Phosphate Uptake Research Articles

Boosting the Phosphorus Uptake of La2(CO3)3·8H2O Based Adsorbents via Sodium Addition: Relationship between Crystal Structure and Adsorption Capacity

Excess phosphate contents in water bodies triggers eutrophication, which posts significant challenges to the aquatic ecosystem. Lanthanum-carbonate based adsorbents exhibit excellent phosphate binding properties for remediating eutrophication. However, they suffer from significant adsorption-capacity loss (>85%) at high pH. Little has been done on understanding this behavior for improving the phosphorus adsorption of lanthanum-carbonate adsorbents in alkaline environments (e.g. eutrophic water bodies). Here, we discover that La2(CO3)3·8H2O, when produced by a conversion reaction from NaLa(CO3)2·xH2O, exhibits high phosphate adsorption capacity in a wide pH window. Under alkaline conditions (e.g. pH = 10), its adsorption capacity decreases by only 8% compared to the value under neutral pH. By isolating three different lanthanum-carbonate based compounds and analyzing their molecular structures, we find that the trace amount of Na+ residual in our La2(CO3)3·8H2O alters the chemical environment surrounding the La3+ ions, which may significantly boost the phosphate uptake at high pH. Our results provide molecular insights for further tuning the material structure of phosphate adsorbents to achieve robust performances.

Understanding the crucial role of phosphate and iron availability in regulating root nodule symbiosis.

The symbiosis between legumes and nitrogen-fixing bacteria (rhizobia) is instrumental in sustaining the nitrogen cycle and providing fixed nitrogen to the food chain. Both partners must maintain an efficient nutrient exchange to ensure a successful symbiosis. This mini-review highlights the intricate phosphate and iron uptake and homeostasis processes taking place in legumes during their interactions with rhizobia. The coordination of transport and homeostasis of these nutrients in host plants and rhizobia ensures an efficient nitrogen fixation process and nutrient use. We discuss the genetic machinery controlling the uptake and homeostasis of these nutrients in the absence of rhizobia and in symbiotic conditions with this soil bacteria. We also highlight the genetic impact of the availability of phosphate and iron to coordinate the activation of the genetic programs that allow legumes to engage in symbiosis with rhizobia. Finally, we discuss how the transcription factor Phosphate Starvation Response (PHR) might be a crucial genetic element to integrate the nitrogen, iron, and phosphate plant's needs while interacting with rhizobia. Understanding the coordination of the iron and phosphate uptake and homeostasis can lead us to better harness the ecological benefits of the legume-rhizobia symbiosis, even under adverse environmental conditions.

Comparative Evaluation of Ion Release and Uptake of Fluoride Varnish Containing Dicalcium Phosphate Dihydrate and Casein Phosphopeptide-Amorphous Calcium Phosphate – An Experimental Approach.

The effectiveness of fluoride varnish may be restricted due to inadequate bioavailability of phosphate and calcium ions in the oral cavity. Dicalcium phosphate dihydrate and Casein phosphopeptide–amorphous calcium phosphate have exhibited ability to enhance absorption of calcium and fluoride. The present study aims to compare the remineralization potential of fluoride varnishes containing DCPD and CPP-ACP. Materials and Method: The ion release, precipitation and surface microhardness of enamel blocks were compared following topical application of various Floride varnishes. Thirty enamel blocks were divided into 3 groups following randomization that included: NaF varnish (Group A), CPP-ACP NaF varnish (Group B) and DCPD- NaF varnish (Group C). Pre- and post-treatment microhardness was evaluated using Vickers Microhardness Tester. UV-Vis Spectroscopy assessed the fluoride release at 2 hrs, 4 hrs and 6 hrs. The uptake of fluoride, calcium and phosphates were determined using SEM-EDX. The statistical significance was tested with One-way ANOVA variance for normality followed by post-hoc tests (p ≤ 0.05). Results: All the groups showed statistically significant increase in microhardness post-treatment (Group A: p=0.03, Group B, C: p=0.00). The mean increase in VHN was Group B (53.67) > Group C (34.75) > Group A (27.40). No significant difference in the F release was noted over time (p=0.00). The fluoride release over all three time intervals was Group C > Group B > Group C. Fluoride, Calcium and Phosphates showed highly significant differences between groups (p=0.00) with Group C > Group A> Group B. Conclusion: The novel NaF-DCPD Varnish displayed a promising remineralization potential, however it cannot be conclusively considered to be superior to the commercially available NaF-CPP ACP Varnish. Further in-vivo investigations need to be undertaken to determine the efficacy of NaF-DCPD varnish to determine its feasibility in clinical practice.

