Alkaline Tolerance Research Articles

Bacillus licheniformis SA03 Confers Increased Saline-Alkaline Tolerance in Chrysanthemum Plants by Induction of Abscisic Acid Accumulation.

Soil saline-alkalization is a major abiotic stress that leads to low iron (Fe) availability and high toxicity of sodium ions (Na+) for plants. It has recently been shown that plant growth promoting rhizobacteria (PGPR) can enhance the ability of plants to tolerate multiple abiotic stresses such as drought, salinity, and nutrient deficiency. However, the possible involvement of PGPR in improving saline–alkaline tolerance of plants and the underlying mechanisms remain largely unknown. In this study, we investigated the effects of Bacillus licheniformis (strain SA03) on the growth of Chrysanthemum plants under saline–alkaline conditions. Our results revealed that inoculation with SA03 alleviated saline–alkaline stress in plants with increased survival rates, photosynthesis and biomass. The inoculated plants accumulated more Fe and lower Na+ concentrations under saline–alkaline stress compared with the non-inoculated plants. RNA-Sequencing analyses further revealed that SA03 significantly activated abiotic stress- and Fe acquisition-related pathways in the stress-treated plants. However, SA03 failed to increase saline–alkaline tolerance in plants when cellular abscisic acid (ABA) and nitric oxide (NO) synthesis were inhibited by treatment with fluridone (FLU) and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO), respectively. Importantly, we also found that NO acted downstream of SA03-induced ABA to activate a series of adaptive responses in host plants under saline–alkaline stress. These findings demonstrated the potential roles of B. licheniformis SA03 in enhancing saline–alkaline tolerance of plants and highlighted the intricate integration of microbial signaling in regulating cellular Fe and Na+ accumulation.

The synthesis and electro-catalytic activity for ORR of the structured electrode material: CP/Fe-N-CNFs

The structured electrode has the advantages of polymer binder-free, non-precious-metal and without multiple and tedious manual assembly, exhibiting superior electro-catalytic activity for oxygen reduction reactions (ORR), compared with the traditional ink-based electrode. The structured CP/Fe-N-CNFs (Fe and N containing carbon nanofibers (CNFs) in-situ grown on carbon paper (CP)), has been one-step synthesized by chemical vapor deposition (CVD). In this paper, it can be concluded that the structured CP/Fe-N-CNFs with 0.30 at.% Fe-Nx moieties exerts the most positive onset-potential (−0.05 V), peak potential, and largest peak current density. The measured current density of the structured Fe-N-CNFs at −0.8 V is increased by 56.3% compared to that of the traditional Fe-N-CNFs. The traditional Fe-N-CNFs exhibit stronger alkaline tolerance comparing with commercial Pt electrode. That is, the pronounced catalytic activity of the structured Fe-N-CNFs might attribute to the homogeneous and undiluted active sites compared to that of the traditional Fe-N-CNFs.

Analysis of differentially expressed genes and adaptive mechanisms of Prunus triloba Lindl. under alkaline stress

BackgroundPrunus triloba Lindl. is a naturally salt-alkaline-tolerant plant with several unique characteristics, and it can be used as the rootstock of Chinese plum (Prunus salicina Lindl.) in saline-alkaline soils. To comprehensively investigate the alkaline acclimation mechanisms in P. triloba, a series of analyses were conducted under alkaline stress, including analyses of the kinetics of molecular and physiological changes, and leaf microstructure.ResultsTo understand the kinetics of molecular changes under short-term alkaline stress, we used Illumina HiSeq 2500 platform to identify alkaline stress-related differentially expressed genes (DEGs) in P. triloba. Approximately 53.0 million high-quality clean reads were generated from 59.6 million raw reads, and a total of 124,786 unigenes were obtained after de novo assembly of P. triloba transcriptome data. After alkaline stress treatment, a total of 8948 unigenes were identified as DEGs. Based on these DEGs, a Gene Ontology (GO) enrichment analysis was conducted, suggesting that 28 genes may play an important role in the early alkaline stress response. In addition, analysis of DEGs with the Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that pathways were significant at different treatment time points. A significant positive correlation was found between the quantitative real-time PCR (qRT-PCR) results and the RNA-Seq data for seven alkaline-related genes, confirming the reliability of the RNA-Seq results. Based on physiological analysis of P. triloba in response to long-term alkaline stress, we found that the internal microstructures of the leaves of P. triloba changed to adapt to long-term alkaline stress. Various physiological indexes indicated that the degree of membrane injury increased with increasing duration of alkaline stress, affecting photosynthesis in P. triloba seedlings.ConclusionsThis represents the first investigation into the physiology and transcriptome of P. triloba in response to alkaline stress. The results of this study can enrich the genomic resources available for P. triloba, as well as deepening our understanding of molecular and physiological alkaline tolerance mechanisms in P. triloba. This will also provide new insights into our understanding of alkaline acclimation mechanisms in Chinese plum (Prunus salicina) trees.

