Ionic Stress Research Articles

Chemogenomic profiling in yeast reveals antifungal mode-of-action of polyene macrolactam auroramycin.

In this study, we report antifungal activity of auroramycin against Candida albicans, Candida tropicalis, and Cryptococcus neoformans. Auroramycin, a potent antimicrobial doubly glycosylated 24-membered polyene macrolactam, was previously isolated and characterized, following CRISPR-Cas9 mediated activation of a silent polyketide synthase biosynthetic gene cluster in Streptomyces rosesporous NRRL 15998. Chemogenomic profiling of auroramycin in yeast has linked its antifungal bioactivity to vacuolar transport and membrane organization. This was verified by disruption of vacuolar structure and membrane integrity of yeast cells with auroramycin treatment. Addition of salt but not sorbitol to the medium rescued the growth of auroramycin-treated yeast cells suggesting that auroramycin causes ionic stress. Furthermore, auroramycin caused hyperpolarization of the yeast plasma membrane and displayed a synergistic interaction with cationic hygromycin. Our data strongly suggest that auroramycin inhibits yeast cells by causing leakage of cations from the cytoplasm. Thus, auroramycin’s mode-of-action is distinct from known antifungal polyenes, reinforcing the importance of natural products in the discovery of new anti-infectives.

Effect of irrigation with saline water on ion homeostasis and forage dry yield in Alfalfa ecotypes application of high salty water for Alfalfa plants irrigation

Salinity stress is a brutal environmental stress which decreases the yield production of plants. Questions rise on which of the ionic stress or lack of water has deleterious effects on plants forage dry yield. Also, questions remain on whether the K+ reduction or Na+ accumulation is more important in forage dry yield reduction under salinity stress. The present experiment was conducted to answer the above questions in four alfalfa ecotypes. To do so, 6-7 weeks seedlings were irrigated with high salty water (EC=20dS m-1) and RWC, MSI, height, forage dry yield, Na+ and K+ were measured 1, 3, 6, 10, and 16 days after the salt shock. The results showed that one day after irrigation with saline water, all measured traits changed adversely. Salinity stress by decreasing K+ and increasing Na+ content reduced the growth of alfalfa plants. RWC reduction was less than K+ reduction or Na+ accumulation, so ionic stress had more deleterious effects on forage dry yield of alfalfa plants. Root cells had a higher content of K+ and Na+ ions compared with leaves, hence, they had a major defensive role against salinity stress. The K+/Na+ ratio reduction in saline condition was the main element for decreasing plant forage dry yield. The application of high salty water for irrigation of alfalfa plants is possible if there is a good subsoil drainage system to remove the leached saline water regularly from the soil. It is also suggested that foliar application of potassium may be ameliorate harmful effects of salinity stress in plant growth.

Functional domain analysis of LmSAP protein reveals the crucial role of the zinc-finger A20 domain in abiotic stress tolerance.

Stress-associated proteins (SAPs), such as A20/AN1 zinc-finger domain-containing proteins, have emerged as a novel class of proteins involved in abiotic stress signaling, and they are important candidates for preventing the loss of yield caused by exposure to environmental stresses. In a previous report, it was found that the ectopic-expression of Lobularia maritima stress-associated protein, LmSAP, conferred tolerance to abiotic and heavy metal stresses in transgenic tobacco plants. This study aimed to investigate the functions of the A20 and AN1 domains of LmSAP in salt and osmotic stress tolerance. To this end, in addition to the full-length LmSAP gene, we have generated three LmSAP-truncated forms (LmSAPΔA20, LmSAPΔAN1, and LmSAPΔA20-ΔAN1). Heterologous expression in Saccharomyces cerevisiae of different truncated forms of LmSAP revealed that the A20 domain is essential to increase cell tolerance to salt, ionic, and osmotic stresses. Transgenic tobacco plants overexpressing LmSAP and LmSAPΔAN1 constructs exhibited higher tolerance to salt and osmotic stresses in comparison to the non-transgenic plants (NT) and lines transformed with LmSAPΔA20 and LmSAPΔA20-ΔAN1 constructs. Similarly, transgenic plants overexpressing the full-length LmSAP gene and LmSAPΔAN1 truncated domain maintained higher superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) enzymatic activities due to the high expression levels of the genes encoding these key antioxidant enzymes, MnSOD, POD, and CAT1, as well as accumulated lower levels of malondialdehyde (MDA) under salt and osmotic stresses compared to NT and LmSAPΔA20 and LmSAPΔA20-ΔAN1 forms. These findings provide insights into the pivotal role of A20 and AN1 domains of LmSAP protein in salt and osmotic stress tolerance.

