Alkaline Stress Research Articles

Identification and Analysis of Long Non-coding RNAs in Leuciscus waleckii Adapted to Highly Alkaline Conditions.

Leuciscus waleckii is a freshwater fish that is known to inhabit the Dali Nor Lake, Inner Mongolia, China. The water in this lake has an HCO3–/CO32– concentration of 54 mM (pH 9.6) and a salinity of 0.6‰. The physiological mechanisms that allow this fish to tolerate these saline/alkaline conditions have yet to be elucidated. Transcriptional component analysis has shown that the expression levels of a large number of genes involved in the pathways responsible for osmo-ionoregulation and arachidonic acid metabolism pathway expression change significantly (p < 0.05) during the regulation of acid–base balance under high alkaline stress. In this study, we investigated the role of long non-coding RNAs (lncRNAs) during adaptation to high alkaline conditions. Fish were challenged to an NaHCO3-adjusted alkalinity of 0 mM, 30 mM (pH 9.44 ± 0.08), and 50 mM (pH 9.55 ± 0.06) for 20 days in the laboratory. Gill and kidney tissues were then collected for high-throughput sequencing assays. A total of 159 million clean reads were obtained by high-throughput sequencing, and 41,248 lncRNA transcripts were identified. Of these, the mean number of exons and the mean length of the lncRNA transcripts were 4.8 and 2,079 bp, respectively. Based on the analysis of differential lncRNA transcript expression, a total of 5,244 and 6,571 lncRNA transcripts were found to be differentially expressed in the gills and kidneys, respectively. Results derived from Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of the coding genes were correlated with the lncRNA expression profiles. GO analysis showed that many lncRNAs were enriched in the following processes: “transporter activity,” “response to stimulus,” and “binding.” KEGG analysis further revealed that metabolic pathways were significantly enriched. A random selection of 16 lncRNA transcripts was tested by RT-qPCR; these results were consistent with our sequencing results. We found that a large number of genes, with the same expression profiles as those with differentially expressed lncRNAs, were associated with the regulation of acid–base balance, ion transport, and the excretion of ammonia and nitrogen. Collectively, our data indicate that lncRNA-regulated gene expression plays an important role in the process of adaptation to high alkaline conditions in L. waleckii.

Differential Morphophysiological, Biochemical, and Molecular Responses of Maize Hybrids to Salinity and Alkalinity Stresses

Salinity and alkalinity stresses are common in arid and semiarid climates. Both these stresses not only retard crop growth but also cause a severe reduction in yields. The present experiment was performed to investigate the morphological, physiological, biochemical, and genetic responses of two maize hybrids (FH-1231 and DK-6714) to salinity and alkalinity stresses. The treatments were comprised of salt stress (NaCl:Na2SO4 at a 9:1 ratio), alkaline stress (NaHCO3:Na2CO3 at a 9:1 ratio), and an unstressed control. The results indicated that salinity and alkalinity significantly reduced shoot fresh weight by 50% and 70%, root fresh weight by 38% and 50%, root dry weight by 69% and 93%, seedling length by 18% and 30%, number of leaves by 27% and 39%, and maximum leaf width by 17% and 24%, respectively, across the two hybrids compared with control, indicating that alkalinity had a greater effect than salinity. Likewise, both the stresses, particularly alkalinity, significantly decreased K+ ion accumulation and chlorophyll content and increased the lipid peroxidation rate, sodium (Na+) concentration, the hydrogen peroxide (H2O2) level, and the activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX). Salinity and alkalinity stresses also induced the expression levels of antioxidant genes (SOD, CAT, POD, APX); however, salinity showed less effect than alkalinity stress. Similarly, hybrid DK-6714 performed comparatively better than FH-1231 with regard to seedling growth, antioxidant activities, and biochemical attributes under stress conditions. Thus, DK-6714 is recommended as a suitable hybrid for soils affected with salt-alkalization.

VTC4 Polyphosphate Polymerase Knockout Increases Stress Resistance of Saccharomyces cerevisiae Cells.

