High Salinity Stress Research Articles

Identification of novel salt tolerance-associated proteins from the secretome of Enterococcus faecalis.

The ability of bacteria to adapt to the external environment is fundamental for their survival. A halotolerant microorganism Enterococcus faecalis able to grow under high salt stress conditions was isolated in the present study. The SDS-PAGE analysis of the secretome showed a protein band with a molecular weight of 28kDa, gradually increased with an increase in salt concentration, and the highest intensity was observed at 15% salt stress condition. LC-MS/MS analysis of this particular band identified fourteen different proteins, out of which nine proteins were uncharacterized. Further, the function of uncharacterized proteins was predicted based on structure-function relationship using areverse template search approach deciphering uncharacterized protein into type III polyketide synthases, stress-induced protein-1, Eed-h3k79me3, ba42 protein, 3-methyladenine DNA glycosylase, Atxa protein, membrane-bound respiratory hydrogenase, type-i restriction-modification system methylation subunit and ManxA. STRING network analysis furthera showed strong association among the proteins. The processes predicted involvement of these proteins in signal transduction, ions transport, synthesis of the protective layer, cellular homeostasis and regulation of gene expression and different metabolic pathways. Thus, the fourteen proteins identified in the secretome play an essential role in maintaining cellular homeostasis in E. faecalis under high-salinity stress. This may represent a novel and previously unreported strategy by E. faecalis to maintain their normal growth and physiology under high salinity conditions.

Assessment of irrigation water salinity effects on red beet under Mediterranean conditions

Plant tolerance to salinity stress is vital for irrigation scheduling, decision-making, planning and operation, and most critically, water resource management. Although there are numerous scientific data on the response of various plants to salinity stress, there are few studies on red beet in the literature, and specifically under Mediterranean conditions. This study aimed to investigate the effects of water salinity stress on water use, growth, yield parameters, and salinity threshold and slope values of red beet in Mediterranean conditions. In addition to control (0.6 dS m-1), five irrigation water salinity levels including low (1.5 dS m-1), medium-low (3.0 dS m-1), medium (4.5 dS m-1), medium-high (6.0 dS m-1) and high salinity (8.0 dS m-1) stresses were used as treatments. Increased water salinities caused increases in electrical conductivity and pH values of saturated soil paste extracts and drainage waters, while decreases in water use affected plant height storage root yield and water use efficiency. The salinity threshold and slope values of red beet were determined as 3.10 dS m-1 and 4.42% per dS m-1.

RNA-seq Provides Novel Insights into Response to Acute Salinity Stress in Oriental River Prawn Macrobrachium nipponense.

The oriental river prawn Macrobrachium nipponense is an important aquaculture species in China, Vietnam, and Japan. This species could survive in the salinity ranging from 7 to 20 ppt and accelerate growth in the salinity of 7 ppt. To identify the genes and pathways in response to acute high salinity stress, M. nipponense was exposed to the acute high salinity of 25 ppt. Total RNA from hepatopancreas, gills, and muscle tissues was isolated and then sequenced using high-throughput sequencing method. Differentially expressed genes (DGEs) were identified, and a total of 632, 836, and 1246 DEGs with a cutoff of significant twofold change were differentially expressed in the hepatopancreas, gills, and muscle tissues, respectively. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genome pathway enrichment analyses were conducted. These DEGs were involved in the GO terms of cellular process, metabolic process, membrane, organelle, binding, and catalytic activity. The DEGs of hepatopancreas and gill tissues were mainly enriched in PPAR signaling pathway, longevity regulating pathway, protein digestion and absorption, and the DEGs of muscle tissue in arginine biosynthesis, adrenergic signaling in cardiomyocytes, cardiac muscle contraction, and cGMP-PKG signaling pathway. Real-time PCR conducted with fifteen selected DEGs indicated high reliability of digital analysis using RNA-Seq. The results indicated that the M. nipponense may regulate essential mechanisms such as metabolism, oxidative stress, and ion exchange to adapt the alternation of environment, when exposed to acute high salinity stress. This work reveals the numbers of genes modified by salinity stress and some important pathways, which could provide a comprehensive insight into the molecular responses to high salinity stress in M. nipponense and further boost the understanding of the potential molecular mechanisms of adaptation to salinity stress for euryhaline crustaceans.

Response of simultaneous sulfide and nitrate removal process on acute toxicity of substrate concentration and salinity: Single toxicity and combined toxicity.