Overexpression of the NAC transcription factor JUNGBRUNNEN1 (JUB1) increases salinity tolerance in tomato

Soil salinity is a major abiotic stress affecting plant growth and yield, due to both osmotic and ionic stresses. JUBGBRUNNEN1 (JUB1) is a NAC family transcription factor that has been shown to be involved in responses to abiotic stresses, such as water deficit, osmotic, salinity, heat and oxidative stress. In Arabidopsis thaliana (Arabidopsis), JUB1 has been shown to improve plant stress tolerance by regulating H2O2 levels. In the horticultural crop, Solanum lycopersicum cv. Moneymaker (tomato), overexpression of AtJUB1 has been shown to partially alleviate water deficit stress at the vegetative stage. In this study, we investigated the effect of Arabidopsis JUB1 overexpression in salinity tolerance in tomato. In hydroponically grown tomato seedlings, AtJUB1 overexpression results in higher prolines levels and improves the maintenance of water content in the plant under salinity stress. The transgenic tomato plants are more tolerant to salinity stress compared to control lines based on plant biomass. However, at the reproductive stage, we found that overexpression of AtJUB1 only provided marginal improvements in yield-related parameters, in the conditions used for the current work. The combination of improved water deficit and salinity stress tolerance conferred by AtJUB1 overexpression may be beneficial when tomato plants are grown in the field under marginal environments.

The Toxoplasma Vacuolar H+-ATPase Regulates Intracellular pH and Impacts the Maturation of Essential Secretory Proteins

SUMMARYVacuolar-proton ATPases (V-ATPases) are conserved complexes that couple the hydrolysis of ATP to the pumping of protons across membranes. V-ATPases are known to play diverse roles in cellular physiology. We studied the Toxoplasma gondii V-ATPase complex and discovered a dual role of the pump in protecting parasites against ionic stress and in the maturation of secretory proteins in endosomal-like compartments. Toxoplasma V-ATPase subunits localize to the plasma membrane and to acidic vesicles, and characterization of conditional mutants of the a1 subunit highlighted the functionality of the complex at both locations. Microneme and rhoptry proteins are required for invasion and modulation of host cells, and they traffic via endosome-like compartments in which proteolytic maturation occurs. We show that the V-ATPase supports the maturation of rhoptry and microneme proteins, and their maturases, during their traffic to their corresponding organelles. This work underscores a role for V-ATPases in regulating virulence pathways.

Different Hydrophobins of Fusarium graminearum Are Involved in Hyphal Growth, Attachment, Water-Air Interface Penetration and Plant Infection.

Hydrophobins (HPs) are small secreted fungal proteins possibly involved in several processes such as formation of fungal aerial structures, attachment to hydrophobic surfaces, interaction with the environment and protection against the host defense system. The genome of the necrotrophic plant pathogen Fusarium graminearum contains five genes encoding for HPs (FgHyd1-5). Single and triple FgHyd mutants were produced and characterized. A reduced growth was observed when the ΔFghyd2 and the three triple mutants including the deletion of FgHyd2 were grown in complete or minimal medium. Surprisingly, the growth of these mutants was similar to wild-type when grown under ionic, osmotic or oxidative stress conditions. All the mutant strains confirmed the ability to develop conidia and perithecia, suggesting that the FgHyds are not involved in normal development of asexual and sexual structures. A reduction in the ability of hyphae to penetrate through the water-air interface was observed for the single mutants ΔFghyd2 and ΔFghyd3 as well as for the triple mutants including the deletion of FgHyd2 and FgHyd3. Besides, ΔFghyd3 and the triple mutant ΔFghyd234 were also affected in the attachment to hydrophobic surface. Indeed, wheat infection experiments showed a reduction of symptomatic spikelets for ΔFghyd2 and ΔFghyd3 and the triple mutants only when spray inoculation was performed. This result could be ascribed to the affected ability of mutants deleted of FgHyd2 and FgHyd3 to penetrate through the water-air interface and to attach to hydrophobic surfaces such as the spike tissue. This hypothesis is strengthened by a histological analysis, performed by fluorescence microscopy, showing no defects in the morphology of infection structures produced by mutant strains. Interestingly, triple hydrophobin mutants were significantly more inhibited than wild-type by the treatment with a systemic triazole fungicide, while no defects at the cell wall level were observed.

