Genome-Wide Identification, Characterization and Expression Analysis of the CIPK Gene Family in Potato (Solanum tuberosum L.) and the Role of StCIPK10 in Response to Drought and Osmotic Stress.

The potato (Solanum tuberosum L.), one of the most important food crops worldwide, is sensitive to environmental stresses. Sensor-responder complexes comprising calcineurin B-like (CBL) proteins and CBL-interacting protein kinases (CIPKs) not only modulate plant growth and development but also mediate numerous stress responses. Here, using a Hidden Markov Model and BLAST searches, 27 CIPK genes were identified in potato and divided into five groups by phylogenetic analysis and into two clades (intron-poor and intron-rich) by gene structure analysis. Quantitative reverse-transcription PCR (qRT-PCR) assays revealed that StCIPK genes play important roles in plant growth, development and abiotic stress tolerance. Up-regulated expression of StCIPK10 was significantly induced by drought, PEG6000 and ABA. StCIPK10 enhances both the ability of potato to scavenge reactive oxygen species and the content of corresponding osmoregulation substances, thereby strengthening tolerance to drought and osmotic stress. StCIPK10 is located at the intersection between the abscisic acid and abiotic stress signaling pathways, which control both root growth and stomatal closure in potato. In addition, StCIPK10 interacts with StCBL1, StCBL4, StCBL6, StCBL7, StCBL8, StCBL11 and StCBL12, and is specifically recruited to the plasma membrane by StCBL11.

Rootstocks Overexpressing StNPR1 and StDREB1 Improve Osmotic Stress Tolerance of Wild-Type Scion in Transgrafted Tobacco Plants.

In grafted plants, the movement of long-distance signals from rootstocks can modulate the development and function of the scion. To understand the mechanisms by which tolerant rootstocks improve scion responses to osmotic stress (OS) conditions, mRNA transport of osmotic responsive genes (ORGs) was evaluated in a tomato/potato heterograft system. In this system, Solanum tuberosum was used as a rootstock and Solanum lycopersicum as a scion. We detected changes in the gene expression levels of 13 out of the 21 ORGs tested in the osmotically stressed plants; of these, only NPR1 transcripts were transported across the graft union under both normal and OS conditions. Importantly, OS increased the abundance of StNPR1 transcripts in the tomato scion. To examine mRNA mobility in transgrafted plants, StNPR1 and StDREB1 genes representing the mobile and non-mobile transcripts, respectively, were overexpressed in tobacco (Nicotiana tabacum). The evaluation of transgenic tobacco plants indicated that overexpression of these genes enhanced the growth and improved the physiological status of transgenic plants growing under OS conditions induced by NaCl, mannitol and polyethylene glycol (PEG). We also found that transgenic tobacco rootstocks increased the OS tolerance of the WT-scion. Indeed, WT scions on transgenic rootstocks had higher ORGs transcript levels than their counterparts on non-transgenic rootstocks. However, neither StNPR1 nor StDREB1 transcripts were transported from the transgenic rootstock to the wild-type (WT) tobacco scion, suggesting that other long-distance signals downstream these transgenes could have moved across the graft union leading to OS tolerance. Overall, our results signify the importance of StNPR1 and StDREB1 as two anticipated candidates for the development of stress-resilient crops through transgrafting technology.

IGFBP-3 Mediates Metabolic Homeostasis During Hyperosmolar Stress in the Corneal Epithelium.

