NaCl Stress Research Articles

Identification of Whirly transcription factors in Triticeae species and functional analysis of TaWHY1-7D in response to osmotic stress.

Osmotic stress poses a threat to the production and quality of crops. Whirly transcription factors have been investigated to enhance stress tolerance. In this study, a total of 18 Whirly genes were identified from six Triticeae species, which were classified into Whirly1 and Whirly2. The exon-intron structure, conserved motif, chromosomal location, collinearity, and regulatory network of Whirly genes were also analyzed. Real-time PCR results indicated that TaWHY1 genes exhibited higher expression levels in leaf sheaths and leaves during the seedling stage, while TaWHY2 genes were predominantly expressed in roots. Under PEG stress, the expression levels of TaWHY1-7A, TaWHY2-6A, TaWHY2-6B, and TaWHY2-6D were increased, TaWHY1-7D was reduced, and TaWHY1-4A had no significant change. All TaWHY genes were significantly up-regulated in response to NaCl stress treatment. In addition, TaWHY1-7A and TaWHY1-7D mainly enhanced the tolerance to oxidative stress in yeast cells. TaWHY2s mainly improved NaCl stress tolerance and were sensitive to oxidative stress in yeast cells. All TaWHYs slightly improved the yeast tolerance to d-sorbitol stress. The heterologous expression of TaWHY1-7D greatly improved drought and salt tolerance in transgenic Arabidopsis. In conclusion, these results provide the foundation for further functional study of Whirly genes aimed at improving osmotic stress tolerance in wheat.

NaCl stress, tissue specific Na+ and K+ up-take and their effect on growth and physiology of Helianthus annuus L. and Solanum lycopersicum L.

Salinity is one of the major abiotic stresses that can threat plant growth and yield. Helianthus annuus L. and Solanum lycopersicum L. are economically important crops and widely cultivated, but the uptake of Na+ and K+ during the NaCl stress in their above and below ground parts is not well-understood. The main objective of this study was to understand the response of leaf structure and function to different concentrations of NaCl and to understand the Na+ and K+ uptake in H. annuus and S. lycopersicum. Four different concentrations of NaCl (H. annuus; 50 mM, 100 mM, 150 mM, 200 mM, and S. lycopersicum; 25 mM, 50 mM, 75 mM, 100 mM) were applied. Plant Biomass and the leaf structure and function (leaf area, midrib length, secondary vein length, petiole diameter, photosynthesis, stomatal conductance, transpiration, and intrinsic water use efficiency) were studied. We found that the salinity concentration of more than 150 mM in H. annuus and 75 mM in S. lycopersicum significantly reduced the plant height and leaf performance. At the same time, the yield (seed and fruit weight) decreased at 100 mM and 50 mM of NaCl concentration of H. annuus and S. lycopersicum, respectively. Maximum Na+ and K+ were accumulated in roots and stem in H. annuus and roots and fruits in S., lycopersicu. At the same time, the minimum Na+ and K+ were detected in seeds of H. annuus and fruit and root of S. lycopersicum. The K+: Na+ showed variation in both crops. We conclude that the vegetative parts of Helianthus annuus can tolerate up to 150 mM and S. lycopersicum up to 75 mM of NaCl concentration. The concentration of Melatonin increases as the stress level increases as it acts to remove the stress. These findings can be helpful to cultivate the Helianthus annuus and S. lycopersicum in saline areas and can also be useful to cultivate other crops when the successive cultivation of both crops is practiced and Na+ is absorbed by the crop from the soil.

