High Salt Conditions Research Articles

Effect of pH, Temperature, and Salinity Levels on Heavy Metal Fraction in Lake Sediments.

Heavy metals (HMs) in aquatic environments are characterized by high toxicity, a propensity for bioaccumulation, and non-degradability, and pose significant risks to biological communities. Previous studies of HMs in lakes have shown that the physical and chemical characteristics of the lake water may control both the migration of HMs in the sediments and the concentration of heavy metals in the lake water. In fact, the change in aquatic environments changes the heavy metal fraction in the sediment, which controls the release of HMs. In this paper, we investigated the effects of the pH, temperature, and salinity levels of overlying water on the chemical fraction of Cu and Zn in Wuliangsuhai Lake surface sediments. The results show that lower water pH and higher water salinity and temperature could increase Cu and Zn release from the sediment. An increase in pH led to changes in the speciation of solid fractions of Zn, namely increases in the residual fraction and decreases in the organic matter and sulfide, whereas acid-extractable and Fe-Mn oxide fractions remained largely the same. Increases in temperature and salinity led to opposite changes in the speciation of solid fractions, namely decreases in the residual fraction and increases in the organic matter and sulfide and Fe-Mn oxide fractions, whereas acid-extractable fractions remained largely the same. The effect of pH, temperature, and salinity on Cu fractions in the solids was much smaller. According to the ratio of the secondary phase to the primary phase (RSP), acidic, high-temperature, and high-salt conditions increase the release risks of Zn. Changes in water temperature have the greatest influence on the risk of Zn and Cu release from sediments, followed by the influence of salinity changes.

Light-driven green synthesis of tea polyphenols-derived temperature-resistant and environmentally friendly filter loss reducer on MIL-100(Fe)–NH2(20) photocatalyst

Currently, most syntheses of filter loss reducers usually require harsh synthesis conditions with high energy consumption, increasing the cost and deteriorating worldwide unsustainable resource crisis. Thus, it is urgent to explore an effective green synthetic strategy for further developing filter loss reducers. In this work, the amino-modified MIL-100(Fe)–NH2(20) sphere acted as photocatalyst for the photoinduced green synthesis and possessed hierarchical mesoporous, exposed active sites, remarkable light harvesting, robust photogenerated e- − h+ pairs separation and excellent photocatalytic activity. Then, tea polyphenol (TP), acrylamide (AM) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) were polymerized to form a temperature-resistant and environmentally friendly filter loss reducer (SPS) successfully through photopolymerization under Xenon lamp irradiation, and the evaluation results demonstrated that the SPS exhibited excellent rheological and loss-reducing properties, even under the high temperature and high salt conditions. During this photocatalysis, the excitation of electrons on MIL-100(Fe)–NH2(20) occurs, and resulted e- ∼ h+ pairs as free radicals were transferred to TP and vinyl monomers. After the generation of active-species-free radical cations (R•) and selective oxidation or propagation and termination, the full green synthesis cycle can be completed. Notably, the localized surface plasmon resonance (LSPR) effect and photothermal transition of MIL-100(Fe)–NH2(20) could provide sufficient temperature at the local reaction sites, enabling the polymerization with mild conditions. This study opens up new insights into the application of MOF photocatalysis in oilfield chemistry.

Evaluation of Chemical and Physical Triggers for Enhanced Photosynthetic Glycerol Production in Different Dunaliella Isolates.

The salt-tolerant marine microalgae Dunaliella tertiolecta is reported to generate significant amounts of intracellular glycerol as an osmoprotectant under high salt conditions. This study highlights the phylogenetic distribution and comparative glycerol biosynthesis of seven new Dunaliella isolates compared to a D. tertiolecta reference strain. Phylogenetic analysis indicates that all Dunaliella isolates are newly discovered and do not relate to the D. tertiolecta reference. Several studies have identified light color and intensity and salt concentration alone as the most inducing factors impacting glycerol productivity. This study aims to optimize glycerol production by investigating these described factors singularly and in combination to improve the glycerol product titer. Glycerol production data indicate that cultivation with white light of an intensity between 500 and 2000 μmol m-2 s-1 as opposed to 100 μmol m-2 s-1 achieves higher biomass and thereby higher glycerol titers for all our tested Dunaliella strains. Moreover, applying higher light intensity in a cultivation of 1.5 M NaCl and an increase to 3 M NaCl resulted in hyperosmotic stress conditions, providing the highest glycerol titer. Under these optimal light intensity and salt conditions, the glycerol titer of D. tertiolecta could be doubled to 0.79 mg mL-1 in comparison to 100 μmol m-2 s-1 and salt stress to 2 M NaCl, and was higher compared to singularly optimized conditions. Furthermore, under the same conditions, glycerol extracts from new Dunaliella isolates did provide up to 0.94 mg mL-1. This highly pure algae-glycerol obtained under optimal production conditions can find widespread applications, e.g., in the pharmaceutical industry or the production of sustainable carbon fibers.

