Osmoregulation Research Articles

Characterization of the PaHAK Gene and Its Expression During the In Vitro Seed Germination of Two Botanical Avocado Varieties Under Saline Stress

Soil salinity is one of the main challenges that modern agriculture faces. Avocado, which is classified as a glycophyte, is very sensitive to salt stress. There are botanical varieties of avocado that differ in their salt tolerance. This study investigated how salt stress affects the in vitro germination of two avocado botanical varieties americana (West Indian breed) and drymifolia (Mexican native) with different salt tolerances. This study also assessed the potential role of the avocado PaHAK2 high-affinity K+ transporter HAK/KUP/KT in response to saline stress during germination. Salinity (60 mM NaCl) delayed the germination speed of the drymifolia variety relative to the americana variety. A computational 3D inference protein model of the PaHAK2 protein showed 10 highly conserved transmembrane domains. During the imbibition period, there was a differential increase in the expression of the PaHAK2 gene at 60 mM NaCl in both varieties, which suggests the presence of osmotic adjustment and regulation. The enhanced expression of PaHAK2 in the americana variety suggests an adaptive advantage to salinity. We conclude that PaHAK2 participates in the response of avocado to salt stress during seed germination.

Salinity Stress in Calendula officinalis: Negative Growth Impacts Offset by Increased Flowering Yield and the Mitigating Role of Zinc

Salinity stress is a significant abiotic factor that limits plant growth and productivity by causing ionic imbalances and oxidative damage. Chelated zinc (Zn) has gained attention as an effective micronutrient to mitigate salinity-induced stress by enhancing antioxidant defense mechanisms, osmotic regulation, and physiological processes. This study aimed to investigate the impact of foliar-sprayed chelated Zn on the alleviation of salinity stress in Calendula officinalis. A pot experiment was conducted with varying salinity levels (0, 1000, 2000, and 3000 ppm NaCl) and Zn concentrations (0, 200, 400, and 600 ppm). The results demonstrated that chelated Zn significantly enhanced the growth parameters, flower yield, and biochemical traits, particularly under high-salinity conditions. Salinity stress was associated with a marked increase in the Na+ and K+ concentrations and a reduction in the Zn levels in the leaves. However, the foliar application of chelated Zn reduced the Na+ and increased the K+ concentrations in the leaves, resulting in an elevated K+/Na+ ratio with higher salinity and Zn application rates. Furthermore, the salinity and chelated Zn treatments stimulated the production of proline, phenols, flavonoids, and antioxidant activity, indicating the plant’s adaptive mechanism to enhance its secondary metabolite production under stress. These findings highlight the potential of chelated Zn to improve the salinity tolerance, supporting sustainable agricultural practices in saline-affected areas. Although salinity reduced the overall growth of C. officinalis, farmers are encouraged to cultivate this plant for its valuable inflorescences under saline irrigation conditions (up to 2000 ppm), combined with chelated Zn foliar applications at 400–600 ppm. We also recommend further research on other micronutrients.

Physiological Evaluation of Salt Tolerance in Sunflower Seedlings Across Different Genotypes

Sunflower (Helianthus annuus L.) is an important oilseed crop cultivated extensively across the globe. High salinity adversely impacts plant growth and physiological processes. In this study, the data on the phenotypes, physiological indices, and expression of relevant genes from different pathways responding to the stress were collected to clarify the physiological mechanisms underlying sunflower’s salt tolerance with the seedlings of two salt-tolerant (182265 and 182283) and two salt-sensitive (182093 and 186096) genotypes, which were exposed to 350 mM NaCl for 5 days. The findings revealed that, during the seedling stage, salt-tolerant sunflowers accumulated less Na+ and more K+, resulting in a higher K+/Na+ ratio that mitigated ionic toxicity throughout the plants, compared to the salt-sensitive resources. Furthermore, the salt-tolerant germplasms also exerted salt tolerance through the following several pathways: they maintained robust osmotic regulation by accumulating higher levels of proline, soluble sugars, and other osmolytes; they neutralized reactive oxygen species (ROS) by elevating the activity of antioxidant enzymes such as POD, SOD, CAT, APX, and GR; and they sustained optimal growth by boosting photosynthesis. Taken together, this study provided a more comprehensive assessment of the sunflower’s physiological salt tolerance, providing insights that will inform further molecular studies on salt tolerance and accelerating the breeding process for sunflower varieties with improved salt resilience.