Purpose: The insulin-like growth factor binding protein-3 (IGFBP-3) is a multifunctional secretory protein with well-known roles in cell growth and survival. Data in our laboratory suggest that IGFBP-3 may be functioning as a stress response protein in the corneal epithelium. The purpose of this study is to determine the role of IGFBP-3 in mediating the corneal epithelial cell stress response to hyperosmolarity, a well-known pathophysiological event in the development of dry eye disease. Methods: Telomerase-immortalized human corneal epithelial (hTCEpi) cells were used in this study. Cells were cultured in serum-free media with (growth) or without (basal) supplements. Hyperosmolarity was achieved by increasing salt concentrations to 450 and 500 mOsM. Metabolic and mitochondrial changes were assessed using Seahorse metabolic flux analysis and assays for mitochondrial calcium, polarization and mtDNA. Levels of IGFBP-3 and inflammatory mediators were quantified using ELISA. Cytotoxicity was evaluated using a lactate dehydrogenase assay. In select experiments, cells were cotreated with 500 ng/mL recombinant human (rh)IGFBP-3. Results: Hyperosmolar stress altered metabolic activity, shifting cells towards a respiratory phenotype. Hyperosmolar stress further altered mitochondrial calcium levels, depolarized mitochondria, decreased levels of ATP, mtDNA, and expression of IGFBP-3. In contrast, hyperosmolar stress increased production of the proinflammatory cytokines IL-6 and IL-8. Supplementation with rhIGFBP-3 abrogated metabolic and mitochondrial changes with only marginal effects on IL-8. Conclusions: These findings indicate that IGFBP-3 is a critical protein involved in hyperosmolar stress responses in the corneal epithelium. These data further support a new role for IGFBP-3 in the control of cellular metabolism.

Allergenicity at component level of sub-pollen particles from different sources obtained by osmolar shock: A molecular approach to thunderstorm-related asthma outbreaks.

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 <50% was considered as negative, 50%-75% moderate and > 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.

Transcriptional analysis reveals sodium nitroprusside affects alfalfa in response to PEG-induced osmotic stress at germination stage.

Drought is one of the most common environmental factors that affect alfalfa germination and development. Nitric oxide (NO) could mediate stress tolerance in plants. The goal of this study was to determine exogenous NO donor-mediated drought adaption molecular mechanisms during the alfalfa germination stage. In this study, physiological and transcriptome analyses were performed on 7 days of the growth period seedlings by sodium nitroprusside (SNP) and polyethylene glycol (PEG) treatment. The results showed that SNP supplementation alleviated malondialdehyde accumulation, increased levels of proline and soluble sugars, and enhanced antioxidant enzyme activity under osmotic stress conditions. RNA-Seq experiments identified 5828 genes exhibiting differential expression in seedlings treated with PEG, SNP, or SNP+PEG relative to seedlings treated with distilled water. Of these DEGs, 3235 were upregulated, and 2593 were downregulated relative to the controls. Fifteen DEGs were amplified by qRT-PCR to verify the changes in expression determined by RNA-Seq, revealing that PIF3, glnA, PLCG1, and RP-S11e exhibited enhanced expression under the SNP+PEG treatment. SNP was found to modulate redox homeostasis-related genes such as GSTs, SOD2, GPX, and RBOH, and triggered calcium signaling transduction. It also induced some key genes relating to the abscisic acid, ethylene, and auxin signaling transduction in response to PEG stress. Conversely, genes associated with secondary metabolite biosynthesis and the metabolism of starch and sucrose during osmotic stress were downregulated by SNP. These results provide new insights into SNP-mediated drought adaption mechanisms at transcriptome-wide in alfalfa and reveal key drought tolerance pathways in this species.

Protective functions of alternative splicing transcripts (CdDHN4-L and CdDHN4-S) of CdDHN4 from bermudagrass under multiple abiotic stresses.

Dehydrins (DHNs) play critical roles in plant adaptation to abiotic stresses. The objective of this study was to characterize DHNs in bermudagrass (Cynodon spp.). CdDHN4 gene was cloned from bermudagrass 'Tifway'. Two CdDHN4 transcripts were detected due to alternative splicing (the nonspliced CdDHN4-L and the spliced CdDHN4-S) and both the CdDHN4-S and CdDHN4-L proteins are YSK2-type DHNs, the Φ-segment is present in CdDHN4-L and absent in CdDHN4-S. Transgenic Arabidopsis thaliana expressing CdDHN4-L or CdDHN4-S exhibited improved tolerance to salt, osmotic, low temperature and drought stress compared to the wild type (WT). The two transgenic lines did not differ in salt or drought tolerance, while plants expressing CdDHN4-S grew better under osmotic stress than those expressing CdDHN4-L. Both transgenic lines exhibited reduced content of malondialdehyde (MDA) and reactive oxygen species (ROS); and higher antioxidant enzymatic activities than the wild type plants under salt or drought stress. CdDHN4-S exhibited a higher ROS-scavenging capacity than CdDHN4-L.

