The information gained through this study will provide guidance to plant breeders and molecular biologists to develop salinity tolerant crop varieties.

SsPsaH, a H subunit of the photosystem I reaction center of Suaeda salsa, confers the capacity of osmotic adjustment in tobacco.

BACKGROUND: Abiotic stress effects agricultural production, so research on improving stress tolerance of crop is important. Suaeda salsa is a halophyte with high salt and drought tolerance and ability to desalinate saline soil and improve soil quality. OBJECTIVE: To discover and utilize of salt and drought tolerance-related genes, we further investigated the mechanisms of salt and drought tolerance. METHODS: Through screening a salt treated Suaeda salsa cDNA library and further cloning a H subunit of the photosystem I reaction center SsPsaH cDNA, and then the protein domain and phylogenetic analyses of PSI genes was conducted with the NCBI Blast, DNAMAN, and MotifScan programs. The S. salsa seedlings were subjected to various stress treatments and analyze expression of SsPsaH under these treatments by real-time RT-PCR. SsPsaH expression construct was introduced into S. pombe cells by electroporation and transformed into N. tabacum plants by the leaf disc transformation method. RESULTS: A member of the H subunit of the Photosystem I reaction center (defined as SsPsaH) was obtained. The expression of SsPsaH was up-regulated by abscisic acid (ABA), salt, and drought stress treatments. Over-expressing SsPsaH in recombinant yeasts enhanced high salinity tolerance and increased tolerance to sorbitol during seed germination and seedling root development in tobacco, respectively. Some stress-related mark genes such as a LEA family gene of NtLEA, a binding protein of a drought response element of NtDREB, the ascorbate peroxidase gene (NtAPX) were also up-regulated in SsPsaH overexpressing transgenic tobacco lines. CONCLUSIONS: These results show that SsPsaH may contribute to the salt and osmotic stress response of plants.

Wild vs cultivated halophytes: Nutritional and functional differences.

Some halophyte plants are currently used in gourmet cuisine due to their unique organoleptic properties. Moreover, they exhibit excellent nutritional and functional properties, being rich in polyphenolics and vitamins. These compounds are associated to strong antioxidant activity and enhanced health benefits. This work compared the nutritional properties and antioxidant potential of three species (Mesembryanthemum nodiflorum, Suaeda maritima and Sarcocornia fruticosa) collected in saltmarshes from Portugal and Spain with those of cultivated plants. The latter were generally more succulent and had higher contents of minerals than plants obtained from the wild and contained less fibre. All species assayed are a good source of proteins, fibres and minerals. Additionally, they are good sources of carotenoids and vitamins A, C and B6 and showed good antioxidant potential particularly S. maritima. Chromatographic analysis of the phenolic profile revealed that ferulic and caffeic acids as the most relevant phenolic compounds detected in the halophytes tested.

A new aryldihydronaphthalene-type lignan and other metabolites with potential anti-​inflammatory activities from Corispermum mongolicum Iljin.

One new aryldihydronaphthalene-type lignan (1) together with eight known lignans (2-4, 7-11) as well as two caffeic-acid dimers (5, 6) were isolated from an ethanol extract of the whole plant of Corispermum mongolicum Iljin (Chenopodiaceae). The chemical structures of these compounds were determined from 1D and 2D NMR and HR-ESI-MS spectra, and results were compared with data from the literature. This study is the first demonstration of nine compounds (2 and 4-11) isolated from the Chenopodiaceae family, with one of these (3) from the genus Corispermum. Anti-inflammatory effects of the isolated compounds were evaluated in terms of inhibition of production of nitric oxide, tumour necrosis factor-α, and interleukin-6 in lipopolysaccharide-induced RAW 264.7 cells.

Aquaponic System with White Shrimp Litopenaeus vannamei Rearing and Production of the Plants Batis maritima, Sarcocornia neei and Sporobolus virginicus

Abstract Aquaponics is a system that integrates aquaculture with plant production in which two species are benefited, and there is water saving. In this study was carried out with an aquaponic system to verify the interaction between the growth of the halophytes Batis maritime, Sarcocornia neei, and Sporobolus virginicus associated with white shrimp Litopenaeus vannamei rearing. We also investigated if there were different responses of physicochemical variables of the water in the experimental shrimp culture ponds integrated into the growth of plants and control ponds, without plants, throughout a 56-day period. The treatment experiment and control presented a statistically significant difference in total dissolved solids, salinity, total suspended solids, ammonia, orthophosphate, and nitrite. In the experimental treatment, with the presence of plants and recirculating water, a reduction of total suspended solids, ammonia and orthophosphate was observed. The rate of shrimp production was not significantly different between treatments, and the performance was similar to that of other studies. The biomass gain of the halophyte B. maritima was 876.6 grams in 0.5 m² and of S. neei was 48.8 grams in 0.16 m². All plants of the species S. virginicus died during the experiment.