Micro-nondestructive detection of the moisture and ion of rice seeds during germination under salt stress

Salt stress is one of the major stress factors limiting rice productivity. Its damaging effects include water deficit due to osmotic stress, and ionic toxicity caused by ionic stress. It is very important to study the salt-tolerance mechanism of rice under salt stress, in order to improve the salt-tolerance capacity of rice and thereby increase the yield. In this experiment, the low field nuclear magnetic resonance (LF NMR) technique and the traditional dry-weight weighing method, the non-invasive micro-test technique (NMT) and the inductively coupled plasma emission spectrometry (ICP-AES) were applied to analyze the distribution of water and the flow of K+ and Na+ of rice seeds during germination under NaCl stress. The results suggested that for all different NaCl concentrations, as germination hours grew, the amplitude of NMR signals of the bound water that of the free water and the total amplitude all increased gradually. And the higher the NaCl concentration is, the weaker the increase trend is. In addition, the moisture content of the seeds and the total amplitude of NMR signals were positively correlated. The regression equation was y =191.53x +1463.6, the correlation coefficient was R=0.9823, and the determination coefficient was R2=0.9650. By this regression equation, the moisture content of each state of water during seed germination can be calculated. When without NaCl stress, the rice seeds absorbed K+ in the germination process. However, when under NaCl stress at different concentrations, K+ efflux was detected. The contents of K+ and K+/Na+ were lower than that under the control condition. The higher NaCl concentration is, the lower the K+ and K+/Na+ contents are. These results are in consistence with the K+ and Na+ contents detected by the inductively coupled technique. These empirical data offer a reference for the study of rice-seeds’ response mechanism under salt stress during germination and the screening of germplasm resources, and also put forward a new method of biopsy micro-nondestructive test for plants under stress. Keywords: nuclear magnetic resonance (NMR), non-invasive micro-test (NMT), NaCl stress, seed germination, moisture, dynamic ion flow DOI: 10.25165/j.ijabe.20191202.4245 Citation: H W Yang, J W Ji, C Wang, L Y Zhang, X D Wang, P Song, et al. Micro-nondestructive detection of the moisture and ion of rice seeds during germination under salt stress. Int J Agric & Biol Eng, 2019; 12(2): 103–110.

NaCl triggers the CRP-dependent increase of cAMP in Mycobacterium tuberculosis

The second messenger 3′,5′-cyclic adenosine monophosphate (3′,5′-cAMP) has been shown to be involved in the regulation of many biological processes ranging from carbon catabolite repression in bacteria to cell signalling in eukaryotes. In mycobacteria, the role of cAMP and the mechanisms utilized by the bacterium to adapt to and resist immune and pharmacological sterilization remain poorly understood. Among the stresses encountered by bacteria, ionic and non-ionic osmotic stresses are among the best studied. However, in mycobacteria, the link between ionic osmotic stress, particularly sodium chloride, and cAMP has been relatively unexplored. Using a targeted metabolic analysis combined with stable isotope tracing, we show that the pathogenic Mycobacterium tuberculosis but not the opportunistic pathogen Mycobacterium marinum nor the non-pathogenic Mycobacterium smegmatis responds to NaCl stress via an increase in intracellular cAMP levels. We further showed that this increase in cAMP is dependent on the cAMP receptor protein and in part on the threonine/serine kinase PnkD, which has previously been associated with the NaCl stress response in mycobacteria.