Molecular genetic markers associated with saltpans effluents (NaCl stress) on Cajanus cajan C3 plant and Sorghum bicolor C4 crop plants at four different agricultural fields

Molecular genetic markers associated with saltpans effluents (NaCl stress) on Cajanus cajan C3 plant and Sorghum bicolor C4 crop plants at four different agricultural fields

Co-production of pigment and high value-added bacterial nanocellulose from Suaeda salsa biomass with improved efficiency of enzymatic saccharification and fermentation

This study evaluated the co-production of pigment and bacterial nanocellulose (BNC) from S. salsa biomass. The extraction of the beet red pigment reduced the salts and flavonoids contents by 82.7%–100%, promoting the efficiencies of enzymatic saccharification of the biomass and the fermentation of BNC from the hydrolysate. SEM analysis revealed that the extraction process disrupted the lignocellulosic fiber structure, and the chemical analysis revealed the lessened cellulase inhibitors, consequently facilitating enzymatic saccharification for 10.4 times. BNC producing strains were found to be hyper-sensitive to NaCl stress, produced up to 400.4% more BNC from the hydrolysate after the extraction. The fermentation results of BNC indicated that the LDU-A strain yielded 2.116 g/L and 0.539 g/L in ES-M and NES-M, respectively. In comparison to the control, the yield in ES-M increased by approximately 20.0%, while the enhancement in NES-M was more significant, reaching 292.6%. After conducting a comprehensive characterization of BNC derived from S. salsa through Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Thermogravimetric Analysis (TGA), the average fiber diameter distribution of these four BNC materials ranges from 22.23 to 33.03 nanometers, with a crystallinity range of 77%–90%. Additionally, they exhibit a consistent trend during the thermal degradation process, further emphasizing their stability in high-temperature environments and similar thermal properties. Our study found an efficient co-production approach of pigment and BNC from S. salsa biomass. Pigment extraction made biomass more physically and chemically digestible to cellulase, and significantly improved BNC productivity and quality.

Transcriptomic Analysis of Cucumis hystrix and the Functional Identification of ChTrxh under NaCl Stress

Salinity is a prominent environmental stressor that significantly impacts plant growth and development. Here, we conducted research on the physiological and transcriptomic mechanism of a wild cucumber, Cucumis hystrix Chakr, under NaCl stress. Physiological data showed that contents of malondialdehyde, peroxide (H2O2), proline, soluble sugar, and activities of antioxidant enzymes of superoxide dismutase, peroxidase, ascorbate peroxidase, and glutathione reductase in wild cucumber plants were increased significantly after NaCl treatment. Transcriptomic analysis revealed that 3509 transcripts were differentially expressed in leaves and 5516 transcripts in roots after NaCl treatment. Numerous genes were related to the signal transduction, transcription factor, ion transport, osmotic metabolism, and reactive oxygen species scavenging. Moreover, the thioredoxin H type gene of Cucumis hystrix Chakr (ChTrxh) was isolated and characterized. Our study demonstrated that the transgenic tobacco plants overexpressing ChTrxh exhibited enhanced tolerance to NaCl stress compared to wild-type plants. These findings contribute valuable insights into the functional characteristics of important genes in wild cucumber under NaCl stress.

Hormesis management of Moringa oleifera with exogenous application of plant growth regulators under saline conditions

The study investigated the adaptability of Moringa oleifera to saline conditions, focusing on its hormesis behavior. It also examined how various plant growth regulators affected growth, physiological parameters, and bioactive compounds of moringa. In the first phase, different NaCl stress levels (0, 50, 100, 150, 200, and 250 mM) were applied. Notably, significant stimulation was observed at 100 mM stress for growth, total phenolics, total flavonoids and total chlorophyll content while 150 mM stress had a marked inhibitory effect, with survival decreasing at 200 and 250 mM NaCl levels. A 38% reduction in root attributes and shoot length, along with a 55% decrease in leaf score, was observed at 150 mM stress. Total phenolics showed a positive correlation with growth attributes. In the second phase, moringa plants grown under 50, 100, and 150 mM NaCl stress were treated with various plant growth regulators, including cytokinin (50 mg L−1), thiourea (5 mM), bezyl amino purine (BAP @50 mg L−1), salicylic acid (50 mg L−1), hydrogen peroxide (H2O2@120 μM), or ascorbic acid (50 mg L−1) to mitigate adverse effects of salinity. Cytokinin, BAP, and salicylic acid applications improved salinity tolerance, enhancing enzymatic, and non-enzymatic antioxidants, and the abundance of kaempferol, quercetin, hydroxybenzoic, and hydroxycinnamic acids. Pearson correlation and principal component analysis manifested relationships among growth parameters, antioxidant activities, flavonoids, and phenolic acids. This study provides new insights into hormesis management for moringa plants and the influence of plant growth regulators on flavonoids and phenolic acid levels in moringa leaves under saline conditions.