Simple SummaryInorganic polyphosphate, a linear polymer of orthophosphoric acid, plays an important role in microorganisms’ stress resistance. Vtc4 protein synthetizes inorganic polyphosphate in yeast. Here we show that yeast lacking this protein exhibit very low polyphosphate level, decreased resistance to alkaline stress, but increased resistance to oxidative and heavy metal stresses. We suggest the increased stress resistance is achieved by constitutive up-regulation of oxidative stress-response genes and decreased expression of Pho84 that is responsible for manganese uptake.Inorganic polyphosphate (polyP) is an important factor of alkaline, heavy metal, and oxidative stress resistance in microbial cells. In yeast, polyP is synthesized by Vtc4, a subunit of the vacuole transporter chaperone complex. Here, we report reduced but reliably detectable amounts of acid-soluble and acid-insoluble polyPs in the Δvtc4 strain of Saccharomyces cerevisiae, reaching 10% and 20% of the respective levels of the wild-type strain. The Δvtc4 strain has decreased resistance to alkaline stress but, unexpectedly, increased resistance to oxidation and heavy metal excess. We suggest that increased resistance is achieved through elevated expression of DDR2, which is implicated in stress response, and reduced expression of PHO84 encoding a phosphate and divalent metal transporter. The decreased Mg2+-dependent phosphate accumulation in Δvtc4 cells is consistent with reduced expression of PHO84. We discuss a possible role that polyP level plays in cellular signaling of stress response mobilization in yeast.

Effects of Organic Polymer Compound Material on K+ and Na+ Distribution and Physiological Characteristics of Cotton Under Saline and Alkaline Stresses.

Soil salinization and alkalization greatly restrict crop growth and yield. In this study, NaCl (8 g kg−1) and Na2CO3 (8 g kg−1) were used to create saline stress and alkaline stress on cotton in pot cultivation in the field, and organic polymer compound material (OPCM) and stem girdling were applied before cotton sowing and at flowering and boll-forming stage, respectively, aiming to determine the effects of OPCM on K+ and Na+ absorption and transport and physiological characteristics of cotton leaf and root. The results showed that after applying the OPCM, the Na+ content in leaf of cotton under saline stress and alkaline stress were decreased by 7.72 and 6.49%, respectively, the K+/Na+ ratio in leaf were increased by 5.65 and 19.10%, respectively, the Na+ content in root were decreased by 9.57 and 0.53%, respectively, the K+/Na+ ratio in root were increased by 65.77 and 55.84%, respectively, and the transport coefficients of K+ and Na+ from leaf to root were increased by 39.59 and 21.38%, respectively. The activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), and the relative electrical conductivity (REC) in cotton leaf were significantly increased, while the content of malondialdehyde (MDA) was decreased; but the changes in those in root were not significant. The boll weights were increased by 11.40 and 13.37%, respectively, compared with those for the control. After stem girdling, the application of OPCM still promoted the ion transport of cotton organs; moreover, the CAT activity in root was increased by 25.09% under saline stress, and the SOD activity in leaf and CAT in root were increased by 42.22 and 6.91%, respectively under alkaline stress. Therefore, OPCM can significantly change the transport of K+ and Na+ to maintain the K+ and Na+ homeostasis in leaf and root, and regulate physiological and biochemical indicators to alleviate the stress-induced damage. Besides, the regulation effect of OPCM on saline stress was better than that on alkaline stress.

Luliconazole: Stability-indicating LC method, structural elucidation of major degradation product by HRMS and in silico studies

Aim: A new stability-indicating liquid chromatography method was developed and validated for the quantitative determination of luliconazole. Materials and methods: Preliminary forced degradation study demonstrated an additional peak of the degradation product at the same retention time to the drug, due to this, the method was developed optimizing the chromatographic conditions to provide sufficient peak resolution (R ≥ 2). The experimental design was evaluated to assess the robustness and the best chromatographic conditions to be used for the validation. Methodology: Luliconazole solutions were exposed to various stress conditions to evaluate the method indication stability, in which the degradation product (DP-1) formed was isolated, identified, and evaluated in silico to predict degradation pathway and toxicity. The procedure was validated by robustness, selectivity, linearity, precision, and accuracy. Liquid chromatography was performed in a Phenomenex® RP-18 column with a mixture of acetonitrile and 0.3% (v/v) triethylamine solution as a mobile phase in isocratic elution. Results and conclusions: The method demonstrated robustness, good recovery, precision, linear response over a range from 5.0 to 40.0 μg.mL-1, and to be stability indicating. The alkaline stress condition resulted in the formation of DP-1. hrms studies identified this product as an hydroxyacetamide derivative, and in silico studies did not show toxic potential.

