Various Types Of Environmental Stress Research Articles

Bioconversion of D-glucose to D-psicose with immobilized D-xylose isomerase and D-psicose 3-epimerase on Saccharomyces cerevisiae spores.

Saccharomyces cerevisiae spores are dormant cells, which can tolerate various types of environmental stress. In our previous work, we successfully developed biological and chemical methods for enzyme immobilization based on the structures of S. cerevisiae spore wall. In this study, we employed biological and chemical approaches for the immobilization of D-xylose isomerase (XI) from Thermus thermophilus and D-psicose 3-epimerase (DPEase) from Agrobacterium tumefaciens with yeast spores, respectively. The enzymatic properties of both immobilized XI and DPEase were characterized and the immobilized enzymes exhibit higher thermostability, broader pH tolerance, and good repeatability compared with free enzymes. Furthermore, we established a two-step approach for the bioconversion of D-glucose to D-psicose using immobilized enzymes. To improve the conversion yield, a multi-pot strategy was adopted for D-psicose production by repeating the two-step process continually. As a result, the yield of D-psicose was obviously improved and the highest yield reached about 12.0%.

Impact of prenatal environmental stress on cortical development.

Prenatal exposure of the developing brain to various types of environmental stress increases susceptibility to neuropsychiatric disorders such as autism, attention deficit hyperactivity disorder and schizophrenia. Given that even subtle perturbations by prenatal environmental stress in the cerebral cortex impair the cognitive and memory functions, this review focuses on underlying molecular mechanisms of pathological cortical development. We especially highlight recent works that utilized animal exposure models, human specimens or/and induced Pluripotent Stem (iPS) cells to demonstrate: (1) molecular mechanisms shared by various types of environmental stressors, (2) the mechanisms by which the affected extracortical tissues indirectly impact the cortical development and function, and (3) interaction between prenatal environmental stress and the genetic predisposition of neuropsychiatric disorders. Finally, we discuss current challenges for achieving a comprehensive understanding of the role of environmentally disturbed molecular expressions in cortical maldevelopment, knowledge of which may eventually facilitate discovery of interventions for prenatal environment-linked neuropsychiatric disorders.

Geophagy (rock eating), experimental stress and cognitive idiosyncrasy

To discusse the impact of geophagy on behavior and conditioned-reflex activity of Wistar rats subjected to instrumental stress under experimental conditions. Experimental geophagy was simulated by adding zeolite-containing tuff (clinoptilolite) to animal feed, the amount relating to 2% of body mass. Tuff was obtained from areas where animals usually eat subsurface rock. Search activity of animals and peculiarities of information and emotional stress were studied through the use of a universal problem chamber. The results of this experimental study showed the negative impact of instrumental stress on laboratory animals, manifested in behavioral dysfunction, in the form of changes in qualitative and quantitative characteristics of search activity. Experimental geophagy contributed to significant improvement in behavioral parameters, confirming the anti-stress effects of the use of natural ingredients. These results suggest that, in natural environmental conditions, "edible" rocks serve as an adaptive tool for recovery from various types of environmental stresses, and are examples of self-medication.

Effect of indole-3-acetic acid on aluminum-induced efflux of malic acid from wheat (Triticum aestivum L.)