Simultaneous sulfide and nitrate removal process has performed excellent to treat nitrogen and sulfur pollutants in wastewater treatment. A high salinity stress poses a great challenge to the treatment of highly saline wastewater containing nitrate and sulfide. In addition, sulfide and nitrates are also toxic for the process, and their high concentration would inhibit the process. Therefore, the current work explores the single acute toxic effect and combined toxic effect of salinity and substrate concentration on the performance of the process from the perspective of toxicology. Considering sulfide and nitrate removal performance as an indicator, the IC50 values of sulfide were 293.20 mg S/L and 572.30 mg S/L, respectively; while those of salinity were 6.14% wt (91.78 mS/cm) and 6.63% wt (98.73 mS/cm), respectively. High substrate concentration or salinity resulted in elemental sulfur generation. The molar ratio of generated elemental sulfur to consumed sulfide(R-Sulfate) was close to 1. The response of nitrate reduction product to the elevating substrate concentration was not obvious, while its response to increasing salinity was on the contrary. With the increasing salinity (1.2% wt to 9.6% wt), molar ratio of generated nitrogen gas to consumed nitrate (R-Nitrogen gas) increased from 0.58 to 1, while molar ratio of generated nitrite to consumed nitrate (R-Nitrite) decreased from 0.43 to 0. Factorial analysis test revealed that the combined acute toxicity of substrate and salinity on sulfide oxidization and nitrate reduction were both antagonistic effects.

Microbial mediation of salinity stress response varies by plant genotype and provenance over time

Although it is becoming widely appreciated that microbes can enhance plant tolerance to environmental stress, the nature of microbial mediation of exposure responses is not well understood. We addressed this deficit by examining whether microbial mediation of plant responses to elevated salinity is contingent on the environment and factors intrinsic to the host. We evaluated the influence of contrasting environmental conditions relative to host genotype, provenance and evolution by conducting a common-garden experiment utilizing ancestral and descendant cohorts of Schoenoplectus americanus genotypes recovered from two 100+ year coastal marsh seed banks. We compared S. americanus productivity and trait variation as well as associated endophytic microbial communities according to plant genotype, provenance, and age cohort under high and low salinity stress with and without native soil inoculation. The magnitude and direction of microbial mediation of S. americanus responses to elevated salinity varied according to individual genotype, provenance, as well as temporal shifts in genotypic variation and G × E (gene by environment) interactions. Relationships differed between plant traits and the structure of endosphere communities. Our findings indicate that plant-microbe associations and microbial mediation of plant stress are not only context-dependent but also dynamic. Our results additionally suggest that evolution can shape the fate of marsh ecosystems by altering how microbes confer plant tolerance to pressures linked to global change.

Overexpression of MxbHLH18 Increased Iron and High Salinity Stress Tolerance in Arabidopsis thaliana.

In the life cycle of apple, it will suffer a variety of abiotic stresses, such as iron stress and salt stress. bHLH transcription factors (TFs) play an indispensable role in the response of plants to stress. In this study, a new bHLH gene named MxbHLH18 was separated from Malus xiaojinensis. According to the results of subcellular localization, MxbHLH18 was localized in the nucleus. Salt stress and iron stress affected the expression of MxbHLH18 in Malus xiaojinensis seedlings to a large extent. Due to the introduction of MxbHLH18, the resistance of Arabidopsis thaliana to salt, high iron and low iron was significantly enhanced. Under the environmental conditions of high iron and low iron, the overexpression of MxbHLH18 increased many physiological indexes of transgenic Arabidopsis compared to wild type (WT), such as root length, fresh weight and iron content. The high level expression of MxbHLH18 in transformed Arabidopsis thaliana can not only increased the content of chlorophyll and proline, as well as increasing the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT); it also reduced the content of malondialdehyde (MDA), which was more obvious under high salt conditions. In addition, the relative conductivity, H2O2 content and O2− content in transgenic Arabidopsis decreased under salt stress. Meanwhile, MxbHLH18 can also regulate the expression of downstream genes associated with salt stress (AtCBF1/2/3, AtKIN1 and AtCOR15a/b) and iron stress (AtIRT1, AtFRO2, AtNAS2, ATACT2, AtZIF1 and AtOPT3). Therefore, MxbHLH18 can actively promote the adaptability of plants to the growth environment of salt and low and/or iron.