Identification of 2, 4-di-tert-butylphenol from Microcystis lysate after bloom control and its potential risks to aquatic ecosystems

With the increasing concern of cyanobacterial blooms, numerous techniques have been developed to mitigate these environmental nuisances. During bloom control, the allelopathic effects of compounds released from cyanobacterial cells are considered as secondary hazards. In this study, the findings indicated that Microcystis lysate inhibited algal proliferation and disrupted the development of zebrafish embryos. Then, allelochemicals in Microcystis lysate were identified using gas chromatography-mass spectrometry, with 2, 4-di-tert-butylphenol (2, 4-DTBP) being the only identified phenol, which was selected for further study. The results showed that 2,4-DTBP caused oxidative damages, disrupted metabolic activity, and suppressed photosynthetic activity, consequently impeding the growth of Microcystis aeruginosa (M. aeruginosa) and Chlorella pyrenoidosa (C. pyrenoidosa). Moreover, it enhanced the interspecies competitive advantages of M. aeruginosa by increasing phosphate uptake rate. Furthermore, at a concentration of 2 mg L−1, 2, 4-DTBP negatively affected the development of zebrafish embryos, manifesting in mortality, malformation, and hatching delay. Therefore, the investigation identified 2, 4-DTBP as a potential allelochemical within Microcystis lysate. Although the effective concentration for freshwater algae and zebrafish embryos was higher than that found in Microcystis lysate, it highlighted the need for careful monitoring of aquatic ecosystem health during cyanobacterial bloom mitigation.

Long-term interaction of metals and phosphate with ferrihydrite in artificial seawater and implications for past and present environments

The FeIII hydroxide ferrihydrite (Fh) is highly reactive towards dissolved metals and other aqueous compounds. This reactivity suggests a possible role for Fh in environmental remediation and in controlling ambient concentrations of metals and nutrients in both modern and ancient aqueous environments. Though the reactivity of Fh towards a variety of aqueous compounds has been determined in previous studies, its reactivity under seawater-like conditions has not been systematically explored. Since solution chemistry can have a profound effect on the uptake of metals and oxyions through its effects on the surface chemistry of Fh and the speciation of metals in solution, the dearth of experiments under seawater-like conditions translates into a knowledge gap of metal-Fh interactions in natural marine systems. Furthermore, metal- and nutrient-Fh interactions have been investigated under dissimilar conditions, making a quantitative comparison of these interactions difficult. Lastly, the fate of the aqueous metals and nutrients taken up by Fh upon its aging has been examined in only a few studies and mostly for a duration up to ∼8 months.We bridged these gaps in a series of adsorption and co-precipitation experiments of various metals and phosphate with Fh, in seawater-analog solutions, at circumneutral pH (pH 7.5 and 8.0) and 25 °C. We quantified the effect of interaction with Fh on the aqueous concentrations of CdII, CoII, CrVI, CuII, MnII, MoVI, NiII, VV, UVI, ZnII, and phosphate (PO43−). The experimental results are provided as uptake percentages (quantified as the metal:Fe ratio in the solid phase relative to the metal:Fe ratio added) at different metal:Fe ratios and as a series of partition coefficients of the studied metals and PO43− between aqueous solution and Fh. Additionally, aging experiments of up to ∼4 years in duration were used to determine the potential effects of grain coarsening, surface modification and mineral transformation on the uptake of the metals and PO43−. Uptake of CrVI, MoVI and UVI was negligible in both the adsorption and co-precipitation experiments. Uptake of VV and PO43− by co-precipitation was as much as twice their uptake by adsorption, and we suggest that stabilization of colloidal Fh with a large surface area explains these findings. For CuII, NiII, CoII, MnII, and CdII differences in uptake between the co-precipitation and adsorption experiments were less pronounced, and we ascribe these differences to relatively minor incorporation of these metals into Fh. No significant transformation of Fh to more stable phases was observed under our experimental conditions and duration. Nevertheless, the uptake of several metals and phosphate was affected by Fh aging. Approximately 75% of the PO43− initially taken up by co-precipitation with Fh was released, as was approximately 30% of the VV. A pronounced increase in the uptake of MnII may be related to its oxidation and precipitation as MnIII,IV oxides. For other metals the changes in uptake were less pronounced.We discuss the mechanisms of metal and PO43− uptake by Fh, the effects of solution composition on uptake, and the implications of our findings for modern and ancient natural environments and for environmental remediation.