Bacillus sphaericus LMG 22257 is physiologically suitable for self-healing concrete.

The suitability of using a spore-forming ureolytic strain, Bacillus sphaericus, was evaluated for self-healing of concrete cracks. The main focus was on alkaline tolerance, calcium tolerance, oxygen dependence, and low-temperature adaptability. Experimental results show that B. sphaericus had a good tolerance. It can grow and germinate in a broad range of alkaline pH. The optimal pH range is 7∼9. High alkaline conditions (pH 10∼11) slow down but not stop the growth and germination. Oxygen was strictly needed during bacterial growth and germination, but not an essential factor during bacterial urea decomposition. B. sphaericus also had a good Ca tolerance, especially at a high bacterial concentration of 108cells/mL; no significant influence was observed on bacterial ureolytic activity of the presence of 0.9M Ca2+. Furthermore, at a low temperature (10°C), bacterial spores germinated and revived ureolytic activity with some retardation. However, this retardation can be counteracted by using a higher bacterial concentration and by supplementing yeast extract. It can be concluded that B. sphaericus is a suitable bacterium for application in bacteria-based self-healing concrete.

GsJ11, identified by genome-wide analysis, facilitates alkaline tolerance in transgenic plants

DnaJ/Hsp40, one of molecular chaperones heat shock proteins (Hsps), is a kind of key components to contribute in cellular homeostasis under adverse growth conditions. However, until now, only few researches focus on its functions under alkaline stress response which tremendously inhibit plant growth and development, especially the DnaJ genes from wild soybean. In this study, we identified and characterized 196 DnaJ genes in soybean genome. We determined sequence information, conserve domains, gene structure, evolutionary relationship and chromosomal location of all the family members. Then, we investigated the expression profiles of DnaJ family genes in wild soybean under alkaline stress. According to heat map and our previous RNA-seq data, GsJ11, significantly induced by NaHCO3 treatment, was further selected. Moreover, we determined the temporal and spatial expression patterns of GsJ11 in wild soybean and characterized its physiological functions by using transgenic Arabidopsis and atj11 mutant Arabidopsis. Our results suggest that GsJ11 was moderately expressed in roots of wild soybean and could highly be induced by NaHCO3 in 3 h, and its Arabidopsis overexpression lines exhibited higher but the atj11 mutant lines showed lower tolerance to NaHCO3 than the WT line. Furthermore, we found that the transcript levels of stress-inducible genes were up-regulated in GsJ11 overexpression lines. Taken together, our results demonstrate that GsJ11 acts as a positive regulator in plant responses to bicarbonate alkaline stress.