Effect of Potassium Optimization on Wheat Drought Tolerance in Controlled Conditions

Potassium is an essential nutrient that influences key processes in plants, including osmotic regulation, photosynthesis, and nitrogen assimilation. This study investigated the drought tolerance of wheat (Triticum spp.) plants treated with sufficient potassium (SK, 1 mM) and low potassium (LK, 0.05 mM) under PEG-induced drought stress. Plant physiological development, canopy temperature, photosynthetic efficiency, antioxidant defense enzymes, and nitrogen assimilation enzymes were assessed. In non-drought conditions, LK increased canopy temperature and reduced dry matter yield and photosynthetic performance, with these effects becoming more pronounced under drought stress. SK-treated plants exhibited higher biomass, chlorophyll content, maximum quantum efficiency of photosystem II, and lower canopy temperatures, even under drought conditions. Furthermore, LK restricted the accumulation of key osmotic regulators, including proline, amino acids, and soluble sugars. Under drought stress, LK plants also showed increased hydrogen peroxide and superoxide anion levels, while SK plants had lower reactive oxygen species accumulation and higher antioxidant enzyme activities (catalase and superoxide dismutase). Additionally, LK resulted in reduced activity of nitrogen assimilation enzymes (nitrate reductase, NR, and nitrite reductase, NiR) under both normal and drought conditions. In contrast, SK-treated wheat seedlings maintained higher NR and NiR activities and higher soluble protein content during drought stress. These findings underscore the critical role of potassium management in enhancing wheat yield, particularly in water-scarce regions, as optimal potassium supply strengthens essential physiological and biochemical mechanisms that improve plant tolerance to drought stress.

Integrating genomic evidence for an updated taxonomy of the bacterial genus Spiribacter

The genus Spiribacter encompasses halophilic bacteria widely distributed in hypersaline environments worldwide. Despite their ecological significance, initially isolating Spiribacter species under laboratory settings was challenging due to the lack of knowledge of their growth and cultivation requirements. However, with improved understanding of their ecological niche and metabolic pathways, additional species of Spiribacter have been successfully isolated and identified from diverse locations around the globe. Enriched media with sodium pyruvate as carbon source facilitated the isolation of twelve new strains closely related to the genus Spiribacter from hypersaline environments in Spain. Genome sequencing and analysis of these new strains and previously described Spiribacter species provided insights into their genomic features and phylogenomic relationships, supporting the delineation of three distinct new species within this genus, designated as Spiribacter insolitus sp. nov., Spiribacter onubensis sp. nov., and Spiribacter pallidus sp. nov. In Spiribacter species, streamlined genomes enhance survival in hypersaline environments by reducing non-essential genes and optimizing resource utilization. Key genes involved in osmoprotectant mechanisms, including those for the metabolism of myo-inositol, hydroxyproline, and L-proline, were identified and numerous transporters were noted, ensuring efficient nutrient acquisition and osmotic balance. Notably, these new species, along with other Spiribacter strains, exhibit metabolic diversity in utilizing inorganic sulfur compounds, including thiosulfate and tetrathionate, for energy production and adaptation to hypersaline environments. The presence of thiosulfate dehydrogenase (TsdA) genes suggests their capability to oxidize thiosulfate to tetrathionate, potentially influencing both aerobic and anaerobic respiration. Furthermore, the prevalence of the sqr gene indicates a role for sulfide oxidation in Spiribacter metabolism, underlining their metabolic versatility in saline habitats. These adaptations allow Spiribacter to thrive in nutrient-limited, high-salinity habitats. Moreover, genome mining analysis and physiological disparities observed in the already described species Spiribacter halobius raise significant challenges to its classification within the genus Spiribacter.

Combined Physiological and Transcriptomic Analysis Reveals Key Regulatory Networks and Potential Hub Genes Controlling Chilling Tolerance During Soybean Germination.