Indole-3-acetic acid (IAA) has been found to be involved in plant resistance to various types of environmental stress. Aluminum (Al) toxicity, as one of the most important environmental stress in acid soils, is coped by most plants through the efflux of organic acids via anion channel. This study aims to evaluate the effect of IAA on efflux of malic acid from wheat (Triticum aestivum L.) under Al stress. Hydroponic experiments were performed by wheat ET8 (Al-tolerant). The efflux of malic acid was investigated under different treatments. Results showed that Al treatments increased the accumulation of endogenous IAA, but decreased the activity of IAA oxidase in a dose-dependent manner. A good correlation between all the data of malic acid efflux rate and endogenous IAA content was obtained (R2 = 0.9859**). IAA treatment alone had no effect on the efflux of malic acid. But compared to Al (50 μM) treatment, the efflux of malic acid increased significantly under the co-treatment of IAA (50 μM) and Al (50 μM). In split-root experiments, the root with half of it being treated with Al (CK/Al), the other part (CK) showed significantly higher malic acid efflux rate and endogenous IAA content in root apexes, compared with the root without such treatment (CK/CK). The Al-induced malic acid efflux decreased under the treatments of IAA transport inhibitor N-1-napthyl-phtalamic acid (NPA) (or 2,3,5-triiodobenzoic acid, TIBA). These above results suggested the possible involvement of IAA in the stimulation of malic acid efflux under Al stress. In addition, anion channel inhibitor treatment experiment showed that IAA (50 μM) relieved the inhibiting effect of 5 μM anthracene-9-carboxylic acid (A9C) (or niflumic acid, NIF) on malic acid efflux induced by Al (50 μM), compared to the co-treatment of Al (50 μM) and 5 μM anion channel inhibitor A9C (or NIF) it is thus speculated that the anion channel might have been activated when IAA was involved in malic acid efflux. This study showed that IAA was involved in aluminum-induced efflux of malic acid from wheat.

HsfA1d and HsfA1e Involved in the Transcriptional Regulation of HsfA2 Function as Key Regulators for the Hsf Signaling Network in Response to Environmental Stress

Heat shock transcription factor A2 (HsfA2) acts as a key component of the Hsf signaling network involved in cellular responses to various types of environmental stress. However, the mechanism governing the regulation of HsfA2 expression is still largely unknown. We demonstrated here that a heat shock element (HSE) cluster in the 5'-flanking region of the HsfA2 gene is involved in high light (HL)-inducible HsfA2 expression. Accordingly, to identify the Hsf regulating the expression of HsfA2, we analyzed the effect of loss-of-function mutations of class A Hsfs on the expression of HsfA2 in response to HL stress. Overexpression of an HsfA1d or HsfA1e chimeric repressor and double knockout of HsfA1d and HsfA1e Arabidopsis mutants (KO-HsfA1d/A1e) significantly suppressed the induction of HsfA2 expression in response to HL and heat shock (HS) stress. Transient reporter assays showed that HsfA1d and HsfA1e activate HsfA2 transcription through the HSEs in the 5'-flanking region of HsfA2. In the KO-HsfA1d/A1e mutants, 560 genes, including a number of stress-related genes and several Hsf genes, HsfA7a, HsfA7b, HsfB1 and HsfB2a, were down-regulated compared with those in the wild-type plants under HL stress. The PSII activity of KO-HsfA1d/A1e mutants decreased under HL stress, while the activity of wild-type plants remained high. Furthermore, double knockout of HsfA1d and HsfA1e impaired tolerance to HS stress. These findings indicated that HsfA1d and HsfA1e not only regulate HsfA2 expression but also function as key regulators of the Hsf signaling network in response to environmental stress.

Stress‐tolerance of baker's‐yeast (Saccharomyces cerevisiae) cells: stress‐protective molecules and genes involved in stress tolerance

During the fermentation of dough and the production of baker's yeast (Saccharomyces cerevisiae), cells are exposed to numerous environmental stresses (baking-associated stresses) such as freeze-thaw, high sugar concentrations, air-drying and oxidative stresses. Cellular macromolecules, including proteins, nucleic acids and membranes, are seriously damaged under stress conditions, leading to the inhibition of cell growth, cell viability and fermentation. To avoid lethal damage, yeast cells need to acquire a variety of stress-tolerant mechanisms, for example the induction of stress proteins, the accumulation of stress protectants, changes in membrane composition and repression of translation, and by regulating the corresponding gene expression via stress-triggered signal-transduction pathways. Trehalose and proline are considered to be critical stress protectants, as is glycerol. It is known that these molecules are effective for providing protection against various types of environmental stresses. Modifications of the metabolic pathways of trehalose and proline by self-cloning methods have significantly increased tolerance to baking-associated stresses. To clarify which genes are required for stress tolerance, both a comprehensive phenomics analysis and a functional genomics analysis were carried out under stress conditions that simulated those occurring during the commercial baking process. These analyses indicated that many genes are involved in stress tolerance in yeast. In particular, it was suggested that vacuolar H+-ATPase plays important roles in yeast cells under stress conditions.