Yeast-based assay to identify inhibitors of the malaria parasite sodium phosphate uptake transporter as potential novel antimalarial drugs

Yeast-based assay to identify inhibitors of the malaria parasite sodium phosphate uptake transporter as potential novel antimalarial drugs

The microRNA399d-PHOSPHATE2 module alters rice sensitivity to rice ragged stunt virus by manipulating phosphate uptake.

Rice (Oryza sativa L.) production frequently faces threats from biotic and abiotic stressors, with rice ragged stunt virus (RRSV) as a substantial biotic factor. The relationship between inorganic phosphorus (Pi) content and susceptibility to RRSV is crucial yet poorly understood. This study investigates how phosphorus metabolism influences rice resistance to RRSV, focusing on genetic manipulations that modulate this relationship. The RRSV infection increased phosphate (Pi) content in the aerial parts of rice plants by enhancing Pi uptake and transport. Furthermore, the upregulation of microRNA399d (miR399d) and the suppression of its target gene OsPHOSPHATE2 (OsPHO2) enhanced Pi accumulation, increasing rice susceptibility to RRSV infection. Additionally, elevated Pi levels, which are associated with altered ROS dynamics, reduced ROS activity and potentially dampened the plant's innate immune response to viral infection. The miR399d-PHO2 module was identified as pivotal in mediating phosphate uptake and influencing susceptibility to RRSV through modulations in the phosphorus and ROS pathways. This study shed light on the regulatory mechanisms of phosphorus nutrition in rice, revealing a critical interaction between phosphorus metabolism, ROS dynamics, and viral defense. The findings suggest potential strategies for manipulating Pi levels to enhance plant resistance against viruses, opening avenues for agricultural improvements and disease management in rice.

Co-utilization of microalgae and heterotrophic microorganisms improves wastewater treatment efficiency

Wastewater treatment using the activated sludge method requires a large amount of electricity for aeration. Therefore, wastewater treatment using co-culture systems of microalgae and heterotrophic microorganisms, which do not require aeration, has attracted attention as an energy-saving alternative to the method. In this study, we investigated different combinations of microalgae and heterotrophic microorganisms to improve the efficiency of wastewater treatment. Three types of microalgae and five heterotrophic microorganisms were used in combination for wastewater treatment. The combination of Chlamydomonas reinhardtii NIES-2238 and Saccharomyces cerevisiae SH-4 showed the highest wastewater treatment efficiency. Using this combination for artificial wastewater treatment, the removal rates of total organic carbon, PO43−, and NH4+ reached 80%, 93%, and 63%, respectively, after 18 h of treatment. To the best of our knowledge, this is the first study to show that a combination of green algae and yeast improves the efficiency of wastewater treatment. Transcriptome analysis revealed that the combined wastewater treatment altered the expression of 1371 and 692 genes in C. reinhardtii and S. cerevisiae, respectively. One of the main reasons for the improved wastewater treatment performance of the combination of green algae and yeast was the increased expression of genes related to the uptake of phosphate and ammonium ions in the green algae. As both the green algae C. reinhardtii and the yeast S. cerevisiae are highly safe microorganisms, the establishment of their effective combination for wastewater treatment is highly significant.Key points• Combination of various microalgae and heterotrophic microorganisms was tested• Combination of green algae and yeast showed the highest efficiency• This is the first report that this combination is effective for wastewater treatment