Suplementación de betaína en la dieta de cerdos en terminación: Revisión

Increasing fat deposition and feed conversion over the days in the finishing phase are factors that directly implicate in pork quality and productive profitability. Nonetheless, heavier pigs result in benefits for the slaughterhouse due lower labor and equipment costs and economic benefits resulting from the dilution of production and processing costs, as well as economic benefits for the pig producer resulting from the dilution of production costs. Therefore, dietary supplementation of betaine for finishing pigs of high lean-genotypes is a strategy to increase lean tissue deposition and minimize fat deposition. Thereby, the aim of this study was to present and discuss the action mechanisms, role and recent results of dietary supplementation of this carcass modifier on performance and carcass traits in finishing pigs. Betaine acts mainly as a methyl groups donor, which increases the methionine availability for protein accretion. On osmoprotective effects, betaine accumulates in cellular organelles, protecting them against osmotic and ionic stresses, which reduce spending energy to keep the cellular homeostasis, becoming an important during the hot periods of the year.

Ionic Stress Prompts Premature Hatching of Zebrafish (Danio rerio) Embryos

Ionic homeostasis is an essential component of functioning cells, and ionic stress imposed by excessive salinity can disrupt cellular and physiological processes. Therefore, increasing salinity of aquatic environments—a consequence of global climate change—has the potential to adversely affect the health of aquatic animals and their ecosystems. The ability to respond adaptively to adverse environmental changes is essential for the survival of species, but animals in early embryonic stages may be particularly vulnerable, as they cannot easily escape from such conditions. Herein, the effects of increasing salinity on the mortality and hatching time of zebrafish (Danio rerio) embryos were investigated. Increasing salinity significantly affected mortality after 24 h of exposure beginning from <2 h post-fertilisation, with 10 parts per thousand (ppt) inducing complete lethality. The 24-h LC50 of NaCl to embryos was estimated to be approximately 5.6 ppt. Interestingly, 5 ppt, a test concentration only slightly lower than the LC50, induced earlier hatching than at lower concentrations. This earlier hatching was also observed even when exposure was commenced at later stages of embryogenesis, despite later-stage embryos not suffering appreciable mortality in response to salinity. The results suggest that earlier hatching is a plastic response which may function to enable embryos to evade unfavourable conditions.

Characterization of the Human Skeletal Muscle Metabolome for Elucidating the Mechanisms of Bicarbonate Ingestion on Strenuous Interval Exercise.

Bicarbonate has long been touted as a putative ergogenic aid that improves exercise performance and blood buffering capacity during strenuous exercise. However, the underlying mechanisms of action of bicarbonate intake on skeletal muscle metabolism have yet to be fully elucidated. Herein, we apply two orthogonal analytical platforms for nontargeted profiling of metabolites and targeted analysis of electrolytes from mass-limited muscle tissue biopsies (∼2 mg dried mass) when multisegment injection-capillary electrophoresis-mass spectrometry (MSI-CE-MS) and CE with indirect UV detection are used, respectively. Seven untrained men performed a standardized bout of high-intensity interval exercise trial following either bicarbonate (0.40 g/kg) or placebo ingestion in a double-blinded, placebo-controlled, crossover study design, where paired skeletal muscle tissue and plasma specimens were collected at three time intervals at rest, postexercise, and recovery. Optimization of a quantitative microextraction procedure was first developed for lyophilized tissue prior to characterization of the human muscle metabolome, which resulted in the identification and quantification of more than 80 polar/ionic metabolites reliably (CV < 30%) detected in a majority (>75%) of samples with quality control. Complementary univariate and multivariate statistical methods were used to identify biomarkers associated with strenuous exercise and/or bicarbonate treatment responses, whereas structural elucidation of biologically significant intramuscular metabolites was performed using high-resolution MS/MS. Importantly, bicarbonate ingestion prior to strenuous interval exercise was found to elicit a modest treatment effect ( p < 0.05) in comparison to placebo on metabolic pathways associated with ionic homeostasis (potassium), purine degradation (uric acid), and oxidative stress as regulated by glutathione metabolism (oxidized mixed glutathione disulfide) and histidine-containing dipeptides (anserine) within muscle tissue that was distinctive from dynamic metabolic changes measured in circulation. This work provides deeper biochemical insights into the effect of acute alkalosis in preserving contracting muscle function during high-intensity exercise, which is also applicable to the study of muscle-related pathologies relevant to human health and aging.