Identification, characterization and expression analysis of wheat RSH family genes under abiotic stress

Guanosine pentaphosphate and guanosine tetraphosphate are collectively called (p)ppGpp (Guanosine tetraphosphate and pentaphosphate). (p)ppGpp content in plants is affected by conditions such as light, salt, pH, UV light, and environmental phytohormones. The synthesis and hydrolysis of (p)ppGpp in plants is accomplished by a class of proteins called RSH (RelA/SpoT homologs). To date, a systematic and comprehensive genome-wide analysis of the RSH gene family in wheat and its closely related species has not been conducted. In this study, 15, 14, 12, and 8 members of RSH were identified in wheat (Triticum aestivum), Triticum dicoccoides, Triticum urartu and Aegilops tauschii respectively. Based on the conserved structural domains of the RSH genes, the TaRSHs have been categorized into TaRSH and TaCRSH. The gene duplications in the TaRSH gene family were all identified as segmental duplications indicating that the TaRSH family plays a significant role in expansion and that segmental duplications maintain a degree of genetic stability. Through the analysis of transcriptome data and RT-qPCR experiments, it was observed that the expression levels of TaRSHs were upregulated in response to abiotic stress. This upregulation suggests that TaRSHs play a crucial role in enhancing the resilience of wheat to adverse environmental conditions during its growth and development. Their increased expression likely contributes to the acquisition of stress tolerance mechanisms in wheat. Especially under NaCl stress, the expression levels increased most significantly. The more detailed systematic analysis provided in this article will help us understand the role of TaRSHs and provide a reference for further research on its molecular biological functions in wheat.

Effects of Inoculation with Stress-Tolerant Rhizobia on the Response of Alfalfa (Medicago sativa L.) to Combined Salinity and Cadmium Stress

Agricultural soil salinization, which is often combined with heavy-metal contamination, is an ever-growing problem in the current era of global change. Legumes have a high potential for nitrogen fixation and are ideal crops for the reclamation of degraded soils. Alfalfa (Medicago sativa) is a valuable forage crop cultivated worldwide. Alfalfa plants fertilized with nitrogen or inoculated with a salt- and cadmium-tolerant Sinorhizobium meliloti strain were subjected to combined NaCl and CdCl2 stresses. Our results showed that inoculated plants presented higher aerial biomass than nitrogen-fertilized plants when they were exposed to salinity and cadmium together. To assess the mechanisms involved in the plant response to the combined stresses, superoxide dismutase and catalase antioxidant enzymatic activities were determined. Both increased upon stress; however, the increase in catalase activity was significantly less marked for inoculated plants, suggesting that other tolerance mechanisms might be active. Cd accumulation was lower in inoculated plants than in fertilized plants, which appears to imply that inoculation somehow prevented cadmium uptake by the plant roots. Expression analyses of several involved genes suggested that inoculation stimulated the biosynthesis of proline, phytochelatins, and homophytochelatins, together indicating that inoculated plants might be better suited to withstand combined salinity and cadmium stress effects.

The role of WRKY transcription factors in exogenous potassium (K+) response to NaCl stress in Tamarix ramosissima.

