Cell surface and intracellular auxin signalling for H+ fluxes in root growth.

Growth regulation tailors development in plants to their environment. A prominent example of this is the response to gravity, in which shoots bend up and roots bend down1. This paradox is based on opposite effects of the phytohormone auxin, which promotes cell expansion in shoots while inhibiting it in roots via a yet unknown cellular mechanism2. Here, by combining microfluidics, live imaging, genetic engineering and phosphoproteomics in Arabidopsis thaliana, we advance understanding of how auxin inhibits root growth. We show that auxin activates two distinct, antagonistically acting signalling pathways that converge on rapid regulation of apoplastic pH, a causative determinant of growth. Cell surface-based TRANSMEMBRANE KINASE1 (TMK1) interacts with and mediates phosphorylation and activation of plasma membrane H+-ATPases for apoplast acidification, while intracellular canonical auxin signalling promotes net cellular H+ influx, causing apoplast alkalinization. Simultaneous activation of these two counteracting mechanisms poises roots for rapid, fine-tuned growth modulation in navigating complex soil environments.

SlWRKY81 regulates Spd synthesis and Na+/K+ homeostasis through interaction with SlJAZ1 mediated JA pathway to improve tomato saline-alkali resistance.

Saline-alkali stress is an important abiotic stress factor affecting tomato (Solanum lycopersicum L.) plant growth. Although the involvement of the tomato SlWRKY gene family in responses to saline-alkali stress has been well established, the mechanism underlying resistance to saline-alkali stress remains unclear. In this study, we investigated the role of SlWRKY81 in conferring saline-alkali stress resistance by using overexpression and knockout tomato seedlings obtained via genetic modification. We demonstrated that SlWRKY81 improves the ability of tomato to withstand saline-alkali stress by enhancing antioxidant capacity, root activity, and proline content while reducing malondialdehyde levels. Saline-alkali stress induces an increase in jasmonic acid (JA) content in tomato seedlings, and the SlWRKY81 promoter responds to JA signaling, leading to an increase in SlWRKY81 expression. Furthermore, the interaction between SlJAZ1 and SlWRKY81 represses the expression of SlWRKY81. SlWRKY81 binds to W-box motifs in the promoter regions of SlSPDS2 and SlNHX4, thereby positively regulating their expression. This regulation results in increased spermidine (Spd) content and enhanced potassium (K+) absorption and sodium (Na+) efflux, which contribute to the resistance of tomato to saline-alkali stress. However, JA and SlJAZ1 exhibit antagonistic effects. Elevated JA content reduces the inhibitory effect of SlJAZ1 on SlWRKY81, leading to the release of additional SlWRKY81 protein and further augmenting the resistance of tomato to saline-alkali stress. In summary, the modulation of Spd synthesis and Na+/K+ homeostasis mediated by the interaction between SlWRKY81 and SlJAZ1 represents a novel pathway underlying tomato response to saline-alkali stress.

Oral Sodium Bicarbonate and Bone Turnover in CKD: A Secondary Analysis of the BASE Pilot Trial.

SIGNIFICANCE STATEMENT: In CKD, metabolic acidosis is commonly treated with alkali in the hope that it will improve bone health. In a post hoc analysis of the Bicarbonate Administration to Stabilize eGFR Pilot Trial, we investigated whether sodium bicarbonate affects serum levels of bone turnover markers and other hormones related to bone health in individuals with CKD who have normal to slightly reduced total CO2 (20-28 mEq/L). Sodium bicarbonate increased serum levels of α-klotho but had no significant effect on other bone health markers, including intact fibroblast growth factor-23 (iFGF-23), intact parathyroid hormone (iPTH), and bone-specific alkaline phosphatase (B-SAP). Further study is needed to determine the effect of bicarbonate administration on clinical aspects of bone health. BACKGROUND: Treatment with alkali has been hypothesized to improve bone health in CKD by mitigating adverse effects of acid on bone mineral. We investigated the effect of treatment with sodium bicarbonate on bone turnover markers and other factors related to bone metabolism in CKD. METHODS: This is a post hoc analysis of the Bicarbonate Administration to Stabilize eGFR Pilot Trial in which 194 individuals with CKD and serum total CO2 20-28 mEq/L were randomly assigned to placebo or one of two doses of sodium bicarbonate (0.5 or 0.8 mEq/kg lean body weight per day) for 28 weeks. The following serum measurements were performed at baseline, week 12, and week 28: B-SAP, c-telopeptide, procollagen type I intact N-terminal propeptide, iPTH, iFGF-23, soluble klotho, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and tartrate-resistant acid phosphatase 5b. The difference (sodium bicarbonate versus placebo) in mean change of each bone biomarker from baseline was determined using linear mixed models. RESULTS: One hundred sixty-eight participants submitted samples for post hoc investigations. Mean eGFR was 37±10 ml/min per 1.73 m2 and mean total CO2 was 24±3 mEq/L at baseline. Sodium bicarbonate induced a dose-dependent increase in soluble klotho levels compared with placebo. There was no significant effect of treatment with either dose of sodium bicarbonate on any of the other bone biomarkers, including iFGF-23, iPTH, and B-SAP. Effects on bone biomarkers were similar in those with baseline serum total CO2 <24 mEq/L compared with those with total CO2 ≥24 mEq/L. CONCLUSIONS: In this pilot trial of individuals with CKD and total CO2 20-28 mEq/L, sodium bicarbonate treatment increased serum klotho levels but did not affect other bone health markers over 28 weeks. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: ClinicalTrials.gov, NCT02521181.