Chilling is an important limiting factor for seed germination of soybean (Glycine max [L.] Merr.). To reveal the regulatory mechanism of chilling tolerance during the soybean germination stage, based on previous studies, the chilling tolerance line R48 and chilling sensitive line R89 in chromosome segment substitution lines were selected for physiological index determination and transcriptome sequencing. It was found that reactive oxygen species (ROS) scavenging system related enzymes, ROS, and osmotic regulators were significantly different between the two lines. Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes enrichment were performed on the differentially expressed genes obtained by transcriptome sequencing. It was found that terms or pathways related to flavonoids, unsaturated fatty acids, and abscisic acid were highly enriched. In addition, weighted gene coexpression network analysis (WGCNA) method was used to analyze the physiological index data and transcriptome sequencing data. Four main coexpression modules significantly related to physiological indicators were obtained, and the hub genes in each module were screened according to eigengene-based connectivity value. Haplotype analysis of important candidate genes using soybean germplasm resources showed that there were significant differences in germination indexes between different major haplotypes of Glyma.17G163200. Based on the results of enrichment analysis and WGCNA, the regulation model of low temperature tolerance during soybean germination was preliminarily drawn. This study will provide theoretical guidance for analyzing the molecular regulation mechanism of cold tolerance in soybean germination stage.

Short-term Administration of Naringin Improves Renal Function in Renal Ischemia-reperfusion by Increasing Aquaporin-1 and Aquaporin-2 Levels

Background: Since renal ischemia-reperfusion (I/R) can lead to a serious health problem, aquaporins have important roles in preventing negative changes in electrolyte-water balance. This study aimed to determine the effect of naringin treatment on renal function and AQP1 and AQP2 levels in the kidney cortex and medulla tissues in experimental renal I/R in rats. Materials and Methods: The study was carried out on 40 male Wistar-type rats, 8-12 weeks old. Experimental groups were formed as follows: 1) Control, 2) Sham+vehicle, 3) Renal (I/R)+vehicle, 4) Renal I/R+ Naringin (50mg/kg/day) (3 days of administration), and 5) Renal I/R+ Naringin( 100mg/kg/day) (3 days supplementation) group. First, the left kidney was removed by nephrectomy under general anesthesia, and then the right kidney was subjected to 45 minutes of ischemia and then 72 hours of reperfusion. Naringin was given to the experimental animals by an intraperitoneal route at the beginning of the reperfusion, after 24 and 48 hours. At the end of the experiments, first of all, blood samples were taken from the heart in animals under general anesthesia, and then the animals were killed by cervical dislocation, and kidney tissue samples were taken. Osmolarity in plasma and urine and plasma creatinine levels were evaluated. AQP1 and AQP2 levels were analyzed in the kidney cortex and medulla tissues by ELISA and PCR methods. Results: In kidney tissues, I/R led to a decrease in plasma and urinary osmolality, AQP1 and AQP2 levels in the cortex and medulla, and an increase in urea and creatinine levels (p < 0.001). However, naringin supplementation corrected the deterioration to a certain extent. Conclusion: The results of the study show that naringin supplementation at different doses, such as 50 or 100 mg/kg, may have protective effects on the deterioration of renal function caused by unilateral nephrectomy and I/R in rats.

Developing drought and heat-resistant grapevine cultivars through marker-assisted breeding

Climate change poses significant challenges to viticulture, particularly through increased drought and heat stress. This study integrates physiological, biochemical, genomic, and field performance assessments to identify traits and genetic markers associated with stress tolerance in five grapevine cultivars: Cabernet Sauvignon, Chardonnay, Syrah, Merlot, and Riesling. Genomic analysis revealed specific SNP markers on chromosomes 4 and 8, linked to water-use efficiency (WUE) and proline accumulation, crucial for osmotic balance under drought conditions. Physiological assessments showed that Cabernet Sauvignon and Merlot maintained high relative water content and low stomatal conductance, reducing water loss. Biochemical analysis indicated that Chardonnay and Syrah had elevated heat shock protein (HSP) expression and low malondialdehyde (MDA) levels, supporting cellular stability under heat. Field trials further validated these traits, with Cabernet Sauvignon and Chardonnay demonstrating yield stability and high sugar content despite stress. This research underscores the potential of marker-assisted breeding to develop climate-resilient grapevine cultivars, offering practical insights for sustainable viticulture in the face of global climate shifts.