1-Methylcyclopropene Modulates Physiological, Biochemical, and Antioxidant Responses of Rice to Different Salt Stress Levels.

Salt stress in soil is a critical constraint that affects the production of rice. Salt stress hinders plant growth through osmotic stress, ionic stress, and a hormonal imbalance (especially ethylene), therefore, thoughtful efforts are needed to devise salt tolerance management strategies. 1-Methylcyclopropene (1-MCP) is an ethylene action inhibitor, which could significantly reduce ethylene production in crops and fruits. However, 1-MCPs response to the physiological, biochemical and antioxidant features of rice under salt stress, are not clear. The present study analyzed whether 1-MCP could modulate salt tolerance for different rice cultivars. Pot culture experiments were conducted in a greenhouse in 2016–2017. Two rice cultivars, Nipponbare (NPBA) and Liangyoupeijiu (LYP9) were used in this trial. The salt stress included four salt levels, 0 g NaCl/kg dry soil (control, CK), 1.5 g NaCl/ kg dry soil (Low Salt stress, LS), 4.5 g NaCl/kg dry soil (Medium Salt stress, MS), and 7.5 g NaCl/kg dry soil (Heavy Salt stress, HS). Two 1-MCP levels, 0 g (CT) and 0.04 g/pot (1-MCP) were applied at the rice booting stage in 2016 and 2017. The results showed that applying 1-MCP significantly reduced ethylene production in rice spikelets from LYP9 and NPBA by 40.2 and 23.9% (CK), 44.3 and 28.6% (LS), 28 and 25.9% (MS), respectively. Rice seedlings for NPBA died under the HS level, while application of 1-MCP reduced the ethylene production in spikelets for LYP9 by 27.4% compared with those that received no 1-MCP treatment. Applying 1-MCP improved the photosynthesis rate and SPAD value in rice leaves for both cultivars. 1-MCP enhanced the superoxide dismutase production, protein synthesis, chlorophyll contents (chl a, b, carotenoids), and decreased malondialdehyde, H2O2, and proline accumulation in rice leaves. Application of 1-MCP also modulated the aboveground biomass, and grain yield for LYP9 and NPBA by 19.4 and 15.1% (CK), 30.3 and 24% (LS), 26.4 and 55.4% (MS), respectively, and 34.5% (HS) for LYP9 compared with those that received no 1-MCP treatment. However, LYP9 displayed a better tolerance than NPBA. The results revealed that 1-MCP could be employed to modulate physiology, biochemical, and antioxidant activities in rice plants, at different levels of salt stress, as a salt stress remedy.

Exogenous 1-Aminocyclopropane-1-carboxylic acid Controls Photosynthetic Activity, Accumulation of Reactive Oxygen or Nitrogen Species and Macroelement Content in Tomato in Long-term Experiments