From furless to heartless—unraveling the diverse functions of cathepsin L.

Cysteine proteases are enzymes that use a cysteine residue, activated by a histidine residue, to serve the role of the nucleophile that attacks the peptide bond. The prototype cysteine protease is papain, an enzyme purified from the fruit of the papaya. Why does the papaya need papain? It turns out that cysteine proteinases are involved in virtually every aspect of plant physiology and development. They play a role in development, senescence, programmed cell death, storage, and mobilization of germinal proteins and enable the plant to deal with various types of environmental stress. Mammalian proteases homologous to papain have been discovered, most notably the cathepsins, cysteine, or aspartyl proteases, which have a role in immune responses, cell survival, and death, and numerous other cell systems and processes. The cathepsin cysteine-based active site apparently arose independently at least twice in the course of evolution. For instance, the caspases are enzymes that play a major role in apoptosis and have active sites similar to papain. However, their structure is otherwise unrelated to cathepsins. Cysteine cathepsins are active in pericellular environments as soluble enzymes or are bound to cell surface receptors at the plasma membrane and possibly even within secretory vesicles, lysosomes, the cytosol, mitochondria, and within the nuclei of eukaryotic cells. The proteolytic actions performed by cysteine cathepsins are essential in the maintenance of homeostasis and depend heavily upon their correct sorting and trafficking within cells.

Plant cysteine proteinases: Evaluation of the pharmacological activity

Cysteine proteinases are involved in virtually every aspect of plant physiology and development. They play a role in development, senescence, programmed cell death, storage and mobilization of germinal proteins, and in response to various types of environmental stress. In this review, we focus on a group of plant defensive enzymes occurring in germinal tissue of Caricaceae. These enzymes elicit a protective response in the unripe fruit after physical stress. We propose that these enzymes follow a strategy similar to mammalian serine proteinases involved in blood clotting and wound healing. We show evidence for the pharmacological role of plant cysteine proteinases in mammalian wound healing, immunomodulation, digestive conditions, and neoplastic alterations.

A Novel Function of eIF2α Kinases as Inducers of the Phosphoinositide-3 Kinase Signaling Pathway

Phosphoinositide-3 kinase (PI3K) plays an important role in signal transduction in response to a wide range of cellular stimuli involved in cellular processes that promote cell proliferation and survival. Phosphorylation of the alpha subunit of the eukaryotic translation initiation factor eIF2 at Ser51 takes place in response to various types of environmental stress and is essential for regulation of translation initiation. Herein, we show that a conditionally active form of the eIF2alpha kinase PKR acts upstream of PI3K and turns on the Akt/PKB-FRAP/mTOR pathway leading to S6 and 4E-BP1 phosphorylation. Also, induction of PI3K signaling antagonizes the apoptotic and protein synthesis inhibitory effects of the conditionally active PKR. Furthermore, induction of the PI3K pathway is impaired in PKR(-/-) or PERK(-/-) mouse embryonic fibroblasts (MEFs) in response to various stimuli that activate each eIF2alpha kinase. Mechanistically, PI3K signaling activation is indirect and requires the inhibition of protein synthesis by eIF2alpha phosphorylation as demonstrated by the inactivation of endogenous eIF2alpha by small interfering RNA or utilization of MEFs bearing the eIF2alpha Ser51Ala mutation. Our data reveal a novel property of eIF2alpha kinases as activators of PI3K signaling and cell survival.