The B1 H + -ATPase ( Atp6v1b1 ) Subunit in Non-Type A Intercalated Cells is Required for Driving Pendrin Activity and the Renal Defense Against Alkalosis.

SIGNIFICANCE STATEMENT: In the kidney, the B1 H + -ATPase subunit is mostly expressed in intercalated cells (IC). Its importance in acid-secreting type A ICs is evident in patients with inborn distal renal tubular acidosis and ATP6V1B1 mutations. However, the protein is also highly expressed in alkali-secreting non-type A ICs where its function is incompletely understood. We demonstrate in Atp6v1b1 knock out mice that the B1 subunit is critical for the renal response to defend against alkalosis during an alkali load or chronic furosemide treatment. These findings highlight the importance of non-type A ICs in maintaining acid-base balance in response to metabolic challenges or commonly used diuretics. BACKGROUND: Non-type A ICs in the collecting duct system express the luminal Cl - /HCO 3- exchanger pendrin and apical and/or basolateral H + -ATPases containing the B1 subunit isoform. Non-type A ICs excrete bicarbonate during metabolic alkalosis. Mutations in the B1 subunit (ATP6V1B1) cause distal renal tubular acidosis due to its role in acid secretory type A ICs. The function of B1 in non-type A ICs has remained elusive. METHODS: We examined the responses of Atp6v1b1-/- and Atp6v1b1+/+ mice to an alkali load and to chronic treatment with furosemide. RESULTS: An alkali load or 1 week of furosemide resulted in a more pronounced hypokalemic alkalosis in male ATP6v1b1-/- versus Atp6v1b1+/+ mice that could not be compensated by respiration. Total pendrin expression and activity in non-type A ICs of ex vivo microperfused cortical collecting ducts were reduced, and ß2 -adrenergic stimulation of pendrin activity was blunted in ATP6v1b1-/- mice. Basolateral H + -ATPase activity was strongly reduced, although the basolateral expression of the B2 isoform was increased. Ligation assays for H + -ATPase subunits indicated impaired assembly of V 0 and V 1 H + -ATPase domains. During chronic furosemide treatment, ATP6v1b1-/- mice also showed polyuria and hyperchloremia versus Atp6v1b1+/+ . The expression of pendrin, the water channel AQP2, and subunits of the epithelial sodium channel ENaC were reduced. CONCLUSIONS: Our data demonstrate a critical role of H + -ATPases in non-type A ICs function protecting against alkalosis and reveal a hitherto unrecognized need of basolateral B1 isoform for a proper H + -ATPase complexes assembly and ability to be stimulated.

Assembly and comparative analysis of the complete mitochondrial and chloroplast genome of Cyperus stoloniferus (Cyperaceae), a coastal plant possessing saline-alkali tolerance.

