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Polyamine (PA), one of the important plant growth regulators, is closely associated with drought stress. However, the function of conjugated PA is not still clear in the roots of cucumber seedlings under polyethylene glycol (PEG) osmotic stress. Therefore, in this study the relationship between the levels of conjugated polyamines and the activity of H+-ATPase in plasma membrane was elucidated with the roots of two cucumber (Cucumis sativus L.) cultivars, which were different in drought tolerance, as experimental materials. Furthermore, the contents of free PAs and the activities of S-adenosylmethionine decarboxylase (SAMDC) and transglutaminase (TGase), which were closely related to the levels of conjugated polyamines, were also determined. Results showed that under osmotic stress, the increases of the levels of non-covalently conjugated (non-CC) spermidine (Spd) and spermine (Spm), covalently conjugated (CC) putrescine (Put) and Spd in plasma membrane of drought-tolerant Tangshan 5 were more obvious than those of drought-sensitive Jinyou 1. Furthermore, the conjugated PAs mentioned above were closely correlated with increase rate of seedling dry weight, plasma membrane permeability, water content and H+-ATPase activity in plasma membrane. Results of the additional tests, in which exogenous Spd, Spm and two inhibitors, MGBG and phenanthrolin were used, were complementary to the results above. From these results, it could be concluded that non-CC Spd and Spm, CC Put and Spd in plasma membrane functioned in enhancing the tolerance of cucumber seedlings to osmotic stress via elevating H+-ATPase activity.

The covalent attachment of ubiquitin to proteins plays a fundamental role in the regulation of cellular function through biological events involving abiotic or biotic stress responses, immune responses, and apoptosis. Here, we characterize the biological function of the Arabidopsis thaliana RING Zinc Finger 1 (AtRZF1) in dehydration response. AtRZF1 was significantly reduced by drought stress. The atrzf1 mutant was less sensitive to osmotic stress than the wild-type during early seedling development, whereas transgenic plants overexpressing AtRZF1 were hypersensitive, indicating that AtRZF1 negatively regulates drought-mediated control of early seedling development. Moreover, the ectopic expression of the AtRZF1 gene was very significantly influential in drought sensitive parameters including proline content, water loss, membrane ion leakage and the expression of dehydration stress-related genes. AtRZF1 is a functional E3 ubiquitin ligase, and its conserved C3H2C3-type RING domain is likely important for the biological function of AtRZF1 in drought response. Together, these results suggest that the E3 ligase AtRZF1 is an important regulator of water deficit stress during early seedling development.

An increase in lipid accumulation in algal cells often occurs under salt-induced osmotic stress, but the link between the two is unclear. In this study, the effects of osmotic stress as a kind of biomechanical stress on lipid biosynthesis and the cAMP signaling pathway were investigated using Chlorella pyrenoidosa, and a plausible and novel mechanism by which cAMP regulates lipid accumulation in C. pyrenoidosa under osmotic stress conditions was proposed. The maximal lipid content in C. pyrenoidosa exposed to osmotic stress (453 mOsm/kg) (38.31 ± 0.99%) was increased by 63% compared to that in the control group (32 mOsm/kg) (23.45 ± 0.61%). Under osmotic stress, the levels of lipogenic genes, cAMP (3.24 ± 0.09 nM), and reactive oxygen species (ROS) (285.46 ± 26.51 DCF fluorescence intensity) and the total antioxidant capacity (T-AOC) (12.14 ± 1.03 U mgprot−1) increased. Activated cAMP downregulated Snf1 levels, resulting in enhanced expression of accD. As a result, the metabolic flow of carbon in C. pyrenoidosa was shifted to lipid biosynthesis, resulting in an improvement in biodiesel quality. This study provides novel insight into the role of signaling pathways in modulating lipid accumulation in algal cells under osmotic stress.

Hydrogen sulfide closed Arabidopsis thaliana stomata by increasing the transcription of melatonin-producing enzymes and the post-translational modification levels to combat osmotic stress. Hydrogen sulfide (H2S) and melatonin (MEL) reportedly have similar functions in many aspects of plant growth, development and stress response. They regulate stomatal movement and enhance drought resistance. However, their physiological relationship is not well understood. Here, their crosstalk involved in osmotic stress resistance in Arabidopsis thaliana was studied. Exogenous H2S and MEL closed stomata under normal or osmotic stress conditions and increased the relative water contents of plants under osmotic stress conditions. At the same time, exogenous H2S and MEL responded to osmotic stress by increasing the content of proline and soluble sugar, and reducing malondialdehyde (MDA) content and relative conductivity. Using mutants in the MEL-associated production of serotonin N-acetyltransferase (snat), caffeic acid O-methyltransferase (comt1) and N-acetylserotonin methyltransferase (asmt), we determined that H2S was partially dependent on MEL to close stomata. Additionally, the overexpression of ASMT promoted stomatal closure. Exogenous H2S increased the transcription levels of SNAT, ASMT and COMT1. Furthermore, exogenous H2S treatments increased the endogenous MEL content significantly. At the post-translational level, H2S sulfhydrated the SNAT and ASMT, but not COMT1, enzymes associated with MEL production. Thus, H2S appeared to promote stomatal closure in response to osmotic stress by increasing the transcription levels of MEL synthesis-related genes and the sulfhydryl modification of the encoded enzymes. These results increased our understanding of H2S and MEL functions and interactions under osmotic stress conditions.

The secondary salinization of soil in facility agriculture is becoming increasingly serious. Cucumber is a moderately salt-sensitive crop, but because of the weak root system and poor resistance to salt stress in cucumber seedlings, it is sensitive to the accumulation of salt in facility soils. Hydrogen, a selective antioxidant and signal molecule, is nontoxic and harmless, and can repair damage in plants under stress. Therefore, the aim of the present paper was to understand the specific mechanism by which hydrogen-rich water (HRW) alleviated salt stress in cucumber seedlings (Cucumis sativus L.). Our results showed that the addition of 50% saturation HRW significantly promoted seedling growth, development and photosynthetic efficiency. Pretreatment with HRW significantly alleviated salt stress symptoms, including the inhibition of fresh and dry weight, root length, lateral roots, and the root/shoot ratio of cucumber seedlings. Pretreatment with HRW increased the chlorophyll content, chlorophyll a/b ratio, and photochemical reaction efficiency, and reduced energy dissipation. These responses to HRW pretreatment were consistent with significant decreases in the superoxide anion, hydrogen peroxide, and malondialdehyde contents and the degree of lipid peroxidation, and increases in the activities of SOD, POD, CAT, APX and GR, and the contents of ASA and GSH in cucumber seedlings under salt stress. In addition, HRW pretreatment under salt stress inhibited the expression of the protein kinase ROP1, which promoted the production of reactive oxygen, but upregulated the protein kinase LecRLK. The transcription factor TGA5, which was involved in osmotic stress, ion stress and ROS clearance, and the expression of NHX1 and SOS2, which were parts of the SOS signaling pathway. HRW enhanced the expression of genes that encoded antioxidant enzymes, including SOD, CAT and POD, and the expressions of GR and APX2, which were key genes in the ASA-GSH cycle under salt stress. Taken together, these results suggested that HRW enhanced the active oxygen scavenging ability in cucumber seedlings, promoted the redox balance in cells, and reduced the degree of oxidative damage in plants under salt stress by reducing the content of active oxygen. Therefore, the application of HRW might be a promising strategy for improving salt stress tolerance in cucumber seedlings.

Soil drought stress is a limiting factor of productivity in walnut (Juglans regia L). Ferredoxin (Fd) level decreases under adverse environmental stress. Functional replacement of decreased Fd by Fld (Flavodoxin) had been shown to have protective effect under abiotic stress condition. This study aimed to evaluate four transgenic lines (L3, L4, L13 and L17) along with non-transgenic line under three osmotic stresses levels (0, 10 and 12% PEG). This experiment carried out based on a completely randomized design with four replications. To confirm that the Fld gene is successfully integrated into the walnut genome, PCR and dot blot analysis were carried out. The transgenic lines of walnut expressing Fld displayed increased tolerance to osmotic stress at 10 and 12% PEG condition. Lines expressing Fld exhibited increasing tolerance to drought stress and maintained health of plants under osmotic conditions. Results of real time PCR showed that expression level of Fld gene in L4 was higher than the others. Among transgenic lines, L4 was more tolerant than other lines under osmotic stress. These findings indicate that expression of Fld gene can increase tolerance to osmotic stress in Persian walnut and is useful tool for walnut production in arid and semi-arid regions.