The spiking and secretory activity of oxytocin neurones in response to osmotic stimulation: a computational model.

KEY POINTS: A quantitative model of oxytocin neurones that combines a spiking model, a model of stimulus-secretion coupling and a model of plasma clearance of oxytocin was tested. To test the model, a variety of sources of published data were used that relate either the electrical activity of oxytocin cells or the secretion of oxytocin to experimentally induced changes in plasma osmotic pressure. To use these data to test the model, the experimental challenges involved were computationally simulated. The model predictions closely matched the reported outcomes of the different experiments. ABSTRACT: Magnocellular vasopressin and oxytocin neurones in the rat hypothalamus project to the posterior pituitary, where they secrete their products into the bloodstream. In rodents, both vasopressin and oxytocin magnocellular neurones are osmoresponsive, and their increased spiking activity is mainly a consequence of an increased synaptic input from osmoresponsive neurons in regions adjacent to the anterior wall of the third ventricle. Osmotically stimulated vasopressin secretion promotes antidiuresis while oxytocin secretion promotes natriuresis. In this work we tested a previously published computational model of the spiking and secretion activity of oxytocin cells against published evidence of changes in spiking activity and plasma oxytocin concentration in response to different osmotic challenges. We show that integrating this oxytocin model with a simple model of the osmoresponsive inputs to oxytocin cells achieves a strikingly close match to diverse sources of data. Comparing model predictions with published data using bicuculline to block inhibitory GABA inputs supports the conclusion that inhibitory inputs and excitatory inputs are co-activated by osmotic stimuli. Finally, we studied how the gain of osmotically stimulated oxytocin release changes in the presence of a hypovolaemic stimulus, showing that this is best explained by an inhibition of an osmotically regulated inhibitory drive to the magnocellular neurones.

γ-aminobutyric acid accumulation enhances the cell growth of Candida glycerinogenes under hyperosmotic conditions.

γ-aminobutyric acid (GABA) is an important non-protein amino acid involved in the response to various environmental stresses in plant cells. The objectives of this study was to test the hypothesis that intracellular accumulation of GABA improves osmotic tolerance in the unconventional yeast Candida glycerinogenes. In C. glycerinogenes, the expression of UGA4 encoding GABA-specific permease is highly induced by hyperosmotic stress. Exogenous GABA application enhanced intracellular GABA accumulation and promoted cell growth under hyperosmotic conditions. Overexpression of the glutamate decarboxylase gene GAD1 resulted in an increased intracellular GABA and improvement in cell growth under hyperosmotic conditions. These results indicated that improving intracellular GABA accumulation of C. glycerinogenes, either through exogenous application or cellular synthesis, is available for improving the tolerance to hyperosmotic stress. We demonstrate that GABA accumulation plays an important role in osmotic stress resistance of the unconventional yeast C. glycerinogenes.

Changes in thermo-tolerance and survival under simulated gastrointestinal conditions of Salmonella Enteritidis PT4 and Salmonella Typhimurium PT4 in chicken breast meat after exposure to sequential stresses.