Potential of selected microalgae in the bioremediation of wastewater impacted dam water: A case of Goreangab Dam in Windhoek, Namibia

The study was aimed at determining the efficacy of freshwater microalgae in the treatment of polluted dam water with respect to the reduction of pathogen loads, as well as heavy metals and nutrients concentrations. Microalgae were collected from the Klein Windhoek River, as well as the Avis and Goreangab Dams in Windhoek, Namibia. Identification of the microalgae species revealed the presence of the Microcystis species in the Goreangab Dam (control), Anabaena species in the Klein Windhoek River (treatment 1) and the Scenesdesmus species as well as the Anabaena species in the Avis Dam (treatment 2). During treatment, the water samples were assessed on day 0, day 6 and day 12 for faecal and total coliform bacteria, heavy metals (Pb and Cd) as well as nutrients (phosphorous and nitrates). A one-way analysis of variance (ANOVA) indicated that there were no statistical differences between the mean values of Pb (p = 0.346) and Cd (p = 0.940) concentrations after treatment with microalgae. The Kruskal Wallis tests indicated statistical differences between the mean values of the nitrate levels (H(3) = 8.597, p = 0.035) before and after treatment with microalgae. However, the ANOVA indicated that there were no significant differences between the mean values of total phosphate uptake (p = 0.052) after treatment with microalgae. The results for pathogen loads in the wastewater samples indicated statistically significant differences between the mean values of total coliforms ((H(3) = 10.352, p = 0.015) as well as faecal coliforms (H(3) = 10.421, p = 0.015) before and after treatment with microalgae. We conclude that while our microalgae species were not effective in the removal of heavy metals from the dam water, they were nonetheless effective in the removal of microbial contaminants as well as excessive nutrients from wastewater.

Distinct and overlapping RGS14 and RGS12 actions regulate NPT2A-mediated phosphate transport

Parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF23) control serum phosphate levels by downregulating the renal Na-phosphate transporter NPT2A, thereby decreasing phosphate absorption and augmenting urinary excretion. This mechanism requires NHERF1, a PDZ scaffold protein, and is governed by the regulator of G protein signaling-14 (RGS14), which harbors a carboxy-terminal PDZ ligand that binds NHERF1. RGS14 is part of a triad of structurally related RGS proteins that includes RGS12 and RGS10. Like RGS14, RGS12 contains a class 1 PDZ ligand. However, unlike RGS14, the larger RGS12 contains an upstream PDZ-binding domain. The studies outlined here examined and characterized the binding of RGS12 with NHERF1 and NPT2A and its function on hormone-regulated phosphate transport. Immunoblotting experiments revealed RGS12 C-terminal PDZ ligand binding to NHERF1. Further structural analysis disclosed that NPT2A engaged full-length RGS12 and the upstream fragment containing the PDZ domain. Neither the downstream RGS12 portion nor RGS14 interacted with NPT2A. PTH and FGF23 profoundly inhibited phosphate uptake in opossum kidney proximal tubule cells. Transfection with human RGS14, or human RGS12, abolished hormone-sensitive phosphate transport as reported for human proximal tubule cells. RGS12 inhibitory activity resides in the downstream region and is comparable to RGS14. The carboxy-terminal RGS12(667–1447) splice variant is prominently expressed in the kidney and may contribute to regulating hormone-sensitive phosphate transport.

Phosphate Uptake over the Innovative La–Fe–CNT Membrane: Structure-Activity Correlation and Mechanism Investigation

Phosphate Uptake over the Innovative La–Fe–CNT Membrane: Structure-Activity Correlation and Mechanism Investigation

Mechanically durable tri-composite polyamide 6/hematite nanoparticle/tetra-n-butylammonium bromide (PA6/α-Fe2O3/TBAB) nanofiber based membranes for phosphate remediation.

