Alkaline Salt Research Articles

The aggregation behavior and structure of blends of κ‐carrageenan and ε‐polylysine hydrochloride

AbstractPolypeptides play a key role in improving food quality, and understanding their interactions with polysaccharides would be beneficial to developing new foods. Herein, κ‐carrageenan (KC) and ε‐polylysine hydrochloride (PLH) were chosen as the model polysaccharide and polypeptide, respectively, to study polysaccharide/polypeptide complexes. The KC/PLH solutions were characterized for turbidity as a function of mass ratio, pH, salts and stirred conditions at 0.5 and 1 mg mL–1 concentrations. The solutions at a KC/PLH mass ratio of 7:3 have the highest turbidity, and the turbidity is stable in acidic conditions, decreases with increase in pH in alkaline conditions and salt concentration, and increases with increase of stirred time and temperature. The Fourier transform infrared spectra suggest that the amide I band of PLH disappears along with a change in the amide II band upon complexing with KC. These changes further influence the microstructure and reveal a rough, non‐uniform and large irregular cavity network structure. Indeed, these observations are intimately associated with the dynamic interactions persistent at the molecular level between the KC and PLH. © 2021 Society of Industrial Chemistry.

Physiological and comparative transcriptome analysis of leaf response and physiological adaption to saline alkali stress across pH values in alfalfa (Medicago sativa)

Soil salinization is a critical factor limiting growth and causing physiological dysfunction in plants. The damage from alkaline salt in most plants is significantly greater than that from neutral salt. However, there is still a lack of research on the action mechanism by which saline alkali stress on plants under the same salt concentration across different pH values. The present study examined the effects of different pH values (7.0, 8.0, 9.0, and 10.0) under the same salt concentration (200 mmolL−1) on photosynthetic function, photoprotective mechanism, nitrogen metabolism, and osmotic regulation in alfalfa (Medicago sativa) leaves, including a transcriptomic analysis of changes in gene expression related to the above metabolic processes. The results showed that low pH saline alkali stress (pH 7.0 and 8.0) promoted chlorophyll synthesis in alfalfa leaves, and non-photochemical quenching (NPQ) and cyclic electron transfer (CEF) were promoted. There was no significant effect on plant growth or photochemical activity. The soluble sugar, proline, and soluble protein contents did not change significantly, and there was no obvious oxidative damage in alfalfa leaves. However, when pH increased to 9.0 and 10.0, KEGG enrichment analysis showed that photosynthesis (map00195) and nitrogen metabolism (map00910) were significantly enriched (P < 0.05), and PSII antenna protein coding genes were down-regulated under pH 9.0 and 10.0 treatments. The activities of PSII and PSI were decreased under high pH saline alkali stress, and the expression levels of the photosynthetic electron transporter-related genes PetA, PetB, petE, and petF were also significantly down-regulated. PSII was more sensitive to high pH saline alkali stress than PSI, and the PSII receptor side was more sensitive to high pH saline alkali stress than the PSII donor side. The activities of the oxygen-evolving complex (OEC) and PSI were significantly damaged only at pH 10.0. The activities of nitrate reductase (NR) and nitrite reductase (NiR), the expression levels of their genes, and the content of soluble protein were also decreased under pH 9.0 and 10.0 treatments. The inhibition of plant growth and oxidative damage to alfalfa leaves caused by high pH saline alkali stress were mainly related to the inhibition of photosynthesis (light energy absorption, electron transfer) and nitrogen metabolism (NO3− reduction). Under high pH saline alkali stress (pH 10.0), the photoprotection mechanisms such as CEF and NPQ were inhibited, which was also one of the important reasons for photoinhibition in alfalfa leaves. The accumulation of osmotic adjustment substances, such as soluble sugar and proline, was an important mechanism by which alfalfa physiologically adapted to high pH alkaline salt stress.