This study assessed changes in thermo-tolerance and capability to survive to simulated gastrointestinal conditions of Salmonella Enteritidis PT4 and Salmonella Typhimurium PT4 inoculated in chicken breast meat following exposure to stresses (cold, acid and osmotic) commonly imposed during food processing. The effects of the stress imposed by exposure to oregano (Origanum vulgare L.) essential oil (OVEO) on thermo-tolerance were also assessed. After exposure to cold stress (5°C for 5h) in chicken breast meat the test strains were sequentially exposed to the different stressing substances (lactic acid, NaCl or OVEO) at sub-lethal amounts, which were defined considering previously determined minimum inhibitory concentrations, and finally to thermal treatment (55°C for 30min). Resistant cells from distinct sequential treatments were exposed to simulated gastrointestinal conditions. The exposure to cold stress did not result in increased tolerance to acid stress (lactic acid: 5 and 2.5µL/g) for both strains. Cells of S. Typhimurium PT4 and S. Enteritidis PT4 previously exposed to acid stress showed higher (p<0.05) tolerance to osmotic stress (NaCl: 75 or 37.5mg/g) compared to non-acid-exposed cells. Exposure to osmotic stress without previous exposure to acid stress caused a salt-concentration dependent decrease in counts for both strains. Exposure to OVEO (1.25 and 0.62µL/g) decreased the acid and osmotic tolerance of both S. Enteritidis PT4 and S. Typhimurium PT4. Sequential exposure to acid and osmotic stress conditions after cold exposure increased (p<0.05) the thermo-tolerance in both strains. The cells that survived the sequential stress exposure (resistant) showed higher tolerance (p<0.05) to acidic conditions during continuous exposure (182min) to simulated gastrointestinal conditions. Resistant cells of S. Enteritidis PT4 and S. Typhimurium PT4 showed higher survival rates (p<0.05) than control cells at the end of the in vitro digestion. These results show that sequential exposure to multiple sub-lethal stresses may increase the thermo-tolerance and enhance the survival under gastrointestinal conditions of S. Enteritidis PT4 and S. Typhimurium PT4.

Alleviation of water and osmotic stress-induced changes in nitrogen metabolizing enzymes in Triticum aestivum L. cultivars by potassium.

Present communication reports laboratory and pot experiments conducted to study the influence of water and osmotic stress on nitrogen uptake and metabolism in two wheat (Triticum aestivum L) cultivars with and without potassium supplementation. Polyethylene glycol 6000-induced osmotic stress/restricted irrigation caused a considerable decline in the activity of nitrate reductase, glutamate synthase, alanine and aspartate aminotransferases, and glutamate dehydrogenase. Potassium considerably improved nitrogen metabolism under normal water supply conditions and also resulted in amelioration of the negative impact of water and osmotic stresses indicating that potassium supplementation can be used as a potential tool for enhancing the nitrogen use efficiency in wheat for exploiting its genetic potential.

The garlic NF-YC gene, AsNF-YC8, positively regulates non-ionic hyperosmotic stress tolerance in tobacco.

To investigate the relationship between nuclear factor Y (NF-Y) and stress tolerance in garlic, we cloned a NF-Y family gene AsNF-YC8 from garlic, which was largely upregulated at dehydrate stage. Expression pattern analyses in garlic revealed that AsNF-YC8 is induced through abscisic acid (ABA) and abiotic stresses, such as NaCl and PEG. Compared with wild-type plants, the overexpressing-AsNF-YC8 transgenic tobacco plants showed higher seed germination rates, longer root length and better plant growth under salt and drought stresses. Under drought stress, the transgenic plants maintained higher relative water content (RWC), net photosynthesis, lower levels of malondialdehyde (MDA), and less ion leakage (IL) than wild-type control plants. These results indicate the high tolerance of the transgenic plants to drought stress compared to the WT. The transgenic tobacco lines accumulated less reactive oxygen species (ROS) and exhibited higher antioxidative enzyme activities compared with wild-type (WT) plants under drought stress, which suggested that the overexpression of AsNF-YC8 improves the antioxidant defense system by regulating the activities of these antioxidant enzymes, which in turn protect transgenic lines against drought stress. These results suggest that AsNF-YC8 plays an important role in tolerance to drought and salt stresses.

Histone acetylation influences the transcriptional activation of POX in Beta vulgaris L. and Beta maritima L. under salt stress.