Introduction: Soil salinization poses a significant challenge to plant growth and vitality. Plants like Tamarix ramosissima Ledeb (T. ramosissima), which are halophytes, are often integrated into planting schemes tailored for saline environments. Yet, the role of WRKY transcription factors in T. ramosissima, especially under sodium chloride (NaCl) stress mitigated by exogenous K+ application, is not well-understood. This research endeavors to bridge this knowledge gap. Methods: Using Pfam protein domain prediction and physicochemical property analysis, we delved into the WRKY genes in T. ramosissima roots that are implicated in counteracting NaCl stress when aided by exogenous K+ applications. By observing shifts in the expression levels of WRKY genes annotated to the KEGG pathway under NaCl stress at 0, 48, and 168h, we aimed to identify potential key WRKY genes. Results: We found that the expression of 56 WRKY genes in T. ramosissima roots responded to exogenous K+ application during NaCl stress at the indicated time points. Particularly, the expression levels of these genes were primarily upregulated within 168h. From these, 10 WRKY genes were found to be relevant in the KEGG pathways. Moreover, six genes, namely Unigene0024962, Unigene0024963, Unigene0010090, Unigene0007135, Unigene0070215, and Unigene0077293, were annotated to the Plant-pathogen interaction pathway or the MAPK signaling pathway in plants. These genes exhibited dynamic expression regulation at 48h with the application of exogenous K+ under NaCl stress. Discussion: Our research highlights that WRKY transcription factors can modulate the activation or inhibition of related genes during NaCl stress with the application of exogenous K+. This regulation enhances the plant's adaptability to saline environments and mitigates the damage induced by NaCl. These findings provide valuable gene resources for future salt-tolerant Tamarix breeding and expand our understanding of the molecular mechanisms of WRKY transcription factors in alleviating NaCl toxicity.

Regulatory effects of Hemin on prevention and rescue of salt stress in rapeseed (Brassica napus L.) seedlings

BackgroundSalt stress severely restricts rapeseed growth and productivity. Hemin can effectively alleviate salt stress in plants. However, the regulatory effect of Hemin on rapeseed in salt stress is unclear. Here, we analyzed the response and remediation mechanism of Hemin application to rapeseed before and after 0.6% (m salt: m soil) NaCl stress. Experiment using two Brassica napus (AACC, 2n = 38) rapeseed varieties Huayouza 158R (moderately salt-tolerant) and Huayouza 62 (strongly salt-tolerant). To explore the best optional ways to improve salt stress resistance in rapeseed.ResultsOur findings revealed that exogenous application of Hemin enhanced morph-physiological traits of rapeseed and significantly attenuate the inhibition of NaCl stress. Compared to Hemin (SH) treatment, Hemin (HS) significantly improved seedlings root length, seedlings height, stem diameter and accumulated more dry matter biomass under NaCl stress. Moreover, Hemin (HS) significantly improved photosynthetic efficiency, activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), and decreased electrolyte leakage (EL) and malondialdehyde (MDA) content, thus resulting in the alleviation of oxidative membrane damage. Hemin (HS) showed better performance than Hemin (SH) under NaCl stress.ConclusionHemin could effectively mitigate the adverse impacts of salt stress by regulating the morph-physiological, photosynthetic and antioxidants traits of rapeseed. This study may provide a basis for Hemin to regulate cultivated rapeseed salt tolerance and explore a better way to alleviate salt stress.

Transcriptome-Wide Analysis of Core Transcription Factors Associated with Defense Responses in Autotetraploid versus Diploid Rice under Saline Stress and Recovery

Saline stress is a major abiotic stress that inhibits plant growth and yields worldwide. The plant transcription factor (TF) family plays an important role in converting abiotic stress signals into gene expression changes. In this study, a transcriptome-based comparative analysis was performed to investigate the global gene expression of all the TFs in diploid and autotetraploid rice during the early stage of NaCl stress and recovery period. The phenotypic data indicated that the tetraploid rice exhibited a superior salt-tolerant ability compared to the diploid rice. A total of 55 TF families were co-expressed in the tetraploid and diploid rice, and the cumulative number of TF-expressed genes was relatively higher in the diploid rice than in the tetraploid rice at all time points. Unlike the diploid rice, the overall gene expression levels of the tetraploid rice were comparable to the control during recovery. The number of differentially expressed TFs (DE-TFs) in the tetraploid rice decreased after recovery, whereas it increased to a large extent in the diploid rice. GO and KEGG pathway enrichment analysis of the DE-TFs discovered the early switching of the ABA-activated signaling pathway and specific circadian rhythm in the tetraploid rice. Combining the PPI network and heatmap analysis, some core DE-TFs were found that may have potential roles to play in tetraploid salt tolerance. This study will pave the way for elucidating the complex network regulatory mechanisms of salt tolerance in tetraploid rice.