Hydrogen Sulfide Alleviates Alkaline Salt Stress by Regulating the Expression of MicroRNAs in Malus hupehensis Rehd. Roots

Malus hupehensis Rehd. var. pingyiensis Jiang (Pingyi Tiancha, PYTC) is an excellent apple rootstock and ornamental tree, but its tolerance to salt stress is weak. Our previous study showed that hydrogen sulfide (H2S) could alleviate damage in M. hupehensis roots under alkaline salt stress. However, the molecular mechanism of H2S mitigation alkaline salt remains to be elucidated. MicroRNAs (miRNAs) play important regulatory roles in plant response to salt stress. Whether miRNAs are involved in the mitigation of alkaline salt stress mediated by H2S remains unclear. In the present study, through the expression analysis of miRNAs and target gene response to H2S and alkaline salt stress in M. hupehensis roots, 115 known miRNAs (belonging to 37 miRNA families) and 15 predicted novel miRNAs were identified. In addition, we identified and analyzed 175 miRNA target genes. We certified the expression levels of 15 miRNAs and nine corresponding target genes by real-time quantitative PCR (qRT-PCR). Interestingly, H2S pretreatment could specifically induce the downregulation of mhp-miR408a expression, and upregulated mhp-miR477a and mhp-miR827. Moreover, root architecture was improved by regulating the expression of mhp-miR159c and mhp-miR169 and their target genes. These results suggest that the miRNA-mediated regulatory network participates in the process of H2S-mitigated alkaline salt stress in M. hupehensis roots. This study provides a further understanding of miRNA regulation in the H2S mitigation of alkaline salt stress in M. hupehensis roots.

Integrated transcriptomics and metabolomics analysis to characterize alkali stress responses in canola (Brassica napus L.)

BackgroundSoil salinization is a major constraint limiting agricultural development and affecting crop growth and productivity, especially in arid and semi-arid regions. Understanding the molecular mechanism of the adaptability of canola to salt stress is very important to improve the salt tolerance of canola and promote its cultivation in saline alkali soil. ResultsTo identify the metabolomic and transcriptomic mechanisms of canola under alkaline salt stress, we collected roots of control (no salt treatment) and 72 h Na2CO3-stressed canola seedlings (hydroponics) for metabolic profiling of metabolites, supplemented with RNA-Seq analysis and real-time quantitative PCR validation. Metabolomic analysis showed that the metabolites of amino acids and fatty acids were higher accumulated under alkaline salt stress, including L-proline, L-glutamate, L-histidine, L-phenylalanine, L-citrulline, L-tyrosine, L-saccharopine, L-tryptophan, linoleic acid, dihomo gamma linolenic acid, alpha linolenic acid, Eric acid, oleic acid and neuronic acid, while the metabolism of carbohydrate (sucrase, alpha, alpha trehalose), polyol (ribitol), UDP-D-galactose, D-mannose, D-fructose and D-glucose 6-phosphate decreased. Transcriptomic and metabolomic pathway analysis indicated that carbohydrate metabolism may not play an important role in the resistance of canola to alkaline salt stress. Organic acid metabolism (fatty acid accumulation) and amino acid metabolism are important metabolic pathways in the root of canola under alkaline salt stress. ConclusionsThese results suggest that the genes and metabolites involved in fatty acid metabolism and amino acids metabolism in roots of canola may regulate salt tolerance of canola seedlings under alkaline salt stress, which improves our understanding of the molecular mechanisms of salt tolerance in canola.

A Case of Arrowroot Starch Adulteration: Importance of Independent Testing of Dietary Supplements in Clinical Nutrition Research

ObjectivesAdulteration of dietary supplements is widespread and can affect the quality and credibility of clinical nutrition research. In this case report, we describe the difficulties encountered with identity testing of one of our dietary supplements – arrowroot starch – chosen as the placebo for our nutrition intervention trial. MethodsTo test the effect of protein and alkali on skeletal muscle health, we planned a randomized controlled trial using a high protein diet supplement with or without an alkaline salt supplement. The study selected Maranta arundinacea L. (arrowroot) starch as placebo because of its neutral potential renal acid load compared to some other starches. Commercially available samples of arrowroot starch were purchased from three different US distributors. Independent identity testing was conducted by digital microscopy by Alkemist Labs (Garden Grove, CA). ResultsAll three commercially available arrowroot starch samples came with an authentication certificate stating that the starch was derived from the Maranta arundinacea L. plant. On gross examination, the appearance, odor, and consistency of all three samples was similar. On microscopy with digital photo documentation, starch granules from the Maranta arundinacea L. plant range in shape from ovoid, pear-shaped to triangular. The expected size would be 40–75 um and the distinct pattern would have concentric striations and a hilum that resembles a bird or “M”. Surprisingly, we found that only one of the three commercially available arrowroot starch samples was characteristic of Maranta arundinacea L. granules on microscopy. The starch granules from samples from the other two US distributors could not be identified. ConclusionsThis case study reveals the extensive adulteration of commercially available arrowroot starch in the US. It also highlights the importance of third-party, independent testing of dietary supplements to confirm authentication of the product composition especially for clinical nutrition trials. Funding SourcesNIA R01AG055443–03 (Ceglia).