ISI ŞOK PROTEİNLER VE FİZYOLOJİK ROLLERİ

Heat shock proteins (HSPs), also called stress proteins, are a gr oup of pro teins that are present in all cells in all life forms. The synthases of these proteins are induced when a cell undergoes various types of environmental stresses like heat, cold and oxygen deprivation. In this article we summarized the structure and physi ology of he at shock proteins which is an important research area for bio logy and medicine.

A knockout strain of CPR1 induced during fermentation of Saccharomyces cerevisiae KNU5377 is susceptible to various types of stress

To investigate the tolerance factor of Saccharomyces cerevisiae KNU5377 against various types of environmental stress during fermentation, we identified the protein that is upregulated at high temperatures. The highly upregulated protein was high-score-matched as a cytoplasmic peptidyl-prolyl cis-trans isomerase, cyclophilin (Cpr1p), by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF). We constructed a CPR1-deleted KNU5377 strain (KNU5377Y cpr1Delta) to determine the roles of the protein under fermentative or stress condition. The growth of the S. cerevisiae KNU5377Y cpr1Delta strain was completely inhibited under the following conditions: heat (40 degrees C), hydrogen peroxide (20-30 mM), menadione (0.3 mM), ethanol (16%), sulfuric acid (5 mm), and lactic acid (0.4-0.8%). However, the wild-type and cpr1Delta mutant of S. cerevisiae BY4741 as a positive control did not show differences in sensitivity to stress. It is interesting to note that the wild-type KNU5377Y and KNU5377Y cpr1Delta mutant showed high sensitivity against various stresses, particularly, acid stress such as in the presence of sulfuric and lactic acid. Although the alcohol fermentation rate of the KNU5377Y cpr1Delta mutant markedly decreased with an increase in temperature up to 40 degrees C, we observed no decrease in that of the wild-type strain under the same conditions. These results suggest that CPR1 contributes to the stress tolerance of KNU5377 against various types of environmental stress caused during fermentation, thus leading to the physiological role of maintaining an alcohol fermentation yield, even at high temperatures such as 40 degrees C.

Mitogen-activated protein kinases and asthma.

Mitogen-activated protein kinases (MAPKs) are evolutionary conserved enzymes which play a key role in signal transduction mediated by cytokines, growth factors, neurotransmitters and various types of environmental stresses. In the airways, these extracellular stimuli elicit complex inflammatory and structural changes leading to the typical features of asthma including T cell activation, eosinophil and mast cell infiltration, as well as bronchial hyperresponsiveness and airway remodelling. Because MAPKs represent an important point of convergence for several different signalling pathways, they affect multiple aspects of normal airway function and also significantly contribute to asthma pathophysiology. Therefore, this review focuses on the crucial involvement of MAPKs in asthma pathogenesis, thus also discussing their emerging role as molecular targets for anti-asthma drugs.

Cloning and characterization of an eukaryotic initiation factor-2α kinase from the silkworm, Bombyx mori

Eukaryotic initiation factor 2α (eIF-2α) kinases are involved in the translational regulations that occur in response to various types of environmental stress, and play an important role in the cellular defense system operating under unfavorable conditions. The identification of additional eIF-2α kinases and the elucidation of their functions are necessary to understand how different eIF-2α kinases can specifically respond to distinct stimuli. Here, we report a novel eIF-2α kinase, termed BeK, from the silkworm, Bombyx mori. This gene encodes 579 amino acids and contains all 11 catalytic domains of protein–serine/threonine kinases. Most notably, it contains an “Ile-Gln-Met-Xaa-Xaa-Cys” motif, which is highly conserved from yeast to mammalian eIF-2α kinases. BeK does not show any significant homology in the NH 2 terminal regulatory domain, suggesting a distinct regulatory mechanism of this novel eIF-2α kinase. BeK is ubiquitously expressed in the various tissues throughout the final larval stage. Importantly, BeK is activated in Drosophila Schneider cells following heat shock and osmotic stress, and activated-BeK has been shown to phosphorylate an eIF-2α subunit at the Ser 50 site. However, other forms of stress, such as immune stress, endoplasmic reticulum stress and oxidative stress, cannot significantly elicit BeK activity. Interestingly, the baculovirus gene product, PK2, can inhibit BeK enzymatic activity, suggesting that BeK may be an endogenous target for a viral gene product. Taken together, these data indicate that BeK is a novel eIF-2α kinase involved in the stress response in B. mori.