Exogenous ethylene (ET) or its precursor, 1-aminocyclopropane-1-carboxylic acid (ACC) may increase stress tolerance of plants in long-term experiments. ACC applied in hydroponic culture of tomato (Solanum lycopersicum L. cv. Rio Fuego) brought about concentration-dependent differences in plant responses. ACC at 0.01 µM changed K+ distribution between shoots and roots but at higher concentrations K+/86Rb+ uptake was inhibited. Surprisingly, excess Na+ and reduced K+ accumulation could be measured in root and leaf tissues, respectively, which at 100 µM ACC led to a decreased K+/Na+ ratio and to a weak ionic stress in these plant organs. ACC at low concentrations increased the net CO2 fixation rate (AN), however, at 100 µM, it triggered a parallel decline in stomatal conductance, AN and in the actual quantum yield of photosystem II. Photosystem I (PSI) was less sensitive to ACC, lower concentrations caused an increasing tendency in the effective quantum yield and changed the non-photochemical quenching profile of PSI from donor-side dominant to acceptor-side-dominant limitation. Photoinhibition was avoided via the dissipation of light energy by regulated non-photochemical quenching and by transiently enhanced cyclic electron flow (CEF) around PSI. The decrease in CEF at 100 µM ACC correlated well with the accumulation of O2•− and H2O2 in the leaf tissues suggesting that molecular oxygen may function as an electron acceptor when natural acceptors of the linear electron transport were over-reduced. Concentration-dependent changes in soluble sugars and sorbitol as osmoprotectants may also contribute to the stress resistance of plants elicited by ET/ACC.

PGPBS, a mitogen-activated protein kinase kinase, is required for vegetative differentiation, cell wall integrity, and pathogenicity of the barley leaf stripe fungus Pyrenophora graminea

The high-osmolarity glycerol (HOG) signaling pathway regulates the adaptation of fungi to environmental stressors. The mitogen-activated protein kinase kinase (MAPKK) PBS2 of Saccharomyces cerevisiae serves as a scaffold protein in the HOG pathway. We characterized the pgpbs gene of Pyrenophora graminea, which encodes a MAPKK that is 56% orthologous to PBS2 of S. cerevisiae. A cloning technique based on homology was applied to amplify the pgpbs gene. Specific silent mutations then were generated in pgpbs. We evaluated the potential roles of PGPBS in the osmotic response, vegetative differentiation, cell wall integrity, drug resistance, and pathogenicity. Our findings indicated that the pgpbs coding region comprises 2075 base pairs and encodes a protein of 676 amino acids. Mutants deficient in pgpbs expression had significant reductions in vegetative growth and were sensitive to calcofluor white (CFW), an inhibitor of cell wall synthesis. Mutants also lost pathogenicity and were sensitive to an osmotic stress–inducing medium containing NaCl and sorbitol. Moreover, mutants had increased resistance to the dicarboximide fungicide iprodione and the triazole fungicide tebuconazole. These findings suggest that pgpbs is involved in the osmotic and ionic stress responses, vegetative differentiation, cell wall integrity, virulence, and tolerance to iprodione and tebuconazole. We expect that our findings will help elucidate the pathogenesis of barley leaf stripe and will inform strategies for breeding resistance to this disease.

The Complex Fine-Tuning of K⁺ Fluxes in Plants in Relation to Osmotic and Ionic Abiotic Stresses.

As the main cation in plant cells, potassium plays an essential role in adaptive responses, especially through its involvement in osmotic pressure and membrane potential adjustments. K+ homeostasis must, therefore, be finely controlled. As a result of different abiotic stresses, especially those resulting from global warming, K+ fluxes and plant distribution of this ion are disturbed. The hormone abscisic acid (ABA) is a key player in responses to these climate stresses. It triggers signaling cascades that ultimately lead to modulation of the activities of K+ channels and transporters. After a brief overview of transcriptional changes induced by abiotic stresses, this review deals with the post-translational molecular mechanisms in different plant organs, in Arabidopsis and species of agronomical interest, triggering changes in K+ uptake from the soil, K+ transport and accumulation throughout the plant, and stomatal regulation. These modifications involve phosphorylation/dephosphorylation mechanisms, modifications of targeting, and interactions with regulatory partner proteins. Interestingly, many signaling pathways are common to K+ and Cl−/NO3− counter-ion transport systems. These cross-talks are also addressed.

Full-length transcript sequencing and comparative transcriptomic analysis to evaluate the contribution of osmotic and ionic stress components towards salinity tolerance in the roots of cultivated alfalfa (Medicago sativa L.)