Essential properties for a Point of Use (POU) water filter include maintaining high removal capacity and rate, with excellent mechanical properties to withstand pressure drop. Herein, mechanically robust tri-composite polyamide 6/iron oxide nanoparticles/tetra-n-butylammonium bromide (PA6/α-Fe2O3/TBAB) nanofiber composite membranes were electrospun for phosphate (P) remediation, where the diameter and composition were tuned by controlling solution compositions and electrospinning conditions. Tri-composite composition and morphology affect phosphate uptake where the adsorption capacity followed Langmuir isotherm whereas the adsorption kinetics followed pseudo second order behavior. Mechanical properties (i.e., Young's Modulus (E) and toughness) were significantly influenced by the composition and morphology of the tri-composite, as well. Although additional TBAB and iron oxide decreased toughness, there are optimum composition ranges which resulted in maximum Young's Modulus. Of the synthesized nanofiber membranes, PA6/α-Fe2O3/TBAB nanofibers with 17% α-Fe2O3 and 2% TBAB showed excellent phosphate uptake capacity [i.e., 8.9mg/g (52mg of P/g of α-Fe2O3)] while it is bendable, stretchable, and able to plastically deform without fracturing (i.e., Young's modulus of 2.06 × 108Pa and Toughness of 1.35 × 106Jm-3). With concerns over the impact of P on water resources and the long-term availability of limited P resources, this tri-composite membrane is well suited for applications in both wastewater treatment and resource recovery.

Effective removal of phosphate using La(OH)3@magnetic graphene: A sustainable approach for water remediation

The global environmental concern over dissolved phosphate (P) in surface water has intensified due to its detrimental impact on water quality, particularly through eutrophication. To address this issue, lanthanum hydroxide (LaH)@magnetic graphene (MG) was synthesized via a green method. The MG, prepared using maleic acid, features a highly intricate pore structure and significant surface area, providing numerous active sites for P adsorption. The adsorbent demonstrated exceptional efficiency, achieving 98.8 % removal at neutral pH and a maximum phosphate uptake capacity of 275.5 mg/g. Characterization techniques including SEM-EDS, FT-IR, and XPS, along with density functional theory (DFT) calculations, were used to elucidate the adsorption mechanism of LaH@MG. These studies indicate that the adsorption mechanism involves chemical interactions through hydrogen bonding and ligand exchange. Additionally, the recyclability and phosphate adsorption performance of LaH@MG in real wastewater were evaluated, underscoring its potential for practical environmental remediation applications.

Chemical genetic analysis of enoxolone inhibition of Clostridioides difficile toxin production reveals adenine deaminase and ATP synthase as antivirulence targets

Toxins TcdA and TcdB are the main virulence factors of Clostridioides difficile, a leading cause of hospital-acquired diarrhea. Despite their importance, there is a significant knowledge gap of druggable targets for inhibiting toxin production. To address this, we screened non-antibiotic phytochemicals to identify potential chemical genetic probes to discover anti-virulence drug targets. This led to the identification of 18β-glycyrrhetinic acid (enoxolone), a licorice metabolite, as an inhibitor of TcdA and TcdB biosynthesis. Using affinity-based proteomics, potential targets were identified as ATP synthase subunit alpha (AtpA) and adenine deaminase (Ade, which catalyzes conversion of adenine to hypoxanthine in the purine salvage pathway). To validate these targets, a multi-faceted approach was adopted. Gene silencing of ade and atpA inhibited toxin biosynthesis, while SPR and ITC molecular interaction analyses revealed direct binding of enoxolone to Ade. Metabolomics demonstrated enoxolone induced the accumulation of adenosine, while depleting hypoxanthine and ATP in C. difficile. Transcriptomics further revealed enoxolone dysregulated phosphate uptake genes, which correlated with reduced cellular phosphate levels. These findings suggest that enoxolone's cellular action is multi-targeted. Accordingly, supplementation with both hypoxanthine and triethyl phosphate (TEP), a phosphate source, was required to fully restore toxin production in the presence of enoxolone. In conclusion, through the characterization of enoxolone, we identified promising anti-virulence targets that interfere with nucleotide salvage and ATP synthesis, which may also block toxin biosynthesis.