Acetate and hypertonic stress stimulate vacuole membrane fission using distinct mechanisms.

Vacuoles in plants and fungi play critical roles in cell metabolism and osmoregulation. To support these functions, vacuoles change their morphology, e.g. they fragment when these organisms are challenged with draught, high salinity or metabolic stress (e.g. acetate accumulation). In turn, morphology reflects an equilibrium between membrane fusion and fission that determines size, shape and copy number. By studying Saccharomyces cerevisiae and its vacuole as models, conserved molecular mechanisms responsible for fusion have been revealed. However, a detailed understanding of vacuole fission and how these opposing processes respond to metabolism or osmoregulation remain elusive. Herein we describe a new fluorometric assay to measure yeast vacuole fission in vitro. For proof–of–concept, we use this assay to confirm that acetate, a metabolic stressor, triggers vacuole fission and show it blocks homotypic vacuole fusion in vitro. Similarly, hypertonic stress induced by sorbitol or glucose caused robust vacuole fission in vitro whilst inhibiting fusion. Using wortmannin to inhibit phosphatidylinositol (PI) -kinases or rGyp1-46 to inactivate Rab–GTPases, we show that acetate stress likely targets PI signaling, whereas osmotic stress affects Rab signaling on vacuole membranes to stimulate fission. This study sets the stage for further investigation into the mechanisms that change vacuole morphology to support cell metabolism and osmoregulation.

In silico analysis of enzymes involved in mycosporine-like amino acids biosynthesis in Euhalothece sp.: Structural and functional characterization

Mycosporine-like amino acids (MAAs) are ultraviolet-absorbing compounds synthesized by photoautotrophic microorganisms such as cyanobacteria. They have applications as UV protectants and antioxidants in the cosmetic and pharmaceutical sectors. To date, >30 different types of MAAs have been identified, having an absorption range between 310 and 365 nm that covers most of the UVR spectrum (~295–400 nm). In the study, MAAs were extracted and partially purified from a euryhaline Euhalothece sp. Thereafter, in silico analysis of the MAAs biosynthetic genes was conducted to determine the physicochemical characteristics, structural properties, functional analysis and homology model. High salinity stress (120 g L−1) significantly enhanced the production of MAAs (~56 %) in Euhalothece sp. Bioinformatics analysis of the genome of Euhalothece sp. revealed a distinctive mys gene cluster that contained six genes (mysA to mysE), compared to four genes commonly found in MAA-producing cyanobacteria. Interestingly, both EEVS and DHQ synthase were present, indicating the potential to synthesize MAAs via both the shikimate and sedoheptulose 7-phosphate pathways. Secondary structure analysis confirmed that in all the biosynthetic enzymes, the major components were the alpha-helices with random coils. This study emphasized the unique genes for MAAs in Euhalothece sp. as well as highlighted the potential metabolite pathways for commercial production. Elucidation of the protein structure, physicochemical properties, and interactions provides scientific insight into the biosynthesis of MAAs from hypersaline cyanobacteria. Additionally, it is essential for determining the applications of these novel photoprotective compounds.

Insights from a Multi-Omics Integration (MOI) Study in Oil Palm (Elaeis guineensis Jacq.) Response to Abiotic Stresses: Part One-Salinity.

Oil palm (Elaeis guineensis Jacq.) is the number one source of consumed vegetable oil nowadays. It is cultivated in areas of tropical rainforest, where it meets its natural condition of high rainfall throughout the year. The palm oil industry faces criticism due to a series of practices that was considered not environmentally sustainable, and it finds itself under pressure to adopt new and innovative procedures to reverse this negative public perception. Cultivating this oilseed crop outside the rainforest zone is only possible using artificial irrigation. Close to 30% of the world’s irrigated agricultural lands also face problems due to salinity stress. Consequently, the research community must consider drought and salinity together when studying to empower breeding programs in order to develop superior genotypes adapted to those potential new areas for oil palm cultivation. Multi-Omics Integration (MOI) offers a new window of opportunity for the non-trivial challenge of unraveling the mechanisms behind multigenic traits, such as drought and salinity tolerance. The current study carried out a comprehensive, large-scale, single-omics analysis (SOA), and MOI study on the leaves of young oil palm plants submitted to very high salinity stress. Taken together, a total of 1239 proteins were positively regulated, and 1660 were negatively regulated in transcriptomics and proteomics analyses. Meanwhile, the metabolomics analysis revealed 37 metabolites that were upregulated and 92 that were downregulated. After performing SOA, 436 differentially expressed (DE) full-length transcripts, 74 DE proteins, and 19 DE metabolites underwent MOI analysis, revealing several pathways affected by this stress, with at least one DE molecule in all three omics platforms used. The Cysteine and methionine metabolism (map00270) and Glycolysis/Gluconeogenesis (map00010) pathways were the most affected ones, each one with 20 DE molecules.