Nitric oxide mediates γ-aminobutyric acid-enhanced muskmelon tolerance to salinity–alkalinity stress conditions

Salinity–alkalinity stress severely limits muskmelon production. γ-Aminobutyric acid (GABA) is a free amino acid that enhances crop resistance to environmental stresses. Nitric oxide (NO) is associated with numerous physiological processes and an important signal molecule in plant response to stress. However, whether NO plays roles in GABA-improved salinity–alkalinity tolerance of muskmelon is unclear. Here, we used exogenous sodium nitroprusside (SNP, NO donor) or 2- (4- carboxyphenyl)- 4,4,5,5-tetramethylimidazoline-1- oxyl-3-oxide (cPTIO, a NO scavenger) or GABA to investigate whether NO mediates GABA-induced muskmelon salinity–alkalinity tolerance by regulating antioxidation and Na+/K+ homeostasis to maintain cell membrane stability/integrity. Salinity–alkalinity stress could induce the NO production, and GABA pretreatment also increased NO content, nitrate reductase activity, and NO synthase activity under salinity–alkalinity conditions. Exogenous SNP could increase the activities of antioxidase and mitigate salinity–alkalinity stress inhibited plant growth and decreased the malondialdehyde content, relative electrical conductivity and Na+/K+ ratio in muskmelon. By contrast, pretreatment of plants subjected to salinity–alkalinity stress with cPTIO abolished the GABA-enhanced plant growth and antioxidation, remediation of membrane peroxidation damage, and restoration of ion balance; but no significant effects on endogenous GABA levels. Thus, NO may act as a downstream signal of GABA to stimulate the antioxidant system which then regulate membrane lipid peroxidation and ion homeostasis, and ultimately increase the salinity–alkalinity stress tolerance of muskmelon and promote the plant growth.

RBOH1-dependent H2O2 mediates spermine-induced antioxidant enzyme system to enhance tomato seedling tolerance to salinity–alkalinity stress

Salinity–alkalinity stress is a limiting factor in tomato production in the world. Plants perceive salinity–alkalinity stress by activating signaling pathways to increase plant tolerance (Xu et al., 2020). Here, we investigated whether spermine (Spm) induces respiratory burst oxidase homolog 1 (RBOH1) and hydrogen peroxide (H2O2) signaling in response to salinity–alkalinity stress in tomato. The results showed that exogenous Spm induced the expression of RBOH1 and the accumulation of H2O2 under normal condition. Accordingly, we tested the function of H2O2 signal in tomato seedlings and found that exogenous H2O2 increased the expression levels of Cu/Zn-superoxide dismutase (Cu/Zn-SOD), catalase 1 (CAT1), cytosolic ascorbate peroxidase (cAPX), and glutathione reductase 1 (GR1) and the activities of SOD (EC 1.15.1.1), CAT (EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11), and GR (EC 1.6.4.2) in tomato seedlings under salinity–alkalinity stress. DMTU increased the malondialdehyde (MDA) content and relative electrical conductivity, and the relative water content (RWC), and accelerated leaf yellowing in tomato seedlings under salinity–alkalinity stress, even though we sprayed Spm on tomato leaves. We also found that RBOH1 silencing decreased the expression levels of Cu/Zn-SOD, CAT1, cAPX, and GR1 and the activities of SOD, CAT, APX, and GR when tomato seedlings were under salinity–alkalinity stress. Exogenous Spm did not increase RWC and decrease MDA content in RBOH1 silencing tomato seedlings under salinity–alkalinity stress.