Genome-Wide Analysis and Expression Profiling of YUCCA Gene Family in Developmental and Environmental Stress Conditions in Tea Plant (Camellia sinensis)

The tea plant is a perennial leaf-used economical crop and cultivated all over the world. Indole-3-acetic acid (IAA) plays key roles in plant development and environmental stress. YUCCA (YUC) flavin monooxygenases are the rate-limiting enzymes of the TAA/YUC pathway, which is the most important IAA biosynthetic pathway in plants. The YUC gene family in tea plants has not been systematically studied so far. A total of 17 CsYUC members were identified from a tea plant genome database and phylogenetically classified into three subfamilies. Phylogenetic analysis showed that the CsYUC gene family is evolutionarily conserved. The physical and chemical properties, gene structures, and conserved domains were analyzed. The expression profiles of CsYUCs were analyzed on the basis of open available RNA-seq data, as well as by RNA-seq and qRT-PCR assays. Combined with previous studies, it can be concluded that YUC10 may play key roles in seed development. The results also showed that CsYUC2.1 may play important roles in the coordinated regulation of the growth of leaf buds and flower buds induced by pruning. Low temperature markedly induced the expression of CsYUC2.2, -11.8, and -11.9. Furthermore, CsYUC genes that might play key roles in the specific development stages and involve enhancing the resistance to drought and NaCl stress were screened, respectively. This study could provide a research basis for deeply studying the gene functions of the CsYUC family in the tea plant.

The role of NaHS pretreatment in improving salt stress resistance in foxtail millet seedlings: physiological and molecular mechanisms

ABSTRACT Salt stress is a prevailing abiotic stress in nature, with soil salinization becoming a pressing issue worldwide. High soil salinity severely hampers plant growth and leads to reduced crop yields. Hydrogen sulfide (H2S), a gas signal molecule, is known to be synthesized in plants exposed to abiotic stress, contributing to enhanced plant stress resistance. To investigate the impact of sodium hydrosulfide hydrate (NaHS, a H2S donor) on millet’s response to salt stress, millet seedlings were subjected to pretreatment with 200 μM NaHS, followed by 100 mM NaCl stress under soil culture conditions. The growth, osmotic adjustment substances, antioxidant characteristics, membrane damage, and expression levels of related genes in millet seedlings were detected and analyzed. The results showed that NaHS pretreatment alleviated the inhibition of salt stress on the growth of foxtail millet seedlings, increased the proline content and antioxidant enzyme activities, as well as the expression levels of SiASR4, SiRPLK35 and SiHAK23 genes under salt stress. These findings demonstrated that NaHS pretreatment can enhance salt tolerance in foxtail millet seedlings by regulating the content of osmotic adjustment substances and antioxidant enzyme activity, reducing electrolyte permeability, and activating the expression of salt-resistant genes.

Systematic identification of reference genes for qRT-PCR of Ardisia kteniophylla A. DC under different experimental conditions and for anthocyanin-related genes studies.