Investigations of Ionic Transport Mechanism of Polyether-Based Polymer Electrolytes for All-Solid-State Batteries

Introduction Recently, renewable energy is expected as new power resource, development of secondary batteries such as high safety and high energy density is desired. Lithium-ion secondary batteries containing the organic electrolyte solution are also desired to improve safety owing to their ignition and liquid properties. Therefore, from the viewpoint of safety, all-solid-state battery have attracted attention. Solid electrolytes are mainly classified into polymer electrolyte (SPE) and inorganic electrolyte. The inorganic electrolytes exhibit relatively high ionic conductivity at room temperature, even though their low mechanical properties. In contrast, ionic conduction of SPE is considered as coupling model from segment motion of ether chain. Furthermore, it has high flexibility and adhesiveness, and achieves suitable interface formation at electrolyte the electrode. However, SPE exhibits relatively low ionic conductivity at room temperature as compared to electrolyte solution. In general, in the case of below glass transition temperature (T g), segmental motion of polymer chain is freezed and also should be stopped ionic motion. Introducing of side chain has reported as method for improving ionic conductivity. The mobility of the side chain is faster and has smaller temperature dependence than segmental motion of main chain. The motion of main chain and side chain are decoupled, carrier ion coordinating to side chain may show the ionic conduct ion below T g. In this study, to investigate ionic conduction behavior below T g, SPE was prepared having side chain with difference chain length. Prepared SPEs were evaluated by physicochemical and electrochemical measurements, respectively. Exerimental SPEs were prepared with LiTFSA as an alkaline salt, polyether-based tri-acrylate macromonomer (P(EO/PO), TA), mono-acrylate monomer (MA, M w=350) in Ar-filled globe box. The mixed solution of TA and MA and LiTFSA ([Li]/[O]=0.1 per molar of oxygen units of P(EO/PO) and MA) were mixed and the solution changed weight ratio to xTA+(10-x)MA (x=10, 8, 6, 4, 2 and 1, respectively). SPE was synthesized by UV irradiation for 5 minutes after addition of DMPA as a photo initiator. The prepared SPEs are expressed as xTA:(10-x)MA (x=10, 8, 6, 4, 2, 1). The prepared SPEs were evaluated for thermal properties by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), and ionic conductivity by the AC impedance method. Result and Discussion Fig.1 shows DSC thermogram of prepared SPE having various segmental compositions. It was confirmed decreasing trend of T g with amount of introduce side chain. Increase of free volume into SPE might be affected for T g changes with introducing side chain. Fig.2 shows the temperature dependence of ionic conductivity of SPE as the Arrhenius-type plots. Ionic conductivity improved by introduction the side chain, and absolutely exsisted ionic conductivity below T g. Temperature dependence of ionic conductivity below T g is extremely smaller than their ionic conductivity over T g. These results suggest that ionic conduction by the motion of the side-chain (β-relaxation) owing to their quite small temperature dependence of mobility below the T g. Figure 1

Increased solubility and functional properties of precipitated Alfalfa protein concentrate subjected to pH shift processes

Protein fractionated from alfalfa exhibits promising properties for exploitation as food ingredient. However, further knowledge and improvement of the functional properties is essential to increase the potential for commercial use. This might be obtained by acid or alkaline pH shift processes. The effect of pH shifting compared to controls (buffer solutions) at different pH-values were investigated concerning protein solubility, foamability, and gelation. The effect of salt (NaCl) concentration was also studied. At pH 12, more cross-linkages were observed as lysinoalanine, lanthionine and also conversion of L-Ser to D-Ser was highest at pH 12. Therefore, the pH-shift method with pH 11 was chosen for further investigation, which increased the solubility from 50% to 70–80%. The alkaline pH shift (pH 11) increased the foam overrun and stability, where pH 7 reached the highest stability with >60% foam volume remaining after 1 h. The protein gel strength showed remarkable potential with the alkaline pH shift method with re-adjusting to pH 7, reaching 2584 Pa with 72 g/L protein. For the acid pH shift with re-adjustment to pH 2 followed by pH 3, the foam overrun increased to 140% and protein solubility to 57% at low protein concentration (2 g/L). Addition of salt (185 mM NaCl) increased the foam overrun at pH 5 and 7 for all samples. Overall, these results indicated that prior alkaline pH treatments and salt can increase the potential of alfalfa protein in terms of certain functionality in foods.