Optimizing carbon sources on performance for enhanced efficacy in single-stage aerobic simultaneous nitrogen and phosphorus removal via biofloc technology

Bioflocs can efficiently achieve simultaneous nitrate and phosphate removal through a single-stage aerobic process, provided they are continuously supplemented with an organic carbon source. This study investigated the effects of different carbon sources on this process. Results revealed that phosphate removal rate in the glucose group was 0.61 ± 0.02 mg/L/h, significantly higher than those in the acetate (0.28 ± 0.01 mg/L/h) and propionate (0.29 ± 0.03 mg/L/h) groups (p < 0.05). However, the three groups observed no significant differences in nitrate removal rates (p > 0.05). The superior performance of the glucose group in simultaneous nitrogen and phosphorus removal is likely due to the higher biomass synthesis. In contrast, nitrate removal in the acetate and propionate groups was primarily driven by denitrification, resulting in lower sludge production and reduced phosphate uptake. For practical application of bioflocs in simultaneous nitrogen and phosphorus removal, glucose is recommended as the optimal carbon source.

Phosphate availability conditions caspofungin tolerance, capsule attachment and titan cell formation in Cryptococcus neoformans.

There is an urgent need for new antifungal drugs to treat invasive fungal diseases. Unfortunately, the echinocandin drugs that are fungicidal against other important fungal pathogens are ineffective against Cryptococcus neoformans, the causative agent of life-threatening meningoencephalitis in immunocompromised people. Contributing mechanisms for echinocandin tolerance are emerging with connections to calcineurin signaling, the cell wall, and membrane composition. In this context, we discovered that a defect in phosphate uptake impairs the tolerance of C. neoformans to the echinocandin caspofungin. Our previous analysis of mutants lacking three high affinity phosphate transporters revealed reduced elaboration of the polysaccharide capsule and attenuated virulence in mice. We investigated the underlying mechanisms and found that loss of the transporters and altered phosphate availability influences the cell wall and membrane composition. These changes contribute to the shedding of capsule polysaccharide thus explaining the reduced size of capsules on mutants lacking the phosphate transporters. We also found an influence of the calcineurin pathway including calcium sensitivity and an involvement of the endoplasmic reticulum in the response to phosphate limitation. Furthermore, we identified membrane and lipid composition changes consistent with the role of phosphate in phospholipid biosynthesis and with previous studies implicating membrane integrity in caspofungin tolerance. Finally, we discovered a contribution of phosphate to titan cell formation, a cell type that displays modified cell wall and capsule composition. Overall, our analysis reinforces the importance of phosphate as a regulator of cell wall and membrane composition with implications for capsule attachment and antifungal drug susceptibility.

Orthophosphate uptake onto woodchips in denitrifying bioreactors is enhanced by anoxic-(anaerobic-)oxic cycling

Woodchips are widely used as a low-cost and renewable organic carbon source for denitrifying biofilms in passive nutrient removal systems. One limitation of wood-based biofiltration systems is their relatively poor removal of phosphorus (P) from subsurface drainage and stormwaters, necessitating the use of additional filter media when co-treatment of nitrogen (N) and P is required. Here, we show that anoxic-oxic cycling of woodchip media, which enhances nitrate (NO3−) removal by increasing the mobilization of organic carbon from wood, also improves orthophosphate (Pi) uptake onto woodchips. Orthophosphate removal rates in flow-through woodchip columns ranged from 0 to 34.9 μg PO43− L−1 h−1 under continuously-saturated (anoxic) conditions, and increased to 17.5 to 71.9 μg PO43− L−1 h−1 in columns undergoing drying-rewetting (oxic-anoxic) cycles. The highest Pi removal efficiencies were observed in the first 20 h after reactors were re-flooded, and were concurrent with maxima in polyphosphate kinase (ppk) gene expression by the polyphosphate accumulating organisms (PAOs) Accumulibacter spp. and Pseudomonas spp. Batch experiments confirmed that anoxic-anaerobic-oxic pre-incubation conditions led to orthophosphate uptake onto woodchips as high as 74.9 ± 0.8 mg PO43−/kg woodchip, and batch tests with autoclaved woodchips demonstrated that Pi uptake was due to biological processes and not adsorption. NO3− removal in batch tests was also greatest under oxic incubation conditions, attributed to greater carbon availability in hypoxic to anoxic zones in woodchip biofilms. While further research is needed to elucidate the mechanisms controlling enhanced Pi uptake by woodchip biofilms under anoxic-(anaerobic-)oxic cycling, these results suggest a role for enhanced Pi uptake by PAOs in a nature-based system for treatment of nonpoint source nutrients.

