Accumulation of trehalose by overexpression of tps1, coding for trehalose-6-phosphate synthase, causes increased resistance to multiple stresses in the fission yeast schizosaccharomyces pombe

Contribution of trehalose to ethanol stress tolerance of Wickerhamomyces anomalus

BACKGROUND

The ascomycetous heterothallic yeast Wickerhamomyces anomalus (WA) has received considerable attention and has been widely reported in the winemaking industry for its distinctive physiological traits and metabolic attributes. An increased concentration of ethanol during ethanol fermentation, however, causes ethanol stress (ES) on the yeast cells. Trehalose has been implicated in improving survival under various stress conditions in microorganisms. Herein, we determined the effects of trehalose supplementation on the survival, differentially expressed genes (DEGs), cellular morphology, and oxidative stress tolerance of WA in response to ES.

RESULTS

The results indicated that trehalose improved the survival and anomalous surface and ultrastructural morphology of WA. Additionally, trehalose improved redox homeostasis by reducing the levels of reactive oxygen species (ROS) and inducing the activities of antioxidant enzymes. In addition, DEGs affected by the application of trehalose were enriched in these categories including in gene expression, protein synthesis, energy metabolism, and cell cycle pathways. Additionally, trehalose increased the content of intracellular malondialdehyde (MDA) and adenosine triphosphate.

CONCLUSIONS

These results reveal the protective role of trehalose in ES mitigation and strengthen the possible uses of WA in the wine fermentation sector.

Lipids and Trehalose Actively Cooperate in Heat Stress Management of Schizosaccharomyces pombe

Homeostatic maintenance of the physicochemical properties of cellular membranes is essential for life. In yeast, trehalose accumulation and lipid remodeling enable rapid adaptation to perturbations, but their crosstalk was not investigated. Here we report about the first in-depth, mass spectrometry-based lipidomic analysis on heat-stressed Schizosaccharomyces pombe mutants which are unable to synthesize (tps1Δ) or degrade (ntp1Δ) trehalose. Our experiments provide data about the role of trehalose as a membrane protectant in heat stress. We show that under conditions of trehalose deficiency, heat stress induced a comprehensive, distinctively high-degree lipidome reshaping in which structural, signaling and storage lipids acted in concert. In the absence of trehalose, membrane lipid remodeling was more pronounced and increased with increasing stress dose. It could be characterized by decreasing unsaturation and increasing acyl chain length, and required de novo synthesis of stearic acid (18:0) and very long-chain fatty acids to serve membrane rigidification. In addition, we detected enhanced and sustained signaling lipid generation to ensure transient cell cycle arrest as well as more intense triglyceride synthesis to accommodate membrane lipid-derived oleic acid (18:1) and newly synthesized but unused fatty acids. We also demonstrate that these changes were able to partially substitute for the missing role of trehalose and conferred measurable stress tolerance to fission yeast cells.

De Novo Transcriptome Analysis Reveals Potential Thermal Adaptation Mechanisms in the Cicada Hyalessa fuscata

Simple Summary

In metropolitan Seoul and its vicinity, cicadas of the species Hyalessa fuscata living in warmer areas could tolerate the heat better than those living in cooler areas, but genetic mechanisms involved in better heat tolerance remained unclear. In this study, we examined differences in gene expression of cicadas living in a warm urban area, a cool urban area and a suburban area in three experimental treatments: no heating, 10 min heating and heating until the cicadas lost their mobility. Cicadas from the warm urban area changed their gene expressions the most. Activated genes were mostly related to heat shock, energy metabolism, and detoxification. These results suggested that under heat stress, cicadas inhabiting warm areas could differentially express genes to increase their thermal tolerance.