Arg18 Substitutions Reveal the Capacity of the HIV-1 Capsid Protein for Non-Fullerene Assembly.

In the fullerene cone HIV-1 capsid, the central channels of the hexameric and pentameric capsomers each contain a ring of arginine (Arg18) residues that perform essential roles in capsid assembly and function. In both the hexamer and pentamer, the Arg18 rings coordinate inositol hexakisphosphate, an assembly and stability factor for the capsid. Previously, it was shown that amino-acid substitutions of Arg18 can promote pentamer incorporation into capsid-like particles (CLPs) that spontaneously assemble in vitro under high-salt conditions. Here, we show that these Arg18 mutant CLPs contain a non-canonical pentamer conformation and distinct lattice characteristics that do not follow the fullerene geometry of retroviral capsids. The Arg18 mutant pentamers resemble the hexamer in intra-oligomeric contacts and form a unique tetramer-of-pentamers that allows for incorporation of an octahedral vertex with a cross-shaped opening in the hexagonal capsid lattice. Our findings highlight an unexpected degree of structural plasticity in HIV-1 capsid assembly.

Method for lysis and paper-based elution-free DNA extraction with colourimetric isothermal amplification

Nucleic acid amplification testing has great potential for point-of-need diagnostic testing with high detection sensitivity and specificity. Current sample preparation is limited by a tedious workflow requiring multiple steps, reagents and instrumentation, hampering nucleic acid testing at point of need. In this study, we present the use of mixed cellulose ester (MCE) paper for DNA binding by ionic interaction under molecular crowding conditions and fluid transport by wicking. The poly(ethylene) glycol-based (PEG) reagent simultaneously provides the high pH for alkaline lysis and crowding effects for ionic binding of the DNA under high salt conditions. In this study, we introduce Paper-based Abridged Solid-Phase Extraction with Alkaline Poly(ethylene) Glycol Lysis (PASAP). The anionic mixed cellulose ester (MCE) paper is used as solid phase and allows for fluid transport by wicking, eliminating the need for pipetting skills and the use of a magnet to retain beads. Following the release of DNA from the cells due to the lytic activity of the PASAP solution, the DNA binds to the anionic surface of the MCE paper, concentrating at the bottom while the sample matrix is transported towards the top by wicking. The paper was washed by dipping it in 40% isopropanol for 10 s. After air-drying for 30 s, the bottom section of the paper (3 mm × 4 mm) was snapped off using the cap of a PCR tube and immersed in the colourimetric loop-mediated isothermal amplification (cLAMP) solution for direct amplification and colourimetric detection. The total sample processing was completed in 15 min and ready for amplification. cLAMP enabled the detection of 102 CFU/mL of Escherichia coli (E. coli) from culture media and the detection of E. coli in milk < 103 CFU/mL (10 CFU) after incubation at 68 °C for 60 min, demonstrating applicability of the method to complex biological samples.

Preparation high-performance cathode of vacancy-free Prussian blue analogues for sodium ion batteries by directional capture of free Mn-ion

To address the issue of poor cycling performance and capacity of Mn-based Prussian Blue analogues (PBAs) as sodium ion battery cathodes due to the solubility of Mn ions, this study utilizes the strong chelating property of EDTA2− with Mn ions to hydrothermally modify the sodium-rich monoclinic Na1.75Mn[Fe(CN)6]0.94·2.25H2O synthesized under high salt conditions, in order to enhance its capacity and stability. The modified Na1.93Mn[Fe(CN)6]•2·.38H2O exhibits a discharge capacity of 156.16 mAh/g at 10 mA g−1 (91.86 % of the theoretical capacity), it still retains the highest discharge capacity (70.23 mAh/g) after 500 cycles at 100 mA g−1. Based on experimental analysis, the improvement in the electrochemical performance of PBAs was attributed to three main factors: (1) enhanced Na content; (2) suppression of defects; and (3) improved crystal structure.