Drought-induced water stress affects the productivity of the Vanilla planifolia Jacks. ex Andrews crop. In vitro culture technique is an effective tool for the study of water stress tolerance mechanisms. This study aimed to evaluate the morphological, physiological and biochemical response of V. planifolia under in vitro water stress conditions induced with polyethylene glycol (PEG). In vitro regenerated shoots of 2 cm in length were subjected to different concentrations of PEG 6000 (0, 1, 2 and 3% w/v) using Murashige and Skoog semi-solid culture medium. At 60 days of culture, different growth variables, dry matter (DM) content, chlorophyll (Chl), soluble proteins (SP), proline (Pro), glycine betaine (GB), stomatal index (SI) and open stomata (%) were evaluated. Results showed a reduction in growth, Chl content, SP, SI and open stomata (%) with increasing PEG concentration, whereas DM, Pro and GB contents rose with increasing PEG concentration. In conclusion, PEG-induced osmotic stress allowed describing physiological and biochemical mechanisms of response to water stress. Furthermore, the determination of compatible Pro and GB osmolytes can be used as biochemical markers in future breeding programs for the early selection of water stress tolerant genotypes.

Osmotic stress substantially affects plant growth and development. Study of plant transcription factors involved in osmotic stress can enhance our understanding of the mechanisms of plant osmotic stress tolerance and how the tolerance of plants to osmotic stress can be improved. Here, we identified the specific function of Arabidopsis thaliana BARLEY B RECOMBINANT/BASIC PENTACYSTEINE transcription factor, BPC2, in the osmotic stress response. Phenotypic analysis showed that loss-of-function of BPC2 led to an increase in osmotic stress tolerance in the seedling growth stage. Physiological analysis showed that mutation of BPC2 in Arabidopsis alleviated osmotic-induced increases in H2O2 accumulation, the malondialdehyde (MDA) content, and percent electrolyte leakage. BPC2 was localized in the nucleus. RNA-seq and qRT-PCR analysis showed that BPC2 could negatively regulate the expression of late embryogenesis abundant (LEA) genes (LEA3, LEA4-2, and LEA4-5). Further analysis showed that BPC2 could directly bind to the promoter of LEA4-5 in vitro and in vivo. Overexpression of BPC2 enhanced hypersensitivity to osmotic stress in the seedling growth stage. Overexpression of BPC2 led to decreases in LEA4-5 expression and aggravated osmotic-induced increases in H2O2 accumulation, the MDA content, and percent electrolyte leakage. Overall, our results indicate that BPC2 negatively regulates LEA4-5 expression to modulate osmotic-induced H2O2 accumulation, the MDA content, and percent electrolyte leakage, all of which affect the osmotic stress response in Arabidopsis thaliana.

Mitigation strategies based on plant–microbe interactions to increase the performance of plants under water-deficit conditions are well documented. However, little is known about a suitable consortium of bacterial inoculants and underlying physiological and enzymatic events to improve drought tolerance in maize. We performed laboratory and pot experiments to understand the synergistic interactions among plant growth-promoting bacteria to alleviate the drought-induced damages in maize. Initially, ten bacterial strains were evaluated for their osmotic stress tolerance capacity by growing them in a media containing 0, 10, 20, and 30% polyethylene glycol (PEG-6000). Also, the seeds of a drought tolerant (NK-6654) and sensitive (SD-626) maize cultivar were inoculated with these bacterial strains in the first pot experiment to determine their effects on the growth and physiological processes. Later, in the second pot experiment, the best performing inoculants were selected to study the individual and synergistic effects of bacterial inoculation to confer drought tolerance in maize. Our findings showed that the inoculation with tolerant strains resulted in higher photosynthetic activity (25–39%), maintenance of leaf water status (14–18%) and pigments (27–32%), and stimulation of antioxidant machinery (28–38%) than no inoculation in water-stressed maize seedlings. Moreover, the treatment with bacteria consortia further stimulated the drought protective mechanisms and resulted in higher efficiency of photosynthetic (47–61%) and antioxidant systems (42–62%) than the individual inoculants under water-deficit conditions. We conclude that the inoculation with microbial consortia regulates water uptake, photosynthetic performance, and stress metabolites to minimize drought-induced damages in maize.

Introduction. The development of new technologies of bacterial cultures for fish products is an important area of re-search. Sodium chloride (NaCl) has an inhibitory effect on most microorganisms and is often used in fish industry. The present research objective was to study the effect of NaCl on the growth of lactic acid bacteria of the species Lactoba-cillus sakei. Study objects and methods. The research featured strains of lactic acid bacteria L. sakei (L. sakei LSK-45 and L. sakei DSM 20017). The bacteria were cultivated in a semi-liquid MRS medium supplemented with sodium chloride at vari-ous concentrations. The optical density (OD) of the medium and the viable cell counts served as indicators of bacterial growth. The morphology of bacterial cells was studied by microscopic examination of Gram-stained bacteria. Results and discussion. Both L. sakei strains proved tolerant to NaCl concentrations up to 6% as proved by the high density of the cell population – 109 CFU/cm3. When NaCl concentration reached 10%, L. sakei LSK-45 demonstrated the highest resistance to osmotic stress. At the end of cultivation, the population density dropped to 108 CFU/cm3, and the survival rate was 92%. The number of viable cells of L. sakei DSM 20017 decreased to 106 CFU/cm3, and the sur-vival rate reached 62%. The high resistance of L. sakei LSK-45 to osmotic stress was caused by cell cohesion, which increased with the growing NaCl concentration and was regulated by the quorum sensing system. Conclusion. L. sakei showed a flexible response to the changes in NaCl concentration. L. sakei LSK-45 strain had the highest resistance to osmotic stress.

SNF1-Related protein kinases Type 2 (SnRK2) are plant-specific enzymes widely distributed across the plant kingdom. They are key players controlling abscisic acid (ABA)-dependent and ABA-independent signaling pathways in the plant response to osmotic stress. Here we established that SnRK2.4 and SnRK2.10, ABA-nonactivated kinases, are activated in Arabidopsis thaliana rosettes during the early response to salt stress and contribute to leaf growth retardation under prolonged salinity but act by maintaining different salt-triggered mechanisms. Under salinity, snrk2.10 insertion mutants were impaired in the reconstruction and rearrangement of damaged core and antenna protein complexes in photosystem II (PSII), which led to stronger non-photochemical quenching, lower maximal quantum yield of PSII, and lower adaptation of the photosynthetic apparatus to high light intensity. The observed effects were likely caused by disturbed accumulation and phosphorylation status of the main PSII core and antenna proteins. Finally, we found a higher accumulation of reactive oxygen species (ROS) in the snrk2.10 mutant leaves under a few-day-long exposure to salinity which also could contribute to the stronger damage of the photosynthetic apparatus and cause other deleterious effects affecting plant growth. We found that the snrk2.4 mutant plants did not display substantial changes in photosynthesis. Overall, our results indicate that SnRK2.10 is activated in leaves shortly after plant exposure to salinity and contributes to salt stress tolerance by maintaining efficient photosynthesis and preventing oxidative damage.