Decreased of calcium oxalate levels in the purple taro flour (Colocasia esculenta) from Aceh Province, Indonesia using three immersion methods

Cocoyam (Araceae family) tuber, like purple taro, traditionally are used as sources of non-rice carbohydrates in Aceh Province, Indonesia. But it contain high calcium oxalate, which contributes to kidney stones formation. Immersion in strong acid (HCl) solution can reduce calcium oxalate. However, it will cause a very strong taste and aroma in cocoyam flour. So, it is necessary to use other immersion methods. This research aimed to examine the effect of the immersion method to reduce calcium oxalate in purple taro flour. The immersion methods used in this research are weak acids (CH3COOH), salt (NaCl), and alkaline salt (NaHCO3). Calcium oxalate, moisture, and ash content were the parameters observed in this study. The result showed that all immersion methods can reduce calcium oxalate levels in purple taro flour. The lowest oxalate content (42.64 mg/100 g) was obtained by the NaHCO3 immersion method. The NaHCO3 had a significant effect to decrease calcium oxalate content in purple flour

De novo transcriptome in roots of switchgrass (Panicum virgatum L.) reveals gene expression dynamic and act network under alkaline salt stress

BackgroundSoil salinization is a major limiting factor for crop cultivation. Switchgrass is a perennial rhizomatous bunchgrass that is considered an ideal plant for marginal lands, including sites with saline soil. Here we investigated the physiological responses and transcriptome changes in the roots of Alamo (alkaline-tolerant genotype) and AM-314/MS-155 (alkaline-sensitive genotype) under alkaline salt stress.ResultsAlkaline salt stress significantly affected the membrane, osmotic adjustment and antioxidant systems in switchgrass roots, and the ASTTI values between Alamo and AM-314/MS-155 were divergent at different time points. A total of 108,319 unigenes were obtained after reassembly, including 73,636 unigenes in AM-314/MS-155 and 65,492 unigenes in Alamo. A total of 10,219 DEGs were identified, and the number of upregulated genes in Alamo was much greater than that in AM-314/MS-155 in both the early and late stages of alkaline salt stress. The DEGs in AM-314/MS-155 were mainly concentrated in the early stage, while Alamo showed greater advantages in the late stage. These DEGs were mainly enriched in plant-pathogen interactions, ubiquitin-mediated proteolysis and glycolysis/gluconeogenesis pathways. We characterized 1480 TF genes into 64 TF families, and the most abundant TF family was the C2H2 family, followed by the bZIP and bHLH families. A total of 1718 PKs were predicted, including CaMK, CDPK, MAPK and RLK. WGCNA revealed that the DEGs in the blue, brown, dark magenta and light steel blue 1 modules were associated with the physiological changes in roots of switchgrass under alkaline salt stress. The consistency between the qRT-PCR and RNA-Seq results confirmed the reliability of the RNA-seq sequencing data. A molecular regulatory network of the switchgrass response to alkaline salt stress was preliminarily constructed on the basis of transcriptional regulation and functional genes.ConclusionsAlkaline salt tolerance of switchgrass may be achieved by the regulation of ion homeostasis, transport proteins, detoxification, heat shock proteins, dehydration and sugar metabolism. These findings provide a comprehensive analysis of gene expression dynamic and act network induced by alkaline salt stress in two switchgrass genotypes and contribute to the understanding of the alkaline salt tolerance mechanism of switchgrass and the improvement of switchgrass germplasm.

Mild and efficient two-step pretreatment of lignocellulose using formic acid solvent followed by alkaline salt