Rational engineering of Halomonas salifodinae to enhance hydroxyectoine production under lower-salt conditions

Hydroxyectoine is an important compatible solute that holds potential for development into a high-value chemical with broad applications. However, the traditional high-salt fermentation for hydroxyectoine production presents challenges in treating the high-salt wastewater. Here, we report the rational engineering of Halomonas salifodinae to improve the bioproduction of hydroxyectoine under lower-salt conditions. The comparative transcriptomic analysis suggested that the increased expression of ectD gene encoding ectoine hydroxylase (EctD) and the decreased expressions of genes responsible for tricarboxylic acid (TCA) cycle contributed to the increased hydroxyectoine production in H. salifodinae IM328 grown under high-salt conditions. By blocking the degradation pathway of ectoine and hydroxyectoine, enhancing the expression of ectD, and increasing the supply of 2-oxoglutarate, the engineered H. salifodinae strain HS328-YNP15 (ΔdoeA::PUP119-ectD p-gdh) produced 8.3-fold higher hydroxyectoine production than the wild-type strain and finally achieved a hydroxyectoine titer of 4.9 g/L in fed-batch fermentation without any detailed process optimization. This study shows the potential to integrate hydroxyectoine production into open unsterile fermentation process that operates under low-salinity and high-alkalinity conditions, paving the way for next-generation industrial biotechnology.Key points• Hydroxyectoine production in H. salifodinae correlates with the salinity of medium• Transcriptomic analysis reveals the limiting factors for hydroxyectoine production• The engineered strain produced 8.3-fold more hydroxyectoine than the wild typeGraphical

Decomposition of Foliar Litter from Dominant Plants of Desert Riparian Forests in Extremely Arid Regions

Litter decomposition is important for understanding the effects of habitat on nutrient cycling. In this study, we investigated the decomposition characteristics, decomposition variability, and regulatory factors restricting the decomposition rates of leaf litter in three different habitats: a flood disturbance habitat, an arid habitat, and a high-salinity habitat. The litter decomposition rates of the habitats decreased in the following order: flood disturbance habit &gt; arid habitat &gt; high-salinity habitat. The organic carbon, total nitrogen, and lignin residues of the litter during the decomposition period were highest in the high-salinity habitat. The litter quality was the main regulator of the release of phosphorus and cellulose residues, which exhibited different release processes and patterns in these three habitats. The litter decomposition coefficient was negatively correlated with litter carbon residue in the flood disturbance habitats, the lignocellulose index in the arid habitats, and soil urease in the high-salinity habitats. It was positively correlated with the lignocellulose index in flood disturbance habitats and litter carbon residue in high-salinity habitats. The litter quality in the flood disturbance area played a significant role in litter decomposition, while environmental quality and litter quality were the dominant factors under arid and high-salt conditions. Litter quality in the flood disturbance area played a significant role in litter decomposition, while both environmental quality and litter quality were the dominant factors under arid and salt conditions.

#1463 Assessment of salt-sensitive hypertension in a novel Lanosterol Synthase knock-in mouse model

Abstract Background and Aims The diversity in blood pressure (BP) response to various salt intakes, known as Salt Sensitivity (SS), exhibits significant differences among individuals within the hypertensive subjects relative to the general population. Hypertension (HT) and SS are correlated to elevated levels of plasma Endogenous Ouabain (EO). We aimed at delineating the role of the missense variation rs2254524 (Val642Leu; C&amp;gt;A) within the Lanosterol Synthase gene (LSS), encoding for an enzyme involved in steroid biosynthesis. Individuals with the AA LSS variant, adherent to a low-salt diet, had a more significant BP reduction compared to those with CC genotype. Method Utilising CRISPR-Cas9, we established a knock-in mouse model carrying the analogous LssV643L/V643L. Male mice were subjected to a normal-salt diet (0.5% NaCl), high-salt diet (4% NaCl), or low-salt diet (&amp;lt;0.03% Na) and BP was monitored every two days using a tail-cuff system for 10 days. Blood and urine were collected separately in metabolic cages. Results Homozygous mice for Lss mutation demonstrated normal viability and healthy phenotype, undistinguishable from the WT. At baseline, the Lss AA mice were affected by a significant augmentation in kidney weight at 3 and 12 months of age, relative to WT. The Lss V643L does not influence EO levels or systolic BP (SBP), specifically at 3 and 12 months, but affects the SBP response to dietary salt. AA mice showed a high SBP in a high-salt diet against control diet at the same time intervals. Moreover, the Lss variant impacted the pressure-natriuresis relationship, with the mutated AA strain showing a less steep curve both in control diet versus the high-salt diet and in control diet versus the low-salt diet, displaying the SS phenotype of the AA mice. The 12-month-old mice in high-salt diet displayed cardiac hypertrophy with the AA genotype exhibiting an elevated prevalence of cardiac fibrosis. The level of Lss mRNA decreased in the adrenal glands in response to a high-salt diet. RNASeq analysis identified distinct patterns in several Slc genes, Cbr2 and Arhgap26 within the kidneys of these mice, in control or high-salt dietary conditions. Conclusion The established LssV643L/V643L mouse model effectively mirrors the SS-HT phenotype. Our findings highlight the significance of the Lss in modulating BP in response to salt stimuli suggesting a potential organ damage pathway requiring further exploration in older mice.