Phenolic profile and antioxidant properties of sand rice (Agriophyllum squarrosum) as affected by cooking and in vitro digestion.

BACKGROUND: Sand rice (Agriophyllum squarrosum) is an underutilized pseudocereal bearing edible seeds. In this study, the phenolics and antioxidant activity of sand rice seeds after cooking and in vitro digestion were extensively investigated. RESULTS: Total phenolic content (TPC) of the sand rice seeds was slightly increased whereas total flavonoid content (TFC) decreased after boiling. Furthermore, nine compounds were detected in the uncooked seeds, with hyperoside (169.19 ± 6.59 µg g-1 dry weight (DW)), protocatechuic acid (167.46 ± 7.21 µg g-1 DW), and rutin (83.15 ± 3.26 µg g-1 DW) as the major components. Apart from the bioaccessible phenolics in the aqueous fraction, these compounds retained in the solid residue of the porridge were released to varying degrees during simulated digestion. In addition, these phenolic extracts also exerted considerable antioxidant potency, which was positively correlated with their corresponding TPC, TFC, and phenolic profiles. CONCLUSION: These results indicated that both boiling and in vitro digestive treatments could considerably enhance the release of bioactive compounds and thus contribute antioxidant properties to sand rice porridge. These findings suggest that sand rice seed is a potential functional food and an excellent natural antioxidant source. © 2019 Society of Chemical Industry.

Higher Novel L-Cys Degradation Activity Results in Lower Organic-S and Biomass in Sarcocornia than the Related Saltwort, Salicornia.

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.

Chemical Composition, Antibacterial, Schistosomicidal, and Cytotoxic Activities of the Essential Oil of Dysphania ambrosioides (L.) Mosyakin & Clemants (Chenopodiaceae).

We have investigated the chemical composition and the antibacterial activity of the essential oil of Dysphania ambrosioides (L.) Mosyakin & Clemants (Chenopodiaceae) (DA-EO) against a representative panel of cariogenic bacteria. We have also assessed the in vitro schistosomicidal effects of DA-EO on Schistosoma mansoni and its cytotoxicity to GM07492-A cells in vitro. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS) revealed that the monoterpenes cis-piperitone oxide (35.2%), p-cymene (14.5%), isoascaridole (14.1%), and α-terpinene (11.6%) were identified by as the major constituents of DA-EO. DA-EO displayed weak activity against Streptococcus sobrinus and Enterococcus faecalis (minimum inhibitory concentration (MIC) = 1000 µg/ml). On the other hand, DA-EO at 25 and 12.5 µg/ml presented remarkable schistosomicidal action in vitro and killed 100% of adult worm pairs within 24 and 72 h, respectively. The LC50 values of DA-EO were 6.50 ± 0.38, 3.66 ± 1.06, and 3.65 ± 0.76 µg/ml at 24, 48, and 72 h, respectively. However, DA-EO at concentrations higher than 312.5 µg/ml significantly reduced the viability of GM07492-A cells (IC50  = 207.1 ± 4.4 µg/ml). The selectivity index showed that DA-EO was 31.8 times more toxic to the adult S. mansoni worms than GM07492-A cells. Taken together, these results demonstrate the promising schistosomicidal potential of the essential oil of Dysphania ambrosioides.

Glassworts as Possible Anticancer Agents Against Human Colorectal Adenocarcinoma Cells with Their Nutritive, Antioxidant and Phytochemical Profiles.

In this study, the possible uses of glassworts as potential food ingredients and their antiproliferative activity against colorectal adenocarcinoma cells together with their antioxidant and phytochemical profiles were investigated for the first time. MeOH extracts of five different taxa collected from different localities were screened for their antioxidant capacities by DPPH (IC50 2.91 - 5.49 mg/ml) and ABTS (24.4 - 38.5 µmol TE/g extract) assays. Salicornia freitagii exhibited the highest DPPH radical scavenging activity. LC/MS/MS analysis displayed that vanillic acid and p-coumaric acid were two main phenolic compounds in the extract. Salicornia freitagii extracts also exhibited high antiproliferative activity against HT-29 (IC50 1.67 mg/ml) and Caco-2 (IC50 3.03 mg/ml) cells for 72 h. Mineral analysis indicated that all the species with different proportions of elemental components contained high amount of cations. These results indicate that investigated glassworts, with their high phenolic and mineral contents and also notable antioxidant and cytotoxic properties, may be utilized as a promising source of therapeutics.