BACKGROUND: Cyperus stoloniferus is an important species in coastal ecosystems and possesses economic and ecological value. To elucidate the structural characteristics, variation, and evolution of the organelle genome of C. stoloniferus, we sequenced, assembled, and compared its mitochondrial and chloroplast genomes. RESULTS: We assembled the mitochondrial and chloroplast genomes of C. stoloniferus. The total length of the mitochondrial genome (mtDNA) was 927,413 bp, with a GC content of 40.59%. It consists of two circular DNAs, including 37 protein-coding genes (PCGs), 22 tRNAs, and five rRNAs. The length of the chloroplast genome (cpDNA) was 186,204 bp, containing 93 PCGs, 40 tRNAs, and 8 rRNAs. The mtDNA and cpDNA contained 81 and 129 tandem repeats, respectively, and 346 and 1,170 dispersed repeats, respectively, both of which have 270 simple sequence repeats. The third high-frequency codon (RSCU > 1) in the organellar genome tended to end at A or U, whereas the low-frequency codon (RSCU < 1) tended to end at G or C. The RNA editing sites of the PCGs were relatively few, with only 9 and 23 sites in the mtDNA and cpDNA, respectively. A total of 28 mitochondrial plastid DNAs (MTPTs) in the mtDNA were derived from cpDNA, including three complete trnT-GGU, trnH-GUG, and trnS-GCU. Phylogeny and collinearity indicated that the relationship between C. stoloniferus and C. rotundus are closest. The mitochondrial rns gene exhibited the greatest nucleotide variability, whereas the chloroplast gene with the greatest nucleotide variability was infA. Most PCGs in the organellar genome are negatively selected and highly evolutionarily conserved. Only six mitochondrial genes and two chloroplast genes exhibited Ka/Ks > 1; in particular, atp9, atp6, and rps7 may have undergone potential positive selection. CONCLUSION: We assembled and validated the mtDNA of C. stoloniferus, which contains a 15,034 bp reverse complementary sequence. The organelle genome sequence of C. stoloniferus provides valuable genomic resources for species identification, evolution, and comparative genomic research in Cyperaceae.

Elucidating the role of exogenous melatonin in mitigating alkaline stress in soybeans across different growth stages: a transcriptomic and metabolomic approach.

BACKGROUND: Soybean (Glycine max), a vital grain and oilseed crop, serves as a primary source of plant protein and oil. Soil salinization poses a significant threat to soybean planting, highlighting the urgency to improve soybean resilience and adaptability to saline stress. Melatonin, recently identified as a key plant growth regulator, plays crucial roles in plant growth, development, and responses to environmental stress. However, the potential of melatonin to mitigate alkali stress in soybeans and the underlying mechanisms remain unclear. RESULTS: This study investigated the effects of exogenous melatonin on the soybean cultivar Zhonghuang 13 under alkaline stress. We employed physiological, biochemical, transcriptomic, and metabolomic analyses throughout both vegetative and pod-filling growth stages. Our findings demonstrate that melatonin significantly counteracts the detrimental effects of alkaline stress on soybean plants, promoting plant growth, photosynthesis, and antioxidant capacity. Transcriptomic analysis during both growth stages under alkaline stress, with and without melatonin treatment, identified 2,834 and 549 differentially expressed genes, respectively. These genes may play a vital role in regulating plant adaptation to abiotic stress. Notably, analysis of phytohormone biosynthesis pathways revealed altered expression of key genes, particularly in the ARF (auxin response factor), AUX/IAA (auxin/indole-3-acetic acid), and GH3 (Gretchen Hagen 3) families, during the early stress response. Metabolomic analysis during the pod-filling stage identified highly expressed metabolites responding to melatonin application, such as uteolin-7-O-(2''-O-rhamnosyl)rutinoside and Hederagenin-3-O-glucuronide-28-O-glucosyl(1,2)glucoside, which helped alleviate the damage caused by alkali stress. Furthermore, we identified 183 differentially expressed transcription factors, potentially playing a critical role in regulating plant adaptation to abiotic stress. Among these, the gene SoyZH13_04G073701 is particularly noteworthy as it regulates the key differentially expressed metabolite, the terpene metabolite Hederagenin-3-O-glucuronide-28-O-glucosyl(1,2)glucoside. WGCNA analysis identified this gene (SoyZH13_04G073701) as a hub gene, positively regulating the crucial differentially expressed metabolite of terpenoids, Hederagenin-3-O-glucuronide-28-O-glucosyl(1,2)glucoside. Our findings provide novel insights into how exogenous melatonin alleviates alkali stress in soybeans at different reproductive stages. CONCLUSIONS: Integrating transcriptomic and metabolomic approaches, our study elucidates the mechanisms by which exogenous melatonin ameliorates the inhibitory effects of alkaline stress on soybean growth and development. This occurs through modulation of biosynthesis pathways for key compounds, including terpenes, flavonoids, and phenolics. Our findings provide initial mechanistic insights into how melatonin mitigates alkaline stress in soybeans, offering a foundation for molecular breeding strategies to enhance salt-alkali tolerance in this crop.