Stability Indicating Method for Known and Unknown Impurities Profiling for Cholecalciferol Tablets

The main objective of this research work was to develop and validate, a new gradient, highly sensitive, specific and stability indicating Reverse Phase HPLC method for quantitative determination of known, unknown impurities and degradant impurities profiling for Cholecalciferol tablets. No Pharmacopoeial method is available to quantify known, unknown impurities and degradants profiling for Cholecalciferol tablets. The impurities were separated on the Hypersil BDS column (150 mm x 4.6mm, 3μm) with a mobile phase of mixture of Trifluoroacetic acid buffer and acetonitrile with flow rate of 1.5 mL minute-1. The column compartment was maintained at 40°C and the detection wavelength was at 265nm. Cholecalciferol, its known impurity and unknown impurities have been well resolved from each other. Recovery of the known and unknown impurities found between 80% to 120% as per ICH guideline. Method found linearity over the working concentration range with acceptance criteria of correlation coefficient greater than 0.99. Method precision and intermediate precision results found with percentage relative standard deviation of impurity content less than 10% for replicated analysis of test samples. A stress study was conducted with a drug product that was exposed to different conditions of acid, base, oxidation, heat, humidity and photolytic degradation. Cholecalciferol was found to degrade significantly under Photolytic, Thermal and Alkaline stress conditions. The degradation products were well resolved from Cholecalciferol and its impurities. For each stress condition, peak purity of Cholecalciferol was assessed using the Photodiode Array detector and found homogeneous in nature. The mass balance for stress study was found in between 95% and 105%. Thus, proving the stability indicating nature of the analytical method. The developed method was validated as per ICH guidelines. The method found accurate, precise, linear, robust, rugged, specific and stability indicating in nature.

A converged pharmaceutical analysis supported with hydrotropy & DoE with dual HPTLC and stress studies for estimation of tolvaptan

The article introduces an inventive, eco-friendly, simple, consistent and coalescing TLC-Densitometry approach to pharmaceutical estimation of Tolvaptan in bulk and tablet matrix. Towards as successful sample preparation and further analysis in both normal and reverse- phases, hydrotropic solubilization was chosen. The determination was performed by employing densitometric estimation using ultraviolet exposure at 271 nm. The separation was achieved on (10 × 10 cm) aluminum backed silica gel 60-F254 and RP-18 F254S as stationary phases separately. Optimized mobile phases were carbon tetrachloride: methanol (3.5: 1.5 v / v); acetonitrile: water (3: 2 v / v) for normal and reverse phase modes respectively. Dual quantitation was conducted over a concentration range of 300–1800 ng/band. The compact and well-resolved bands for the Tolvaptan standard and samples were obtained in both methods at a retention factor (Rf) value of 0.39 ± 0.2 and 0.42 ± 0.2 respectively. In order to examine the stability-indicating characteristics of the process, the compound was subjected to acidic and alkaline, oxidative, film, thermal (dry heat) and neutral stress conditions. Extensive degradation has been observed in conditions with acidic, alkaline and oxidative stress. Box-Behnken design was applied as a DoE approach to evaluate method robustness and to ensure system efficiency. The methods developed were validated according to the International Conference on Harmonization (ICH) for accuracy, robustness and ruggedness.

Aequorin as a Useful Calcium-Sensing Reporter in Candida albicans.