Effects of bicarbonate on osmotic regulation, immunity, and antioxidant capacity in mud crab (Scylla paramamosain) based on transcriptomic analysis

Carbonate saline-alkali water has significant potential in the development of saline-alkali fisheries, but the effects of bicarbonate stress on crustaceans have not been fully studied. In this study, we investigated the changes in osmotic regulation, immune, and antioxidant capacity of the Scylla paramamosain at 1, 7, and 28 d at different carbonate concentrations (CK: 220 mg/L; AB1: 300 mg/L; AB2: 380 mg/L; AB3: 700 mg/L), and conducted transcriptome analysis. The results showed that Ca2+/Mg2+-ATPase in the gills of the AB3 group was significantly lower than that of the AB2 group, while the AB2 group was lower than the CK group and the AB1 group (P<0.05). CA activity was positively correlated with bicarbonate concentration, while the AB3 group was significantly higher than the other groups. ALT and AST in groups AB1 and AB2 showed a trend of first increasing and then decreasing, and roughly returned to their initial levels at 28 d, while AB3 continued to increase with time and was significantly higher than the initial level. At 28 d, ACP and AKP in the AB3 group were significantly lower than those in the other groups. The MDA content in the hepatopancreas also showed similar trend, with a positive correlation between the T-AOC, GSH and bicarbonate concentration. At 28 d, the AB1 group was able to recover to its initial level, while the AB3 group decreased with time and reached its minimum value at 28 d. Transcriptomic analysis identified 283 DEGs, and KEGG enrichment analysis showed antioxidant pathways, including the ascendate and alderate metabolism, were up-regulated to cope with stress. In addition, it shows many immune related pathways, including the mTOR signaling pathway, were significantly down-regulated. This study explores the effects of bicarbonate stress on the S. paramamosain, providing theoretical guidance for the utilization of carbonate saline-alkali water.

Role of UeMsb2 in Filamentous Growth and Pathogenicity of Ustilago esculenta

Ustilago esculenta is a dimorphic fungus that specifically infects Zizania latifolia, causing stem swelling and the formation of an edible fleshy stem known as jiaobai. The pathogenicity of U. esculenta is closely associated with the development of jiaobai and phenotypic differentiation. Msb2 acts as a key upstream sensor in the MAPK (mitogen-activated protein kinase) signaling pathway, playing critical roles in fungal hyphal growth, osmotic regulation, maintenance of cell wall integrity, temperature adaptation, and pathogenicity. In this study, we cloned the UeMsb2 gene from U. esculenta (GenBank No. MW768949). The open reading frame of UeMsb2 is 3015 bp in length, lacks introns, encodes a 1004-amino-acid protein with a conserved serine-rich domain, and is localized to the vacuole. Expression analysis revealed that UeMsb2 is inducibly expressed during both hyphal growth and infection processes. Deletion of UeMsb2 did not affect haploid morphology or growth rate in vitro but significantly impaired the strain’s mating ability, suppressed filamentous growth, slowed host infection progression, and downregulated the expression of b signaling pathway genes associated with pathogenicity. Notably, the deletion of UeMsb2 did not influence the in vitro growth of U. esculenta under hyperosmotic, thermal, or oxidative stress conditions. These findings underscore the critical role of UeMsb2 in regulating the pathogenicity of U. esculenta. This study provides insights into the interaction between U. esculenta and Z. latifolia, particularly the mechanisms that drive host stem swelling.

Physiological and biochemical changes induced by drought stress during the stem elongation and anthesis stages in the Triticum genus

Drought stress negatively influences the growth, development, and grain yield of wheat by disrupting its morphological, physiological, and biochemical processes. This study examined the effects of drought stress during the stem elongation and anthesis developmental stages of species within the Triticum genus along with their drought adaptation mechanisms under fully watered and drought conditions. We tested the following two hypotheses: (1) drought tolerance mechanisms for osmotic and stomatal regulation that lead to oxidative stress are correlated between the stem elongation and anthesis stages and affect grain yield loss, and (2) compared with modern cultivars, wild wheat cultivars exhibit greater drought tolerance. To test these hypotheses, a greenhouse pot experiment was conducted using 17 genotypes of wild wheat relatives and landraces, with modern cultivars included for comparison. Drought stress was induced during the stem elongation and anthesis stages until the average soil moisture was approximately 15 % and 18 %, respectively, of the pot’s water holding capacity. The soil moisture was maintained at 80–90 % for the fully watered treatment. An examination of physiological and biochemical traits revealed that drought significantly reduced stomatal conductance (gsw) and relative water content (RWC) during both developmental stages. However, significant increases occurred in the malondialdehyde (MDA) content during both stages and in the proline content during the anthesis stage. Drought stress significantly decreased the number of days to heading and anthesis, indicating that drought escape occurs under severe drought stress. Furthermore, drought significantly decreased morphological and yield-related traits, with the greatest reduction (51 %) occurring in grain yield. Weakly significant positive associations of biochemical and some physiological traits between the stem elongation and anthesis stages partially confirmed our first hypothesis, whereas our results relating to the second hypothesis were inconclusive. We observed genotype-dependent responses to drought stress during both stages for various measured traits. No associations of RWC, proline, or MDA with grain yield were found. However, stomatal conductance was negatively correlated with grain yield under drought stress at the anthesis stage. Certain wild wheat genotypes and landraces exhibited drought avoidance, escape, and tolerance mechanisms, which positively contributed to grain yield. We identified T. monococcum subsp. sinskajae, T. boeoticum and T. dicoccoides as the most drought-tolerant genotypes. The findings of this study provide important insight for understanding the drought adaptation traits and their use in wheat breeding programs.