Osmotic stress influences root system architecture, and polar auxin transport (PAT) is well established to regulate root growth and development. However, how PAT responds to osmotic stress at the molecular level remains poorly understood. In this study, we explored whether and how the auxin efflux carrier PIN-FORMED3 (PIN3) participates in osmotic stress-induced root growth inhibition in Arabidopsis (Arabidopsis thaliana). We observed that osmotic stress induces a HD-ZIP II transcription factor-encoding gene HOMEODOMAIN ARABIDOPSIS THALIANA2 (HAT2) expression in roots. The hat2 loss-of-function mutant is less sensitive to osmotic stress in terms of root meristem growth. Consistent with this phenotype, whereas the auxin response is downregulated in wild-type roots under osmotic stress, the inhibition of auxin response by osmotic stress was alleviated in hat2 roots. Conversely, transgenic lines overexpressing HAT2 (Pro35S::HAT2) had shorter roots and reduced auxin accumulation compared with wild-type plants. PIN3 expression was significantly reduced in the Pro35S::HAT2 lines. We determined that osmotic stress-mediated repression of PIN3 was alleviated in the hat2 mutant because HAT2 normally binds to the promoter of PIN3 and inhibits its expression. Taken together, our data revealed that osmotic stress inhibits root growth via HAT2, which regulates auxin activity by directly repressing PIN3 transcription.

Suaeda fruticosa and S. monoica are important halophytes for ecological rehabilitation of saline lands. We report differential physio-chemical, photosynthetic, and chlorophyll fluorescence responses in these halophytes under 100 mM sodium chloride (NaCl), 50% strength (16.25 ppt) of seawater (SW)-imposed salinity, and 10% polyethylene glycol 6000 imposed osmotic stress at 380 (ambient) and 1200 (elevated) µmol mol–1 CO2 concentrations. SW salinity enhanced the growth in both species; however, compared with S. fruticosa, the S. monoica exhibited comparatively better growth and biomass accumulation under saline conditions at elevated CO2. Results demonstrated better photosynthetic performances of S. monoica under stress conditions at both levels of CO2, and this resulted in higher accumulation of carbon, nitrogen, sugar, and starch contents. S. monoica exhibited improved antenna size, electron transfer at PSII donor side, and efficient working of photosynthetic machinery at elevated CO2, which might be due to efficient upstream utilization of reducing power to fix the CO2. The δ13C results supported the operation of C4 CO2 fixation in S. monoica and C3 or intermediate pathway of CO2 fixation in S. fruticosa. Lower accumulation of reactive oxygen species, reduced membrane damage, lowered solute potential, and higher accumulation of proline and polyphenol contents indicated elevated CO2-induced abiotic stress tolerance in Suaeda. Higher activity of antioxidant enzymes in both species at both levels of CO2 help plants to combat the oxidative stress. Upregulation of NADP-dependent malic enzyme and NADP-dependent malate dehydrogenase genes indicated their role in abiotic stress tolerance as well as photosynthetic carbon (C) sequestration. Operation of C4 type CO2 fixation in S. monoica and an intermediate CO2 fixation in S. fruticosa could be the possible reason for the superior photosynthetic efficiency of S. monoica under stress conditions at elevated CO2.

Yeast is a dominant host for recombinant production of heterologous proteins, high-value biochemical compounds, and microbial fermentation. During bioprocess operations, pH fluctuations, organic solvents, drying, starvation, osmotic pressure, and often a combination of these stresses cause growth inhibition or death, markedly limiting its industrial use. Thus, stress-tolerant yeast strains with balanced energy-bioenergetics are highly desirous for sustainable improvement of quality biotechnological production. We isolated two NAC transcription factors (TFs), VuNAC1 and VuNAC2, from a wild cowpea genotype, improving both stress tolerance and growth when expressed in yeast. The GFP-fused proteins were localized to the nucleus. Y2H and reporter assay demonstrated the dimerization and transactivation abilities of the VuNAC proteins having structural folds similar to rice SNAC1. The gel-shift assay indicated that the TFs recognize an "ATGCGTG" motif for DNA-binding shared by several native TFs in yeast. The heterologous expression of VuNAC1/2 in yeast improved growth, biomass, lifespan, fermentation efficiency, and altered cellular composition of biomolecules. The transgenic strains conferred tolerance to multiple stresses such as high salinity, osmotic stress, freezing, and aluminum toxicity. Analysis of the metabolome revealed reprogramming of major pathways synthesizing nucleotides, vitamin B complex, amino acids, antioxidants, flavonoids, and other energy currencies and cofactors. Consequently, the transcriptional tuning of stress signaling and biomolecule metabolism improved the survival of the transgenic strains during starvation and stress recovery. VuNAC1/2-based synthetic gene expression control may contribute to designing robust industrial yeast strains with value-added productivity.

One of the significant challenges of food waste anaerobic digestion (AD) is the negative effect of high NaCl concentrations. This study investigated the effects of NaCl fluctuation on the methane generation of food waste AD under thermophilic and mesophilic conditions. Particularly, the effects of the shock loading of high NaCl concentration with/ without water dilution treatment were investigated. Generally, the methane generation decreased with increasing NaCl concentration. In addition, the sensitivity of the thermophilic AD to NaCl concentrations (5-10 g/L) was higher than that of the mesophilic AD. Furthermore, with an increase in the NaCl concentration from 0 to 30 g/L, the accumulative methane volumes of the thermophilic reactors decreased from 210 to 45 mL/gVS, and those of the mesophilic reactors decreased from 265 to 67 mL/gVS. Additionally, the pH of digestate decreased with increasing NaCl concentration. In contrast, the concentrations of the chemical oxygen demand and volatile fatty acid increased with increasing NaCl concentration. These results indicated that a shock loading of NaCl significantly reduced methane generation. In addition, the methane generation rates could be recovered up to 64-72% using water dilution as a remedial measure. Further investigation using 16S rRNA analysis revealed that the predominant genus of the methanogens shifted from Methanoculleus to Methanosarcina after the removal of the osmotic stress using water dilution.

Seed germination is generally the critical step in seed establishment and thus the determination of successful crop production. This study was focused at examination of the biochemical and germination parameters effected by low water potential which was generated by polyethylene glycol (PEG) 6000 and mannitol, related to drought stress and growth of Waha durum wheat genotype. Two tests were carried out in a growth chamber; the first comprises seed germination into Petri dishes in the presence of different concentrations of the two osmoticums (0, 5, 10, 15 and 20 % of PEG6000 and mannitol). The second test was carried out in nutrient solution BD medium. Our results shows that Both PEG -6000 and mannitol reduced germination. Therefore, a rapid increase was observed in the rate of germination both for the control plants and the plants subjected to a concentration of 5 g/L and 10 g/L and changes in proportion to the time. For the concentration of 15 g/L and 20 g/L, this phase is very short, which explains the reduced germination rate due to the inhibitory effect of the two osmoticums on germination. In this study, PEG-6000 treatments resulted in an increase of some proteins and a decrease of others. Waha displayed 12 bands for control plants, 40 bands for PEG-6000 stressed plants (all treatments) and 35 bands for mannitol treatments.

Summary The abscisic acid (ABA) signalling pathway is involved in the plant response to osmotic stress caused by drought and/or salinity. Although the ABA signalling pathway has been elucidated in Arabidopsis, it remains elusive in woody poplars. In this study, genome‐wide analyses of U‐box genes in poplars revealed that a U‐box E3 ubiquitin ligase gene, PalPUB79, is significantly induced following drought, salinity and ABA signalling. PalPUB79 overexpression enhanced drought tolerance in transgenic poplars, while PalPUB79 RNAi lines were more sensitive to drought. PalPUB79 positively regulated ABA signalling pathway. Furthermore, PalPUB79 interacted with PalWRKY77, a negative transcriptional regulator of ABA signalling, and mediated its ubiquitination for degradation, therefore counteracting its inhibitory effect on PalRD26 transcription. However, the finding that PalWRKY77 negatively regulates PalPUB79 expression was indicative of a negative feedback loop between PalWRKY77 and PalPUB79 during ABA signalling in poplar. These findings provide novel insight into the mechanism through which PalPUB79 enhances the ABA‐mediated stress response in woody poplars.