Phosphorous accumulation associated with mitochondrial PHT3-mediated enhanced arsenate tolerance in Chlamydomonas reinhardtii

Arsenate is a highly toxic element and excessive accumulation of arsenic in the aquatic environment easily triggers a problem threatening the ecological health. Phytoremediation has been widely explored as a method to alleviate As contamination. Here, the green algae, Chlamydomonas reinhardtii was investigated by profiling the accumulation of arsenate and phosphorus, which share the same uptake pathway, in response to arsenic stress. Both C. reinhardtii wild type C30 and the Crpht3 mutant were cultured under arsenic stress, and demonstrated a similar growth phenotype under limited phosphate supply. Sufficient phosphate obviously increased the uptake of polyphosphate and intercellular phosphate in the Crpht3 mutant, which increased the arsenic tolerance of the Crpht3 mutant under stress from 500 µmol L−1 As(V). Upregulation of the PHT3 gene in the Crpht3 mutant increased accumulation of phosphate in the cytoplasm under arsenate stress, which triggered a regulatory role for the differentially expressed genes that mediated improvement of the glutathione redox cycle, antioxidant activity and detoxification. While the wild type C30 showed weak arsenate tolerance because of little phosphate accumulation. These results suggest that the enhanced arsenic tolerance of the Crpht3 mutant is regulated by the PHT3 gene mediation. This study provides insight onto the responsive mechanisms of the PHT3 gene-mediated in alleviating arsenic toxicity in plants.

Asymptotic and Transient Dynamics of a Stoichiometric Algal Growth Model with Two-Stage Phosphate Uptake

Asymptotic and Transient Dynamics of a Stoichiometric Algal Growth Model with Two-Stage Phosphate Uptake

Chronic Kidney Disease-associated Lung Injury Is Mediated by Phosphate-induced MAPK/AKT Signaling.

Chronic kidney disease (CKD) is associated with systemic phosphate elevations, called hyperphosphatemia. Translational studies have shown that hyperphosphatemia contributes to CKD-associated inflammation and injury in various tissues, including the kidney, heart, liver, and parathyroid gland. Mechanisms underlying pathologic actions of elevated phosphate on cells are not well understood but seem to involve uptake of phosphate through sodium-phosphate cotransporters and phosphate-induced signaling via fibroblast growth factor receptor (FGFR) 1. Clinical studies indicate CKD patients are more likely to develop inflammatory and restrictive lung diseases, such as fibrotic interstitial lung diseases, and here we aimed to determine whether hyperphosphatemia can cause lung injury. We found that a mouse model of CKD and hyperphosphatemia, induced by an adenine-rich diet, develops lung fibrosis and inflammation. Elevation of systemic phosphate levels by administration of a high-phosphate diet in a mouse model of primary lung inflammation and fibrosis, induced by bleomycin, exacerbated lung injury in the absence of kidney damage. Our in vitro studies identified increases of proinflammatory cytokines in human lung fibroblasts exposed to phosphate elevations. Phosphate activated extracellular signal related kinase (ERK) 1/2 and protein kinase B (PKB/AKT) signaling, and pharmacological inhibition of ERK, AKT, FGFR1, or sodium-phosphate cotransporters prevented phosphate-induced proinflammatory cytokine upregulation. Additionally, inhibition of FGFR1 or sodium-phosphate cotransporters decreased the phosphate-induced activation of ERK and AKT. Our study suggests that phosphate can directly target lung fibroblasts and induce an inflammatory response and that hyperphosphatemia in CKD and non-CKD models contributes to lung injury. Phosphate-lowering strategies might protect from CKD-associated lung injury.