An efficient fractionation of three main components of corn cob and a good delignification effect were reported with formic acid (88%) pretreatment at 80 °C for 3 h. The pretreated substrate demonstrated a poor enzymatic digestibility with a mere 9.1% hydrolysis yield. Subsequently, various post-treatment processes after pretreatment were conducted and the mechanisms behind the effect on the hydrolysis were investigated. During pretreatment, formic acid adsorption occurred, which resulted in a significant inhibiting effect for the hydrolysis of the pretreated substrate. Mild post-treatment quickly removed the easily desorbed formic acid in the solid and cellulose accessibility was found to be increased greatly along with the decrease of formic content. After hot water and alkaline salt post-treatment, the hydrolysis yield increased to 81.2% and 98.5%, respectively. Meanwhile, the formic acid content of the substrate decreased by 15.9% and 61.4%. The restarted hydrolysis performance indicated that the factor associated with the nature of substrate, such as formic acid content, cellulose accessibility, and the existence of ester bonds, should be responsible for the enzymatic digestibility of the substrate. Herein, the proposed two-step pretreatment with formic acid (88%) followed by alkaline salt solution at room temperature demonstrates a remarkable effect on the conversion of lignocellulose material and has high feasibility for industrial application since it is mild to environment and requires low energy.

Enhanced alkali tolerance of rhizobia-inoculated alfalfa correlates with altered proteins and metabolic processes as well as decreased oxidative damage

AimsAlkaline salt is one of the most devastating environmental factors limiting alfalfa productivity, however, the mechanisms underlying adaptation of alfalfa to alkaline remain unclear. Our aim is to investigate proteomic and metabolomic differences in growth and root of alfalfa under alkaline salt in Rhizobium-alfalfa symbiotic relationships. MethodsRhizobium-inoculated and non-inoculated alfalfa plants were treated with 200 mmol/L NaHCO3 to investigate physiological, metabolic, and proteomic responses of root-nodule symbiosis under alkaline-induced stress, using an integrated approach combining metabolome and proteome analysis with measurements of physiological parameters. ResultsThe improved tolerance to alkalinity was observed in RI-plants compared with NI-plants. RI-plants accumulated more proline and MDH, and had higher antioxidant activity and relatively high RWC but low MDA content and low Na+/K+ ratio. The stress-related genes (P5CS, GST13, H+-Ppase, NADP-Me, SDH, and CS) were actively upregulated in RI plants under alkaline stress. In RI-plants, damage caused by alkaline stress was mainly alleviated by decreasing oxidative damage, enhancing the organic acid and amino acid metabolic processes, and scavenging harmful ROS by activating the phenylpropanoid biosynthetic pathway. ConclusionsWe revealed distinct proteins and metabolites related to alkali tolerance in RI-plants compared to NI-plants. Alkali tolerance of rhizobia-inoculated alfalfa was enhanced by altered proteins and metabolic processes as well as decreased oxidative damage.

Mycobiota on exoskeleton debris of Neohelice granulata in an alkaline-sodic salt marsh: in vitro enzyme ability at different temperatures and pH.

This study analysed the mycobiota on exoskeleton debris of the crab Neohelice granulata collected from an alkaline salt marsh and assessed the in vitro enzyme ability of selected isolates at different temperatures and pH. Exoskeleton fragments were incubated in moist chambers on paper and on agar medium. Growth and enzyme ability of selected fungi were also evaluated in agar media with 0.5 % casein, 1% Tween®20, and Chitin-Azure® by the production of a halo/growth ratio. We identified 22 fungal species using both methods. Since the two isolation methods added information to one another, both ones are necessary to recover the cultivable mycobiota associated with the exoskeleton debris. All fungi showed greater levels of enzyme activity in alkaline than acid medium with Tween®20. The halo diameter on casein and chitin varied according to the fungal isolate and pH. Most fungi had a larger halo at 4°C than at the other temperatures tested. Clonostachys rosea showed the greatest activity in all media at 4ºC. We conclude that exoskeletons of the N. granulata are a source of fungi able to produce enzyme activities that show differences upon incubation conditions to which they are cultivated such as ones including specific temperatures and pH values.

Physiological effects of cutting on Secale cereale L. seedlings under freeze–thaw and alkaline salt stress

AbstractSecale cereale L. (rye) as an overwinter forage usually harvested in the autumn, widely grows in the northeastern China, where the temperature varies widely from day to night. In this area, the crop is confronted with not only freeze–thaw stress, but also the soil salinization. In this study, the rye seedlings under alkaline salt (AS) stress were subjected to both cutting treatment (CT) after growing for 7 days and freeze–thaw (FT) stress（10/−5°C) after 6 days regrowth. The changes of soluble protein (SP), malondialdehyde (MDA), relative water content (RWC), catalase (CAT) and superoxide dismutase (SOD) activities in seedlings were studied to analyze the physiological effects of FT and AS stress with CT. The results indicated, under the combined stress, the enzyme activity and RWC decreased and the soluble protein and MDA content increased. Cutting treatment led to the accumulated of MDA, increase of enzyme activity and decrease of RWC in seedlings. The finding from the study indicates that the CT could aggravate the membrane peroxidation under the combined stress of FT and AS and enhance the osmotic adjustment ability of rye and activated the antioxidant enzyme system. The rye having been cut is more sensitive to the compound stress.