MsCML46 enhances tolerance to abiotic stresses through alleviating osmotic stress and oxidative damage by regulating the expression of stress-related genes to optimize osmolytes levels and antioxidant enzyme activity in transgenic tobacco. Abiotic stresses are major environmental factors that constraint crop productivity worldwide. Various stimuli regulate intracellular calcium levels and calcium-mediated signal transduction, and cellular responses. Ca2+ signals are perceived by different Ca2+ receptors. Calmodulin-like protein (CML) is one of the best-characterized Ca2+ sensors which shares sequence similarity with highly conserved calmodulin (CaM) ubiquitously expressed in plants. Currently, the molecular and physiological functions of CMLs are largely unknown. In this study, the MsCML46 was characterized in alfalfa (Medicago sativa cv. Zhaodong) under freezing stress. Results showed that MsCML46 was localized to the cytoplasm of Arabidopsis, and its expression was strongly elevated by cold, drought, salt, saline-alkali, and ABA treatments. Overexpressing MsCML46 in tobacco enhanced tolerance to freezing, drought, and salt stresses as evidenced by improved contents of osmotic regulatory solutes and antioxidant enzyme activity but decreased reactive oxygen species (ROS) accumulation. Furthermore, cold, drought, and salt stresses increased the expression of stress-related genes in transgenic tobacco. MsCML46 binds free Ca2+ to promote signal transduction and maintain higher K+/Na+ ratio. In this way, it protects intracellular homeostasis under sodium ion toxicity. These results suggest that MsCML46 plays a crucial role in resisting abiotic stresses and can be exploited in genetic engineering for crops.

Cowpea (Vigna unguiculata) plays a strategic role in arid and semi-arid regions being used in both human food and animal supplementation. Although it is described as moderately tolerant plant to soil salinity, little is known about the salinity tolerance amongst different cultivars and phenological phases. In this study, we investigated the response of seed germination and seedling establishment of V. unguiculata cv. BRS Imponente under conditions of both salt (NaCl) and osmotic stress (Polyethylene glycol 6000; PEG). Although such conditions lead to an accumulation of hydrogen peroxide (H2O2), oxidative damage was observed only in seeds exposed to PEG. The maintenance of H2O2 concentrations in seeds exposed to NaCl, as well as the increase in respiratory activity, were the main mechanisms of tolerance identified in seeds exposed to NaCl. However, although germination was not affected, NaCl concentrations ≥75 mM were phytotoxic, reducing seedling growth. The osmotic component of salinity (PEG) reduced germination (Ѱo

Polysaccharides derived from seaweeds can be used as biostimulants to enhance plant resistance to different stressors. In this study, we investigated the effects of applying low molecular weight polysaccharides (LPU) derived from Ulva prolifera with 14.2 kDa on the responses of wheat (Triticum aestivum) to osmotic stress. The results showed that osmotic stress simulated using polyethylene glycol inhibited seedling growth, whereas we observed increases in the fresh weights and shoot lengths of seedlings treated with polysaccharide for 120 h. Furthermore, we observed enhanced activities of antioxidant enzymes, and significant reductions in malondialdehyde content of 23.13%, 19.82%, and 20.04% in response treatment for 120 h with 0.01%, 0.03%, and 0.05% LPU, respectively, relative to those in the group treated with polyethylene glycol alone. In all treatments, expression of the P5CS gene was upregulated to promote proline accumulation. Moreover, after 120 h, exogenously applied LPU induced the expression of stress-related genes, including SnRK2, Wabi5, Wrab18, and Wdhn13. Collectively, these findings indicate that LPU might have the effect of regulating the abscisic acid-dependent pathway in wheat, thereby increasing seedling antioxidant capacity and growth. Application of LPU may accordingly represent an effective approach for enhancing the resistance to osmotic stress in wheat.

Dehydration-responsive element binding proteins (DREBs) constitute a large subfamily in the plant-specific APETALA2/ethylene-responsive factor (ERF) family and play crucial roles in plant stress tolerance. So far, studies on the A-5 subgroup DREBs which comprise the largest proportion of the DREB subfamily are limited. Here, we report functional characterization of two A-5 subgroup genes named AmDREB1 and AmDREB2 from Ammopiptanthus mongolicus, a desert shrub with high abiotic stress tolerance. Both AmDREB1 and AmDREB2 proteins contain an ERF-associated amphiphilic repression (EAR)-like motif and were localized in the nucleus. The transcription levels of AmDREB1 and AmDREB2 in laboratory-cultured seedlings increased differentially under dehydration, salt, cold and/or heat stresses as well as under abscisic acid (ABA) treatment. In leaves of naturally growing shrubs in the wild, the transcription level of AmDREB2 also increased in response to seasonal cold weather of a year. Moreover, AmDREB1 was most abundantly expressed in leaves, followed by immature pods; AmDREB2 was abundantly expressed in all examined organs. Constitutively expressing AmDREB1 in Arabidopsis significantly enhanced drought and salt tolerances of transgenic lines, likely by inducing the expression of some stress-inducible genes and accumulating more proline and less Na+. Constitutive expression of AmDREB2 conferred only osmotic stress tolerance in transgenic Arabidopsis at the seed germination stage. Both AmDREBs also conferred ABA insensitivity in transgenics. This study provides important evidence that the A-5 subgroup EAR motif-containing DREBs can positively regulate stress response and tolerance in plants, and that AmDREB1 may have potential application in improving drought and salt tolerances in crop plants. AmDREB1 and AmDREB2 were differentially induced by abiotic stressors, exogenous ABA and seasonal cold weather. The tolerances of their transgenics to drought and/or salt as well as ABA were enhanced.

Soil salinity is an increasingly global problem which hampers plant growth and crop yield. Plant productivity depends on optimal water-use efficiency and photosynthetic capacity balanced by stomatal conductance. Whether and how stomatal behavior contributes to salt sensitivity or tolerance is currently unknown. This work identifies guard cell-specific signaling networks exerted by a salt-sensitive and salt-tolerant plant under ionic and osmotic stress conditions accompanied by increasing NaCl loads. We challenged soil-grown Arabidopsis thaliana and Thellungiella salsuginea plants with short- and long-term salinity stress and monitored genome-wide gene expression and signals of guard cells that determine their function. Arabidopsis plants suffered from both salt regimes and showed reduced stomatal conductance while Thellungiella displayed no obvious stress symptoms. The salt-dependent gene expression changes of guard cells supported the ability of the halophyte to maintain high potassium to sodium ratios and to attenuate the abscisic acid (ABA) signaling pathway which the glycophyte kept activated despite fading ABA concentrations. Our study shows that salinity stress and even the different tolerances are manifested on a single cell level. Halophytic guard cells are less sensitive than glycophytic guard cells, providing opportunities to manipulate stomatal behavior and improve plant productivity.

Ubiquitination, one of the most frequently occurring post-translational modifications, is essential for regulating diverse cellular processes in plants during abiotic stress. The E3 ubiquitin (Ub) ligase Arabidopsis thaliana really interesting new gene (RING) zinc finger 1 (AtRZF1) mutation is known to enhance drought tolerance in A. thaliana seedlings. To further investigate the function of AtRZF1 in osmotic stress, we isolated Ub-associated protein 1 (AtUAP1) which interacts with AtRZF1 using a yeast two-hybrid system. AtUAP1, a Ub-associated motif containing protein, increased the amount of Ub-conjugated AtRZF1. Moreover, AtUAP1 RNA interference lines were more tolerant to osmotic stress than wild type, whereas AtUAP1-overexpressing (OX) transgenic lines showed sensitive responses, including cotyledon greening, water loss, proline accumulation and changes in stress-related genes expression, indicating that AtUAP1 could negatively regulate dehydration-mediated signaling. In addition, AtUAP1-green fluorescent protein fusion protein was observed in the nuclei of root cells of transgenic seedlings. Genetic studies showed that the AtRZF1 mutation could rescue the sensitive phenotype of AtUAP1-OX lines in response to osmotic stress, suggesting that AtRZF1 was epistatic to AtUAP1 in dehydration signaling. Taken together, our findings describe a new component in the AtRZF1 ubiquitination pathway which controls the dehydration response in A. thaliana.