Physiological, transcriptomic, and metabolomic analyses of the chilling stress response in two melon (Cucumis melo L.) genotypes

BackgroundChilling stress is a key abiotic stress that severely restricts the growth and quality of melon (Cucumis melo L.). Few studies have investigated the mechanism of response to chilling stress in melon.ResultsWe characterized the physiological, transcriptomic, and metabolomic response of melon to chilling stress using two genotypes with different chilling sensitivity (“162” and “13-5A”). “162” showed higher osmotic regulation ability and antioxidant capacity to withstand chilling stress. Transcriptome analysis identified 4395 and 4957 differentially expressed genes (DEGs) in “162” and “13-5A” under chilling stress, respectively. Metabolome analysis identified 615 and 489 differential enriched metabolites (DEMs) were identified in “162” and “13-5A” under chilling stress condition, respectively. Integrated transcriptomic and metabolomic analysis showed enrichment of glutathione metabolism, and arginine (Arg) and proline (Pro) metabolism, with differential expression patterns in the two genotypes. Under chilling stress, glutathione metabolism-related DEGs, 6-phosphogluconate dehydrogenase (G6PDH), glutathione peroxidase (GPX), and glutathione s-transferase (GST) were upregulated in “162,” and GSH conjugates (L-gamma-glutamyl-L-amino acid and L-glutamate) were accumulated. Additionally, “162” showed upregulation of DEGs encoding ornithine decarboxylase, Pro dehydrogenase, aspartate aminotransferase, pyrroline-5-carboxylate reductase, and spermidine synthase and increased Arg, ornithine, and Pro. Furthermore, the transcription factors (TFs), MYB, ERF, MADS-box, and bZIP were significantly upregulated, suggesting their crucial role in chilling tolerance of melon.ConclusionsThese findings elucidate the molecular response mechanism to chilling stress in melon and provide insights for breeding chilling-tolerant melon.

Internal physiological drivers of leaf development in trees: Understanding the relationship between non‐structural carbohydrates and leaf phenology

Abstract Plant phenology is crucial for understanding plant growth and climate feedback. It affects canopy structure, surface albedo, and carbon and water fluxes. While the influence of environmental factors on phenology is well‐documented, the role of plant intrinsic factors, particularly internal physiological processes and their interaction with external conditions, has received less attention. Non‐structural carbohydrates (NSC), which include sugars and starch essential for growth, metabolism and osmotic regulation, serve as indicators of carbon availability in plants. NSC levels reflect the carbon balance between photosynthesis (source activity) and the demands of growth and respiration (sink activity), making them key physiological traits that potentially influence phenology during critical periods such as spring leaf‐out and autumn leaf senescence. However, the connections between NSC concentrations in various organs and phenological events are poorly understood. This review synthesizes current research on the relationship between leaf phenology and NSC dynamics. We qualitatively delineate seasonal NSC variations in deciduous and evergreen trees and propose testable hypotheses about how NSC may interact with phenological stages such as bud break and leaf senescence. We also discuss how seasonal variations in NSC levels, align with existing conceptual models of carbon allocation. Accurate characterization and simulation of NSC dynamics are crucial and should be incorporated into carbon allocation models. By comparing and reviewing the development of carbon allocation models, we highlight the shortcomings in current methodologies and recommend directions to address these gaps in future research. Understanding the relationship between NSC, source–sink relationships, and leaf phenology poses challenges due to the difficulty of characterizing NSC dynamics with high temporal resolution. We advocate for a multi‐scale approach that combines various methods, which include deepening our mechanistic understanding through manipulative experiments, integrating carbon sink and source data from multiple observational networks with carbon allocation models to better characterize the NSC dynamics, and quantifying the spatial pattern and temporal trends of the NSC‐phenology relationship using remote sensing and modelling. This will enhance our comprehension of how NSC dynamics impact leaf phenology across different scales and environments. Read the free Plain Language Summary for this article on the Journal blog.