Enhancement of thermostability of Bacillus subtilis endoglucanase by error-prone PCR and DNA shuffling

The Bacillus subtilis endo-β-1,4-glucanase gene (beg), which encodes the enzyme BEG that comprises 499 amino acid residues, was mutated by error-prone polymerase chain reaction and DNA shuffling to make variants with improved functionalities. The mutated DNAs were transformed into Escherichia coli DH5α, and among the 1370 transformants, a positive clone 8-20 was obtained finally based on a halo assay and thermostability and alkaline tolerance analyses. The mutated enzyme BEG8-20 of clone 8-20 was changed at seven amino acid residues compared to the wild-type enzyme BEGwt: K45E, I102Y, M112V, D226Y, D295E, L423S, and D460G. The optimum temperature and pH of BEG8-20 were nearly the same as those of BEGwt. However, the thermostability of BEG8-20 was increased 1.53-fold (21.4 min vs. 14.0 min) based on the half-life of the residual activity at 70 °C. This increase in enzyme thermostability is advantageous for the hydrolysis of lignocellulosic materials to produce fermentable sugars. In the activity staining experiment, only a truncated smaller enzyme was observed for BEG8-20, whereas two forms, a matured (52 kDa) and a truncated smaller (34.5 kDa) enzyme, were observed for BEGwt owing to proteolytic internal cleavage at the linker region between the 297th and 356th amino acid residues. These results indicate that amino acid substitutions in the mutant enzyme have rendered the protein prone to cleavage at the C-terminal region.

Cloning of Gene GsWRKY15 Related to Alkaline Stress and Alkaline Tolerance of Transgenic Plants

Cloning of Gene <i>GsWRKY15</i> Related to Alkaline Stress and Alkaline Tolerance of Transgenic Plants

Functional analysis of PrkA - a putative serine protein kinase from Mesorhizobium alhagi CCNWXJ12-2 - in stress resistance.

BackgroundSerine/threonine protein kinases are highly conserved kinases with a wide distribution in microbes and with multiple functions. Mesorhizobium alhagi CCNWXJ12-2, a α-proteobacterium which could be able to form symbiosis with Alhagi sparsifolia in northwest of China, contains a putative PrkA-family serine protein kinase, PrkA. In our previous study, the expression of prkA was found to be downregulated in high-salt conditions. To elucidate the function of M. alhagi PrkA, a prkA deletion mutant was constructed and the phenotypes of the mutant were analyzed.ResultsThe salt and alkaline tolerance and antioxidant capacity of the wild-type strain and the prkA deletion mutant was measured. Our results showed that the deletion mutant had higher salt and alkaline tolerance than the wild-type strain. The total cellular Na+ content was measured and showed no significant difference between the wild-type strain and the mutant. The prkA deletion mutant also showed a higher H2O2 tolerance than the wild-type strain. Therefore the activities of antioxidant enzymes were measured. Catalase activity was similar in the wild-type and the deletion mutant, while the superoxide dismutase activity in the mutant was higher than that in the wild-type.ConclusionsWe firstly analyze the function of a serine protein kinase, PrkA, in M. alhagi. Our data indicate that PrkA could reduce the survival of M. alhagi under environmental stress and deletion of prkA dramatically improved the salt and alkaline tolerance and antioxidant capacity of M. alhagi.

The alkaline tolerance in Lotus japonicus is associated with mechanisms of iron acquisition and modification of the architectural pattern of the root

The response of fifty-four Lotus japonicus ecotypes, and of six selected ecotypes was investigated under alkaline conditions. Sensitive, but not tolerant ecotypes, showed interveinal chlorosis under all alkalinity conditions and high mortality under extreme alkalinity. Interveinal chlorosis was associated with Fe deficiency, as a reduced Fe2+ shoot content was observed in all sensitive ecotypes. In addition, some showed a decline in photosynthesis rate and PSII performance compared to the control. In contrast, some tolerant ecotypes did not change these parameters between treatments. Alkaline tolerance could be explained by a mechanism of Fe acquisition and a root structural modification. This conclusion was based on the fact that all tolerant, but not the sensitive ecotypes, presented high ferric reductase oxidase activity under alkaline stress compared to the control, and a Herringbone root pattern modification. On this basis, the analysis of these mechanisms of alkaline tolerance could be used in screening programs for the selection of new tolerant genotypes in the Lotus genus.