In Candida albicans, calcium ions (Ca2+) regulate the activity of several signaling pathways, especially the calcineurin signaling pathway. Ca2+ homeostasis is also important for cell polarization, hyphal extension, and plays a role in contact sensing. It is therefore important to obtain accurate tools with which Ca2+ homeostasis can be addressed in this fungal pathogen. Aequorin from Aequorea victoria has been used in eukaryotic cells for detecting intracellular Ca2+. A codon-adapted aequorin Ca2+-sensing expression system was therefore designed for probing cytosolic Ca2+ flux in C. albicans. The availability of a novel water-soluble formulation of coelenterazine, which is required as a co-factor, made it possible to measure bioluminescence as a readout of intracellular Ca2+ levels in C. albicans. Alkaline stress resulted in an immediate influx of Ca2+ from the extracellular medium. This increase was exacerbated in a mutant lacking the vacuolar Ca2+ transporter VCX1, thus confirming its role in Ca2+ homeostasis. Using mutants in components of a principal Ca2+ channel (MID1, CCH1), the alkaline-dependent Ca2+ spike was greatly reduced, thus highlighting the crucial role of this channel complex in Ca2+ uptake and homeostasis. Exposure to the antiarrhythmic drug amiodarone, known to perturb Ca2+ trafficking, resulted in increased cytoplasmic Ca2+ within seconds that was abrogated by the chelation of Ca2+ in the external medium. Ca2+ import was also dependent on the Cch1/Mid1 Ca2+ channel in amiodarone-exposed cells. In conclusion, the aequorin Ca2+ sensing reporter developed here is an adequate tool with which Ca2+ homeostasis can be investigated in C. albicans.

Seed germination and biochemical responses of two Elytrigia elongata accessions exposed to abiotic stresses

AbstractElytrigia elongata, a rhizomatous and sparse‐type perennial herb of the Triticeae tribe, with stronger drought and salt tolerance, is an important wild genetic resource for wheat variety improvement. However, no precise information about seed germination and biochemical responses of this species to drought, salinity and mixed saline–alkaline stresses is available. Hence, this experiment was conducted to investigate the effects of three abiotic stresses on seed germination and physiological characteristics of two E. elongata accessions. The results showed that drought and mixed saline–alkaline stresses impair seed germination and bud seedling growth of E. elongata. However, seed germination and bud seedling growth were promoted by 50 mmol/L, but inhibited by 100–200 mmol/L salinity treatments. The malondialdehyde (MDA) content was increased and the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in the bud seedlings were significantly increased (p &lt;.05) with increasing osmotic stress from 0 to −0.4 MPa, and salinity and mixed saline–alkaline from 0 to 150 mmol/L, but reduced at −0.75 MPa osmotic stress and 200 mmol/L salinity and mixed saline–alkaline stresses. Under the same salinity and mixed saline–alkaline treatment, the activities of SOD and CAT of EE030 were higher than those of EE024 except in 200 mmol/L salinity treatment; however, the MDA content of EE030 was lower than that of EE024, except in 150 mmol/L salinity treatment. In conclusion, the results of this study demonstrated that E. elongata seeds are more tolerant to salinity stress than to drought and mixed saline–alkaline stresses, and EE030 seed are more tolerant to three abiotic stresses than are the seeds of EE024.

Identification and Characterization of Osmoregulation Related MicroRNAs in Gills of Hybrid Tilapia Under Three Types of Osmotic Stress.

Researchers have increasingly suggested that microRNAs (miRNAs) are small non-coding RNAs that post-transcriptionally regulate gene expression and protein translation in organs and respond to abiotic and biotic stressors. To understand the function of miRNAs in osmotic stress regulation of the gills of hybrid tilapia (Oreochromis mossambicus ♀ × Oreochromis urolepis hornorum ♂), high-throughput Illumina deep sequencing technology was used to investigate the expression profiles of miRNAs under salinity stress (S, 25‰), alkalinity stress (A, 4‰) and salinity–alkalinity stress (SA, S: 15‰, A: 4‰) challenges. The results showed that 31, 41, and 27 upregulated and 33, 42, and 40 downregulated miRNAs (P < 0.05) were identified in the salt stress, alkali stress, and saline–alkali stress group, respectively, which were compared with those in the control group (C). Fourteen significantly differently expressed miRNAs were selected randomly and then validated by a quantitative polymerase chain reaction. On the basis of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis, genes related to osmoregulation and biosynthesis were enriched in the three types of osmotic stress. In addition, three miRNAs and three predicted target genes were chosen to conduct a quantitative polymerase chain reaction in the hybrid tilapia and its parents during 96-h osmotic stress. Differential expression patterns of miRNAs provided the basis for research data to further investigate the miRNA-modulating networks in osmoregulation of teleost.