Effects of Salinity Stress at Reproductive Growth Stage on Rice (Oryza sativa L.) Composition, Starch Structure, and Physicochemical Properties.

This study aimed to investigate the changes in polished rice composition, starch structure, and physicochemical properties from three rice cultivars treated with medium and high salinity stress at the reproductive growth stage. The results showed that salt stress led to poor milling and appearance quality, higher total starch content, protein content, higher proportion of the medium, and long chains of amylopectin, as well as gelatinization temperature (GT) but lower amylose content and lower proportion of the short chain of amylopectin. Compared with salt-sensitive cultivars, the salt-tolerant cultivars exhibited lower GT and gelatinization enthalpy, better pasting properties, and more stable crystal structure; therefore, their eating and cooking quality (ECQ) was less affected. The above results imply that salt stress at the reproductive growth stage can degrade ECQ and can slightly increase the pasting property of starch from salt-tolerant rice cultivar.

Label-free quantification proteomics analysis reveals acute hyper-osmotic responsive proteins in the gills of Chinese mitten crab (Eriocheir sinensis)

Chinese mitten crab (Eriocheir sinensis) is a typical euryhaline crustacean to study osmotic regulation of crustaceans. Osmotic-regulation of Chinese mitten crab is a complex process. In order to study the osmotic-regulation related proteins of Chinese mitten crab, we domesticated Chinese mitten crab for 144 h with 25 salinity sea water (SW) and 0 salinity fresh water (FW) respectively, and then analyzed the proteome of its posterior gills. A total of 1453 proteins were identified by label free proteomics. Under the threshold of 2 fold change (FC), 242 differentially expressed proteins (DEPs) were screened, including 122 up-regulated DEPs and 120 down-regulated DEPs. GO database and KEGG database were used to annotate and enrich DEPs. It was found that DEPs were significantly enriched in energy metabolism, signal transduction, ion transport, actin cytoskeleton, immunity, lipid metabolism, amino acid metabolism and other biological functions. After 144 h of high salinity stress, the energy metabolism of Chinese mitten crab decreased and the expression of actin and cytoskeleton protein increased. In order to cope with oxidative damage caused by high salinity, Chinese mitten crab improved its immunity and antioxidant capacity.

The Sweetpotato Voltage-Gated K+ Channel β Subunit, KIbB1, Positively Regulates Low-K+ and High-Salinity Tolerance by Maintaining Ion Homeostasis.

Voltage-gated K+ channel β subunits act as a structural component of Kin channels in different species. The β subunits are not essential to the channel activity but confer different properties through binding the T1 domain or the C-terminal of α subunits. Here, we studied the physiological function of a novel gene, KIbB1, encoding a voltage-gated K+ channel β subunit in sweetpotato. The transcriptional level of this gene was significantly higher in the low-K+-tolerant line than that in the low-K+-sensitive line under K+ deficiency conditions. In Arabidopsis, KIbB1 positively regulated low-K+ tolerance through regulating K+ uptake and translocation. Under high-salinity stress, the growth conditions of transgenic lines were obviously better than wild typr (WT). Enzymatic and non-enzymatic reactive oxygen species (ROS) scavenging were activated in transgenic plants. Accordingly, the malondialdehyde (MDA) content and the accumulation of ROS such as H2O2 and O2− were lower in transgenic lines under salt stress. It was also found that the overexpression of KIbB1 enhanced K+ uptake, but the translocation from root to shoot was not affected under salt stress. This demonstrates that KIbB1 acted as a positive regulator in high-salinity stress resistance through regulating Na+ and K+ uptake to maintain K+/Na+ homeostasis. These results collectively suggest that the mechanisms of KIbB1 in regulating K+ were somewhat different between low-K+ and high-salinity conditions.