Acetylation of histone proteins is a type of chromatin modification which facilitates the activation of genes. Recent studies brought up the importance of this reversible and rapid process for the regulation of gene expression especially in plant defense against a variety of environmental stresses. Deciphering the exact mechanisms of chromatin modifications under abiotic stress conditions is important for improving crop plants' performance and yield. In a previous study we compared the salt stress responses of Beta vulgaris (sugar beet) and Beta maritima (wild beet). In accordance with those results we suggested that chromatin remodeling can be an active process in the regulation of genes related to salt stress tolerance of these plants. Therefore we performed ChIP assay in control and salt stressed (250 and 500 mM NaCl) plants and compared the enrichment of acetylation in the associated chromatin sites. We found that the transcriptional activation of one peroxidase (POX) encoding gene was associated with the elevated levels of acetylation in H3K9 and H3K27 sites. The acetylation patterns were remarkably different between two species in which the highest acetylation levels were found at H3K9 and H3K27 in wild beet and sugar beet respectively.

ΔN-TRPV1: A Molecular Co-detector of Body Temperature and Osmotic Stress.

Thirst and antidiuretic hormone secretion occur during hyperthermia or hypertonicity to preserve body hydration. These vital responses are triggered when hypothalamic osmoregulatory neurons become depolarized by ion channels encoded by an unknown product of the transient receptor potential vanilloid-1 gene (Trpv1). Here, we show that rodent osmoregulatory neurons express a transcript of Trpv1 that mediates the selective translation of a TRPV1 variant that lacks a significant portion of the channel's amino terminus (ΔN-TRPV1). The mRNA transcript encoding this variant (Trpv1dn) is widely expressed in the brains of osmoregulating vertebrates, including the human hypothalamus. Transfection of Trpv1dn into heterologous cells induced the expression of ion channels that could be activated by either hypertonicity or by heating in the physiological range. Moreover, expression of Trpv1dn rescued the osmosensory and thermosensory responses of single hypothalamic neurons obtained from Trpv1 knockout mice. ΔN-TRPV1 is therefore a co-detector of core body temperature and fluid tonicity.

Effect of hyperbaric oxygen conditions on the ordering of interfacial water.

Hyperbaric oxygen (HBO2) conditions are applied clinically to treat diverse conditions. There is a lack of a unifying consensus as to how HBO2 acts effectively against a broad range of medical conditions, and numerous differing biological explanations have been offered. The possibility of a mechanism dependent on the extensive ordering of interfacial water has not yet been investigated. We examined the hypothesis that zones of ordered water, dubbed "exclusion zones" or "EZ," are expanded under hyperbaric oxygen conditions. Specifically, we tested whether there are significant quantitative differences in EZ size at steady state under high-pressure and/or high-oxygen conditions, compared to normal atmospheric conditions. Oxygen concentration and mechanical pressure were examined separately and in combination. Statistically significant increases in EZ size were seen at elevated air pressures and at high oxygen concentrations. These experimental results suggest the possibility of an ordered water-mediated mechanism of action for hyperbaric oxygen therapy.

Chondrocytic cells express the taurine transporter on their plasma membrane and regulate its expression under anisotonic conditions.

Taurine is a small organic osmolyte which participates in cell volume regulation. Chondrocytes have been shown to accumulate and release taurine; in bone, taurine participates in bone metabolism. However, its role in skeletal cells is poorly understood, especially in chondrocytes. This study investigated the regulation of taurine transporter in chondrocytic cells. We examined the transcriptional regulation of the taurine transporter under anisotonia by reporter gene and real-time RT-PCR assays. The effect of providing supplementary taurine on cell viability was evaluated with the lactate dehydrogenase release assay. The localization of the taurine transporter in human chondrosarcoma cells was studied by overexpressing a taurine transporter-enhanced green fluorescent protein. We observed that the transcription of the taurine transporter gene was up-regulated in hypertonic conditions. Hyperosmolarity-related cell death could be partly abolished by taurine supplementation in the medium. As expected, the fluorescently labeled taurine transporter localized at the plasma membrane. In polarized epithelial MDCK cells, the strongest fluorescence signal was located in the lateral cell membrane area. We also observed that the taurine transporter gene was expressed in several human tissues and malignant cell lines. This is the first study to present information on the transcriptional regulation of taurine transporter gene and the localization of the taurine transporter protein in chondrocytic cells.