Dual-cation comb-shaped anion exchange membranes: Structure, morphology and properties

Anion exchange membranes (AEMs) are employed as the gas separator and hydroxide ion conductor between the anode and the cathode of alkaline polyelectrolyte fuel cell (APEFC). Highly conductive and stable AEMs are urgently needed in order to achieve satisfactory fuel cell performance. Nevertheless, the low hydroxide conductivity remains major challenge that limits the development and application of APEFC. In order to improve the hydroxide conductivity of AEMs, highly ordered ion conducting channels must be constructed within the membrane matrix. In this study, an AEM with particular polymer structure was designed to achieve fine ion conducting channels by facilitating the hydrophilic-hydrophobic phase separation. Concretely, the side chain of this polyelectrolyte contains two quaternary ammonium groups and terminates with one long hydrophobic tail. Ascribing to the enhanced nano-phase separation ability, inter-connected ion conducting channels were observed by AFM as well as SAXS. A high hydroxide conductivity of 47mS/cm at 25°C and 85mS/cm at 80°C was achieved. In addition, when applied in an APEFC system, the synthesized AEM showed an outstanding peak power density of 369.3mW/cm2. Good alkaline tolerance, lowered water uptake and swelling ratio were also observed attributing to its carefully designed polymer structure.

The Conserved DedA/Tvp38 Membrane Protein Family Plays a Role in Antibiotic Resistance in Pseudomonas aeruginosa

The highly conserved DedA/Tvp38 family of membrane proteins (DedA for short) is found in most bacterial species. Our laboratory has characterized DedA family members in the model organism Escherichia coli where deletion of the gene encoding one member of this family, YqjA, results in a sensitivity to alkaline pH. Additional deletion of a gene encoding a partially redundant protein YghB, with 62% amino acid sequence identity to YqjA, results in several phenotypes including a cell division defect and sensitivity to certain antibiotics and toxic compounds that are effluxed via known proton motive force (PMF) energized transporters. Based on these and other results we hypothesize that the DedA family is a new family of proton‐dependent membrane transporters.Pseudomonas aeruginosa is an opportunistic pathogen that is a major concern in hospitals as a nosocomial infection that easily takes advantage of weakened immune systems of patients. It is prevalent in burn wards, as well as among cancer patients, but it is most commonly associated with cystic fibrosis patients. Due to extensive drug resistance, this pathogen is notoriously difficult to treat. This is due in part to a multitude of PMF dependent antibiotic extrusion pumps from the multidrug and toxic compound extrusion (MATE) family, major facilitator superfamily (MFS), small multidrug resistance (SMR) family and the resistance‐nodulation‐division (RND) family. We therefore were interested in studying the effect of loss of DedA family members on drug resistance of P. aeruginosa.The genome of Pseudomonas aeruginosa PAO1 encodes five proteins belonging to the DedA family: PA1209, PA2752, PA4011, PA4029, and PA5244 (denoted PDedA1, PDedA2, PDedA3, PDedA4, and PDedA5, respectively). Transposon insertion mutants in each gene were acquired from the Manoil lab at the University of Washington. These studies were carried out by plating serial dilutions of strains on selective media and by directly measuring the minimal inhibitory concentrations (MIC) of antibiotics against the mutants. P. aeruginosa DedA family transposon mutants were each found to be 3–16 fold more sensitive to the clinically relevant fluoroquinolones antibiotics, ciprofloxacin and norfloxacin, as well as to acriflavine, chloramphenicol, and nalidixic acid as compared to the wild type.We also asked whether the P. aeruginosa DedA family genes could function in E. coli by measuring their ability to correct the phenotypes of E. coli DedA family mutants. We report that overexpression of PDedA4 and PDedA5 is able to correct the cell division defect and the antibiotic sensitivity of E. coli DyqjA, DyghB (denoted strain BC202). In addition, overexpression of these genes restores alkaline tolerance to the alkaline sensitive strain ΔyqjA.We conclude that DedA/Tvp38 family proteins are required for antibiotic resistance of Pseudomonas aeruginosa and at least two (PDedA4 and PDedA5) share common functions with and can substitute for Escherichia coli YqjA and YghB.