Physiological and Transcriptome Analysis of Sugar Beet Reveals Different Mechanisms of Response to Neutral Salt and Alkaline Salt Stresses.

The salinization and alkalization of soil are widespread environmental problems. Sugar beet (B. vulgaris L.) is a moderately salt tolerant glycophyte, but little is known about the different mechanisms of sugar beet response to salt and alkaline stresses. The aim of this study was to investigate the influence of neutral salt (NaCl:Na2SO4, 1:1) and alkaline salt (Na2CO3) treatment on physiological and transcriptome changes in sugar beet. We found that a low level of neutral salt (NaCl:Na2SO4; 1:1, Na+ 25 mM) or alkaline salt (Na2CO3, Na+ 25 mM) significantly enhanced total biomass, leaf area and photosynthesis indictors in sugar beet. Under a high concentration of alkaline salt (Na2CO3, Na+ 100 mM), the growth of plants was not significantly affected compared with the control. But a high level of neutral salt (NaCl: Na2SO4; 1:1, Na+ 100 mM) significantly inhibited plant growth and photosynthesis. Furthermore, sugar beet tends to synthesize higher levels of soluble sugar and reducing sugar to cope with high neutral salt stress, and more drastic changes in indole acetic acid (IAA) and abscisic acid (ABA) contents were detected. We used next-generation RNA-Seq technique to analyze transcriptional changes under neutral salt and alkaline salt treatment in sugar beet. Overall, 4,773 and 2,251 differentially expressed genes (DEGs) were identified in leaves and roots, respectively. Kyoto encyclopedia of genes and genomes (KEGG) analysis showed that genes involving cutin, suberine and wax biosynthesis, sesquiterpenoid and triterpenoid biosynthesis and flavonoid biosynthesis had simultaneously changed expression under low neutral salt or alkaline salt, so these genes may be related to stimulating sugar beet growth in both low salt treatments. Genes enriched in monoterpenoid biosynthesis, amino acids metabolism and starch and sucrose metabolism were specifically regulated to respond to the high alkaline salt. Meanwhile, compared with high alkaline salt, high neutral salt induced the expression change of genes involved in DNA replication, and decreased the expression of genes participating in cutin, suberine and wax biosynthesis, and linoleic acid metabolism. These results indicate the presence of different mechanisms responsible for sugar beet responses to neutral salt and alkaline salt stresses.

Overexpression of transcription factor SlWRKY28 improved the tolerance of Populus davidiana \xd7 P. bolleana to alkaline salt stress

BackgroundWRKY transcription factors (TFs) have been suggested to play crucial roles in the response to biotic and abiotic stresses. This study is the first to report the alkaline salt regulation of the WRKY gene.ResultsIn this study, we cloned a WRKY gene (SlWRKY28) from the Salix linearistipularis and then transferred to the Populus davidiana × P. bolleana for expression. Sequence analysis on the transcriptome of Salix linearistipular showed the significant up-regulation of WRKY gene expression in response to salt-alkali stress in seedlings. Our data showed that SlWRKY28 localized to the nucleus. Furthermore, the expression of the SlWRKY28 from female plants increased with saline-alkali stress according to the northern blot analysis results. The results of 3,3′-Diaminobenzidine (DAB) staining showed that hydrogen peroxide (H2O2) concentration was lower under stress, but ascorbate peroxidase (APX) enzyme activity was significantly higher in the overexpressed plants than that in non-transgenic (NT) plants.ConclusionsWe found out the SlWRKY28 induced regulation of the enzyme gene in the reactive oxygen species (ROS) scavenging pathway is a potential mechanism for transgenic lines to improve their resistance to alkaline salt. This study shows theoretical and practical significance in determining SlWRKY28 transcription factors involved in the regulation of alkaline salt tolerance.