Changes in the cellular components of sugar beet under salt stress

The acclimation of a plant to a constantly changing environment involves the accumulation of certain organic compounds of low molecular mass, known collectively as compatible solutes, in the cytoplasm. Evidence from numerous investigations of plants strongly suggests that glycine betaine (GB), an amphoteric quaternary amine, plays an important role as a compatible solute under various types of environmental stress, such as high levels of salts and low temperature. In this work, sugar beet (Beta vulgaris) was grown at NaCl concentrations of up to 300 mmol/l soil, and the effects of salt on the growth, contents of water, chlorophyll, soluble protein, soluble saccharide and GB in leaf were measured. The addition of NaCl up to 300 mmol/l soil significantly affected the growth, and the contents of water and chlorophyll decreased, whereas the soluble protein and saccharide concentrations in the leaf changed little. On the other hand, the GB concentration increased 6-fold with increasing the salinity of the medium, suggesting that GB is a main osmoprotectant in this plant. The induction of GB was monitored by cultivating the plant seed under salt stress. It was found that the GB originally contained in the seed was lost during the early stage of cultivation, and new GB was synthesized in the stage of germination in a dose-dependent fashion with respect to the salt concentration.

The role of glycine betaine in the protection of plants from stress: clues from transgenic plants.

The acclimation of a plant to a constantly changing environment involves the accumulation of certain organic compounds of low molecular mass, known collectively as compatible solutes, in the cytoplasm. The evidence from numerous investigations of the physiology, genetics, biophysics and biochemistry of plants strongly suggests that glycine betaine (GB), an amphoteric quaternary amine, plays an important role as a compatible solute in plants under various types of environmental stress, such as high levels of salts and low temperature. Plant species vary in their capacity to synthesize GB and some plants, such as spinach and barley, accumulate relatively high levels of GB in their chloroplasts while others, such as Arabidopsis and tobacco, do not synthesize this compound. Genetic engineering has allowed the introduction into GB-deficient species of biosynthetic pathways to GB from both micro-organisms and higher plants; this approach has facilitated investigations of the importance of GB in stress protection. In this review, we summarize recent progress in the genetic manipulation of the synthesis of GB, with special emphasis on the relationship between the protective effects of GB in vivo and those documented in vitro.

Hemolymph levels of methyl farnesoate increase in response to osmotic stress in the green crab, Carcinus maenas

The salinity of estuarine environments can vary widely, exposing resident organisms to considerable osmotic stress. The green crab Carcinus maenas is well known for its ability to osmoregulate in response to such stress. Therefore, we tested the relationship between osmoregulation and hemolymph levels of methyl farnesoate (MF), a compound previously shown to rise in response to various types of environmental stresses. When crabs were transferred from 100% seawater to dilute (hypo-osmotic) seawater, hemolymph osmolality dropped rapidly, reaching an acclimation level 48 h after transfer. Hemolymph levels of MF also rose in these animals after a delay of 6 h, and reached a maximum level at 48 h. MF levels remained elevated as long as the crabs were maintained in dilute seawater, and quickly returned to basal levels when the animals were returned to full strength seawater. In most (but not all) animals, MF levels were elevated when hemolymph osmolality fell below the isosmotic point (approx. 800 mOsm/kg). These data suggest that MF may have a role in osmoregulation by this species. In addition, the elevation of MF by hypo-osmotic seawater suggests an experimental strategy for manipulating MF levels in crustaceans.