BackgroundAlfalfa is the most extensively cultivated forage legume. Salinity is a major environmental factor that impacts on alfalfa’s productivity. However, little is known about the molecular mechanisms underlying alfalfa responses to salinity, especially the relative contribution of the two important components of osmotic and ionic stress.ResultsIn this study, we constructed the first full-length transcriptome database for alfalfa root tips under continuous NaCl and mannitol treatments for 1, 3, 6, 12, and 24 h (three biological replicates for each time points, including the control group) via PacBio Iso-Seq. This resulted in the identification of 52,787 full-length transcripts, with an average length of 2551 bp. Global transcriptional changes in the same 33 stressed samples were then analyzed via BGISEQ-500 RNA-Seq. Totals of 8861 NaCl-regulated and 8016 mannitol-regulated differentially expressed genes (DEGs) were identified. Metabolic analyses revealed that these DEGs overlapped or diverged in the cascades of molecular networks involved in signal perception, signal transduction, transcriptional regulation, and antioxidative defense. Notably, several well characterized signalling pathways, such as CDPK, MAPK, CIPK, and PYL-PP2C-SnRK2, were shown to be involved in osmotic stress, while the SOS core pathway was activated by ionic stress. Moreover, the physiological shifts of catalase and peroxidase activity, glutathione and proline content were in accordance with dynamic transcript profiles of the relevant genes, indicating that antioxidative defense system plays critical roles in response to salinity stress.ConclusionsOverall, our study provides evidence that the response to salinity stress in alfalfa includes both osmotic and ionic components. The key osmotic and ionic stress-related genes are candidates for future studies as potential targets to improve resistance to salinity stress via genetic engineering.

Ionic stress enhances ER–PM connectivity via phosphoinositide-associated SYT1 contact site expansion in Arabidopsis

The interorganelle communication mediated by membrane contact sites (MCSs) is an evolutionary hallmark of eukaryotic cells. MCS connections enable the nonvesicular exchange of information between organelles and allow them to coordinate responses to changing cellular environments. In plants, the importance of MCS components in the responses to environmental stress has been widely established, but the molecular mechanisms regulating interorganelle connectivity during stress still remain opaque. In this report, we use the model plant Arabidopsis thaliana to show that ionic stress increases endoplasmic reticulum (ER)-plasma membrane (PM) connectivity by promoting the cortical expansion of synaptotagmin 1 (SYT1)-enriched ER-PM contact sites (S-EPCSs). We define differential roles for the cortical cytoskeleton in the regulation of S-EPCS dynamics and ER-PM connectivity, and we identify the accumulation of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] at the PM as a molecular signal associated with the ER-PM connectivity changes. Our study highlights the functional conservation of EPCS components and PM phosphoinositides as modulators of ER-PM connectivity in eukaryotes, and uncovers unique aspects of the spatiotemporal regulation of ER-PM connectivity in plants.

Micro-nondestructive detection of the moisture and ion of rice seeds during germination under salt stress

Salt stress is one of the major stress factors limiting rice productivity. Its damaging effects include water deficit due to osmotic stress, and ionic toxicity caused by ionic stress. It is very important to study the salt-tolerance mechanism of rice under salt stress, in order to improve the salt-tolerance capacity of rice and thereby increase the yield. In this experiment, the low field nuclear magnetic resonance (LF NMR) technique and the traditional dry-weight weighing method, the non-invasive micro-test technique (NMT) and the inductively coupled plasma emission spectrometry (ICP-AES) were applied to analyze the distribution of water and the flow of K+ and Na+ of rice seeds during germination under NaCl stress. The results suggested that for all different NaCl concentrations, as germination hours grew, the amplitude of NMR signals of the bound water that of the free water and the total amplitude all increased gradually. And the higher the NaCl concentration is, the weaker the increase trend is. In addition, the moisture content of the seeds and the total amplitude of NMR signals were positively correlated. The regression equation was y =191.53x +1463.6, the correlation coefficient was R=0.9823, and the determination coefficient was R2=0.9650. By this regression equation, the moisture content of each state of water during seed germination can be calculated. When without NaCl stress, the rice seeds absorbed K+ in the germination process. However, when under NaCl stress at different concentrations, K+ efflux was detected. The contents of K+ and K+/Na+ were lower than that under the control condition. The higher NaCl concentration is, the lower the K+ and K+/Na+ contents are. These results are in consistence with the K+ and Na+ contents detected by the inductively coupled technique. These empirical data offer a reference for the study of rice-seeds’ response mechanism under salt stress during germination and the screening of germplasm resources, and also put forward a new method of biopsy micro-nondestructive test for plants under stress. Keywords: nuclear magnetic resonance (NMR), non-invasive micro-test (NMT), NaCl stress, seed germination, moisture, dynamic ion flow DOI: 10.25165/j.ijabe.20191202.4245 Citation: H W Yang, J W Ji, C Wang, L Y Zhang, X D Wang, P Song, et al. Micro-nondestructive detection of the moisture and ion of rice seeds during germination under salt stress. Int J Agric & Biol Eng, 2019; 12(2): 103–110.