Multi-omics Analysis of Young Portulaca oleracea L. Plants' Responses to High NaCl Doses Reveals Insights into Pathways and Genes Responsive to Salinity Stress in this Halophyte Species.

The online version contains supplementary material available at 10.1007/s43657-022-00061-2.

Modulating effect of elevated water hardness on growth performance, ammonia dynamics and ion-regulatory capacity in channel catfish (Ictalurus punctatus) following chronic challenge with high environmental ammonia and salinity stress

The aim of this study was to assess whether rearing fish at increased water hardness could assist channel catfish (Ictalurus punctatus) juveniles to efficiently cope with later (sub)lethal ammonia exposure or salinity stress. Fish were subjected to 100, 494 (10% of 96 h-LC50) or 1250 mg/L (25% of 96 h-LC50) CaCO3 water hardness levels for two months. Afterwards, fish were challenged with high environmental ammonia (HEA; 12.2 mg/L total ammonia ~25% of 96 h-LC50 value) or salinity stress (SST;10 ppt) separately for 21 days at their respective water hardness levels. Results show that after two months, weight gain (%), specific growth rate and feed conversion in 1250 mg/L CaCO3 group were markedly worse than 100 and 494 mg/L CaCO3 groups. This finding was accompanied with a down-regulation of hepatic IGF-I and growth hormone receptors (GHR) mRNA levels. During SST, growth was still significantly worse for those at 1250 mg/L CaCO3 (1250SST). However, exposure to HEA inhibited growth for 100HEA and 494HEA relative to 1250HEA. Ammonia excretion rate (Jamm) remained similar at different hardness levels; however, this was strongly inhibited at 100HEA, 494HEA and 100SST. This appeared to align to some degree with high water hardness having a protective effect on the gill histomorphology. In fact, fish at 1250HEA were able to increase Jamm efficiently, which was associated with upregulated branchial expression of ammonia transporters (Rhesus glycoproteins ‘Rhcg’) and Na+/H+ exchanger, as well as augmented gill H+-ATPase activity. These responses prevented a build-up of excess ammonia in plasma. In contrast, both 1250 mg/L CaCO3 and 1250HEA groups displayed inhibited branchial Na+/K+-ATPase activity indicating this unlikely has a major role in ammonia excretion. Gill Ca2+-ATPase activities reduced at the highest hardness (1250 mg/L CaCO3) and 1250HEA groups, likely to prevent hypercalcemia in plasma. No differences among hardness levels were noted for ion-regulation or Ca2+- homeostasis under SST. Overall, findings suggest that although elevated water hardness up to 1250 mg/L CaCO3 adversely affects the growth performance of channel catfish, it can ameliorate the inhibitory growth effects of HEA. This was partly attributed to 1250 mg/L CaCO3 protecting the gills as well as mitigating HEA-induced ammonia excretory and ion-regulatory disruption. However, elevated hardness may not be as effective in alleviating salinity stress in catfish.

Comparative Transcriptome Analysis Reveals the Adaptation Mechanism to High Salinity in Litopenaeus vannamei

As an euryhaline commercial species, the Pacific white shrimp Litopenaeus vannamei can be cultured under a wide range of salinities. However, different families showed various tolerance to high salinity. In order to elucidate the underlying mechanisms, a comparative transcriptome approach was used to find the differences between tolerant families and susceptible families at the transcriptional level. There were 98 and 58 differentially expressed genes (DEGs) between tolerant and susceptible families under normal and high-salinity conditions, respectively. The DEGs upregulated in tolerant families were mostly enriched in the biological process of response to a stimulus. Nine crustacyanin (CRCN)-encoding genes in this Gene Ontology (GO) term showed significantly higher expression levels in the tolerant families than those in susceptible families, suggesting that crustacyanins might play important roles in shrimp tolerance to high salinity. After high-salinity treatment, a total of 233 and 109 DEGs were identified from tolerant and susceptible families, respectively. Serine-type endopeptidase activity, serine-type peptidase activity, and serine hydrolase activity were the top three GO terms in the tolerant families after high-salinity treatment. Further analysis illustrated that these three GO terms were also the top three enriched GO terms for the DEGs specifically upregulated in the tolerant families after high-salinity stress. Meanwhile, four genes annotated in serine proteases families in these three GO terms were upregulated in the tolerant families but not changed in the susceptible families after high-salinity stress. These results indicated that serine proteases should play key roles in shrimp tolerance to high salinity. This study provides important information for understanding the mechanism of shrimp tolerance to high-salinity stress and would be useful for further molecular breeding of shrimp varieties with high-salinity tolerance.