Ardisia kteniophylla A. DC, widely known as folk medicinal herb and ornamental plant, has been extensively investigated due to its unique leaf color, anti-cancer and other pharmacological activities. The quantitative real-time PCR (qRT-PCR) was an excellent tool for the analysis of gene expression with its high sensitivity and quantitative properties. Normalizing gene expression with stable reference genes was essential for qRT-PCR accuracy. In addition, no studies have yet been performed on the selection, verification and stability of internal reference genes suitable for A. kteniophylla, which has greatly hindered the biomolecular researches of this species. In this study, 29 candidate genes were successfully screened according to stable expression patterns of large-scale RNA seq data that from a variety of tissues and the roots of different growth stages in A. kteniophylla. The candidates were then further determined via qRT-PCR in various experimental samples, including MeJA, ABA, SA, NaCl, CuSO4, AgNO3, MnSO4, CoCl2, drought, low temperature, heat, waterlogging, wounding and oxidative stress. To assess the stability of the candidates, five commonly used strategies were employed: delta-CT, geNorm, BestKeeper, NormFinder, and the comprehensive tool RefFinder. In summary, UBC2 and UBA1 were found to be effective in accurately normalizing target gene expression in A. kteniophella regardless of experimental conditions, while PP2A-2 had the lowest stability. Additionally, to verify the reliability of the recommended reference genes under different colored leaf samples, we examined the expression patterns of six genes associated with anthocyanin synthesis and regulation. Our findings suggested that PAP1 and ANS3 may be involved in leaf color change in A. kteniphella. This study successfully identified the ideal reference gene for qRT-PCR analysis in A. kteniphella, providing a foundation for future research on gene function, particularly in the biosynthesis of anthocyanins.

Foliar Application of Melatonin Positively Affects the Physio-Biochemical Characteristics of Cotton (Gossypium hirsutum L.) under the Combined Effects of Low Temperature and Salinity Stress.

Low temperature and soil salinization during cotton sowing and seedling adversely affect cotton productivity. Exogenous melatonin (MT) can alleviate the damage caused to plants under non-biological stress; thus, applying MT is a means to improve the growth condition of crops under stress. However, achieving this goal requires a thorough understanding of the physiological regulatory mechanisms of MT on cotton seedlings under low temperature and salinity stress. This study could bring new knowledge on physio-biochemical mechanisms that improve the tolerance of cotton seedlings to combined effects of low temperature and salt stress using an exogenous foliar application of MT. The phytotron experiment comprised two temperature levels of cold stress and control and five MT treatments of 0, 50, 100, 150, and 200 μM and two salinity levels of 0 and 150 mM NaCl. Compared with the control treatments (non-salinity stress under cold stress and control), the combined stress of salt and low temperature reduced cotton seedlings' biomass and net photosynthetic rate (Pn), aggravated the membrane damage, reduced the potassium (K+) content, and increased the sodium (Na+) accumulation in the leaves and roots. Under NaCl stress, exogenously sprayed 50-150 μM MT increased the biomass and gas exchange parameters of cotton seedlings under salt and low temperature combined with salt stress, reduced the degree of membrane damage, and regulated the antioxidant enzyme, ion homeostasis, transport, and absorption of cotton seedlings. The pairwise correlation analysis of each parameter using MT shows that the parameters with higher correlation with MT at cold stress are mainly malondialdehyde (MDA), peroxidase (POD), and catalase (CAT). The highest correlation coefficient at 25 °C is observed between the K+ and Na+ content in cotton seedlings. The conclusion indicates that under salt and low-temperature stress conditions, exogenous application of MT primarily regulates the levels of Pn, superoxide dismutase (SOD), andPOD in cotton seedlings, reduces Na+ and MDA content, alleviates damage to cotton seedlings. Moreover, the most significant effect was observed when an exogenous application of 50-150 μM of MT was administered under these conditions. The current study's findings could serve as a scientific foundation for salinity and low-temperature stress alleviation during the seedling stage of cotton growth.