H2S pretreatment mitigates the alkaline salt stress on Malus hupehensis roots by regulating Na+/K+ homeostasis and oxidative stress

Hydrogen sulfide (H2S) plays an important role in the plant salt stress response. The main component of salt stress is neutral salt (NaCl); NaHCO3 and Na2CO3 play a key role in soil alkaline due to the influence of pH. Malus hupehensis Rehd. var. pingyiensis Jiang (Pingyi Tiancha, PYTC) is a salt-sensitive apple rootstock. Seedlings of PYTC pretreated with NaHS (an H2S donor) were exposed to an alkaline salt solution, and then the plant growth, root architecture, oxidative damage, Na+/K+ homeostasis and gene expression of MhSOS1 and MhSKOR were investigated. The results showed that NaHS pretreatment increased the endogenous H2S content in seedlings, significantly alleviated the alkaline salt stress-induced growth inhibition and oxidative damage by inducing antioxidant enzymes activities, and sustained the root activity and root architecture of PYTC in the alkaline salt solution. NaHS pretreatment significantly decreased the root Na+ content and increased K+ content to maintain the homeostasis of Na+/K+, and effect the expression of MhSOS1 and MhSKOR at the transcription level in the presence of the alkaline salt. Our study reveals that application of H2S could mitigate the toxic effect of alkaline salt stress on Malus hupehensis seedlings, thus providing a foundation for improved plant tolerance to alkaline salt stress.

Differences in Physiological Responses of Two Oat (Avena nuda L.) Lines to Sodic-Alkalinity in the Vegetative Stage

Sodic-alkalinity is a more seriously limiting factor in agricultural productivity than salinity. Oat (Avena nuda) is a salt-tolerant crop species and is therefore useful in studying the physiological responses of cereals to alkalinity. We evaluated the differential effects of sodic-alkalinity on two naked oat lines, Caoyou1 and Yanke1. Seedlings of the two lines were exposed to 50 mM alkaline salt mixture of NaHCO3 and Na2CO3 (18:1 molar ratio; pH 8.5) for 2 weeks in a soil environment. Sodic-alkalinity exposure led the assimilation of abundant Na+ at similar concentrations in the organs of both lines. However, Caoyou1 showed much stronger growth than Yanke1, exhibiting a higher dry weight, total leaf area, and shoot height under sodic-alkalinity. Further analysis showed that Caoyou1 was more sodic-alkalinity tolerance than Yanke1. This was firstly because of differences in the oxidative stress defense mechanisms in leaves of the two lines. Antioxidant enzyme activities were either slightly elevated (catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GP), glutathione reductase (GR)) or unaltered (superoxide dismutase (SOD)) in Caoyou1 leaves, but some enzyme (SOD, GPOX, GR) activities were significantly reduced in Yanke1. AnAPX1 transcript levels significantly increased in Caoyou1 under sodic-alkalinity conditions compared with Yanke1, indicating its better antioxidant capacity. Secondly, the related parameters of Mg2+ concentration, phosphoenolpyruvate carboxylase (PEPC) activity, and AnPEPC transcript levels in the leaves showed significantly higher values in Caoyou1 compared with Yanke1. This demonstrated the effective utilization by Caoyou1 of accumulated HCO3− in the irreversible reaction from phosphoenolpyruvate to oxaloacetate to produce inorganic phosphorus, which was elevated in Caoyou1 leaves under alkalinity stress. Overall, the results demonstrated that the greater sodic-alkalinity tolerance of Caoyou1 is the result of: (1) maintained antioxidant enzyme activities; and (2) a higher capacity for the phosphoenolpyruvate to oxaloacetate reactions, as shown by the higher PEPC activity, Mg2+ concentration, and total phosphorus concentration in its leaves, despite the lower soil pH.

A novel self-buffering membrane distillation-based thermophilic anaerobic bioreactor