A comparative meta-proteomic pipeline for the identification of plasmodesmata proteins and regulatory conditions in diverse plant species

BackgroundA major route for cell-to-cell signalling in plants is mediated by cell wall-embedded pores termed plasmodesmata forming the symplasm. Plasmodesmata regulate the plant development and responses to the environment; however, our understanding of what factors or regulatory cues affect their structure and permeability is still limited. In this paper, a meta-analysis was carried out for the identification of conditions affecting plasmodesmata transport and for the in silico prediction of plasmodesmata proteins in species for which the plasmodesmata proteome has not been experimentally determined.ResultsUsing the information obtained from experimental proteomes, an analysis pipeline (named plasmodesmata in silico proteome 1 or PIP1) was developed to rapidly generate candidate plasmodesmata proteomes for 22 plant species. Using the in silico proteomes to interrogate published transcriptomes, gene interaction networks were identified pointing to conditions likely affecting plasmodesmata transport capacity. High salinity, drought and osmotic stress regulate the expression of clusters enriched in genes encoding plasmodesmata proteins, including those involved in the metabolism of the cell wall polysaccharide callose. Experimental determinations showed restriction in the intercellular transport of the symplasmic reporter GFP and enhanced callose deposition in Arabidopsis roots exposed to 75-mM NaCl and 3% PEG (polyethylene glycol). Using PIP1 and transcriptome meta-analyses, candidate plasmodesmata proteins for the legume Medicago truncatula were generated, leading to the identification of Medtr1g073320, a novel receptor-like protein that localises at plasmodesmata. Expression of Medtr1g073320 affects callose deposition and the root response to infection with the soil-borne bacteria rhizobia in the presence of nitrate.ConclusionsOur study shows that combining proteomic meta-analysis and transcriptomic data can be a valuable tool for the identification of new proteins and regulatory mechanisms affecting plasmodesmata function. We have created the freely accessible pipeline PIP1 as a resource for the screening of experimental proteomes and for the in silico prediction of PD proteins in diverse plant species.

Evaluating soil salts dynamics under biodegradable film mulching with different disintegration rates in an arid region with shallow and saline groundwater: Experimental and modeling study

Soil salinization caused by shallow, saline groundwater represents a serious threat to field productivity, especially in arid regions with intense soil evaporation. Plastic film mulching (PM) has been increasingly applied to reduce soil evaporation and alleviate soil salinity stress. However, PM introduces into the soil a significant amount of plastic residues. Although biodegradable film mulching (BM) is an ideal alternative to PM due to the degradability of these films, unreasonably high disintegration rates may reduce the benefits of the proposed solution. Understanding the effects of these factors on soil salinity is essential for designing management options for improving water productivity. A two-year cornfield experiment was therefore carried out during 2019–2020 to evaluate differences in soil salt dynamics among treatments with BMs with low, medium, and high disintegration rates (BML, BMM, BMH), one polyethylene film mulching (PM), and no mulching (NM). Additionally, the HYDRUS-2D model was used to evaluate the electrical conductivity of the saturation paste extract (ECe), soil salt fluxes, salt distributions, and salt mass balances in two-dimensional soil profiles under BML, BMM, BMH, PM, and NM. The results showed that calibrated HYDRUS-2D could precisely simulate soil salinity under different mulching treatments. There were large differences between various treatments in the middle and late crop growth stages (Days After Sowing [DAS] 61–140). The highest ECe among different BM treatments occurred in BMH. Additionally, the two-dimensional distribution of soil salinity under BM was affected by irrigation events. The high soil salinity stress area (ECe > 3.80 dS m−1) occurred one day after irrigation (DAS 108) only under BMH among different BM treatments. Meanwhile, root water uptake (RWU) and crop yield (CY) under BMH were significantly reduced due to excessive accumulation of soil salinity in the root zone under intensive soil evaporation conditions. Compared with BMH and BMM, BML increased CY and the leaching ratio of soil salts from the root zone due to its good performance in water conservation. Thus, BM with a low disintegration rate is more efficient in controlling soil salinization in soils with a shallow groundwater table than BMs with higher disintegration rates due to lower soil evaporation. The findings of this study improve the understanding of the mechanisms of salt dynamics under biodegradable film mulching with different disintegration rates. The study also recommends to the farmers and government a suitable disintegration rate of the biodegradable film that can be adopted to promote field productivity.