Inroads into saline-alkaline stress response in plants: unravelling morphological, physiological, biochemical, and molecular mechanisms.

MAIN CONCLUSION: This article discusses the complex network of ion transporters, genes, microRNAs, and transcription factors that regulate crop tolerance to saline-alkaline stress. The framework aids scientists produce stress-tolerant crops for smart agriculture. Salinity and alkalinity are frequently coexisting abiotic limitations that have emerged as archetypal mediators of low yield in many semi-arid and arid regions throughout the world. Saline-alkaline stress, which occurs in an environment with high concentrations of salts and a high pH, negatively impacts plant metabolism to a greater extent than either stress alone. Of late, saline stress has been the focus of the majority of investigations, and saline-alkaline mixed studies are largely lacking. Therefore, a thorough understanding and integration of how plants and crops rewire metabolic pathways to repair damage caused by saline-alkaline stress is of particular interest. This review discusses the multitude of resistance mechanisms that plants develop to cope with saline-alkaline stress, including morphological and physiological adaptations as well as molecular regulation. We examine the role of various ion transporters, transcription factors (TFs), differentially expressed genes (DEGs), microRNAs (miRNAs), or quantitative trait loci (QTLs) activated under saline-alkaline stress in achieving opportunistic modes of growth, development, and survival. The review provides a background for understanding the transport of micronutrients, specifically iron (Fe), in conditions of iron deficiency produced by high pH. Additionally, it discusses the role of calcium in enhancing stress tolerance. The review highlights that to encourage biomolecular architects to reconsider molecular responses as auxiliary for developing tolerant crops and raising crop production, it is essential to (a) close the major gaps in our understanding of saline-alkaline resistance genes, (b) identify and take into account crop-specific responses, and (c) target stress-tolerant genes to specific crops.

Alkaline Water: Help or Hype for Uric Acid and Cystine Urolithiasis?

PURPOSE: The consumption of alkaline water, water with an average pH of 8 to 10, has been steadily increasing globally as proponents claim it to be a healthier alternative to regular water. Urinary alkalinization therapy is frequently prescribed in patients with uric acid and cystine urolithiasis, and as such we analyzed commercially available alkaline waters to assess their potential to increase urinary pH. MATERIALS AND METHODS: Five commercially available alkaline water brands (Essentia, Smart Water Alkaline, Great Value Hydrate Alkaline Water, Body Armor SportWater, and Perfect Hydration) underwent anion chromatography and direct chemical measurements to determine the mineral contents of each product. The alkaline content of each bottle of water was then compared to that of potassium citrate (the gold standard for urinary alkalinization) as well as to other beverages and supplements used to augment urinary citrate and/or the urine pH. RESULTS: The pH levels of the bottled alkaline water ranged from 9.69 to 10.15. Electrolyte content was minimal, and the physiologic alkali content was below 1 mEq/L for all brands of alkaline water. The alkali content of alkaline water is minimal when compared to common stone treatment alternatives such as potassium citrate. In addition, several organic beverages, synthetic beverages, and other supplements contain more alkali content than alkaline water, and can achieve the AUA and European Association of Urology alkali recommendation of 30 to 60 mEq per day with ≤ 3 servings/d. CONCLUSIONS: Commercially available alkaline water has negligible alkali content and thus provides no added benefit over tap water for patients with uric acid and cystine urolithiasis.

Redesigning a S-nitrosylated pyruvate-dependent GABA transaminase 1 to generate high-malate and saline-alkali-tolerant tomato.