Abstract

In metropolitan Seoul, populations of the cicada Hyalessa fuscata in hotter urban heat islands (“high UHIs”) exhibit higher thermal tolerance than those in cooler UHIs (“low UHIs”). We hypothesized that heat stress may activate the expression of genes that facilitate greater thermal tolerance in high-UHI cicadas than in those from cooler areas. Differences in the transcriptomes of adult female cicadas from high-UHI, low-UHI, and suburban areas were analyzed at the unheated level, after acute heat stress, and after heat torpor. No noticeable differences in unheated gene expression patterns were observed. After 10 min of acute heat stress, however, low-UHI and suburban cicadas expressed more heat shock protein genes than high-UHI counterparts. More specifically, remarkable changes in the gene expression of cicadas across areas were observed after heat torpor stimulus, as represented by a large number of up- and downregulated genes in the heat torpor groups compared with the 10 min acute heat stress and control groups. High-UHI cicadas expressed the most differentially expressed genes, followed by the low-UHI and suburban cicadas. There was a notable increase in the expression of heat shock, metabolism, and detoxification genes; meanwhile, immune-related, signal transduction, and protein turnover genes were downregulated in high-UHI cicadas versus the other cicada groups. These results suggested that under heat stress, cicadas inhabiting high-UHIs could rapidly express genes related to heat shock, energy metabolism, and detoxification to protect cells from stress-induced damage and to increase their thermal tolerance toward heat stress. The downregulation of apoptosis mechanisms in high-UHI cicadas suggested that there was less cellular damage, which likely contributed to their high tolerance of heat stress.

Uncoupling glucose sensing from GAL metabolism for heterologous lactose fermentation in Saccharomyces cerevisiae

OBJECTIVES

Development of a system for direct lactose to ethanol fermentation provides a market for the massive amounts of underutilized whey permeate made by the dairy industry. For this system, glucose and galactose metabolism were uncoupled in Saccharomyces cerevisiae by deleting two negative regulatory genes, GAL80 and MIG1, and introducing the essential lactose hydrolase LAC4 and lactose transporter LAC12, from the native but inefficient lactose fermenting yeast Kluyveromyces marxianus.

RESULTS

Previously, integration of the LAC4 and LAC12 genes into the MIG1 and NTH1 loci was achieved to construct strain AY-51024M. Low rates of lactose conversion led us to generate the Δmig1Δgal80 diploid mutant strain AY-GM from AY-5, which exhibited loss of diauxic growth and glucose repression, subsequently taking up galactose for consumption at a significantly higher rate and yielding higher ethanol concentrations than strain AY-51024M. Similarly, in cheese whey permeate powder solution (CWPS) during three, repeated, batch processes in a 5L bioreactor containing either 100 g/L or 150 g/L lactose, the lactose uptake and ethanol productivity rates were both significantly greater than that of AY-51024M, while the overall fermentation times were considerably lower.

CONCLUSIONS

Using the Cre-loxp system for deletion of the MIG1 and GAL80 genes to relieve glucose repression, and LAC4 and LAC12 overexpression to increase lactose uptake and conversion provides an efficient basis for yeast fermentation of whey permeate by-product into ethanol.

Cryopreservation and the Freeze-Thaw Stress Response in Yeast

The ability of yeast to survive freezing and thawing is most frequently considered in the context of cryopreservation, a practical step in both industrial and research applications of these organisms. However, it also relates to an evolved ability to withstand freeze-thaw stress that is integrated with a larger network of survival responses. These responses vary between different strains and species of yeast according to the environments to which they are adapted, and the basis of this adaptation appears to be both conditioned and genetic in origin. This review article briefly touches upon common yeast cryopreservation methods and describes in detail what is known about the biochemical and genetic determinants of cell viability following freeze-thaw stress. While we focus on the budding yeast Saccharomyces cerevisiae, in which the freeze-thaw stress response is best understood, we also highlight the emerging diversity of yeast freeze-thaw responses as a manifestation of biodiversity among these organisms.