Variations in the expression of vasotocin and isotocin receptor genes in the gilthead sea bream Sparus aurata during different osmotic challenges.

The dynamic changes in mRNA expression levels for vasotocin (AVT) and isotocin (IT) receptor gene levels were assessed in a time-course response study in immature male specimens of the gilthead sea bream (Sparus aurata) submitted to hyper- (55‰ salinity) and hypo-osmotic (5‰ salinity) challenges. Two different cDNAs for the AVT receptor and one for the IT receptor (V1a2-type and V2-type AVTR, and ITR, respectively) were cloned by screening an S. aurata brain cDNA library. Genes for these receptors were expressed differentially and is nearly ubiquitously in 26 of the examined tissues. In the gills, both environmental salinity challenges up-regulated AVTR V1a2-type gene expression concomitantly with mRNA expression protein activity of Na(+), K(+)-ATPase gene expression and protein, whereas the AVTR V2-type and cystic fibrosis transmembrane conductance regulator (CFTR) mRNA levels were associated with mRNAs environmental salinity, indicating a possible connection between AVTRs and these transporters. In kidney, AVTR V1a2-type gene expression peaked rapidly and lasted only a short time (12-24h) in response to both osmotic challenges. In contrast, AVTR V2-type mRNA levels were enhanced in specimens exposed to hyperosmotic conditions, whereas they decreased under hypoosmotic environments, suggesting an antidiuretic role related to the vasoconstriction function. In the hypothalamus, only the expression of the AVTR V2-type gene was enhanced at 7 and 14 days under both experimental conditions. In the liver, both AVTRs had increased mRNA levels, with the upregulation of their AVTR V2-type gene increasing faster than the V1a2-type. The ITR gene was not sensitive to variations of external salinity in any of the analyzed tissues. Our results demonstrate the involvement of the vasotocinergic, but not the isotocinergic, pathway as well as the hypothalamic function, in the adjustments of both osmoregulatory and metabolic processes after osmotic challenges.

Rapid identification of potential drought tolerance genes from Solanum tuberosum by using a yeast functional screening method.

Identification of major stress tolerance genes of a crop plant is important for the rapid development of its stress-tolerant cultivar. Here, we used a yeast functional screen method to identify potential drought-tolerance genes from a potato plant. A cDNA expression library was constructed from hyperosmotic stressed potato plants. The yeast transformants expressing different cDNAs were selected for their ability to survive in hyperosmotic stress conditions. The relative tolerances of the selected yeast transformants to multiple abiotic stresses were also studied. Specific potato cDNAs expressed in the tolerant yeast transformants were identified. Sixty-nine genes were found capable of enhancing hyperosmotic stress tolerance of yeast. Based on the relative tolerance data generated, 12 genes were selected, which could be most effective in imparting higher drought tolerance to potato with better survival in salt and high-temperature stresses. Orthologues of few genes identified here are previously known to increase osmotic stress tolerance of yeast and plants; however, specific studies are needed to confirm their role in the osmotic stress tolerance of potato.

NaV1.7: stress-induced changes in immunoreactivity within magnocellular neurosecretory neurons of the supraoptic nucleus.