Hydrogen sulfide priming enhanced salinity tolerance in sunflower by modulating ion hemostasis, cellular redox balance, and gene expression

BackgroundThe salinity threat represents an environmental challenge that drastically affects plant growth and yield. Besides salinity stress, the escalating world population will greatly influence the world’s food security in the future. Therefore, searching for effective strategies to improve crop salinity resilience and sustain agricultural productivity under high salinity is a must. Seed priming is a reliable, simple, low-risk, and low-cost technique. Therefore, this work aimed to evaluate the impact of seed priming with 0.5 mM NaHS, as a donor of H2S, in mitigating salinity effects on sunflower seedlings. Primed and nonprime seeds were established in nonsaline soil irrigated with tape water for 14 d, and then exposed to 150 mM NaCl for 7 d.ResultsSalinity stress significantly reduced the seedling growth, biomass accumulation, K+, Ca2+, and salinity tolerance index while elevating Na+ uptake and translocation. Salinity-induced adverse effects were significantly alleviated by H2S priming. Upregulation in gene expression (HaSOS2, HaGST) under NaCl stress was further enhanced by H2S priming. Also, H2S reduced lipid peroxidation, electrolyte leakage, and H2O2 content, but elevated the antioxidant defense system. NaCl-induced levels of ascorbate, glutathione, and α tocopherol, as well as the activities of AsA-GSH cycle enzymes: ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, and glutathione S-transferase, were further enhanced by H2S priming. Increased level of H2S and total thiol by NaCl was also further stimulated by H2S priming.ConclusionH2S priming has proved to be an efficient strategy to improve sunflower seedlings’ salinity tolerance by retaining ion homeostasis, detoxifying oxidative damage, modulating gene expression involved in ion homeostasis and ROS scavenging, and boosting endogenous H2S. These findings suggested that H2S acts as a regulatory molecule activating the functional processes responsible for sunflower adaptive mechanisms and could be adopted as a crucial crop management strategy to combat saline conditions. However, it would be of great interest to conduct further studies in the natural saline field to broaden our understanding of crop adaptive mechanisms and to support our claims.

Mechanism of Salt Tolerance and Plant Growth Promotion in Priestia megaterium ZS-3 Revealed by Cellular Metabolism and Whole-Genome Studies

Approximately one-third of agricultural land worldwide is affected by salinity, which limits the productivity and sustainability of crop ecosystems. Plant-growth-promoting rhizobacteria (PGPR) are a potential solution to this problem, as PGPR increases crop yield through improving soil fertility and stress resistance. Previous studies have shown that Priestia megaterium ZS-3(ZS-3) can effectively help plants tolerate salinity stress. However, how ZS-3 regulates its metabolic adaptations in saline environments remains unclear. In this study, we monitored the metabolic rearrangement of compatibilisers in ZS-3 and combined the findings with genomic data to reveal how ZS-3 survives in stressful environments, induces plant growth, and tolerates stress. The results showed that ZS-3 tolerated salinity levels up to 9%. In addition, glutamate and trehalose help ZS-3 adapt to osmotic stress under low NaCl stress, whereas proline, K+, and extracellular polysaccharides regulate the osmotic responses of ZS-3 exposed to high salt stress. Potting experiments showed that applying the ZS-3 strain in saline and neutral soils could effectively increase the activities of soil acid phosphatase, urease, and invertase in both soils, thus improving soil fertility and promoting plant growth. In addition, strain ZS-3-GFP colonised the rhizosphere and leaves of Cinnamomum camphora well, as confirmed by confocal microscopy and resistance plate count analysis. Genomic studies and in vitro experiments have shown that ZS-3 exhibits a variety of beneficial traits, including plant-promoting, antagonistic, and other related traits (such as resistance to saline and heavy metal stress/tolerance, amino acid synthesis and transport, volatile compound synthesis, micronutrient utilisation, and phytohormone biosynthesis/regulatory potential). The results support that ZS-3 can induce plant tolerance to abiotic stresses. These data provide important clues to further reveal the interactions between plants and microbiomes, as well as the mechanisms by which micro-organisms control plant health.

Comprehensive Genome-Wide Identification of the RNA-Binding Glycine-Rich Gene Family and Expression Profiling under Abiotic Stress in Brassica oleracea.