Compatible solutes adaptive alterations in Arthrobacter simplex during exposure to ethanol, and the effect of trehalose on the stress resistance and biotransformation performance

Ethanol-tolerant Arthrobacter simplex is desirable since ethanol facilitates hydrophobic substrates dissolution on an industrial scale. Herein, alterations in compatible solutes were investigated under ethanol stress. The results showed that the amount of trehalose and glycerol increased while that of glutamate and proline decreased. The trehalose protectant role was verified and its concentration was positively related to the degree of cell tolerance. otsA, otsB and treS, three trehalose biosynthesis genes in A. simplex, also enhanced Escherichia coli stress tolerance, but the increased tolerance was dependent on the type and level of the stress. A. simplex strains accumulating trehalose showed a higher productivity in systems containing more ethanol and substrate because of better viability. The underlying mechanisms of trehalose were involved in better cell integrity, higher membrane stability, stronger reactive oxygen species scavenging capacity and higher energy level. Therefore, trehalose was a general protectant and the upregulation of its biosynthesis by genetic modification enhanced cell stress tolerance, consequently promoted productivity.

Reversible solidification of fission yeast cytoplasm after prolonged nutrient starvation

Cells depend on a highly ordered organisation of their content and must develop strategies to maintain the anisotropic distribution of organelles during periods of nutrient shortage. One of these strategies is to solidify the cytoplasm, which was observed in bacteria and yeast cells with acutely interrupted energy production. Here, we describe a different type of cytoplasm solidification fission yeast cells switch to, after having run out of nutrients during multiple days in culture. It provides the most profound reversible cytoplasmic solidification of yeast cells described to date. Our data exclude the previously proposed mechanisms for cytoplasm solidification in yeasts and suggest a mechanism that immobilises cellular components in a size-dependent manner. We provide experimental evidence that, in addition to time, cells use intrinsic nutrients and energy sources to reach this state. Such cytoplasmic solidification may provide a robust means to protect cellular architecture in dormant cells.

Summary: After prolonged quiescence, fission yeast cell populations switch state to immobilise subcellular components much more profoundly than cells experiencing acute energy depletion.

Trehalose supplementation during porcine oocytes in vitro maturation improves the developmental capacity of parthenotes

Autophagy is a critical process in early mammalian embryogenesis. Mammalian target of rapamycin (mTOR) inhibitors are major regulators of autophagy. However, mTOR plays a vital role in major signaling pathways controlling cell growth and metabolism; thus, more secure autophagy activation methods should be considered. The present study investigated the effects of supplementary trehalose, a novel mTOR-independent autophagy enhancer, on oocyte maturation and embryonic development after parthenogenetic activation (PA). Trehalose treatment during in vitro maturation (IVM) did not affect the nuclear maturation rates of oocytes. Oocytes treated with 25 mM trehalose during IVM had a significantly higher (P < 0.05) blastocyst formation rate (64.2%) after PA compared to that in control oocytes (52.0%). Blastocyst quality was also improved in the trehalose-treated group. The total cell numbers for blastocyst formation and expanded blastocyst formation were significantly increased in the trehalose-treated group (52.2% and 27.7%, respectively) compared to those in the control group (36.9% and 11.0%, respectively). Trehalose treatment led to the increased expression of LC3, an autophagy marker, in metaphase II oocytes and 4-cell stage embryos. Gene expression analysis revealed that the expression of several autophagy related genes (LAMP2, pATG5, and LC3) increased, while the Bax/Bcl2 ratio and pro-apoptotic Bak transcript levels were decreased in the trehalose-treated group. In conclusion, these results indicate that treatment with trehalose during IVM improved the developmental potential of porcine embryos by down-regulation of pro-apoptotic genes and up-regulation of autophagy-related genes and marker. Trehalose may be useful for the large-scale production of high-quality porcine blastocysts in vitro.

Allosteric activation of yeast enzyme neutral trehalase by calcium and 14-3-3 protein

Neutral trehalase 1 (Nth1) from Saccharomyces cerevisiae catalyzes disaccharide trehalose hydrolysis and helps yeast to survive adverse conditions, such as heat shock, starvation or oxidative stress. 14-3-3 proteins, master regulators of hundreds of partner proteins, participate in many key cellular processes. Nth1 is activated by phosphorylation followed by 14-3-3 protein (Bmh) binding. The activation mechanism is also potentiated by Ca(2+) binding within the EF-hand-like motif. This review summarizes the current knowledge about trehalases and the molecular and structural basis of Nth1 activation. The crystal structure of fully active Nth1 bound to 14-3-3 protein provided the first high-resolution view of a trehalase from a eukaryotic organism and showed 14-3-3 proteins as structural modulators and allosteric effectors of multi-domain binding partners.