Marine Pediococcus pentosaceus E3 Probiotic Properties, Whole-Genome Sequence Analysis, and Safety Assessment.

Probiotics play a significant role in enhancing health, and they are well known for bacteriocins production. Evaluating probiotics' whole-genome sequence provides insights into their consumption outcomes. Thus, genomic studies have a significant role in assessing the safety of probiotics more in-depth and offer valuable information regarding probiotics' functional diversity, metabolic pathways, and health-promoting mechanisms. Marine Pediococcus pentosaceus E3, isolated from shrimp gut, exhibited beneficial properties, indicating its potential as a probiotic candidate. Phenotypically, E3 strain was susceptible to most antibiotics assessed, tolerant to low pH and high bile salt conditions, and revealed no hemolysin activity. Interestingly, E3-neutralized CFS revealed significant antibacterial activity against pathogens under investigation. Therefore, the concentrated CFS was prepared and evaluated as a natural biopreservative and showed outstanding antimicrobial activity. Furthermore, integrated-based genome assessment has provided insight into probiotic characteristics at the genomic level. Whole-genome sequencing analysis revealed that the E3 genome possesses 1805 protein-coding genes, and the genome size was about 1.8Mb with a G + C content of 37.28%. Moreover, the genome revealed the absence of virulence factors and clinically related antibiotic genes. Moreover, several genes consistent with probiotic microorganisms' features were estimated in the genome, including stress response, carbohydrate metabolism, and vitamin biosynthesis. In addition, several genes associated with survival and colonization within the gastrointestinal tract were also detected across the E3 genome. Therefore, the findings suggest that insights into the genetic characteristics of E3 guarantee the safety of the strain and facilitate future development of E3 isolate as a health-promoting probiotic and source of biopreservative.

Wood Distillate Promotes the Tolerance of Lettuce in Extreme Salt Stress Conditions.

Soil salinization is an adverse phenomenon in agriculture that severely affects crop growth and yield. The use of natural products, such as wood distillate (WD, derived from the pyrolysis of woody biomass), could be a sustainable approach to enhance the tolerance of plants cultivated in the saline soils. Hence, this study aimed to evaluate the potential of WD, a foliar sprayed at 0.2% (v/v), in lettuce plants subjected to grow under both moderate and high soil sodium chloride (NaCl) concentrations (ranging from 0 to 300 mM). The changes in the physiological and biochemical responses of these plants to the varying salt stress conditions allowed the identification of a maximum tolerance threshold (100 mM NaCl), specific to lettuce. Beyond this threshold, levels related to plant defense antioxidant power (antiradical activity) were lowered, while those indicative of oxidative stress (malondialdehyde content and electrolyte leakage) were raised, causing significant losses in leaf fresh biomass. On the other hand, WD significantly improved plant growth, enabling plants to survive high salt conditions >200 mM NaCl. Collectively, these observations highlight that treatments with WD could be of paramount importance in coping with current environmental challenges to have better yields under soil conditions of high salt concentrations.