Salt effects on carbon mineralization in southeastern coastal wetland soils of the United States

Widespread saltwater intrusion into freshwater coastal ecosystems could dramatically alter the fate of stored carbon as well as the rate of future soil carbon (C) sequestration. We carried out a large survey of soil C at 51 freshwater wetland sites across the coastal plain of North Carolina. We then conducted a microcosm experiment with soils from a subset of eight sites that spanned the full range of observed soil solution salinity, ranging from oligohaline (ca. 0.09–2.84 ppt) to brackish (ca. 5.8–15 ppt) conditions. Each soil in the microcosm experiment was exposed to four salinity treatments, i.e., deionized water (DIW), artificial sea water with sulfate (ASW), artificial sea water without SO42− (ASW − SO4), and deionized water with SO42− (DIW + SO4) under both oxic and anoxic conditions. Here we focused on whether background salinity affected C use efficiency (or the rate of C mineralization divided by the mass of soil C). Across all 51 surveyed sites, neither soil organic C content nor microbial biomass was correlated with soil salinity. Soil organic C content was however the primary predictor of microbial biomass and rates of C mineralization, and soil chloride concentrations were positively correlated with soil organic C for the eight selected sites. We found that C use efficiency was higher in oligohaline soils, suggesting that organic C compounds in the oligohaline wetland soils may contain more labile fractions. In the microcosm experiment, the addition of marine salts, with or without SO42− ions, inhibited soil C use efficiency. Sulfate added alone had little effect on C use efficiency, but substantially inhibited CH4 production efficiency in anoxic assays for the sites with low soil Cl− concentration. Sulfate additions had no effect on CH4 production for soils from sites with prior salinity exposure. Ionic stress exerted larger inhibitory effect on both aerobic and anaerobic C mineralization than the SO42− effect in the short-term, regardless of the prior exposure to marine salts or not, while SO42− exerted far greater control on the CH4 potential only in sites that have not experienced saltwater intrusion before. Overall our findings suggest that long-term effects of salinity on shifts in C mineralization may differ from short-term experimental responses, likely due to other factors (e.g., microbial tolerance, hydrology, temperature) under field conditions.

In Silico Design of PCR Primers to Amplify the Salt Tolerance Gene in Soybean

Soybean yield is decreased because of many stresses such as salt stress. Ionic and osmotic stresses are the effects of salt stress. An effective way of maintaining sustainable production in salt-affected soil is through breeding high salt tolerance soybean, which can be detected by PCR. The optimal PCR plays an important role in gene expression analysis. The success of a PCR-based method largely depends on the optimal primer sequence analysis in silico prior to a wet-bench experiment. Here we described designing of primer using web-based tools. Many types of online primer design software are available, which can be used free of charge to design desirable primers. The objective was to design of PCR primers to amplify the salt tolerance gene in soybean. A highly conserved region of 411 bases was detected by Clustal Omega. Primers were predicted using Primer3 based on conserved region, considering ideal conditions for primer length, hairpin, dimer, Tm, and GC%. The predicted forward and reverse primers were validated using NetPrimer. Both forward and reverse primers have shown significant similarity with salt tolerance gene and recommended to be used to amplify the salt tolerance gene in soybean.