The stability of an anaerobic bioreactor is a function of alkalinity that provides buffer capacity to maintain a suitable pH for anaerobic microorganisms. The greatest advantage of membrane distillation (MD) is the high rejection of most solutes, including alkaline salt, and it has a high potential to retain alkalinity for the anaerobic system. For the first time, a thermophilic anaerobic granular bioreactor integrated with an MD membrane to maintain the buffered pH was studied in an anaerobic bioreactor without alkalinity supplement. This study presented a comparison between a conventional thermophilic anaerobic bioreactor (TAn1) and a thermophilic anaerobic bioreactor integrated with a MD (TAn2-MD). The two TAns (TAn1 and TAn2) were operated in the same conditions except there was no alkalinity feeding for the TAn2-MD. The results showed that the pH in the TAn2-MD unit was always higher than 6.8 with the organic loading rates from 6 to 18 kg COD/m3/day. However, to maintain the pH of the TAn1 unit at the same level as the TAn2-MD unit, the minimum alkalinity requirements for TAn1 were 1.5, 1.56, 1.62, and 1.8 g/L as CaCO3 at an organic loading rate of 6, 10, 14, and 18 kg COD/m3/day, respectively. Although there was no alkalinity supplement for the TAn2-MD system, two stability indexes, FOS/TAC (volatile organic acids to buffer capacity) and IA/PA (intermediate alkalinity to partial alkalinity), indicated the system was operated at a stable condition. In summary, the designed TAn2-MD can accomplish high-efficiency organic carbon removal (higher than 99.4%) without alkalinity supplement, achieve zero-liquid-discharge, and reclaim high-quality wastewater in one step.

QTL Mapping and Candidate Gene Analysis for Alkali Tolerance in Japonica Rice at the bud Stage Based on Linkage Mapping and Genome-Wide Association Study

BackgroundSalinity-alkalinity stress is one of the major factors limiting rice production. Damage caused by alkaline salt stress is more severe than that caused by neutral salt stress. Alkali tolerance at the bud stage in rice directly affects seedling survival and final yield when using the direct seeding cultivation model. However, genetic resources (QTLs and genes) for rice breeders to improve alkali tolerance are limited. In this study, we combined linkage mapping and a genome-wide association study (GWAS) to analyze the genetic structure of this trait in japonica rice at the bud stage.ResultsA population of 184 recombinant inbred lines (RILs) was utilized to map quantitative trait loci (QTLs) for the root length under control condition (RL), alkaline stress (ARL) and relative root length (RRL) at the bud stage. A major QTL related to alkali tolerance at the rice bud stage, qAT11, was detected on chromosome 11. Interestingly, a GWAS identified a lead SNP (Chr_21,999,659) in qAT11 that was significantly associated with alkaline tolerance. After filtering by linkage disequilibrium (LD), haplotype analysis, quantitative real-time PCR, we obtained three candidate genes (LOC_Os11g37300, LOC_Os11g37320 and LOC_Os11g37390). In addition, we performed phenotype verification on the CRISPR/Cas9 mutant of LOC_Os11g37390.ConclusionBased on these results, LOC_Os11g37300, LOC_Os11g37320 and LOC_Os11g37390 were the candidate genes contributing to alkaline tolerance in japonica rice. This study provides resources for breeding aimed at improving rice responses to alkalinity stress.

Effectiveness of Resistive Vibration Exercise and Whey Protein Supplementation Plus Alkaline Salt on the Skeletal Muscle Proteome Following 21 Days of Bed Rest in Healthy Males.

Muscle atrophy is a deleterious consequence of physical inactivity and is associated with increased morbidity and mortality. The aim of this study was to decipher the mechanisms involved in disuse muscle atrophy in eight healthy men using a 21 day bed rest with a cross-over design (control, with resistive vibration exercise (RVE), or RVE combined with whey protein supplementation and an alkaline salt (NEX)). The main physiological findings show a significant reduction in whole-body fat-free mass (CON -4.1%, RVE -4.3%, NEX -2.7%, p < 0.05), maximal oxygen consumption (CON -20.5%, RVE -6.46%, NEX -7.9%, p < 0.05), and maximal voluntary contraction (CON -15%, RVE -12%, and NEX -9.5%, p < 0.05) and a reduction in mitochondrial enzyme activity (CON -30.7%, RVE -31.3%, NEX -17%, p < 0.05). The benefits of nutrition and exercise countermeasure were evident with an increase in leg lean mass (CON -1.7%, RVE +8.9%, NEX +15%, p < 0.05). Changes to the vastus lateralis muscle proteome were characterized using mass spectrometry-based label-free quantitative proteomics, the findings of which suggest alterations to cell metabolism, mitochondrial metabolism, protein synthesis, and degradation pathways during bed rest. The observed changes were partially mitigated during RVE, but there were no significant pathway changes during the NEX trial. The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium with the dataset identifier PXD006882. In conclusion, resistive vibration exercise, when combined with whey/alkalizing salt supplementation, could be an effective strategy to prevent skeletal muscle protein changes, muscle atrophy, and insulin sensitivity during medium duration bed rest.