Integrated multi-omic approach reveals the effect of a Graminaceae-derived biostimulant and its lighter fraction on salt-stressed lettuce plants

Plant biostimulants are widely applied in agriculture for their ability to improve plant fitness. In the present work, the impact of Graminaceae-derived protein hydrolysate (P) and its lighter molecular fraction F3 (< 1 kDa) on lettuce plants, subjected to either no salt or high salt conditions, was investigated through the combination of metabolomics and transcriptomics. The results showed that both treatments significantly modulated the transcriptome and metabolome of plants under salinity stress, highlighting an induction of the hormonal response. Nevertheless, P and F3 also displayed several peculiarities. F3 specifically modulated the response to ethylene and MAPK signaling pathway, whereas P treatment induced a down-accumulation of secondary metabolites, albeit genes controlling the biosynthesis of osmoprotectants and antioxidants were up-regulated. Moreover, according with the auxin response modulation, P promoted cell wall biogenesis and plasticity in salt-stressed plants. Notably, our data also outlined an epigenetic control of gene expression induced by P treatment. Contrarily, experimental data are just partially in agreement when not stressed plants, treated with P or F3, were considered. Indeed, the reduced accumulation of secondary metabolites and the analyses of hormone pathways modulation would suggest a preferential allocation of resources towards growth, that is not coherent with the down-regulation of the photosynthetic machinery, the CO2 assimilation rate and leaves biomass. In conclusion, our data demonstrate that, although they might activate different mechanisms, both the P and F3 can result in similar benefits, as far as the accumulation of protective osmolytes and the enhanced tolerance to oxidative stress are concerned. Notably, the F3 fraction exhibits slightly greater growth promotion effects under high salt conditions. Most importantly, this research further corroborates that biostimulants’ mode of action is dependent on plants’ physiological status and their composition, underscoring the importance of investigating the bioactivity of the different molecular components to design tailored applications for the agricultural practice.

In-situ poly(hexahydrotriazine) gels temporary plugging agent suitable for high-temperature reservoirs: Regulation by inorganic chloride salts

A new acid-soluble in-situ temporary plugging agent suitable for high-temperature reservoirs was developed. By regulating the aldehyde-amine condensation reaction using inorganic chlorine salts, the poly(hexahydrotriazine) gels (PHT gels) exhibit good plugging performance and high-temperature resistance and can be degraded in weak acid solutions without residue. Results show that inorganic chlorine salts have a regulating effect on the gelling time of the gelant. Without the salt or the addition of monovalent chlorine salt, the gelant gels at room temperature but does not form a gel at high temperatures. After adding divalent or trivalent inorganic salts, PHT gels are formed at high temperatures, and their gelling time increases with the increase in salt content. Mechanical compression experiments show that the compression resistance of PHT gels is almost unchanged after exposure to high temperature (140 °C) and high salt (200 g/L NaCl and 10 g/L CaCl2). Displacement experiments show that PHT gels have excellent plugging performance with a plugging rate of more than 98.50% and a maximum plugging pressure of 5.34 MPa under the high temperature and high-salt conditions mentioned above. In addition, a hydrochloric acid solution with pH ≤ 5 can achieve residue-free breakage of PHT gels. The gel-breaking fluid has a high surface activity to facilitate flowback and a core unblocking rate of more than 100% after gel-breaking, making the reservoir permeability recoverable. The plugging and acidolysis ability of PHT gels make them excellent in-situ temporary plugging agents. This study aims to provide insights into the preparation of PHT gels and their use in high-temperature reservoirs.

Treatment of Pickle Wastewater under Varying Salinity Conditions within the Sequencing Batch Biofilm Reactor System

Pickle wastewater is a highly saline organic effluent that poses a significant ecological risk. In this study, a sequencing batch biofilm reactor (SBBR) was used to treat such wastewater, and a denitrification system capable of simultaneously removing high levels of nitrogen and organic matter was successfully established. Through salinity incremental increase, the system operated stably, and the removal rates of COD, TN, and NH4+-N could be maintained at about 96%, 93%, and 99% under the salinity of 3.0%. The effect of salinity on the structure and function of microbial communities in the reactor was investigated by high-throughput sequencing. The results showed that increasing salinity could reduce the diversity, change the structure, and reduce the functionality of the microbial community. Under high-salt conditions (salt content of 3.0%), salt-tolerant microorganisms such as Actinobacteriota became dominant populations. As salinity increased, NOB (nitrite oxidizing bacteria) was strongly inhibited, and its abundance decreased rapidly until it disappeared. Partial nitrification–denitrification (PND) gradually became the main denitrification pathway. In conclusion, this experiment not only shows that SBBR treatment of pickle wastewater has strong feasibility, but also provides a theoretical research basis for the engineering treatment of pickle wastewater.