Cloning, purification and characterization of trehalose-6-phosphate synthase from Pleurotus tuoliensis

Pleurotus tuoliensis, a kind of valuable and favorable edible mushroom in China, is always subjected to high environmental temperature during cultivation. In our previous study with P. tuoliensis, trehalose proved to be effective for tolerating heat stress. Trehalose-6-phosphate synthase (TPS; EC2.4.1.15) plays a key role in the biosynthesis of trehalose in fungi. In this study, a full-length of cDNA with 1,665 nucleotides encoding TPS (PtTPS) in P. tuoliensis was cloned. The PtTPS amino acid was aligned with other homologues and several highly conserved regions were analyzed. Thus, the TPS protein was expressed in Escherichia coli and purified by affinity chromatography to test its biochemical properties. The molecular mass of the enzyme is about 60 kDa and the optimum reaction temperature and pH is 30 °C and 7, respectively. The UDP-glucose and glucose-6-phosphate were the optimum substrates among all the tested glucosyl donors and acceptors. Metal cations like Mg²⁺, Co²⁺, Mn²⁺, Ni²⁺, K⁺, Ag⁺ stimulated PtTPS activity significantly. Metal chelators such as sodium citrate, citric acid, EDTA, EGTA and CDTA inhibited enzyme activity. Polyanions like heparin and chondroitin sulfate were shown to stimulate TPS activity.

A novel wheat NAC transcription factor, TaNAC30, negatively regulates resistance of wheat to stripe rust

NAC transcription factors are widespread in the plant kingdom and play essential roles in the transcriptional regulation of defense responses. In this study, we isolated a novel NAC transcription factor gene, TaNAC30, from a cDNA library constructed from wheat (Triticum aestivum) plants inoculated with the stripe rust pathogen Puccinia striiformis f. sp. tritici (Pst). TaNAC30 contains a typical NAM domain and localizes to the nucleus. Yeast one-hybrid assays revealed that TaNAC30 exhibits transcriptional activity and that its C-terminus is necessary for the activation of transcription. Expression of TaNAC30 increased when host plants were infected with a virulent race (CYR31) of the rust fungus Pst. Silencing of TaNAC30 by virus-induced gene silencing inhibited colonization of the virulent Pst isolate CYR31. Moreover, detailed histological analyses showed that silencing of TaNAC30 enhanced resistance to Pst by inducing a significant increase in the accumulation of H₂ O₂ . Finally, we overexpressed TaNAC30 in fission yeast and determined that cell viability was severely reduced in TaNAC30-transformed cells grown on medium containing H₂ O₂ . These results suggest that TaNAC30 negatively regulates plant resistance in a compatible wheat-Pst interaction.

Invertebrate Trehalose-6-Phosphate Synthase Gene: Genetic Architecture, Biochemistry, Physiological Function, and Potential Applications

The non-reducing disaccharide trehalose is widely distributed among various organisms. It plays a crucial role as an instant source of energy, being the major blood sugar in insects. In addition, it helps countering abiotic stresses. Trehalose synthesis in insects and other invertebrates is thought to occur via the trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP) pathways. In many insects, the TPP gene has not been identified, whereas multiple TPS genes that encode proteins harboring TPS/OtsA and TPP/OtsB conserved domains have been found and cloned in the same species. The function of the TPS gene in insects and other invertebrates has not been reviewed in depth, and the available information is quite fragmented. The present review discusses the current understanding of the trehalose synthesis pathway, TPS genetic architecture, biochemistry, physiological function, and potential sensitivity to insecticides. We note the variability in the number of TPS genes in different invertebrate species, consider whether trehalose synthesis may rely only on the TPS gene, and discuss the results of in vitro TPS overexpression experiment. Tissue expression profile and developmental characteristics of the TPS gene indicate that it is important in energy production, growth and development, metamorphosis, stress recovery, chitin synthesis, insect flight, and other biological processes. We highlight the molecular and biochemical properties of insect TPS that make it a suitable target of potential pest control inhibitors. The application of trehalose synthesis inhibitors is a promising direction in insect pest control because vertebrates do not synthesize trehalose; therefore, TPS inhibitors would be relatively safe for humans and higher animals, making them ideal insecticidal agents without off-target effects.