Although saline-alkali stress can improve tomato quality, the detailed molecular processes that balance stress tolerance and quality are not well-understood. Our research links nitric oxide (NO) and γ-aminobutyric acid (GABA) with the control of root malate exudation and fruit malate storage, mediated by aluminium-activated malate transporter 9/14 (SlALMT9/14). By modifying a specific S-nitrosylated site on pyruvate-dependent GABA transaminase 1 (SlGABA-TP1), we have found a way to enhance both plant's saline-alkali tolerance and fruit quality. Under saline-alkali stress, NO levels vary in tomato roots and fruits. High NO in roots leads to S-nitrosylation of SlGABA-TP1/2/3 at Cys316/258/316, reducing their activity and increasing GABA. This GABA then reduces malate exudation from roots and affects saline-alkali tolerance by interacting with SlALMT14. In fruits, a moderate NO level boosts SlGABA-TP1 expression and GABA breakdown, easing GABA's block on SlALMT9 and increasing malate storage. Mutants of SlGABA-TP1C316S that do not undergo S-nitrosylation maintain high activity, supporting malate movement in both roots and fruits under stress. This study suggests targeting SlGABA-TP1Cys316 in tomato breeding could significantly improve plant's saline-alkali tolerance and fruit quality, offering a promising strategy for agricultural development.

Subconjunctival Administration of Mesenchymal Stem Cells Alleviates Ocular Inflammation in a Murine Model of Corneal Alkali Burn.

Corneal alkali burns cause extensive damage not only to the cornea but also to the intraocular tissues. As an anti-inflammatory therapy, subconjunctival administration of mesenchymal stem cells (MSCs) for corneal protection after corneal alkali burn has been explored. Little evidence demonstrates the potential of subconjunctival MSCs delivery in protecting the post-burn intraocular tissues. This study aimed to evaluate the therapeutic efficacy of subconjunctival injection of human placental (hP)-MSCs in protecting against ocular destruction after the burn. hP-MSCs were subconjunctivally administered to C57/BL mice after corneal alkali burn. Western blot of iNOS and CD206 was performed to determine the M1 and M2 macrophage infiltration in the cornea. Infiltration of inflammatory cells in the anterior uvea and retina was analyzed by flow cytometry. The TUNEL assay or Western blot of Bax and Bcl2 was used to evaluate the anti-apoptotic effects of MSCs. MSCs could effectively facilitate cornea repair by suppressing inflammatory cytokines IL-1ß, MCP-1, and MMP9, and polarizing CD206 positive M2 macrophages. Anterior uveal and retinal inflammatory cytokines expression and inflammatory cell infiltration were inhibited in the MSC-treated group. Reduced TUNEL positive staining and Bax/Bcl2 ratio indicated the anti-apoptosis of MSCs. MSC-conditioned medium promoted human corneal epithelial cell proliferation and regulated LPS-stimulated inflammation in RAW 264.7 macrophages, confirming the trophic and immunoregulatory effects of MSCs. Our findings demonstrate that subconjunctival administration of MSCs exerted anti-inflammatory and anti-apoptotic effects in the cornea, anterior uvea, and retina after corneal alkali burn. This strategy may provide a new direction for preventing post-event complications after corneal alkali burn.

URP20 improves corneal injury caused by alkali burns combined with pathogenic bacterial infection in rats.

Corneal alkali burns often occur in industrial production and daily life, combined with infection, and may cause severe eye disease. Oxidative stress and neovascularization (NV) are important factors leading to a poor prognosis. URP20 is an antimicrobial peptide that has been proven to treat bacterial keratitis in rats through antibacterial and anti-NV effects. Therefore, in this study, the protective effect and influence mechanism of URP20 were explored in a rat model of alkali burn together with pathogenic bacteria (Staphylococcus aureus and Escherichia coli) infection. In addition, human umbilical vein endothelial cells (HUVECs) and human corneal epithelial cells (HCECs) were selected to verify the effects of URP20 on vascularization and oxidative stress. The results showed that URP20 treatment could protect corneal tissue, reduce corneal turbidity, and reduce the NV pathological score. Furthermore, URP20 significantly inhibited the expression of the vascularization marker proteins VEGFR2 and CD31. URP20 also reduced the migration ability of HUVECs. In terms of oxidative stress, URP20 significantly upregulated SOD and GSH contents in corneal tissue and HCECs (treated with 200 µM H2O2) and promoted the expression of the antioxidant protein Nrf2/HO-1. At the same time, MDA and ROS levels were also inhibited. In conclusion, URP20 could improve corneal injury combined with bacterial infection in rats caused by alkali burns through antibacterial, anti-NV, and antioxidant activities.

Enhancing grain shape, thermotolerance, and alkaline tolerance via Gγ protein manipulation in rice.