Consumption of a Branched-Chain Amino Acids-Containing Sports Beverage During 21 km of Running Reduces Dehydration, Lowers Muscle Damage, and Prevents a Decline in Lower Limb Strength.

The purpose of this study was to examine the acute effects of branched-chain amino acids (BCAAs)-containing electrolyte beverage (AE) on water-electrolyte balance, muscle damage, time to finish the final 5 km, and muscle strength compared to a standard commercially available carbohydrate-electrolyte sports beverage (CE), pure water (W), and no rehydration (N). Fourteen trained male participants (20 ± 2 years old) completed four randomized 21 km running trials. The participants were instructed to consume their drink (150 mL W, 150 mL CE, or 150 mL AE) or no rehydration (N) at 5 km, 10 km, and 15 km. Body mass and muscle strength were assessed, and blood samples were collected before and after exercise. Perceptual scales were administered during and after running. Blood electrolyte levels (sodium, potassium, and chloride) and creatine kinase (CK) concentration were analyzed. The change in plasma volume with AE was significantly smaller than that with N (p < 0.05). Consuming AE maintained the best potassium balance (p < 0.05). Twenty-four hours after exercise, serum CK concentrations significantly elevated in N, W, and CE (p < 0.05), but did not reach statistical significance in the AE group (p > 0.05). Compared to N, consuming AE resulted in significantly less soreness 24 h after exercise (p < 0.05). There was no difference in time to finish the final 5 km (p > 0.05). Maximal voluntary isometric force output was significantly lower after exercise with N and W (p < 0.05) but not with CE or AE (p > 0.05). Consuming a BCAAs-containing sports beverage during a 21 km run can help reduce dehydration, maintain potassium balance, lower muscle damage, and prevent the decline in lower limb strength after 21 km running.

Enhancing strawberry resilience to saline, alkaline, and combined stresses with light spectra: impacts on growth, enzymatic activity, nutrient uptake, and osmotic regulation

BackgroundThis study examines the effects of various complementary light spectra on the growth, development, antioxidant activity, and nutrient absorption in strawberry plants under stress conditions. Light-emitting diodes (LEDs) were used to provide specific wavelengths, including monochromatic blue (460 nm), monochromatic red (660 nm), a dichromatic mix of blue and red (1:3 ratio), full-spectrum white light (400–700 nm), and ambient light as a control (no LED treatment). The stress treatments applied were: control (no stress), salinity (80 mM NaCl), alkalinity (40 mM NaHCO₃), and a combined salinity/alkalinity condition.ResultsOur results indicated that complementary light spectra, especially red and blue/red, helped mitigate the adverse effects of stress on plant growth and development. These spectra improved plant tolerance by enhancing the activity of polyphenol oxidase and peroxidase enzymes and increasing starch accumulation in the leaves. Furthermore, under stress conditions, red and blue-red light significantly boosted fruit anthocyanin levels. Although stress elevated antioxidant activity, supplementary light reduced this activity by alleviating stress compared to ambient light. While stress led to increased Na and Cl ion concentrations in leaves, treatments with blue, red, and blue-red light minimized these harmful effects and promoted the absorption of beneficial ions such as K, Mg, Fe, and Cu.ConclusionsAdjusting light quality significantly influences the morphology and physiology of strawberry plants, underscoring the role of specific light spectra in promoting optimal growth under stress conditions.Clinical trial numberNot applicable

Enhanced anaerobic reduction of nitrobenzene under hypersaline fluctuation: Glycine betaine metabolism and microbial osmoadaptation mechanisms