A mechanically robust anion exchange membrane with high hydroxide conductivity

As a key component of various electrochemical systems, such as alkaline polyelectrolyte fuel cells (APEFCs), flow batteries and electrolyzers, anion exchange membranes (AEMs) need to be both mechanically robust and highly conductive to hydroxide ions. In this work, a polyelectrolyte with a particular polymer structure was designed by combining phase-separation architecture and a crosslinking strategy to improve both the mechanical properties and hydroxide conductivity. The side chain of this type of polyelectrolyte was incorporated by two quaternary ammonium groups and terminated with a cross-linkable unsaturated bond. After being simply heated at 80°C for 24h, the crosslinked AEMs exhibited enhanced tensile strength ranging from 23.1MPa to 14.7MPa under hydrated conditions. These values are several times higher than the values of conventional AEMs. As a result of the high flexibility and hydrophilicity of the dual-cation-functionalized side chain, an outstanding hydroxide conductivity was observed (43mS/cm at room temperature and 88.7mS/cm at 80°C). Also considering its good dimensional stability and satisfying alkaline tolerance, this strategy combining phase separation architecture and crosslinking has perfectly solved the several obstacles blocking the development of AEMs and thus possesses a great potential for practical application.

Electrochemical Cr(III) Oxidation and Mobilization by In Situ Generated Reactive Oxygen Species in Alkaline Solution

A novel electrochemical chromium oxidation strategy by in situ electro-generated reactive oxygen species was developed in this study. Activated multi-walled carbon nanotubes modified electrode was employed to produce H2O2 via two-electron-pathway oxygen reduction reaction with onset potential of −0.06 V (vs Hg/HgO) and peak current density of 1.54 mA·cm−2. The H2O2 formation was confirmed by selective luminescent probes with UV-vis spectroscopy, and the Cr(III) can be efficiently oxidized by the as formed H2O2. Interestingly, ·OH can also be obtained by the Cr(III)-induced Fenton-like reaction, and offer further oxidative stress to enhance the Cr(III) oxidation. Consequently, a significantly enhanced Cr(III) conversion of 98.5 ± 1.0% was achieved in this indirect oxidation as compared to 29.8 ± 1.3% in the corresponding direct electrochemical oxidation. Besides, indirect pathway exhibited a considerable improvement for the Cr(III) oligomers oxidation (from 17.6 ± 1.0% to 93.5 ± 1.5%), indicating a potential solution to overcome the polymerization bottleneck of Cr(III) oxidation. Moreover, the electrolysis current well maintained the original value after stability test, suggesting favorable alkaline tolerance. The proposed method provided a cleaner approach for Cr(III) oxidative mobilization in alkaline media, and new insight on the redox cycle of electro-generated reactive oxygen species.

An ENA ATPase, MaENA1, of Metarhizium acridum influences the Na+-, thermo- and UV-tolerances of conidia and is involved in multiple mechanisms of stress tolerance

In fungi, ENA ATPases play key roles in osmotic and alkaline pH tolerance, although their functions in thermo- and UV-tolerances have not been explored. Entomopathogenic fungi are naturally widespread and have considerable potential in pest control. An ENA ATPase gene, MaENA1, from the entomopathogenic fungus Metarhizium acridum was functionally analyzed by deletion. MaENA1-disruption strain (ΔMaENA1) was less tolerant to NaCl, heat, and UV radiation than a wild-type strain (WT). Digital Gene Expression profiling of conidial RNAs resulted in 281 differentially expressed genes (DEGs) between the WT and ΔMaENA1 strains. Eighty-five DEGs, 56 of which were down-regulated in the ΔMaENA1 strain, were shown to be associated with heat/UV tolerance, including six cytochrome P450 superfamily genes, 35 oxidoreductase genes, 24 ion-binding genes, seven DNA repair genes, and five other genes. In addition, eight genes were components of stress responsive pathways, including the Ras-cAMP PKA pathway, the RIM101 pathway, the Ca2+/calmodulin pathway, the TOR pathway, and the HOG/Spc1/Sty1/JNK pathway. These results demonstrated that MaENA1 influences fungal tolerances to Na+, heat, and UV radiation in M. acridum, and is involved in multiple mechanisms of stress tolerance. Therefore, MaENA1 is required for the adaptation and survival of entomopathogenic fungi in stressful conditions in the environment and in their hosts.