Growth and photosynthetic limitation analysis of the Cd-accumulator Salicornia ramosissima under excessive cadmium concentrations and optimum salinity conditions.

Cadmium (Cd) is a non-essential element for plants, and its excess impairs plant performance. Physiological impacts of Cd excess are well known in non-tolerant plants, however this information is scarce for Cd-tolerant plants. A glasshouse experiment was designed to investigate the effect of five different Cd levels (0, 0.05, 0.20, 0.65 and 1.35 mM Cd) on the growth, photosynthetic apparatus (PSII chemistry), gas exchange characteristics, photosynthetic pigments profiles, water relations and nutritional balance of the Cd-accumulator Salicornia ramosissima. Ours results confirmed the accumulation capacity of S. ramosissima, as indicated the bioaccumulation factor (BC) greater than 1.0 for all Cd levels. Furthermore, after 21 days of treatment S. ramosissima growth was not highly affected by Cd. Total photosynthetic limitation increased from 38% at 0.05 mM Cd to 70% at 1.35 mM Cd. CO2 diffusion restriction imposed the main contribution to total photosynthetic limitation. Mesophyll conductance reduction was of major importance (with between 69 and 86%), followed by stomatal conductance (with between 9 and 20%). Maximum carboxylation rate (Vc,max), remained stable until 0.2 mM Cd, and chlorophyll fluorescence parameters (Fv/Fm, qP) and pigments concentrations were not significantly decreased by increased Cd supply. Finally, S. ramosissima water relations (intrinsic water use efficiency and relative water content) and nutritional level did not highly vary between Cd treatments. Thus, our finding suggested that Cd tolerance S. ramosissima is in certain degree supported by the tolerance of its carbon assimilation enzyme (RuBisCO) and with the high functionality and integrity of the PSII reaction center under Cd excess.

A novel transcription factor-like gene SbSDR1 acts as a molecular switch and confers salt and osmotic endurance to transgenic tobacco.

A salt- and drought-responsive novel gene SbSDR1 is predominantly localised to the nucleus, up-regulated under abiotic stresses and is involved in the regulation of metabolic processes. SbSDR1 showed DNA-binding activity to genomic DNA, microarray analysis revealed the upregulation of host stress-responsive genes and the results suggest that SbSDR1 acts as a transcription factor. Overexpression of SbSDR1 did not affect the growth and yield of transgenic plants in non-stress conditions. Moreover, the overexpression of SbSDR1 stimulates the growth of plants and enhances their physiological status by modulating the physiology and inhibiting the accumulation of reactive oxygen species under salt and osmotic stress. Transgenic plants that overexpressed SbSDR1 had a higher relative water content, membrane integrity and concentration of proline and total soluble sugars, whereas they showed less electrolyte leakage and lipid peroxidation than wild type plants under stress conditions. In field conditions, SbSDR1 plants recovered from stress-induced injuries and could complete their life cycle. This study suggests that SbSDR1 functions as a molecular switch and contributes to salt and osmotic tolerance at different growth stages. Overall, SbSDR1 is a potential candidate to be used for engineering salt and drought tolerance in crops without adverse effects on growth and yield.

Reactivity of Biliatresone, a Natural Biliary Toxin, with Glutathione, Histamine, and Amino Acids.