The Response and Survival Mechanisms of Staphylococcus aureus under High Salinity Stress in Salted Foods.

Staphylococcus aureus (S. aureus) has a strong tolerance to high salt stress. It is a major reason as to why the contamination of S. aureus in salted food cannot be eradicated. To elucidate its response and survival mechanisms, changes in the morphology, biofilm formation, virulence, transcriptome, and metabolome of S. aureus were investigated. IsaA positively regulates and participates in the formation of biofilm. Virulence was downregulated to reduce the depletion of nonessential cellular functions. Inositol phosphate metabolism was downregulated to reduce the conversion of functional molecules. The MtsABC transport system was downregulated to reduce ion transport and signaling. Aminoacyl-tRNA biosynthesis was upregulated to improve cellular homeostasis. The betaine biosynthesis pathway was upregulated to protect the active structure of proteins and nucleic acids. Within a 10% NaCl concentration, the L-proline content was upregulated to increase osmotic stability. In addition, 20 hub genes were identified through an interaction analysis. The findings provide theoretical support for the prevention and control of salt-tolerant bacteria in salted foods.

Deep Untargeted Metabolomics Analysis to Further Characterize the Adaptation Response of Gliricidia sepium (Jacq.) Walp. to Very High Salinity Stress.

The multipurpose tree Gliricidia sepium (Jacq.) Walp. adapts to a very high level of salt stress (≥20 dS m−1) and resumes the production of new leaves around 2 weeks after losing all leaves due to abrupt salinity stress. The integration of metabolome and transcriptome profiles from gliricidia leaves points to a central role of the phenylpropanoid biosynthesis pathway in the short-term response to salinity stress. In this study, a deeper untargeted metabolomics analysis of the leaves and roots of young gliricidia plants was conducted to characterize the mechanism(s) behind this adaptation response. The polar and lipidic fractions from leaf and root samples were extracted and analyzed on a UHPLC.ESI.Q-TOF.HRMS system. Acquired data were analyzed using the XCMS Online, and MetaboAnalyst platforms, via three distinct and complementary strategies. Together, the results obtained first led us to postulate that these plants are salt-excluding plants, which adapted to high salinity stress via two salt-excluding mechanisms, starting in the canopy—severe defoliation—and concluding in the roots—limited entry of Na. Besides that, it was possible to show that the phenylpropanoid biosynthesis pathway plays a role throughout the entire adaptation response, starting in the short term and continuing in the long one. The roots metabolome analysis revealed 11 distinct metabolic pathways affected by salt stress, and the initial analysis of the two most affected ones—steroid biosynthesis and lysine biosynthesis—led us also to postulate that the accumulation of lignin and some phytosterols, as well as lysine biosynthesis—but not degradation, play a role in promoting the adaptation response. However, additional studies are necessary to investigate these hypotheses.

Molecular mechanisms affecting the difference in salinity adaptability between juvenile and adult Hong Kong oysters

The Hong Kong oyster (Crassostrea hongkongensis) lives in the brackish waters of estuaries in the intertidal zone and has a high resistance to low levels of salinity, but low resistance to higher levels. Juveniles are more sensitive to high levels of salinity than adults. To better understand the mechanisms underlying these differences, we performed a high-salinity stress analysis of juvenile and adult Hong Kong oysters. Trait analysis between groups showed that Na+-K+-ATPase activity, T-AOC, betaine, taurine and glycogen content of the high-salinity group were almost all higher than that of the control group at 8 h under high-salt stress, but lower than that of the control group at 96 h. The differences are more significant in Adult population. The results indicate that these indexes are related to the salinity adaptability of oysters. Enrichment analysis and protein-protein interaction (PPI) network analysis of the differentially expressed genes (DEGs) screened from transcriptomic data showed that their functions were mainly related to the oxidation-reduction process, immune response, protein ubiquitination and ATP synthesis. Furthermore, a weighted gene co-expression network analysis (WGCNA) of all samples showed that the hub gene functions were mainly associated with the oxidation-reduction process and immune response. These results indicate that immune response-related and antioxidant genes play key roles in the adaptability of Hong Kong oysters to high salinity. This study provides new insights and enriches our current understanding of the salinity adaptation mechanisms in oysters.