High salinity, particularly large fluctuations in salinity, poses a significant threat to the biological treatment of high-salt industrial wastewater, while glycine betaine (GB) is commonly used for osmotic pressure balance. However, the GB metabolism mechanism and the effect of GB addition on microbial osmoadaptation responding to salt perturbations are still unclear. This study investigated the effect of GB on the stability of anaerobic process in nitrobenzene reduction under various salt perturbations and further explored the microbial osmoadaptation and metabolism mechanism. The nitrobenzene reduction was observably improved with GB addition (R+), and the microbial resilience increased due to repeated salt shocks. The generation of acetic acid showed a 46.21 % decrease in R+ compared to that without GB addition (R-) at 3 % salinity. Meanwhile, the intracellular GB concentration reached 10.76 mg L−1 to 54.76 mg L−1 with salinity increasing from 1.5 % to 6 %. 16S rRNA analysis revealed that the osmoadaptation period was shortened in R+ through the rapid osmoadaptation of salt-intolerant microorganisms (such as Propionibacteriaceae and SBR1031) and the massive enrichment of salt-tolerant microorganisms (such as Glutamicibacter). Besides, the resistance to hypersaline disturbance improved by the increasing size and complexity of the microbial community network. Moreover, the metagenomic analysis revealed that the abundance of genes involved in microbial metabolism was significantly enhanced in R+, indicating a more efficient metabolic efficiency and electrons transfer with GB addition under high-salt environments. This study provides vital insights into GB metabolism and microbial osmoadaptation responding to salt perturbations in long-term high-salt wastewater biotreatment.

Early rearing of European seabass (Dicentrarchus labrax) with mild current enrichment modifies fish swimming behavior without altering their growth performance

The implementation of conditions that favor optimum swimming activity (e.g., suitable flow regimes), has been associated with enhanced growth and improved welfare in some farmed fish species. Despite the importance of European seabass in aquaculture, the potential beneficial effects of rearing flow conditions have not been sufficiently explored in this species. This study investigates how the application of fast (F, 0.01–0.20 m s-1) or slow (S, <0.01 m s-1) steady flows in rearing tanks for 75-77 days affected physiological and behavioral traits in seabass fingerlings. Growth performance, external and internal morphology, and several physiological variables, including hematocrit, plasma cortisol concentration, and osmotic and ionic balance were not affected by flow conditions during rearing. Also, behavioral tests implemented in groups or isolated individuals suggest that coping styles were not affected by the two tank-rearing conditions. On the contrary, the swimming behavior assessed in tests was modified by the flow condition experienced during rearing. Mean swimming speed, peak acceleration, swimming distance, angular velocity, and meander showed some variability across different tests and time, although consistently displaying higher values in seabass reared in the F condition, suggesting increased activity and more consistent swimming patterns in that group. However, the cumulative time in proximity between individuals measured in behavioral group tests suggested that group cohesion was variable, without displaying differences between F and S groups. These findings have particularly important implications for fish welfare and may suggest plasticity in the behavioral response to rearing conditions for this species, although not affecting the assignment of the individuals to the different coping styles. Summary statementWe investigated how mild current enrichment applied during early rearing in seabass modifies physiological and behavioral responses involving swimming activity, exploring the potential associations to fish welfare.

Drought and heat stress interactions: Unveiling the molecular and physiological responses of Persian walnut

While numerous studies explored the response of walnut plants to drought stress (DS), there remains a significant gap in the knowledge regarding the impact of heat stress (HS) and the combined effects of DS and HS on the recovery capacity of walnut trees. This study aimed to investigate the mechanism of Persian walnut (cv. Chandler) response to the combined DS and HS, focusing on various aspects including photosynthesis, water relations, and osmotic regulation. The treatments involved subjecting plants to DS (through a withholding method for 24 d), HS (gradually up to 40 °C for 8 d), and a combined DS and HS, which were compared to a control group (no stress) during the stress and recovery phases. The results showed that DS had significantly more negative effects on chlorophyll content, relative water content (RWC), leaf water potential (WP), osmotic potential (OP) compared to HS. Involvement of osmoregulation mechanism was detected more in DS and HS plants through the accumulation of proline, glycine Betaine and total soluble carbohydrates. The functionality of photosynthesis was significantly impacted by both HS and DS, respectively. While the HS accelerated the change of the abovementioned physiological processes in drought-stressed seedlings. Consistently, more pronounced damage was found in leaves under the combined stress, alongside the decrease RWC, chlorophyll content and fluorescence ratios. Based on the analysis of the linear mixed-effect model, the effects of combined stress and HS on photosynthesis parameters were detected in the early stages of stress compared to DS. Within a range of stresses, the abovementioned physiological processes of individual and combined-stressed plants recovered to levels comparable to those of the control. Our results also showed a substantial reduction in the expression of the photosynthetic genes (Fd, Cyt b6f, and PsbB) in Persian walnut saplings under abiotic stress conditions indicating significant damage to their photosynthetic apparatus. This study highlights that, under scenarios of aggravating drought occurring with heat, walnut seedlings could face a high risk of damage to physiological structures in relation to the synergistically increased hydraulic and thermal impairments.