A Novel Methodology to Synthesize Highly Conductive Anion Exchange Membranes.

Alkaline polyelectrolyte fuel cell now receives growing attention as a promising candidate to serve as the next generation energy-generating device by enabling the use of non-precious metal catalysts (silver, cobalt, nickel et al.). However, the development and application of alkaline polyelectrolyte fuel cell is still blocked by the poor hydroxide conductivity of anion exchange membranes. In order to solve this problem, we demonstrate a methodology for the preparation of highly OH− conductive anion exchange polyelectrolytes with good alkaline tolerance and excellent dimensional stability. Polymer backbones were grafted with flexible aliphatic chains containing two or three quaternized ammonium groups. The highly flexible and hydrophilic multi-functionalized side chains prefer to aggregate together to facilitate the formation of well-defined hydrophilic-hydrophobic microphase separation, which is crucial for the superior OH− conductivity of 69 mS/cm at room temperature. Besides, the as-prepared AEMs also exhibit excellent alkaline tolerance as well as improved dimensional stability due to their carefully designed polymer architecture, which provide new directions to pursue high performance AEMs and are promising to serve as a candidate for fuel cell technology.

Ectopic Expression of a Glycine soja myo-Inositol Oxygenase Gene (GsMIOX1a) in Arabidopsis Enhances Tolerance to Alkaline Stress.

Myo-inositol participates in various aspects of plant physiology, and myo-inositol oxygenase is the key enzyme of the myo-inositol oxygenation pathway. Previous studies indicated that myo-inositol oxygenase may play a role in plant responses to abiotic stresses. In this study, we focused on the functional characterization of GsMIOX1a, a remarkable alkaline stress-responsive gene of Glycine soja 07256, based on RNA-seq data. Using quantitative real-time PCR, we demonstrated that GsMIOX1a is rapidly induced by alkaline stress and expressed predominantly in flowers. We also elucidated the positive function of GsMIOX1a in the alkaline response in the wild type, atmiox1 mutant as well as GsMIOX1a-overexpressing Arabidopsis. We determined that atmiox1 mutant decreased Arabidopsis tolerance to alkaline stress, whereas GsMIOX1a overexpression increased tolerance. Moreover, the expression levels of some alkaline stress-responsive and inducible marker genes, including H+-Ppase, NADP-ME, KIN1 and RD29B, were also up-regulated in GsMIOX1a overexpression lines compared with the wild type and atmiox1 mutant. Together, these results suggest that the GsMIOX1a gene positively regulates plant tolerance to alkaline stress. This is the first report to demonstrate that ectopic expression of myo-inositol oxygenase improves alkaline tolerance in plants.

Wild soybean roots depend on specific transcription factors and oxidation reduction related genesin response to alkaline stress.

Soil alkalinity is an important environmental problem limiting agricultural productivity. Wild soybean (Glycine soja) shows strong alkaline stress tolerance, so it is an ideal plant candidate for studying the molecular mechanisms of alkaline tolerance and identifying alkaline stress-responsive genes. However, limited information is available about G. soja responses to alkaline stress on a genomic scale. Therefore, in the present study, we used RNA sequencing to compare transcript profiles of G. soja root responses to sodium bicarbonate (NaHCO3) at six time points, and a total of 68,138,478 pairs of clean reads were obtained using the Illumina GAIIX. Expression patterns of 46,404 G. soja genes were profiled in all six samples based on RNA-seq data using Cufflinks software. Then, t12 transcription factors from MYB, WRKY, NAC, bZIP, C2H2, HB, and TIFY families and 12 oxidation reduction related genes were chosen and verified to be induced in response to alkaline stress by using quantitative real-time polymerase chain reaction (qRT-PCR). The GO functional annotation analysis showed that besides "transcriptional regulation" and "oxidation reduction," these genes were involved in a variety of processes, such as "binding" and "response to stress." This is the first comprehensive transcriptome profiling analysis of wild soybean root under alkaline stress by RNA sequencing. Our results highlight changes in the gene expression patterns and identify a set of genes induced by NaHCO3 stress. These findings provide a base for the global analyses of G. soja alkaline stress tolerance mechanisms.