Masson pine (Pinus massoniana Lamb.) is an important tree species of high economic value in southern China, but osmotic stress threatens its growth and development. In this study, physiological measurements and RNA-Seq analysis were used to clarify the physiological and molecular responses of P. massoniana under osmotic stress. Osmotic treatment caused cell membrane damage and reactive oxygen species (ROS) accumulation in the tree seedlings, but it also increased their antioxidant enzyme (superoxide dismutase, peroxidase, and catalase) activities and osmotic substances (soluble sugars, proline, and trehalose) content so as to adjust to osmotic stress conditions. A total of 1 789 differentially expressed genes (DEGs) were identified by transcriptome sequencing, of which 962 were up-regulated and 827 genes down-regulated. A series of stress-induced genes associated with signal transduction, ROS-scavenging, osmotic regulation, late embryogenesis abundant (LEA) protein, pentatricopeptide repeat-containing protein, and transcription factors' regulation were distinguishable. This detailed investigation of the stress-responsive genes and pathways provides new insight into molecular mechanism of abiotic stress response in P. massoniana. Further, this study's data can contribute to genetic engineering or molecular breeding efforts to enhance osmotic resistance in P. massoniana stands.

In this study, homology- and cross-resistance of Lactobacillus plantarum L1 and Lactobacillus plantarum L2 to acid and osmotic stress were investigated. Meanwhile, its proliferation mechanism was demonstrated by transcriptomic analysis using RNA sequencing. We found that the homologous-resistance and cross-resistance of L. plantarum L1 and L. plantarum L2 increased after acid and osmotic induction treatment by lactic acid and sodium lactate solution in advance, and the survival rate of live bacteria was improved. In addition, the count of viable bacteria of L. plantarum L2 significantly increased cultivated at a pH 5.0 with a 15% sodium lactate sublethal treatment, compared with the control group. Further study revealed that genes related to membrane transport, amino acid metabolism, nucleotide metabolism, and cell growth were significantly upregulated. These findings will contribute to promote high-density cell culture of starter cultures production in the fermented food industry.

Primary metabolism in cyanobacteria is built on the Calvin-Benson-Bassham (CBB) cycle, oxidative pentose phosphate (OPP) pathway, Embden-Meyerhof-Parnas (EMP) pathway, and the tricarboxylic acid (TCA) cycle. Phosphoketolase (Xpk), commonly found in cyanobacteria, is an enzyme that is linked to all these pathways. However, little is known about its physiological role. Here, we show that most of the cyanobacterial Xpk surveyed are inhibited by ATP, and both copies of Xpk in nitrogen-fixing Cyanothece ATCC51142 are further activated by ADP, suggesting their role in energy regulation. Moreover, Xpk in Synechococcus elongatus PCC7942 and Cyanothece ATCC51142 show that their expressions are dusk-peaked, suggesting their roles in dark conditions. Finally, we find that Xpk in S. elongatus PCC7942 is responsible for survival using ATP produced from the glycogen-to-acetate pathway under dark, anaerobic condition. Interestingly, under this condition, xpk deletion causes glucose secretion in response to osmotic shock such as NaHCO3, KHCO3 and NaCl as part of incomplete glycogen degradation. These findings unveiled the role of this widespread enzyme and open the possibility for enhanced glucose secretion from cyanobacteria.

Osmotic stresses, such as salinity and drought, have deleterious effects on uptake and translocation of essential mineral nutrients. Iron (Fe) is an important micronutrient that regulates many processes in plants. Plants have adopted various molecular and physiological strategies for Fe acquisition from soil and transport to and within plants. Dynamic Fe signalling in plants tightly regulates Fe uptake and homeostasis. In this way, Fe nutrition is adjusted to growth and stress conditions, and Fe deficiency-regulated transcription factors, such as FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR (FIT), act as regulatory hubs in these responses. Here, we review and analyse expression of the various components of the Fe signalling during osmotic stresses. We discuss common players in the Fe and osmotic stress signalling. Furthermore, this review focuses on exploring a novel and exciting direct connection of regulatory mechanisms of Fe intake and acquisition with ABA-mediated environmental stress cues, like salt/drought. We propose a model that discuss how environmental stress affects Fe uptake and acquisition and vice versa at molecular-physiological levels in plants.

Dehydrins are well-known components of plant responses to different stresses that cause dehydration, including drought, freezing, salinity, etc. In conifers, the dehydrin gene family is very large, implying that the members of this family have important physiological functions in conifer stress tolerance. However, dehydrin gene expression displays a wide range of responses to stress, from thousand-fold increased expression to decreased expression, and it is generally unknown how regulatory systems are connected at the mRNA and protein levels. Therefore, we studied these aspects of dehydrin regulation in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst) seedlings under polyethylene glycol 6000-induced osmotic stress ranging from relatively low (culture medium water potential of −0.15 MPa) to very high (−1.0 MPa) intensities. In pine, the major dehydrin protein was Dhn1 in both the roots and needles, and in spruce, two isoforms of the Dhn4 protein were the major dehydrins; both of these proteins are AESK-type dehydrins. The genes encoding these major proteins were highly expressed even under control conditions; surprisingly, we also observed several highly expressed dehydrin genes that were not abundantly translated. Under osmotic stress, the most prominent expression changes were observed for the dehydrin genes with low basal expression levels, whereas highly expressed genes generally demonstrated rather modest changes in expression. We report proposed constitutive physiological functions of the AESK-type dehydrins in Pinaceae plants.

Penium margaritaceum is a unicellular zygnematophyte (basal Streptophyteor Charophyte) that has been used as a model organism for the study of cell walls of Streptophytes and for elucidating organismal adaptations that were key in the evolution of land plants.. When Penium is incubated in sorbitol-enhance medium, i.e., hyperosmotic medium, 1000-1500 Hechtian strands form within minutes and connect the plasma membrane to the cell wall. As cells acclimate to this osmotic stress over time, further significant changes occur at the cell wall and plasma membrane domains. The homogalacturonan lattice of the outer cell wall layer is significantly reduced and is accompanied by the formation of a highly elongate, "filamentous" phenotype. Distinct peripheral thickenings appear between the CW and plasma membrane and contain membranous components and a branched granular matrix. Monoclonal antibody labeling of these thickenings indicates the presence of rhamnogalacturonan-I epitopes. Acclimatization also results in the proliferation of the cell's vacuolar networks and macroautophagy. Penium's ability to acclimatize to osmotic stress offers insight into the transition of ancient zygnematophytes from an aquatic to terrestrial existence.

Amphibian’s skin bacterial community may help them to cope with several types of environmental perturbations, including osmotic stress caused by increased salinity. This work assessed whether an amphibian skin bacterium could increase its tolerance to NaCl after a long-term exposure to this salt. A strain of Erwinia toletana, isolated from the skin of Pelophylax perezi, was exposed to two salinity scenarios (with 18 g/L of NaCl): (1) long-term exposure (for 46 days; Et-NaCl), and (2) long-term exposure followed by a recovery period (exposure for 30 days to NaCl and then to LB medium for 16 days; Et-R). After exposure, the sensitivity of E. toletana clonal populations to NaCl was assessed by exposing them to 6 NaCl concentrations (LB medium spiked with NaCl) plus a control (LB medium). Genotypic alterations were assessed by PCR-based molecular typing method (BOX-PCR). The results showed that tolerance of E. toletana to NaCl slightly increased after the long-term exposure, EC50 for growth were: 22.5 g/L (8.64–36.4) for Et-LB; 30.3 g/L (23.2–37.4) for Et-NaCl; and 26.1 g/L (19.332.9) for Et-R. Differences in metabolic activity were observed between Et-LB and Et-R and between Et-NaCl and Et-R, suggesting the use of different substrates by this bacterium when exposed to salinized environments. NaCl-induced genotypic alterations were not detected. This work suggests that E. toletana exposed to low levels of salinity, activate different metabolic pathways to cope with osmotic stress. These findings may be further explored to be used in bioaugmentation procedures through the supplementation with this bacterium of the skin microbiome of natural populations of amphibians exposed to salinization.