In our previous work, we identified a natural toxin, biliatresone, from Dysphania glomulifera and D. littoralis, endemic plants associated with outbreaks of biliary atresia in Australian neonatal livestock. Biliatresone is a very rare isoflavonoid with an α-methylene ketone between two phenyls, 1,2-diaryl-2-propenone, along with methylenedioxy, dimethoxyl, and hydroxyl functional groups, that causes extrahepatic biliary toxicity in zebrafish. The toxic core of biliatresone is a methylene in the α-position relative to the ketone of 1,2-diaryl-2-propenone that serves as an electrophilic Michael acceptor. The α-methylene of biliatresone spontaneously conjugated with water and methanol (MeOH), respectively, via Michael addition in a reverse phase high-performance liquid chromatography (RP-HPLC) analysis. We here report the reactivity of biliatresone toward glutathione (GSH), several amino acids, and other thiol- or imidazole-containing biomolecules. LC-MS and HPLC analysis of the conjugation reaction showed the reactivity of biliatresone to be in the order histidine > N-acetyl-d-cysteine (D-NAC) = N-acetyl-l-cysteine (L-NAC) > histamine > glutathione ≥ cysteine ≫ glycine > glutamate > phenylalanine, while serine and adenine had no reactivity due to intramolecular hydrogen bonding in the protic solvents. The reactivity of ethyl vinyl ketone (EVK, 1-penten-3-one), an example of a highly reactive α,ß-unsaturated ketone, toward GSH gave a 6.7-fold lower reaction rate constant than that of biliatresone. The reaction rate constant of synthetic 1,2-diaryl-2-propen-1-one (DP), a core structure of the toxic molecule, was 10-fold and 1.5-fold weaker in potency compared to the reaction rate constants of biliatresone and EVK, respectively. These results demostrated that the methylenedioxy, dimethoxyl, and hydroxyl functional groups of biliatresone contribute to the stronger reactivity of the Michael acceptor α-methylene ketone toward nucleophiles compared to that of DP and EVK.

Cloning and characterization of a Ca(2+)/H(+) exchanger from the halophyte Salicornia europaea L.

The calcium ion (Ca(2+)), which functions as a second messenger, plays an important role in plants' responses to various abiotic stresses, and Ca(2+)/H(+) exchangers (CAXs) are an important part of this process. In this study, we isolated and characterized a putative Ca(2+)/H(+) exchanger gene (SeCAX3) from Salicornia europaea L., a succulent, leafless euhalophyte. The SeCAX3 open reading frame was 1368 bp long and encoded a 455-amino-acid polypeptide that showed 67.9% similarity to AtCAX3. SeCAX3 was expressed in the shoots and roots of S. europaea. Expression of SeCAX3 was up-regulated by Ca(2+), Na(+), sorbitol, Li(+), abscisic acid, and cold treatments in shoots, but down-regulated by Ca(2+), sorbitol, abscisic acid, and cold treatments in roots. When SeCAX3 was transformed into a Ca-sensitive yeast strain, the transformed cells were able to grow in the presence of 200 mM Ca(2+). Furthermore, SeCAX3 conferred drought, salt, and cold tolerance in yeast. Compared with the control strains, the yeast transformants expressing SeCAX3 were able to grow well in the presence of 30 mM Li(+), 150 mM Mg(2+), or 6 mM Ba(2+). These results showed that the expression of SeCAX3 in yeast suppressed its Ca(2+) hypersensitivity and conferred tolerance to Mg(2+) and Ba(2+). Together, these findings suggest that SeCAX3 might be a Ca(2+) transporter that plays a role in regulating cation tolerance and the responses of S. europaea to various abiotic stresses.

Physiological and biochemical responses of Suaeda fruticosa to cadmium and copper stresses: growth, nutrient uptake, antioxidant enzymes, phytochelatin, and glutathione levels.

Environmental pollution by trace metal elements (TMEs) is a serious problem worldwide, increasing in parallel with the development of human technology. The present research aimed to examine the response of halophytic species Suaeda fruticosa to oxidative stress posed by combined abiotic stresses. Plants have been grown for 1 month with an irrigation solution supplemented with 200 mM NaCl and 400 µM Cd(2+) or 400 µM Cu(2+). The level of glutathione (GSH), phytochelatins (PCs), and antioxidant enzyme activities [ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and catalase (CAT)] as well as lipid peroxidation was studied to see the stress exerted by the TME and the level of tolerance and detoxification strategy adopted by S. fruticosa. Relative growth rate (RGR) decreased under Cd(2+) stress in this species, whereas Cu(2+) did not have any impact on S. fruticosa performance. Cd(2+) or Cu(2+) enhanced malondialdehyde, suggesting reactive oxygen species-induced disruption of membrane integrity and oxidative stress in S. fruticosa. On the other hand, the activities of the antioxidant enzymes CAT, APX, and GPX diminished and mineral nutrition was disturbed by metal stress. S. fruticosa was able to synthesize PCs in response to TME toxicity. However, data indicate that GSH levels underwent a significant decrease in roots and leaves of S. fruticosa stressed by Cd(2+) or Cu(2+). The GSH depletion accompanied by the increase of phytochelatin concentration suggests the involvement of GSH in the synthesis of phytochelatins.