Effects of different treatments of pH on growth and photosynthesis of Phoebe bournei seedlings

To provide theoretical basis for the cultivation and landscape application of Phoebe bournei seedlings, the photosynthetic and physiological characteristics of the seedlings were determined in the experience. In this study, the growth, photosynthesis and physiological indexes of P. bournei seedlings under different pH conditions were tested every 15 days for a total of 45 days by using 2-year-old seedlings with different solutions with ph of 4.0, 5.0, 6.0, 7.0, 8.0, 8.5 and 9.0 as 7 different irrigation treatments. The results showed that the growth of P. bournei seedlings grew significantly in acid environment and inhibited in alkaline environment, and the growth rate of plant height in acid environment is significantly higher than natural condition of ph7.0. The chlorophyll and carotenoid contents increase with the increase of acid, and decrease in alkaline environment above ph8.0, which indicate that P. bournei seedlings has better adaptability to acid environment than alkaline environment. The net photosynthetic rate (Pn) and transpiration rate (Tr) of P. bournei seedlings reach the highest level at pH6.0, and the stomatal conductance (Gs) and intercellular CO2 concentration (Ci) reach the highest level at pH 4.0. However, these indicators are low in alkaline environment above pH 8.0. Under acid stress, all physiological indexes of P. bournei are increased; under alkaline stress, the superoxide dismutase (SOD) activity and the soluble protein (SP) content show a trend of increasing, and the peroxidase (POD) activity, MDA content and proline (Pro) show a trend of decreasing later under the treatment of pH 8.5 ~ 9.0. According to all the above, P. bournei seedlings has good tolerance to acid environment, and the suitable pH value of solution for P. bournei seedlings growth is pH 5.0-8.0.

Effects of acid, alkaline, cold, and heat environmental stresses on the antibiotic resistance of the Salmonella enterica serovar Typhimurium

Antibiotic resistance in Salmonella enterica serovar Typhimurium (S. ser. Typhimurium) has become a critical safety hazard in food. Sublethal environmental stresses can influence resistance in Salmonella during food processing. This study simulated environmental stresses in food processing. The antibiotic resistance of three strains of S. ser. Typhimurium (the ATCC 14028 strain and two wild-type isolates from chicken and pork product processing) was evaluated under different pH levels (5.0, 5.5, 6.0, 8.0, and 9.0). Also, dynamic changes in resistance with treatment duration under cold (4 °C, −20 °C) and heat (55 °C) treatment were studied. The results showed that acid and alkaline stresses reduced the resistance of S. ser. Typhimurium to eight antibiotics; meanwhile, the resistance of meropenem (MERO) increased. The minimal inhibitory concentration (MIC) of MERO was increased 16- to 64-fold. With acid or alkaline stress, the extracellular ATP content increased, and the scanning electron microscopy (SEM) result clearly revealed the appearance of wrinkles and holes on the outer membrane of Salmonella. These observations imply changes in membrane permeability, which may decrease the antibiotic resistance of Salmonella. Cold or heat stress increased the resistance of S. ser. Typhimurium to tetracycline, cefotaxime, ceftazidime, nalidixic acid, azithromycin, and ampicillin; the MIC increased 2- to 4-fold. The antibiotic resistance only changed when cold and heat stresses occurred over a certain period of time and remained unchanged when the stress persisted. This study reports on the ability of S. ser. Typhimurium to develop antibiotic resistance after environmental stresses. It can provide valuable information for meat processing to improve interventions and risk management.

Proteomic Responses to Alkali Stress in Oats and the Alleviatory Effects of Exogenous Spermine Application.