Japanese honewort (Cryptotaenia japonica) is consumed as a traditional vegetable and has medicinal applications. In Japan, C. japonica is mainly produced using hydroponic culture systems; however, damping-off is often caused by the adherence of pathogens to its seeds. Therefore, the use of sterile artificial seeds in hydroponic culture is likely to be effective for preventing disease. In this study, we established methods for stress-induced somatic embryogenesis and artificial seed production in Japanese honewort. Shoot apex explants from seedlings were treated with 0.7 M sucrose as a hyperosmotic stress for 3 or 6 weeks, and then transferred to stress-free conditions. Somatic embryos were formed after culture in stress-free conditions for 7 weeks. Stress-treated shoot apex explants that formed somatic embryos were cultured in Murashige and Skoog liquid medium with shaking. After 2 weeks of culture, approximately 800 somatic embryos were formed from each explant. Somatic embryos were formed continuously during 37 weeks under the same culture conditions. Thus, somatic embryogenesis was effectively induced in Japanese honewort via hyperosmotic stress, and embryogenic competence was maintained under stress- and phytohormone-free conditions. The somatic embryos produced by liquid culture were used to produce artificial seeds by enveloping the embryos in whipped alginate gel to avoid hypoxic conditions. The artificial seeds had a high germination rate (72%). This system is suitable for the sterile, highly productive hydroponic culture of Japanese honewort.

Atmospheric nitrogen (N) deposition (AtNiDe) and drought stress (DS) have strongly affected plant growth. However, previous research has primarily focused on the effects of AtNiDe with various levels and DS on plant growth (especially seed germination and seedling growth). This study aimed to evaluate the single and combined effects of AtNiDe with four types (compounds: NH4-N, NO3-N, CO(NH2)2-N, and a mixture of the three types of N) and DS (three levels: control, low, and high) on wheat seed germination and seedling growth. The AtNiDe treatment increased wheat seed germination and seedling growth. Mixed N exerted a greater positive effect on wheat seed germination and seedling growth than single N forms. Organic N also had a greater positive effect on wheat seed germination and seedling growth than reduced inorganic N. The DS treatment decreased wheat seed germination and seedling growth. The AtNiDe treatment alleviated the adverse effects of DS on wheat seed germination and seedling growth. Mixed N had the greatest effect on alleviating the adverse effects of DS on wheat seed germination and seedling growth. Thus, AtNiDe and DS antagonistically affected wheat seed germination and seedling growth. NOVELTY STATEMENT This study assessed the single and combined effects of atmospheric nitrogen deposition with four types and drought stress at three levels on wheat seed germination and seedling growth. Generally, nitrogen and drought antagonistically affected wheat seed germination and seedling growth.

The high osmolarity glycerol (HOG) pathway, comprising a two-component system and the Hog1 mitogen-activated protein kinase (MAPK) cascade, plays a pivotal role in eukaryotic organisms. Previous studies suggested that the biological functions of some key genes in the HOG pathway varied in filamentous fungi. In this study, we characterized a putative MAPK kinase kinase gene, Ssos4, in Sclerotinia sclerotiorum, which encoded a phosphotransferase in the MAPK cascade. Compared with the wild-type progenitor HA61, the deletion mutant ∆Ssos4-63 exhibited impaired mycelial growth, sclerotia formation, increased hyphal branches, and decreased virulence. The deficiencies of the deletion mutant ∆Ssos4-63 were recovered when the full-length Ssos4 gene was complemented. Deletion of Ssos4 increased the sensitivity to osmotic stresses and cell wall agents and the resistance to fludioxonil and dimethachlon. Intracellular glycerol accumulation was not induced in the deletion mutant ∆Ssos4-63 when treated with fludioxonil and NaCl and the phosphorylation of SsHog1 was also cancelled by the deletion of Ssos4. Consistent with the glycerol accumulation and increased expression levels of SsglpA and Ssfps1, controlling glycerol synthesis and close of glycerol channel under hyperosmotic stress, respectively, were detected in the wild-type strain HA61 but not in the deletion mutant ∆Ssos4-63. Moreover, the relative expression level of Sshog1 significantly decreased, whereas the expression level of Ssos5 increased in the deletion mutant ∆Ssos4-63. These results indicated that Ssos4 played important roles in mycelial growth and differentiation, sclerotia formation, virulence, hyperosmotic adaptation, fungicide sensitivity, and the phosphorylation of SsHog1 in S. sclerotiorum.

TdAnn6 is a gene encoding an annexin protein in durum wheat (Triticum durum). The function of TdAnn6 in plant response to stress is not yet clearly understood. Here, we isolated TdAnn6 and characterized it in genetically modified Arabidopsis thaliana. Expressing TdAnn6 in Arabidopsis coincided with an improvement in stress tolerance at germination and seedling stages. In addition, TdAnn6-expressing seedling antioxidant activities were improved with lower level of malondialdehyde, and enhanced transcript levels of six stress-related genes during salt/osmotic stresses. Under greenhouse conditions, the TdAnn6 plants exhibited increased tolerance to salt or drought stress. To deepen our understanding of TdAnn6 function, we isolated a 1515-bp genomic fragment upstream of its coding sequence, designated as PrTdAnn6. The PrTdAnn6 promoter was fused to the β-glucuronidase reporter gene and transferred to Arabidopsis. By histochemical GUS staining, GUS activity was detected in the roots, leaves, and floral organs, but no activity was detected in the seeds. Furthermore, we noticed a high stimulation of promoter activity when A. thaliana seedlings were exposed to NaCl, mannitol, ABA, GA, and cold conditions. This cross-talk between tissue-specific expression and exogenous stress stimulation may provide additional layers of regulation for salt and osmotic stress responses in crops.

Nitrate (NO3 - ) is a source of plant nutrients and osmolytes, but its delivery machineries under osmotic and low-nutrient stress remain largely unknown. Here, we report that AtICln, an Arabidopsis homolog of the nucleotide-sensitive chloride-conductance regulatory protein family (ICln), is involved in response to osmotic and low-NO3 - stress. The gene AtICln, encoding plasma membrane-anchored proteins, was upregulated by various osmotic stresses, and its disruption impaired plant tolerance to osmotic stress. Compared with the wild type, the aticln mutant retained lower anions, particularly NO3 - , and its growth retardation was not rescued by NO3 - supply under osmotic stress. Interestingly, this mutant also displayed growth defects under low-NO3 stress, which were accompanied by decreases in NO3 - accumulation, suggesting that AtICln may facilitate the NO3 - accumulation under NO3 - deficiency. Moreover, the low-NO3 - hypersensitive phenotype of aticln mutant was overridden by the overexpression of NRT1.1, an important NO3 - transporter in Arabidopsis low-NO3 - responses. Further genetic analysis in the plants with altered activity of AtICln and NRT1.1 indicated that AtICln and NRT1.1 play a compensatory role in maintaining NO3 - homeostasis under low-NO3 - environments. These results suggest that AtICln is involved in cellular NO3 - accumulation and thus determines osmotic adjustment and low-NO3 - tolerance in plants.

Silicon (Si), a nutrient that currently arousing more and more interest from researchers, particularly in relation to water deficit resistance for durum wheat (Triticum turgidum L. ssp. Durum). The present study aimed to explore the effectiveness of Si seed priming and foliar application on durum wheat performances. Thus, a seed bioassay was conducted to assess the effect of three Si levels (15 and 20 mg/l from Na2SiO3H2O (sodium metasilicate powder extra pure) on the germination of 25 durum wheat genotypes under osmotic stress (150 g/l of PEG6000). Under field conditions in semi-arid environment, we evaluated the Si foliar application potential benefits on the physiological and agro-morphological traits. Results showed that Si application, in particular using 15 mg/l, increased significantly the germination percentage (23.96 and 22.37%) the germination index (24.67 and 25.69%), the length of shoot (23.58 and 21.65%) and roots (22.40 and 20.81%), the seedling fresh weight (35.82% and 27.80%), and the seedling vigor index (41.58% and 38.95%) under non-stressed and stressed conditions, respectively. L6 showed the highest value of germination percentage, shoot and root length, and seedling vigor index for all treatments. In semi-arid conditions, Si foliar application enhanced the relative water content (11.66%) and the chlorophyll index (13.60%). In addition, Si increased spike length (8.47%), seed number/spike (19.01%) and grain yield (19.90%) of all durum wheat genotypes. Differential genotypic responses to Si application were observed at both seedling and adult stages.