The yeast histidine protein kinase, Sln1p, mediates phosphotransfer to two response regulators, Ssk1p and Skn7p.

The Saccharomyces cerevisiae Sln1 protein is a 'two-component' regulator involved in osmotolerance. Two-component regulators are a family of signal-transduction molecules with histidine kinase activity common in prokaryotes and recently identified in eukaryotes. Phosphorylation of Sln1p inhibits the HOG1 MAP kinase osmosensing pathway via a phosphorelay mechanism including Ypd1p and the response regulator, Ssk1p. SLN1 also activates an MCM1-dependent reporter gene, P-lacZ, but this function is independent of Ssk1p. We present genetic and biochemical evidence that Skn7p is the response regulator for this alternative Sln1p signaling pathway. Thus, the yeast Sln1 phosphorelay is actually more complex than appreciated previously; the Sln1 kinase and Ypd1 phosphorelay intermediate regulate the activity of two distinct response regulators, Ssk1p and Skn7p. The established role of Skn7p in oxidative stress is independent of the conserved receiver domain aspartate, D427. In contrast, we show that Sln1p activation of Skn7p requires phosphorylation of D427. The expression of TRX2, previously shown to exhibit Skn7p-dependent oxidative-stress activation, is also regulated by the SLN1 phosphorelay functions of Skn7p. The identification of genes responsive to both classes of Skn7p function suggests a central role for Skn7p and the SLN1-SKN7 pathway in integrating and coordinating cellular response to various types of environmental stress.

Is there a gas (general adaptation syndrome) response to various types of environmental stress?

A hypothesis of existence of a general adaptation syndrome (GAS), in which different types of stress evoke similar coping mechanisms, resulting in adaptations, is tested for plants. As stress coping mechanisms, oxy-free radical scavengers and antioxidants, osmoregulation, the role of abscisic acid, jasmonates, nitric oxide, synthesis of heat shock proteins and phytochelatins as heavy metal detoxifiers are discussed.

Fibromyalgia: a clinical challenge

The syndrome of fibromyalgia includes an unusually large and heterogeneous number of symptoms apart from the core features of generalized pain and widespread tenderness. Widespread tenderness is the only objective criterion. There is no evidence that fibromyalgia is a disease of the muscles or a rheumatic syndrome. The experience from an Australian epidemic of fibromyalgia indicates that there is an important psychosomatic component in the pathogenesis. Probably, fibromyalgia is not a disease entity; rather, the symptoms reflect difficulties in coping with various types of environmental stress. Secondary to this, sleep disturbances, fatigue, a low level of physical activity and poor physical fitness may develop, rendering the patients susceptible to muscle pain and tenderness elicited by sleep disturbances. A vicious circle may be responsible for the chronicity of the syndrome. Identification of environmental factors and early intervention should be given a high priority.

Classification of water regimes in systems of fluctuating water level

Aquatic macrophyte communities have been shown to form sequences along water depth gradients, and water depth has been related to various types of environmental stresses. However, in semi-permanent wetlands, water depth is rarely constant through time; there are large fluctuations in water level between seasons and years, and the relative lengths of wet and dry periods may be as important a stress as the average (or maximum) depth of water. This paper presents a method of quantifying water regimes on the basis of infrequently sampled water level data and of comparing and defining regime-types within and between semi-permanent swamps. Time periods per depth class are calculated from water depth data for each gradient position from the bottom of the swamp to the high-water mark. These data can be represented as a histogram that describes the wetldry pattern of each gradient position. A multivariate clustering is used to compare gradient positions in different swamps on the basis of depth and period of inundation. Water regime types are then defined on the basis of the groups derived in the clustering. The method is illustrated for the Bool Lagoon system in the south-east of South Australia.