KEY MESSAGE: Our findings highlight a valuable breeding resource, demonstrating the potential to concurrently enhance grain shape, thermotolerance, and alkaline tolerance by manipulating Gγ protein in rice. Temperate Geng/Japonica (GJ) rice yields have improved significantly, bolstering global food security. However, GJ rice breeding faces challenges, including enhancing grain quality, ensuring stable yields at warmer temperatures, and utilizing alkaline land. In this study, we employed CRISPR/Cas9 gene-editing technology to knock out the GS3 locus in seven elite GJ varieties with superior yield performance. Yield component measurements revealed that GS3 knockout mutants consistently enhanced grain length and reduced plant height in diverse genetic backgrounds. The impact of GS3 on the grain number per panicle and setting rate depended on the genetic background. GS3 knockout did not affect milling quality and minimally altered protein and amylose content but notably influenced chalkiness-related traits. GS3 knockout indiscriminately improved heat and alkali stress tolerance in the GJ varieties studied. Transcriptome analysis indicated differential gene expression between the GS3 mutants and their wild-type counterparts, enriched in biological processes related to photosynthesis, photosystem II stabilization, and pathways associated with photosynthesis and cutin, suberine, and wax biosynthesis. Our findings highlight GS3 as a breeding resource for concurrently improving grain shape, thermotolerance, and alkaline tolerance through Gγ protein manipulation in rice.

Biodegradable Alkali-Swellable Emulsion Polymers: Industrial and Commercial Thickeners.

Sustainability and circularity are key issues facing the global polymer industry. The search for biodegradable and environmentally-friendly polymers that can replace conventional materials is a difficult challenge that has been met with limited success. Alternatives must be cost-effective, scalable, and provide equivalent performance. We report that latexes made by the conventional emulsion polymerization of vinyl acetate and functional vinyl ester monomers are efficient thickeners for consumer products and biodegrade in wastewater. This approach uses readily-available starting materials and polymerization is carried out in water at room temperature, in one pot, and generates negligible waste. Moreover, the knowledge that poly(vinyl ester)s are biodegradable will lead to the design of new green polymer materials.

Metagenomic analysis revealed the potential of lactic acid bacteria in improving natural saline-alkali land.

Management and improving saline-alkali land is necessary for sustainable agricultural development. We conducted a field experiment to investigate the effects of spraying lactic acid bacteria (LAB) on the cucumber and tomato plant soils. Three treatments were designed, including spraying of water, viable or sterilized LAB preparations to the soils of cucumber and tomato plants every 20 days. Spraying sterilized or viable LAB could reduce the soil pH, with a more obvious effect by using viable LAB, particularly after multiple applications. Metagenomic sequencing revealed that the soil microbiota in LAB-treated groups had higher alpha-diversity and more nitrogen-fixing bacteria compared with the water-treated groups. Both viable and sterilized LAB, but not water application, increased the complexity of the soil microbiota interactive network. The LAB-treated subgroups were enriched in some KEGG pathways compared with water or sterilized LAB subgroups, such as environmental information processing-related pathways in cucumber plant; and metabolism-related pathways in tomato plant, respectively. Redundancy analysis revealed association between some soil physico-chemical parameters (namely soil pH and total nitrogen) and bacterial biomarkers (namely Rhodocyclaceae, Pseudomonadaceae, Gemmatimonadaceae, and Nitrosomonadales). Our study demonstrated that LAB is a suitable strategy for decreasing soil pH and improving the microbial communities in saline-alkali land.

The Glycine soja cytochrome P450 gene GsCYP82C4 confers alkaline tolerance by promoting reactive oxygen species scavenging.

Recent studies have demonstrated the crucial role of Cytochrome P450 enzymes (CYPs) in the production of secondary metabolites, phytohormones and antioxidants in plants. However, their functional characterization specifically under alkaline stress remains elusive. CYP82C4 was the key gene screened from a family of wild soybean CYPs in our previous studies. The aim of this present study was to clone the Glycine soja GsCYP82C4 gene and characterize its functions in Arabidopsis and Glycine max. The results showed that the GsCYP82C4 gene displayed a high expression in different plant tissues at mature stages compared to young stages. Further, higher temporal expression of the GsCYP82C4 gene was noted at 6, 12 and 24 h time points after alkali treatment in leaves compared to roots. In addition, overexpression of GsCYP82C4 improved alkaline stress tolerance in Arabidopsis via increased root lengths and fresh biomass and strengthened the antioxidant defense system via a reduction in superoxide radicals in transgenic lines compared to wild type (WT) and atcyp82c4 mutants. Further, the expression levels of stress-related marker genes were up-regulated in GsCYP82C4 OX lines under alkali stress. The functional analysis of GsCYP82C4 overexpression in soybean displayed better hairy root growth, increased fresh weight, higher antioxidant enzyme activities and reduced lipid peroxidation rates in OX lines compared to the soybean WT (K599) line. In total, our study displayed positive roles of GsCYP82C4 overexpression in both Arabidopsis and Glycine max to alleviate alkaline stress via altering expression abundance of stress responsive genes, stronger roots, higher antioxidant enzyme activities as well as reduced rates of lipid peroxidation and superoxide radicals.