Root growth is essential for plant survival under drought stress. Root growth includes diameter growth and longitudinal growth, which play different roles in the regulation of drought tolerance. However, the specific role of root growth in woody and herbaceous plants under drought stress remains largely uncharacterized. In a previous study, we confirmed that a root-specific transcription factor, NUCLEAR FACTOR Y subunit B21 (NF-YB21), positively regulated drought resistance by promoting root diameter growth and longitudinal growth in poplar. In the present study, we further analyzed induction of NF-YB21 in Arabidopsis in response to drought and exogenous abscisic acid (ABA) treatment. In PdNF-YB21 promoter-driven GUS transgenic Arabidopsis plants, PdNF-YB21 was predominantly expressed in the root and was induced by osmotic stress. Overexpression of PdNF-YB21 in Arabidopsis enhanced drought resistance by promoting growth in root length but not in root diameter. Physiological analysis suggested that PdNF-YB21 promoted increase in root length, root hydraulic conductivity, root water-use efficiency (WUE), chlorophyll content, photosynthetic rate, and biomass accumulation under drought stress. The present findings suggest that PdNF-YB21 plays an important role in regulation of root length and drought resistance in a herbaceous plant species. The results provide an explanation for the different mechanisms in herbaceous and woody plants involved in regulation of drought resistance by promoting growth in root length or diameter, and will be useful for breeding cultivars with enhanced drought tolerance. This study reported the important role of root-specific transcription factor PdNF-YB21 in regulating root length and improving drought tolerance in Arabidopsis thaliana.

Background Saccharomyces cerevisiae is well-known as an ideal model system for basic research and important industrial microorganism for biotechnological applications. Acetic acid is an important growth inhibitor that has deleterious effects on both the growth and fermentation performance of yeast cells. Comprehensive understanding of the mechanisms underlying S. cerevisiae adaptive response to acetic acid is always a focus and indispensable for development of robust industrial strains. eIF5A is a specific translation factor that is especially required for the formation of peptide bond between certain residues including proline regarded as poor substrates for slow peptide bond formation. Decrease of eIF5A activity resulted in temperature-sensitive phenotype of yeast, while up-regulation of eIF5A protected transgenic Arabidopsis against high temperature, oxidative or osmotic stress. However, the exact roles and functional mechanisms of eIF5A in stress response are as yet largely unknown. Results In this research, we compared cell growth between the eIF5A overexpressing and the control S. cerevisiae strains under various stressed conditions. Improvement of acetic acid tolerance by enhanced eIF5A activity was observed all in spot assay, growth profiles and survival assay. eIF5A prompts the synthesis of Ume6p, a pleiotropic transcriptional factor containing polyproline motifs, mainly in a translational related way. As a consequence, BEM4, BUD21 and IME4, the direct targets of Ume6p, were up-regulated in eIF5A overexpressing strain, especially under acetic acid stress. Overexpression of UME6 results in similar profiles of cell growth and target genes transcription to eIF5A overexpression, confirming the role of Ume6p and its association between eIF5A and acetic acid tolerance. Conclusion Translation factor eIF5A protects yeast cells against acetic acid challenge by the eIF5A-Ume6p-Bud21p/Ime4p/Bem4p axles, which provides new insights into the molecular mechanisms underlying the adaptive response and tolerance to acetic acid in S. cerevisiae and novel targets for construction of robust industrial strains.

Drought induces osmotic stress in roots, a condition simulated by the application of high-molecular-weight polyethylene glycol. Osmotic stress results in the reduction of Arabidopsis thaliana root growth and production of 1O2 from an unknown non-photosynthetic source. Reduced root growth can be alleviated by application of the 1O2 scavenger histidine (HIS). Here, we examined the possibility that 1O2 production involves Russell reactions occurring among the enzymatic products of lipoxygenases (LOXs), the fatty acid hydroperoxides. LOX activity was measured for purified soybean (Glycine max) LOX1 and in crude Arabidopsis root extracts using linoleic acid as substrate. Formation of the 13(S)-Hydroperoxy-9(Z),11(E)-octadecadienoic acid product was inhibited by salicylhdroxamic acid, which is a LOX inhibitor, but not by HIS, whereas 1O2 production was inhibited by both. D2O, which specifically extends the half-life of 1O2, augmented the LOX-dependent generation of 1O2, as expected from a Russell-type reaction. The addition of linoleic acid to roots stimulated 1O2 production and inhibited growth, suggesting that the availability of LOX substrate is a rate-limiting step. Indeed, water stress rapidly increased linoleic and linolenic acids by 2.5-fold in roots. Mutants with root-specific microRNA repression of LOXs showed downregulation of LOX protein and activity. The lines with downregulated LOX displayed significantly less 1O2 formation, improved root growth in osmotic stress, and an altered transcriptome response compared with wild type. The results show that LOXs can serve as an enzymatic source of “dark” 1O2 during osmotic stress and demonstrate a role for 1O2 in defining the physiological response.

Background: The so-called “thunderstorm asthma” (TA) is an uncommon but dramatic outbreak of asthma attacks occurring during a thunderstorm in the pollen and moulds season. Mechanisms which make the pollen able to enter the deeper airways and provoke severe asthma symptoms are still unclear. Objective: To test the hypothesis that sub-pollen particles (SPPs) originated from the rupture by an osmotic shock of pollen associated with TA contain allergens. Methods: After hydration, SPPs released from pollen grains of grass, pellitory, olive, cypress, ragweed and birch were isolated and determined by microscopy. Allergens were determined by in vitro ELISA inhibition tests indirectly using the sera from 10 polyreactive patients. An inhibition 75% complete. Results: The inhibition experiments showed that the SPPs from birch and cypress were unable to inhibit serum IgE reactivity to Bet v 1 and Cup a 1, respectively. Ragweed SPPs inhibited ragweed pollen extract and Amb a 1 by 75.8±0.11% and 81.2±0.15%, respectively. Olive and pellitory SPPs retained almost the whole IgE-binding capability in all cases tested. Grass SPPs inhibited 32±0.06% of Lolium perenne Lol p 1 and 65% of Phleum pratense extracts, but results were highly variable for individual allergens (97.5%-0.03% for Phl p 2, 45.3±0.12% for Phl p 5, 24.7±0.22% for Phl p 6, and 38.3±0.2% for Phl p 1). Conclusions: Inhibition experiments confirm the hypothesis that SSPs obtained after the osmotic shock of pollen involved in TA, namely grass, pellitory and olive tree pollen, contain allergens and therefore they can induce severe asthma attacks during thunderstorms.

Hydrophobins are relatively small proteins produced naturally by filamentous fungi with interesting biotechnological and biomedical applications given their self-assembly capacity, efficient adherence to natural and artificial surfaces, and to introduce modifications on the hydrophobicity/hydrophilicity of surfaces. In this work we demonstrate the efficient expression on the S. cerevisiae cell surface of class II HFBI of Trichoderma reesei and class I DewA of Aspergillus nidulans, a hydrophobin not previously exposed, using the Yeast Surface Display a-agglutinin (Aga1-Aga2) system. We show that the resulting modifications affect surface properties, and also yeast cells’ resistance to several adverse conditions. The fact that viability of the engineered strains increases under heat and osmotic stress is particularly interesting. Besides, improved biocatalytic activity toward the reduction of ketone 1-phenoxypropan-2-one takes place in the reactions carried out at both 30 °C and 40 °C, within a concentration range between 0.65 and 2.5 mg/mL. These results suggest interesting potential applications for hydrophobin-exposing yeasts. • Class I hydrophobin DewA can be efficiently exposed on S. cerevisiae cell surfaces. • Yeast exposure of HFBI and DewA increases osmotic and heat resistance. • Engineered strains show modified biocatalytic behavior

Objective — comparative study of protein expression in typical and genetically altered Vibrio cholerae strains of O1 serogroup, biovar El Tor by means of proteomic analysis. Materials and methods . Clinical V. cholerae strains — typical strain, M106 (Astrakhan, 1970) and genetically altered one, M1509 (Moscow, 2012) — were used as model ones. Strains were cultivated in LB broth (pH7.2). Then, cell and exoprotein lysate fractions were obtained and investigated in 2D electrophoresis. Different protein stains were examined using mass spectrometry. Survivability of V. cholerae strains under osmotic and oxidative stresses was studied during incubation of the strains in 3 M NaCl solution or 20 mM H 2 O 2 solution. Results and discussion . When analyzing cell lysates, significant differences in protein expression with known function between studied strains were not detected. The great majority of identified proteins in the lysates is functionally associated with carbohydrate metabolism, amino acid metabolism, and energy processes in a cell. At the same time, exoprotein fraction of M1509 genovariant contained increased amount of proteins (peroxidase, superoxide dismutase, thioredoxin, outer membrane proteins OmpW, OmpT) protecting the cells of cholera vibrio from effect of stress factors of the environment. Further study of the resistance to osmotic and oxidative stresses revealed better survivability in the genovariant when exposed to the stated factors. Conclusion . The data of proteomic analysis of the typical and genetically altered V. cholera strains, biovar El Tor, testify to high levels of expression of the proteins that provide for vibrio resistance to the effect of environmental stress factors in genovariants, which is possibly one of the causes of their wide dissemination. In addition, the results obtained will allow for identification of new biomarkers which can be used for differentiation of typical strains and genovariants of V. cholerae , biovar El Tor.