Global Deletion of DPP4 Prevents the Development of Salt-sensitive Hypertension in Obese Mice via Regulation of Sodium and Water Excretion

Salt-sensitivity of hypertension (HTN) occurs in up to 50% of hypertensive patients and is more common in the older population, Blacks and the obesity/diabetes/hypertension subsets. The renin-angiotensin aldosterone system (RAAS), in particular Angiotensin II (Ang II) and aldosterone known to regulate the Na+/H+ exchanger isoform 3 (NHE3) and ENaC respectively, is thought to be activated in the obesity/diabetes/hypertension subsets and thereby plays an important role in salt-sensitive HTN. RAAS blockade is an acceptable treatment for salt-sensitive HTN along with the use of diuretics. However, not every patient can tolerate RAAS blockade. Recently, dipeptidyl peptidase 4 (DPP4) has been shown to bind to NHE3, colocalizes to the microvillar fractions with active NHE3 and DPP4 inhibition reduces sodium uptake into proximal tubule cells and isolated rat proximal tubules. In addition, DPP4 may act on more distal transporters. Furthermore, data from our lab has revealed that DPP4 knockout (DPP4KO) mice have a lower sodium balance both under conditions of high salt (1.23%) and low salt (0.02%) ingestion suggesting that DPP4 regulates sodium transport and/or balance under physiological conditions. However, whether DPP4 has any effects on salt-sensitive HTN and the underlying mechanisms remain unknown. Therefore, we hypothesized that the absence of DPP4 could mitigate the development of salt-sensitive HTN in an obesity model, by improving the natriuretic and diuretic response mediated by NHE3 and/or distal mechanisms. To this end, 6-8wk old DPP4KO and C57Bl/6 littermate wild-type (WT) mice were fed a control (CD) or Western diet (WD, high in refined fats and sugars) to induce obesity. Circulating (175%) and kidney (125%) DPP4 activity were both elevated in the obese WT mice compared to the CD-fed WT mice (100%) and DPP4KO mice had minimal DPP4 activity as expected. The lack of DPP4 prevented the increase in systolic blood pressure (~15 mmHg) in the obese animals, and the absence of the development of cardiac hypertrophy in this group corroborated the pressure effect. The development of salt-sensitive HTN in the obese WT mice was associated with a lower natriuretic and diuretic response assessed by the salt overload experiment, suggesting higher tubular reabsorption of sodium and water by the nephrons. In turn, the lack of DPP4 prevented the lowering of natriuretic and diuretic response in obese mice, indicating that the beneficial effect of the absence of DPP4 on the development of salt-sensitive HTN is closely related to effects on renal tubule transport. Importantly, a high salt diet increased sodium balance and blood pressure in the obese WT mice and DPP4 deletion mitigated this increase. Furthermore, on low salt diet, the absence of DPP4 led to “salt wasting” in the obese mice similar to the CD-fed mice. Surprisingly, gene and protein expression measurements showed involvement of distal tubule sodium transporters and aquaporins and not NHE3. In contrast, assessment of the DPP4 interactome in obese mice showed binding to Myosin 6 and APN, which may regulate proximal tubule transporters and hypertension. Transdermal measurements showed no changes in the glomerular filtration rate. In conclusion, deletion of DPP4 protects against the development of salt-sensitive hypertension in obese mice by improving the natriuretic and diuretic response likely via regulation of sodium and water transporters. FAPESP, Brazil NIH K08DK115886, USA. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

CD4+ T Cell Effector Status Is Dependent on Aryl Hydrocarbon Receptor Activation during High Salt Diet