Construction and integrative analysis of miRNA-mRNA response to salinity stress in Oreochromis mossambicus cells

This study investigated the genetic response of tilapia (Oreochromis mossambicus) brain cells to hypertonic stress, focusing on miRNAs regulation. Three hundred and thirty-one known miRNAs and 163 novel miRNAs which responded to hypertonic stress were identified by high-throughput sequencing in tilapia brain cells. Differential expression analysis revealed that 16 miRNAs were significantly upregulated, while 11 miRNAs were significantly downregulated. These differentially expressed miRNAs are closely related to metabolism, immune response, and neural regulation. The target genes of these miRNAs are implicated in neurotrophic and synaptic signaling pathways, potentially affecting metabolic and apoptotic processes. GO and KEGG enrichment analyses provided insights into the biological processes and pathways affected by hypertonic stress. Furthermore, correlation analysis between mRNA and miRNA highlighted miRNA-mRNA interactions related to cell cycle and apoptosis regulation. These results indicated significant changes of miRNA expression under hypertonic stress and their crucial role in osmotic pressure regulation. This study offers a basis for further exploration of miRNA functions and molecular mechanisms in tilapia, potentially informing practices for aquaculture in challenging environments such as saline-alkaline waters.

Synergistic effects of SAP and PGPR on physiological characteristics of leaves and soil enzyme activities in the rhizosphere of poplar seedlings under drought stress.

Super absorbent polymers (SAP) provide moisture conditions that allow plant growth-promoting rhizobacteria (PGPR) to enter the soil for acclimatization and strain propagation. However, the effects of SAP co-applied with PGPR on the physiological characteristics of leaves and rhizosphere soil enzyme activities of poplar seedlings are not well understood. Here, a pot experiment using one-year-old poplar seedlings with five treatments, normal watering, drought stress (DR), drought stress + SAP (DR+SAP), drought stress + Priestia megaterium (DR +PGPR) and drought stress + SAP + P. megaterium (DR+S+P), was performed to analyze the contents of non-enzymatic antioxidants, osmotic regulators and hormones in leaves, as well as rhizosphere soil enzyme activities. Compared with normal watering, the DR treatment significantly decreased the contents of dehydroascorbate (DHA; 19.08%), reduced glutathione (GSH; 14.18%), oxidized glutathione, soluble protein (26.84%), indoleacetic acid (IAA; 9.47%), gibberellin (GA) and zeatin (ZT), the IAA/abscisic acid (ABA), GA/ABA, ZT/ABA and (IAA+GA+ZT)/ABA (34.67%) ratios in leaves, and the urease and sucrase activities in the rhizosphere soil. Additionally, it significantly increased the soluble sugar, proline and ABA contents in leaves. However, in comparison with the DR treatment, the DR+S+P treatment significantly increased the DHA (29.63%), GSH (15.13%), oxidized glutathione, soluble protein (29.15%), IAA (12.55%) and GA contents, the IAA/ABA, GA/ABA, ZT/ABA and (IAA+GA+ZT)/ABA (46.85%) ratios in leaves, and the urease, sucrose and catalase activities in rhizosphere soil to different degrees. The soluble sugar, proline and ABA contents markedly reduced in comparison to the DR treatment. The effects of the DR+SAP and DR+PGPR treatments were generally weaker than those of the DR+S+P treatment. Thus, under drought-stress conditions, the simultaneous addition of SAP and P. megaterium enhanced the drought adaptive capacities of poplar seedlings by regulating the non-enzymatic antioxidants, osmotic regulators, and endogenous hormone content and balance in poplar seedling leaves, as well as by improving the rhizosphere soil enzyme activities.