Rhizophagus irregularis and biochar can synergistically improve the physiological characteristics of saline-alkali resistance of switchgrass.

Inoculation of arbuscular mycorrhizal fungi (AMF) or biochar (BC) application can improve photosynthesis and promote plant growth under saline-alkali stress. However, little is known about the effects of the two combined on growth and physiological characteristics of switchgrass under saline-alkali stress. This study examined the effects of four treatments: (1) no AMF inoculation and no biochar addition (control), (2) biochar (BC) alone, (3) AMF (Rhizophagus irregularis, Ri) alone, and (4) the combination of both (BC+Ri) on the plant biomass, antioxidant enzymes, chlorophyll, and photosynthetic parameters of switchgrass under saline-alkali stress. The results showed that the above-ground, belowground and total biomass of switchgrass in the BC+Ri treatment group was significantly higher (+136.7%, 120.2% and 132.4%, respectively) than in other treatments compared with Control. BC+Ri treatment significantly increased plant leaves' relative chlorophyll content, antioxidant enzyme activity, and photosynthesis parameters. It is worth noting that the transpiration rate, stomatal conductance, net photosynthetic rate, PSII efficiency and other photosynthetic-related indexes of the BC+Ri treatment group were the highest (38% to 54% higher than other treatments). The fitting results of light response and CO2 response curves showed that the light saturation point, light compensation point, maximum carboxylation rate and maximum electron transfer rate of switchgrass in the Ri+BC treatment group were the highest. In conclusion, biochar combined with Ri has potential beneficial effects on promoting switchgrass growth under saline-alkali stress and improving the activity of antioxidant enzymes and photosynthetic characteristics of plants.

Bacillus licheniformis Jrh14-10 enhances alkaline tolerance in Arabidopsis thaliana by regulating crosstalk between ethylene and polyamine pathways.

Plant growth-promoting rhizobacteria (PGPR) are known for their role in ameliorating plant stress, including alkaline stress, yet the mechanisms involved are not fully understood. This study investigates the impact of various inoculum doses of Bacillus licheniformis Jrh14-10 on Arabidopsis growth under alkaline stress and explores the underlying mechanisms of tolerance enhancement. We found that all tested doses improved the growth of NaHCO3-treated seedlings, with 109 cfu/mL being the most effective. Transcriptome analysis indicated downregulation of ethylene-related genes and an upregulation of polyamine biosynthesis genes following Jrh14-10 treatment under alkaline conditions. Further qRT-PCR analysis confirmed the suppression of ethylene biosynthesis and signaling genes, alongside the activation of polyamine biosynthesis genes in NaHCO3-stressed seedlings treated with Jrh14-10. Genetic analysis showed that ethylene signaling-deficient mutants (etr1-3 and ein3-1) exhibited greater tolerance to NaHCO3 than the wild type, and the growth-promoting effect of Jrh14-10 was significantly diminished in these mutants. Additionally, Jrh14-10 was found unable to produce 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, indicating it does not reduce the ethylene precursor ACC in Arabidopsis. However, Jrh14-10 treatment increased the levels of polyamines (putrescine, spermidine, and spermine) in stressed seedlings, with spermidine particularly effective in reducing H2O2 levels and enhancing Fv/Fm under NaHCO3 stress. These findings reveal a novel mechanism of PGPR-induced alkaline tolerance, highlighting the crosstalk between ethylene and polyamine pathways, and suggest a strategic redirection of S-adenosylmethionine towards polyamine biosynthesis to combat alkaline stress.

Metal Ion-Directed Functional Metal-Phenolic Materials.