Alkali stress limits plant growth and yield more strongly than salt stress and can lead to the appearance of yellow leaves; however, the reasons remain unclear. In this study, we found that (1) the down-regulation of coproporphyrinogen III oxidase, protoporphyrinogen oxidase, and Pheophorbide a oxygenase in oats under alkali stress contributes to the appearance of yellow leaves (as assessed by proteome and western blot analyses). (2) Some oat proteins that are involved in the antioxidant system, root growth, and jasmonic acid (JA) and indole-3-acetic acid (IAA) synthesis are up-regulated in response to alkalinity and help increase alkali tolerance. (3) We added exogenous spermine to oat plants to improve their alkali tolerance, which resulted in higher chlorophyll contents and plant dry weights than in plants subjected to alkaline stress alone. This was due to up-regulation of chitinase and proteins related to chloroplast structure, root growth, and the antioxidant system. Spermine addition increased sucrose utilization efficiency, and promoted carbohydrate export from leaves to roots to increase energy storage in roots. Spermine addition also increased the IAA and JA contents required for root growth.

RETRACTED ARTICLE: Effects of saline-alkali stress on seed germination of Haloxylon ammodendron and Nitraria roborowskii Kom in Qaidam Basin

This article has been retracted from publication in the Taylor & Francis journal, Acta Agriculturae Scandinavica, Section B — Soil & Plant Science. Following publication, concerns were raised by multiple third-parties around the content of the special issue and the decision-making process. Following an investigation by the Taylor & Francis Publishing Ethics & Integrity team in full cooperation with the Editor-in-Chief, it was confirmed that this article included in Special Issue titled “ Envisage Computer Modelling and Statistics for Agriculture”, guest edited by Gunasekaran Manogaran was not peer-reviewed appropriately, in line with the Journal's peer review standards and policy. As the stringency of the peer review process is core to the integrity of the publication process, the Editor and Publisher have decided to retract all of the articles within the above-named Special Issue. The journal has not confirmed if the authors were aware of this compromised peer review process. The journal is committed to correcting the scientific record and will fully cooperate with any institutional investigations into this matter. The authors have been informed of this decision. We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines.

The Adjustment of Membrane Lipid Metabolism Pathways in Maize Roots Under Saline-Alkaline Stress.

Plants are frequently confronted by diverse environmental stress, and the membrane lipids remodeling and signaling are essential for modulating the stress responses. Saline–alkaline stress is a major osmotic stress affecting the growth and development of crops. In this study, an integrated transcriptomic and lipidomic analysis was performed, and the metabolic changes of membrane lipid metabolism in maize (Zea mays) roots under saline–alkaline stress were investigated. The results revealed that phospholipids were major membrane lipids in maize roots, and phosphatidylcholine (PC) accounts for approximately 40% of the total lipids. Under 100 mmol NaHCO3 treatment, the level of PC decreased significantly (11–16%) and the parallel transcriptomic analysis showed an increased expression of genes encoding phospholipase A and phospholipase D/non-specific phospholipase C, which suggested an activated PC turnover under saline–alkaline stress. The plastidic galactolipid synthesis was also activated, and an abnormal generation of C34:6 galactolipids in 18:3 plants maize implied a plausible contribution from the prokaryotic pathway, which could be partially supported by the up-regulated expression of three putative plastid-localized phosphatidic acid phosphatase/lipid phosphate phosphatase. A comprehensive gene–metabolite network was constructed, and the regulation of membrane lipid metabolism under saline–alkaline stress in maize was discussed.

Cotton transcriptome analysis reveals novel biological pathways that eliminate reactive oxygen species (ROS) under sodium bicarbonate (NaHCO3) alkaline stress

Alkaline stress is one of the abiotic stresses limiting cotton production. Though RNA-Seq analyses, have been conducted to investigate genome-wide gene expression in response to alkaline stress in plants, the response of sodium bicarbonate (NaHCO3) stress-related genes in cotton has not been reported. To explore the mechanisms of cotton response to this alkaline stress, we used next-generation sequencing (NGS) technology to study transcriptional changes of cotton under NaHCO3 alkaline stress. A total of 18,230 and 11,177 differentially expressed genes (DEGs) were identified in cotton roots and leaves, respectively. Gene ontology (GO) analysis indicated the enrichment of DEGs involved in various stimuli or stress responses. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that DEGs associated with plant hormone signal transduction, amino acid biosynthesis, and biosynthesis of secondary metabolites were regulated in response to the NaHCO3 stress. We further analyzed genes enriched in secondary metabolic pathways and found that secondary metabolites were regulated to eliminate the reactive oxygen species (ROS) and improve the cotton tolerance to the NaHCO3 stress. In this study, we learned that the toxic effect of NaHCO3 was more profound than that of NaOH at the same pH. Thus, Na+, HCO3− and pH had a great impact on the growth of cotton plant. The novel biological pathways and candidate genes for the cotton tolerance to NaHCO3 stress identified from the study would be useful in the genetic improvement of the alkaline tolerance in cotton.