Increasing drought stress poses a severe threat to agricultural productivity. Plants, however, have evolved numerous mechanisms to cope with such environmental stress. Here we report that the stress-induced production of a peptide signal contributes to stress tolerance. The expression of phytosulfokine (PSK) peptide precursor genes, and transcripts of three subtilisin-like serine proteases, SBT1.4, SBT3.7, and SBT3.8, were found to be up-regulated in response to osmotic stress. Stress symptoms were more pronounced in sbt3.8 loss-of-function mutants and could be alleviated by PSK treatment. Osmotic stress tolerance was improved in plants overexpressing the PSK1 precursor (proPSK1) or SBT3.8, resulting in higher fresh weight and improved lateral root development in transgenic plants compared with wild-type plants. We further showed that SBT3.8 is involved in the biogenesis of the bioactive PSK peptide. ProPSK1 was cleaved by SBT3.8 at the C-terminus of the PSK pentapeptide. Processing by SBT3.8 depended on the aspartic acid residue directly following the cleavage site. ProPSK1 processing was impaired in the sbt3.8 mutant. The data suggest that increased expression of proPSK1 in response to osmotic stress followed by the post-translational processing of proPSK1 by SBT3.8 leads to the production of PSK as a peptide signal for stress mitigation.

Assessment of bacterial growth is an essential tool in many fields of study. Numerous methods are available for that purpose, but they are not without disadvantages. The present study aimed to investigate the application of a water soluble oxygen sensor [Ru(dpp(SO3Na)2)3]Cl2x6H2O (RuBPS) in physiological and biochemical studies of Pectobacterium spp. and other bacteria in 96-well microplate systems. The method was optimized with respect to compound concentration, microplate type, and measurement parameters. The growth of bacteria was assessed under increased salinity, acidic and alkaline pH, decreased water availability, and osmotic stress. Utilization of various sugars by bacteria as the only carbon source and the usefulness of RuBPS in antibiotic susceptibility assays were also investigated. The studies confirmed that the respirometry assay can be successfully used to assess bacterial growth in place of the optical density measurement and the resazurin assay, or in conjugation with those methods. The assay is of special value when growth media are non-homogeneous, bacteria produce reductive compounds during growth, or when bacteria do not grow well in the medium of choice. It may be used to study adaptation potential of plant pathogenic bacteria and other bacteria, and their possible spread into new ecological niches.

Hydroponic systems are known to provide a platform for uniform growth conditions until the reproductive stage. However, many plant species, including sunflower, show poor growth and survivability under conventional hydroponic systems due to poor nutrient availability, hypoxia and algal contamination. Thus, we tested various hydroponic systems to select a hydroponic system suitable for screening of sunflower germplasm. Sunflower accessions showed better growth and leaf gas exchange in newly-designed over conventional hydroponic systems. Selected hydroponic systems were further engaged in sunflower accession screening under heat and osmotic stress in a two-pan system (210 cm × 60 cm). Heat stress treatment was applied by growing sunflower germplasm at 42 °C and osmotic stress by adding polyethylene glycol 8000 which decreased the osmotic potential to − 0.6 MPa. There was significant variability among the sunflower accessions for their ability to survive under stress. Accessions such as C-2721 (43%), C-291 (46%) and D-14 (43%) had lower cell membrane injury percentage under osmotic stress and high seedling survivability (60‒80%) under heat stress when compared with susceptible accessions. Moreover, resistant accessions exhibited greater cuticular waxes and root length but lower transpiration losses. The newly designed hydroponic platform proved reliable for the selection of resistant sunflower accessions. Selected parental lines were validated by assessing their hybrids under field trials across two seasons under water and temperature stress during the reproductive phase (autumn). Hybrid H3 obtained by crossing drought and heat resistant parents had the highest seed yield and water use efficiency.

Being the principal elements of secondary cell wall, cellulose and lignin both play a strengthening role in plant structures and stress resistance. However, little research has been done regarding the molecular mechanisms involved in the formation of cellulose and lignin in apple. In this study, in order to better understand the regulatory network in the formation of secondary cell wall, an R2R3 MYB transcriptional factor MdMYB5 was identified and explored. The subcellular localization experiments showed that MdMYB5 could function in the nucleus. Even though lignin and cellulose content, and the expression of their biosynthesis related genes decreased in the MdMYB5-RNAi apple, the ectopic overexpression of MdMYB5 promotes lignin and cellulose content in Arabidopsis, which contributes to the dwarf phenotype. At the same time, salt and osmotic stress affect MdMYB5-RNAi apple tissue cultures. Further transcriptional activation assays carried out demonstrated that MdMYB5 could be activated by MdMYB46 and MdSND1. In conclusion, MdMYB5 was required for the normal formation of secondary cell wall in apple and could be activated by the key regulatory factors MdMYB46 and MdSND1.

A strain of Kytococcus sedentarius was isolated from a dehumidifier operating in a university lecture theatre. Genome analysis and phenotypic characterisation showed that this strain, K. sedentarius MBB13, was a moderately halotolerant aerobe with a branched aerobic electron transport chain and genes that could contribute to erythromycin resistance. The major compatible solute was glycine betaine, with ectoine and proline being deployed at higher osmolarities. Actinobacteria possess multiple WhiB-like (Wbl) regulatory proteins, and K. sedentarius MBB13 has four (WhiB1, WhiB2, WhiB3, and WhiB7). Wbls are iron-sulfur proteins that regulate gene expression through interactions with RNA polymerase sigma factors and/or other regulatory proteins. Bacterial two-hybrid analyses suggested that WhiB1 and WhiB2, but not WhiB3 and WhiB7, interact with the C-terminal domain of the major sigma factor, σA; no interaction was detected between any of the Wbl proteins and the only alternative sigma factors, σB, σH, or σJ. The interaction between σA and WhiB1 or WhiB2 was disrupted in a heterologous system under growth conditions that produce nitric oxide and the iron-sulfur clusters of the isolated WhiB1 and WhiB2 proteins reacted with nitric oxide. Thus, K. sedentarius strain exhibits the major phenotypic characteristics of the type strain and a comprehensive examination of the interactions between its four Wbl proteins and four sigma factors suggested that the Wbl proteins all operate through interaction with σA.

Tubby-like protein genes (TULPs), present in the form of large multigene families, play important roles in environmental stress. However, little is known regarding the TULP family genes in cotton. In this study, we systematically identified and analyzed the membership, characterization, and evolutionary relationship of TULPs in four species of cotton. Transcriptome analysis indicated that GhTULPs participate in environmental stress and cotton tissue development. At the same time, we also predicted and analyzed the potential molecular regulatory mechanisms and functions of TULPs. GhTULP34, as a candidate gene, significantly reduced the germination rate of transgenic Arabidopsis plants under salt stress, and inhibited root development and stomatal closure under mannitol stress. The yeast two-hybrid and luciferase (LUC) systems showed that GhTULP34 can interact with GhSKP1A, a subunit of the SCF-type (Skp1-Cullin-1-F-box) complex. This study will provide a basis and reference for future research on their roles in stress tolerance.