The RNA-binding glycine-rich proteins (RBGs) of the glycine-rich protein family play vital roles in regulating gene expression both at the transcriptional and post-transcriptional levels. However, the members and functions in response to abiotic stresses of the RBG gene family remain unclear in Brassica oleracea. In this study, a total of 19 BoiRBG genes were identified through genome-wide analysis in broccoli. The characteristics of BoiRBG sequences and their evolution were examined. An analysis of synteny indicated that the expansion of the BoiRBG gene family was primarily driven by whole-genome duplication and tandem duplication events. The BoiRBG expression patterns revealed that these genes are involved in reaction to diverse abiotic stress conditions (i.e., simulated drought, salinity, heat, cold, and abscisic acid) and different organs. In the present research, the up-regulation of BoiRBGA13 expression was observed when subjected to both NaCl-induced and cold stress conditions in broccoli. Moreover, the overexpression of BoiRBGA13 resulted in a noteworthy reduction in taproot lengths under NaCl stress, as well as the inhibition of seed germination under cold stress in broccoli, indicating that RBGs play different roles under various stresses. This study provides insights into the evolution and functions of BoiRBG genes in Brassica oleracea and other Brassicaceae family plants.

Study on the intracellular adaptative mechanism of Acidithiobacillus caldus MTH-04 to NaCl stress

To understand the adaptive mechanism of bioleaching microorganism Acidithiobacillus caldus MTH-04, its physiology and metabolic changes at the transcriptional level were systemically studied. The results of growth curves, SO42− content, pH and flow cytometry analyses indicated that the higher the NaCl concentration, the more the strain was inhibited. The transcriptome response of A. caldus to elevated NaCl concentrations included changes in carbon flux, elevated glutathione synthesis, alterations in cell wall and membrane composition, the down-regulation in genes involved in flagellar synthesis and rotation, the reduced energy generation through sulfur oxidation, and the up-regulation in genes involved in DNA and protein repair. Based on the transcriptome results, the effects of proline and glutathione on NaCl adaptation in A. caldus were analyzed separately. We found that either the exogenous addition of proline and glutathione or the intracellular overexpression of the enzymes responsible for the synthesis of these two substances contributed to the enhancement of the adaptive capacity of A. caldus under NaCl stress. The findings offer insight into the design of chloride-based techniques for the bioprocessing of minerals.

Nitric oxide and hydrogen sulfide alleviates salt incited oxidative stress in Coriandrum sativum L

Soil salinity accelerates osmotic, ionic and oxidative pressure that suppresses plant growth and crop production. The objective of of the present investigation was to analyse protective function of nitric oxide (NO) and hydrogen sulfide (H2S) against salt (NaCl) stress in coriander plants. Different morphological, biochemical parameters, enzymatic and non-enzymatic antioxidants were analysed. Exposure of Coriandrum sativum L. to NaCl reduced length of root and shoot, biomass, relative water content and biochemical attributes. Exogenous use of SNP and NaHS individually or in combined treatment increased all the above-mentioned growth variables and inhibited NaCl incited biochemical alterations and oxidative damages in Coriandrum sativum L. Synergistic treatment (SNP + NaHS) exhibited increase in the morphological parameters, pigment and osmolyte contents. The oxidative stress biomarkers, hydrogen peroxide and superoxide generation were declined by SNP and NaHS as evidenced by reduced peroxidation of lipids. Activities of both glyoxylase as well as antioxidant enzymes were enhanced with presence of SNP and NaHS. Coriander seedlings treated with NaCl + SNP + NaHS exhibited 21 %, 7 %, 31 % and 59 % increase in superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), respectively over NaCl treated plants. Level of methylglyoxal was decreased in Coriandrum sativum with rise in glyoxalase I and II enzymes. Therefore, synergistic supplementation of NO and H2S alleviates salt stress in coriander plants more efficiently than individual treatment and it might be because of crosstalk mechanism that facilitate salt stress resistance in plants.