A novel hybrid proline-rich type gene GsEARLI17 from Glycine soja participated in leaf cuticle synthesis and plant tolerance to salt and alkali stresses

Recent discoveries showed that hybrid proline rich type proteins were involved in plant responses to several environmental stresses. However, little is known about their roles in plant alkali stress adaptation, especially in wild soybean. Here, we isolated and characterized GsEARLI17, a novel the hybrid proline-rich protein type EARLI family gene from Glycine soja. Bioinformatic analysis showed that GsEARLI17 protein contained a conserved N-terminus hybrid proline-rich domain in and a C-terminus 8CM domain. Transcript abundance of GsEARLI17 was higher in young tissues than that in old tissues, and induced following exposure to salt and alkali treatments. GsEARLI17 overexpression in Arabidopsis influenced cuticles formation, as evidenced by thicker cuticles of transgenic lines, and enhanced plant tolerance to salt stress. Further observation was found that compared to the wild type Arabidopsis, overexpression of GsEARLI17 in Arabidopsis improved seed germination with higher leaf opening and greening rate during the early stages under alkali stress. GsEARLI17 exhibited enhanced alkaline tolerance with higher chlorophyll content, and lower malondialdehyde content at the adult developmental stage, and the expression levels of some alkali stress response marker genes NADP-ME, H + Ppase were higher in the GsEARLI17 overexpression lines than in wild-type plants. Taken together we suggest that GsEARLI17 reveal a positive role in enhancing plant tolerance of alkali stress in Arabidopsis.

A Facile Approach To Remediate the Microenvironment of Saline–Alkali Soil

A facile approach to remediate the microenvironment of saline–alkali soil (SS) was developed using a novel fertilizer named saline–alkali soil remediating fertilizer (SSRF). SSRF was obtained by adding a nanocomposite as the saline–alkali soil remediating agent (SSRA) made up of attapulgite (ATP), phosphogypsum (PG), sodium polyacrylate (SP), and weathered coal (WC) to a traditional fertilizer (TF). SSRF could form micro/nanonetworks in SS and display a high retaining capacity on water and fertilizer nutrients because of the hydrogen bonds between SSRA and water molecules, urea, or NH4Cl. In addition, SSRF could effectively reduce the salinity and alkalinity in SS through ion exchange, deactivation, and pH adjusting. Thus, SSRF could significantly improve the microenvironment of SS, which could facilitate the growth of crops and increase the saline–alkaline tolerance of crops.

GsSKP21, a Glycine soja S-phase kinase-associated protein, mediates the regulation of plant alkaline tolerance and ABA sensitivity.

Plant SKP1-like family proteins, components of the SCF complex E3 ligases, are involved in the regulation of plant development and stress responses. Little is known about the precise function of SKP genes in plant responses to environmental stresses. GsSKP21 was initially identified as a potential stress-responsive gene based on the transcriptome sequencing of Glycine soja. In this study, we found that GsSKP21 protein contains highly conserved SKP domains in its N terminus and an extra unidentified domain in its C terminus. The transcript abundance of GsSKP21, detected by quantitative real-time PCR, was induced under the treatment of alkali and salt stresses. Overexpression of GsSKP21 in Arabidopsis dramatically increased plant tolerance to alkali stress. Furthermore, we found that overexpression of GsSKP21 resulted in decreased ABA sensitivity during both the seed germination and early seedling growth stages. GsSKP21 mediated ABA signaling by altering the expression levels of the ABA signaling-related and ABA-induced genes. We also investigated the tissue expression specificity and subcellular localization of GsSKP21. These results suggest that GsSKP21 is important for plant tolerance to alkali stress and plays a critical regulatory role in the ABA-mediated stress response.