Recent studies suggest that patients with hypertension and individuals that consume a HSD are depleted of numerous tryptophan-derived indoles and other AHR-binding metabolites that are key in intestinal CD4+ T cell homeostasis. Thus, the inappropriate immunologic response by CD4+ T cells, and their role in hypertension, may be due in part to loss of AHR activation. Therefore, we hypothesized that AHR activation contributes to maintaining effector T cell status in salt-sensitive mice. To examine the influence of a representative homeostatic or proinflammatory environment and the subsequent response to salt, we cultured naïve CD4+ T cells under homeostatic cytokine or pathogenic cytokine conditions and exposed the cultures to increased NaCl conditions with or without the AHR-activating metabolite, FICZ (6-Formylindolo(3,2-b)-carbazole). TH17 cells cultured under homeostatic high salt conditions were depressed with a concomitant increase in response to FICZ. In contrast, TH17 cells cultured under pathogenic high salt conditions had augmented IL-17A-expressing cells without a response to AHR activation. These data suggest that excess salt is disrupting the ability to induce IL-17A and increasing AHR activity overcomes this disruption to promote IL-17A, without expansion of the pathogenic TH17 pool, and this observation was specific to non-pathogenic microenvironments (homeostatic TH17: media: 11±0.6%, +NaCl: 4.9±0.3%*, +NaCl/FICZ: 9.9±0.8%, of CD4; pathogenic TH17: media: 1.0±0.2%, +NaCl: 2.2±0.2%*, +NaCl/FICZ: 2.2±0.2%*, *vs respective media, n=8/group). Given these data, we then fed salt-sensitive mice (nitric oxide synthase inhibition) a HSD or a HSD supplemented with the AHR agonist indole-3-carbinol (I3C) and examined Peyer’s patches, a lymphoid tissue in close proximity to intestinal lumen contents enriched with salt and the I3C-metabolites and noted expansion of non-pathogenic TH17 cells. In conclusion, increasing AHR ligand availability through supplementing I3C may provide a gut-centric experimental approach in targeting experimental salt-sensitivity as it relates to immunologic disturbances. F31HL151264. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Role of Interleukin-6 in Regulating Glomerular Filtration Rate during Angiotensin II and High Salt Conditions

Previous results demonstrate that interleukin-6 (IL-6) increases mean arterial pressure (MAP) during Angiotensin II (Ang II)-salt hypertension. In addition, albumin excretion was lower in IL-6 knockout mice (KO) when compared to wild-type (WT). This study investigated the role of IL-6 on regulating glomerular filtration rate (GFR), renal plasma flow (RPF) and MAP in WT and IL-6 KO mice treated with a slow pressor dose of Ang II (200 ng/kg/min) +/- 6% high-salt (HS) diet. Male C57BL6 and IL-6 KO mice (12 weeks old) were treated with Ang II +/- 6% HS diet for 12 – 14 days. Mean arterial pressure, RPF and GFR were measured in anesthetized mice. MAP was 130 ± 7 mmHg and 91 ± 4 mmHg in control WT and IL-6 KO mice, respectively. Ang II treatment increased MAP in WT (153 ± 5 mmHg) and no change in IL-6 KO (83 ± 4 mmHg) mice. Ang II + 6% HS increased MAP to 150 ± 11 mmHg in WT and 93 ± 4 mmHg in IL-6 KO mice. Baseline RPF was 1822 ± 229 and 1912 ± 402 ml/min/g in control WT and IL-6 KO mice, respectively. Ang II treatment increased RPF in WT (3156 ± 753 ml/min/g), while lowering RPF in IL-6 KO (1648 ± 422 ml/min/g) mice. RPF during Ang II + 6% HS treatment was decreased in WT (1095 ± 305 ml/min/g) and IL-6 KO (1133 ml/min/g) mice. GFR was 756 ± ml/min/g and 788 ± ml/min/g in control WT and IL-6 KO mice, respectively. Ang II increased GFR in WT (1009 ± 63 ml/min/g) and no change in IL-6 KO (756 ± 23 ml/min/g). Ang II + 6% HS increased GFR in WT (1095 ± 146 ml/min/g) and no change in GFR of IL-6 KO (540 ± 207 ml/min/g) mice. Our results suggest that IL-6 reduces MAP during baseline, Ang II, and Ang II + 6% HS. The absence of IL-6 prevented increases in MAP, RPF and GFR during Ang II treatment. Our data also suggest that IL-6 contributes to increased MAP and GFR during Ang II + 6% HS treatment. K01HL092593-05. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

NtHD9 modulates plant salt tolerance by regulating the formation of glandular trichome heads in Nicotiana tabacum