Morphological and Physiological Traits Related to the Response and Adaption of Bolboschoenus planiculmis Seedlings Grown Under Salt-Alkaline Stress Conditions.

Soil saline-alkalization is expanding and becoming a serious threat to the initial establishment of plants in inland salt marshes on the Songnen Plain in Northeast China. Bolboschoenus planiculmis is a key wetland plant in this area, and its root tubers provide food for an endangered migratory Siberian crane (Grus leucogeranus). However, the survival of this plant in many wetlands is threatened by increased soil saline-alkalization. The early establishment of B. planiculmis populations under salt and alkaline stress conditions has not been well understood. The aim of this study was to investigate the response and adaption of the seedling emergence and growth of B. planiculmis to salt-alkaline mixed stress. In this study, B. planiculmis root tubers were planted into saline-sodic soils with five pH levels (7.31–7.49, 8.48–8.59, 9.10–9.28, 10.07–10.19, and 10.66–10.73) and five salinity levels (40, 80, 120, 160, and 200 mmol⋅L–1). The emergence and growth metrics, as well as the underlying morphological and physiological traits in response to salt-alkaline stress were explored for 2-week-old seedlings. The seedling emergence, growth, and leaf and root traits showed distinct responses to the pH and salt gradients. Under the lower saline-alkaline condition (pH ≤ 9.10–9.28 and salinity ≤ 80 mmol⋅L–1), the seedling growth was substantially facilitated or not significantly altered. Salinity affected the seedlings more significantly than alkalinity did. In particular, among the salt ions, the Na+ concentration had predominantly negative effects on all the morphological and physiological traits of the seedlings. Seedling emergence was more tolerant to salinity and, based on its observed close relationships with pH and the alkaline ion CO32–, was highly alkalinity-dependent. Moreover, the leaf area and photosynthetic rate, as well as the root surface area and tip number mainly accounted for the response of the seedling biomass to salt-alkaline stress. This is evidence of the adaption of B. planiculmis to saline-alkaline conditions largely due to the responses of its morphological and physiological traits. This study provides a mechanistic process-based understanding of the early seedling establishment of B. planiculmis populations in response to increased soil saline-alkalization in natural wetlands.

Inhibition of nitric oxide production under alkaline conditions regulates iron homeostasis in rice.

Rice is one of the most susceptible plants to iron (Fe) deficiency under neutral and alkaline conditions. Alkaline stress induces H2 O2 production and increases the deposition of Fe on the root surface, which causes leaf chlorosis and Fe deficiency in rice. Gene chip and qRT-PCR analysis indicated that the expression of the nitrate reductase (NR) genes were downregulated by alkaline treatment, which resulted in significantly decreased nitrate activity and nitric oxide (NO) production in the epidermis and stele, where H2 O2 accumulated. In contrast, treatment with sodium nitroprusside (SNP), a NO donor, strongly alleviated alkaline-induced Fe deficiency by limiting Fe plaque formation. Increasing the NO signal significantly reduced the accumulation of H2 O2 and the lignin barrier but enhanced phenolic acid secretion in the root epidermis and stele under alkaline conditions. The secreted phenolic acid effectively mobilized the apoplast Fe and increased Fe uptake in roots, thereby alleviating the Fe-deficiency response and downregulating the expressions of Fe-uptake genes under alkaline conditions. In conclusion, alkaline stress inhibits NR activity and NO production in the roots of rice, which play vital roles in the mobilization of the apoplast Fe by regulation of H2 O2 and phenolic acid concentrations.