BACKGROUND: NaV1.7 is preferentially expressed, at relatively high levels, in peripheral neurons, and is often referred to as a "peripheral" sodium channel, and NaV1.7-specific blockers are under study as potential pain therapeutics which might be expected to have minimal CNS side effects. However, occasional reports of patients with NaV1.7 gain-of-function mutations and apparent hypothalamic dysfunction have appeared. The two sodium channels previously studied within the rat hypothalamic supraoptic nucleus, NaV1.2 and NaV1.6, display up-regulated expression in response to osmotic stress. RESULTS: Here we show that NaV1.7 is present within vasopressin-producing neurons and oxytocin-producing neurons within the rat hypothalamus, and demonstrate that the level of Nav1.7 immunoreactivity is increased in these cells in response to osmotic stress. CONCLUSIONS: NaV1.7 is present within neurosecretory neurons of rat supraoptic nucleus, where the level of immunoreactivity is dynamic, increasing in response to osmotic stress. Whether NaV1.7 levels are up-regulated within the human hypothalamus in response to environmental factors or stress, and whether NaV1.7 plays a functional role in human hypothalamus, is not yet known. Until these questions are resolved, the present findings suggest the need for careful assessment of hypothalamic function in patients with NaV1.7 mutations, especially when subjected to stress, and for monitoring of hypothalamic function as NaV1.7 blocking agents are studied.

Genome-wide analysis of lysine catabolism in bacteria reveals new connections with osmotic stress resistance.

Lysine is catabolized via the saccharopine pathway in plants and mammals. In this pathway, lysine is converted to α-aminoadipic-δ-semialdehyde (AASA) by lysine-ketoglutarate reductase/saccharopine dehydrogenase (LKR/SDH); thereafter, AASA is converted to aminoadipic acid (AAA) by α-aminoadipic-δ-semialdehyde dehydrogenase (AASADH). Here, we investigate the occurrence, genomic organization and functional role of lysine catabolic pathways among prokaryotes. Surprisingly, only 27 species of the 1478 analyzed contain the lkr and sdh genes, whereas 323 species contain aasadh orthologs. A sdh-related gene, identified in 159 organisms, was frequently found contiguously to an aasadh gene. This gene, annotated as lysine dehydrogenase (lysdh), encodes LYSDH an enzyme that directly converts lysine to AASA. Pipecolate oxidase (PIPOX) and lysine-6-aminotransferase (LAT), that converts lysine to AASA, were also found associated with aasadh. Interestingly, many lysdh-aasadh-containing organisms live under hyperosmotic stress. To test the role of the lysine-to-AASA pathways in the bacterial stress response, we subjected Silicibacter pomeroyi to salt stress. All but lkr, sdh, lysdh and aasadh were upregulated under salt stress conditions. In addition, lysine-supplemented culture medium increased the growth rate of S. pomeroyi under high-salt conditions and induced high-level expression of the lysdh-aasadh operon. Finally, transformation of Escherichia coli with the S. pomeroyi lysdh-aasadh operon resulted in increased salt tolerance. The transformed E. coli accumulated high levels of the compatible solute pipecolate, which may account for the salt resistance. These findings suggest that the lysine-to-AASA pathways identified in this work may have a broad evolutionary importance in osmotic stress resistance.

Evaluation of abiotic stress tolerance in transgenic potato plants with reduced expression of PSII manganese stabilizing protein.

Manganese stabilizing protein (MSP) is an important component of the Photosystem II (PSII) oxygen evolving complex. In our previous work, transgenic potato plants with reduced expression of MSP (MSP-As) were developed and their physiological and biochemical responses were studied. In this report, we address the response of MSP-As plants toward salinity, heavy metal and osmotic stresses. MSP-As plants treated with NaCl, ZnCl(2) or mannitol solution showed significant level of tolerance under all the stress conditions. Specific enzyme activities of major ROS-scavenging enzymes were found significantly higher in MSP-As plants than the control plants. MSP-As plants accumulated increased levels of proline and low molecular weight metabolites such as ascorbate and α-tocopherol, which indicated that these plants were much more resistant to stress compared to the corresponding control plants. The primary photochemical efficiencies and the OJIP kinetics analyses further confirmed that MSP-As plants were in better optimal health under stress compared to the control plants. Although the exact reason behind the increased stress tolerance in stressed MSP-As plants is unclear, our results strongly indicate the role of MSP of unknown function in abiotic stress tolerance.