Salt stress is one of the main abiotic factor affecting plant growth. We have previously identified a key gene (NtHD9) in Nicotiana tabacum L. that positively regulates the formation of long glandular trichomes (LGTs). Here, we verified that both abiotic stress (aphids, drought and salt stress) could restore the phenotype lacking LGTs in NtHD9-knockout (NtHD9-KO) plants. The abiotic stress response assays indicated that NtHD9 is highly sensitive to salt stress. Compared with cultivated tobacco “K326” (CK) plants, NtHD9-overexpressing (NtHD9-OE) plants with more LGTs exhibited stronger salt tolerance, whereas NtHD9-KO with no LGTs showed weaker tolerance to salt. The densities and sizes of the glandular heads gradually increased with increasing NaCl concentrations in NtHD9-KO plants. Mineral element determination showed that leaves and trichomes of NtHD9-OE plants accumulated less Na+ but had higher K+ contents under salt stress, thus maintaining ion homeostasis in plants, which could contribute to a robust photosynthetic and antioxidant system under salt stress. Therefore, NtHD9-OE plants maintained a larger leaf area and root length under high-salt conditions than CK and NtHD9-KO plants. We verified that NtHD9 could individually interact with NtHD5, NtHD7, NtHD12, and NtJAZ10 proteins. Salt stress led to an increase in jasmonic acid (JA) levels and activated the expression of NtHDs while inhibiting the expression of NtJAZ. This study suggests that the glandular heads play an important role in plant resistance to salt stress. The activation of JA signaling leading to JAZ protein degradation may be key factors regulating the glandular heads development under salt stress.

The Spartina alterniflora genome sequence provides insights into the salt-tolerance mechanisms of exo-recretohalophytes.

Spartina alterniflora is an exo-recretohalophyte Poaceae species that is able to grow well in seashore, but the genomic basis underlying its adaptation to salt tolerance remains unknown. Here, we report a high-quality, chromosome-level genome assembly of S. alterniflora constructed through PacBio HiFi sequencing, combined with high-throughput chromosome conformation capture (Hi-C) technology and Illumina-based transcriptomic analyses. The final 1.58 Gb genome assembly has a contig N50 size of 46.74 Mb. Phylogenetic analysis suggests that S. alterniflora diverged from Zoysia japonica approximately 21.72 million years ago (MYA). Moreover, whole-genome duplication (WGD) events in S. alterniflora appear to have expanded gene families and transcription factors relevant to salt tolerance and adaptation to saline environments. Comparative genomics analyses identified numerous species-specific genes, significantly expanded genes and positively selected genes that are enriched for 'ion transport' and 'response to salt stress'. RNA-seq analysis identified several ion transporter genes including the high-affinity K+ transporters (HKTs), SaHKT1;2, SaHKT1;3 and SaHKT1;8, and high copy number of Salt Overly Sensitive (SOS) up-regulated under high salt conditions, and the overexpression of SaHKT2;4 in Arabidopsis thaliana conferred salt tolerance to the plant, suggesting specialized roles for S. alterniflora to adapt to saline environments. Integrated metabolomics and transcriptomics analyses revealed that salt stress activate glutathione metabolism, with differential expressions of several genes such as γ-ECS, GSH-S, GPX, GST and PCS in the glutathione metabolism. This study suggests several adaptive mechanisms that could contribute our understanding of evolutional basis of the halophyte.

From swamp to field: how genes from mangroves and its associates can enhance crop salinity tolerance.

Salinity stress is a critical challenge in crop production and requires innovative strategies to enhance the salt tolerance of plants. Insights from mangrove species, which are renowned for their adaptability to high-salinity environments, provides valuable genetic targets and resources for improving crops. A significant hurdle in salinity stress is the excessive uptake of sodium ions (Na+) by plant roots, causing disruptions in cellular balance, nutrient deficiencies, and hampered growth. Specific ion transporters and channels play crucial roles in maintaining a low Na+/K+ ratio in root cells which is pivotal for salt tolerance. The family of high-affinity potassium transporters, recently characterized in Avicennia officinalis, contributes to K+ homeostasis in transgenic Arabidopsis plants even under high-salt conditions. The salt overly sensitive pathway and genes related to vacuolar-type H+-ATPases hold promise for expelling cytosolic Na+ and sequestering Na+ in transgenic plants, respectively. Aquaporins contribute to mangroves' adaptation to saline environments by regulating water uptake, transpiration, and osmotic balance. Antioxidant enzymes mitigate oxidative damage, whereas genes regulating osmolytes, such as glycine betaine and proline, provide osmoprotection. Mangroves exhibit increased expression of stress-responsive transcription factors such as MYB, NAC, and CBFs under high salinity. Moreover, genes involved in various metabolic pathways, including jasmonate synthesis, triterpenoid production, and protein stability under salt stress, have been identified. This review highlights the potential of mangrove genes to enhance salt tolerance of crops. Further research is imperative to fully comprehend and apply these genes to crop breeding to improve salinity resilience.