Metal ions are ubiquitous in nature and play significant roles in assembling functional materials in fields spanning chemistry, biology, and materials science. Metal-phenolic materials are assembled from phenolic components in the presence of metal ions through the formation of metal-organic complexes. Alkali, alkali-earth, transition, and noble metal ions as well as metalloids interacting with phenolic building blocks have been widely exploited to generate diverse hybrid materials. Despite extensive studies on the synthesis of metal-phenolic materials, a comprehensive summary of how metal ions guide the assembly of phenolic compounds is lacking. A fundamental understanding of the roles of metal ions in metal-phenolic materials engineering will facilitate the assembly of materials with specific and functional properties. In this review, we focus on the diversity and function of metal ions in metal-phenolic material engineering and emerging applications. Specifically, we discuss the range of underlying interactions, including (i) cation-π, (ii) coordination, (iii) redox, and (iv) dynamic covalent interactions, and highlight the wide range of material properties resulting from these interactions. Applications (e.g., biological, catalytic, and environmental) and perspectives of metal-phenolic materials are also highlighted.

Insight into the Alkali Resistance Mechanism of FeMoTiOx Catalysts for NH3 Selective Catalytic Reduction of NO: Self-Defense Effects of MoOx for Alkali Capture.

The deactivation of selective catalytic reduction (SCR) catalysts caused by alkali metal poisoning remains an insurmountable challenge. In this study, we examined the impact of Na poisoning on the performance of Fe and Mo co-doped TiO2 (FeaMobTiOx) catalysts in the SCR reaction and revealed the related alkali resistance mechanism. On the obtained Fe1Mo2.6TiOx catalyst, the synergistic catalytic effect of uniformly dispersed FeOx and MoOx species leads to remarkable catalytic activity, with over 90% NO conversion achieved in a wide temperature range of 210-410 °C. During the Na poisoning process, Na ions predominantly adsorb on the MoOx species, which exhibit stronger alkali resistance, effectively safeguarding the FeOx species. This preferential adsorption minimizes the negative effect of Na poisoning on Fe1Mo2.6TiOx. Moreover, Na poisoning has little influence on the Eley-Rideal reaction pathway involving adsorbed NHx reacting with gaseous NOx. After Na poisoning, the Lewis acid sites were deteriorated, while the abundant Brønsted acid sites ensured sufficient NHx adsorption. As a benefit from the self-defense effects of active MoOx species for alkali capture, FeaMobTiOx exhibits exceptional alkali resistance in the SCR reaction. This research provides valuable insights for the design of highly efficient and alkali-resistant SCR catalysts.

Boosting N2O Decomposition by Fabricating the Cs-O-Co Structure over Co3O4 with Single-Layer Atoms of Cs.

Developing effective catalysts for N2O decomposition at low temperatures is challenging. Herein, the Cs-O-Co structure, as the active species fabricated by single-layer atoms of Cs over pure Co3O4, originally exhibited great catalytic activity of N2O decomposition in simulated vehicle exhaust and flue gas from nitric acid plants. A similar catalytic performance was also observed for Na, K, and Rb alkali metals over Co3O4 catalysts for N2O decomposition, illustrating the prevalence of alkali-metal-promotion over Co3O4 in practical applications. The catalytic results indicated that the TOF of Co3O4 catalysts loaded by 4 wt% Cs was nearly 2 orders of magnitude higher than that of pure Co3O4 catalysts at 300 °C. Interestingly, the conversions of N2O decomposition over Co3O4 catalysts doped by the same Cs loadings were significantly inhibited. Characterization results indicated that the primary active Cs-O-Co structure was formed by highly orbital hybridization between the Cs 6s and the O 2p orbital over the supported Co3O4 catalysts, where Cs could donate electrons to Co3+ and produce much more Co2+. In contrast, the doped Co3O4 catalysts were dominated by Cs2O2 species; meanwhile, CsOH species was generated by adsorbed water vapor led to a significant decrease in catalytic activity. In situ DRIFTS, rigorous kinetics, and DFT results elaborated the reaction mechanism of N2O decomposition, where the direct decomposition of adsorbed N2O was the kinetically relevant step over supported catalysts in the absence of O2. Meanwhile, the assistance of adsorbed N2O decomposition by activated oxygen was observed as the kinetically relevant step in the presence of O2. The results may pave a promising path toward developing alkali-metal-promotion catalysts for efficient N2O decomposition.