Comparative transcriptional profiling of tildipirosin-resistant and sensitive Haemophilus parasuis

Numerous studies have been conducted to examine the molecular mechanism of Haemophilus parasuis resistance to antibiotic, but rarely to tildipirosin. In the current study, transcriptional profiling was applied to analyse the variation in gene expression of JS0135 and tildipirosin-resistant JS32. The growth curves showed that JS32 had a higher growth rate but fewer bacteria than JS0135. The cell membranes of JS32 and a resistant clinical isolate (HB32) were observed to be smoother than those of JS0135. From the comparative gene expression profile 349 up- and 113 downregulated genes were observed, covering 37 GO and 63 KEGG pathways which are involved in biological processes (11), cellular components (17), molecular function (9), cellular processes (1), environmental information processing (4), genetic information processing (9) and metabolism (49) affected in JS32. In addition, the relative overexpression of genes of the metabolism pathway (HAPS_RS09315, HAPS_RS09320), ribosomes (HAPS_RS07815) and ABC transporters (HAPS_RS10945) was detected, particularly the metabolism pathway, and verified with RT-qPCR. Collectively, the gene expression profile in connection with tildipirosin resistance factors revealed unique and highly resistant determinants of H. parasuis to macrolides that warrant further attention due to the significant threat of bacterial resistance.

Metabolic engineering of Saccharomyces cerevisiae for improvement in stresses tolerance

Lignocellulosic biomass is an attractive low-cost feedstock for bioethanol production. During bioethanol production, Saccharomyces cerevisiae, the common used starter, faces several environmental stresses such as aldehydes, glucose, ethanol, high temperature, acid, alkaline and osmotic pressure. The aim of this study was to construct a genetic recombinant S. cerevisiae starter with high tolerance against various environmental stresses. Trehalose-6-phosphate synthase gene (tps1) and aldehyde reductase gene (ari1) were co-overexpressed in nth1 (coded for neutral trehalase gene, trehalose degrading enzyme) deleted S. cerevisiae. The engineered strain exhibited ethanol tolerance up to 14% of ethanol, while the growth of wild strain was inhibited by 6% of ethanol. Compared with the wild strain, the engineered strain showed greater ethanol yield under high stress condition induced by combining 30% glucose, 30 mM furfural and 30 mM 5-hydroxymethylfurfural (HMF).

Involvement of small heat shock proteins, trehalose, and lipids in the thermal stress management in Schizosaccharomyces pombe

Changes in the levels of three structurally and functionally different important thermoprotectant molecules, namely small heat shock proteins (sHsps), trehalose, and lipids, have been investigated upon heat shock in Schizosaccharomyces pombe. Both α-crystallin-type sHsps (Hsp15.8 and Hsp16) were induced after prolonged high-temperature treatment but with different kinetic profiles. The shsp null mutants display a weak, but significant, heat sensitivity indicating their importance in the thermal stress management. The heat induction of sHsps is different in wild type and in highly heat-sensitive trehalose-deficient (tps1Δ) cells; however, trehalose level did not show significant alteration in shsp mutants. The altered timing of trehalose accumulation and induction of sHsps suggest that the disaccharide might provide protection at the early stage of the heat stress while elevated amount of sHsps are required at the later phase. The cellular lipid compositions of two different temperature-adapted wild-type S. pombe cells are also altered according to the rule of homeoviscous adaptation, indicating their crucial role in adapting to the environmental temperature changes. Both Hsp15.8 and Hsp16 are able to bind to different lipids isolated from S. pombe, whose interaction might provide a powerful protection against heat-induced damages of the membranes. Our data suggest that all the three investigated thermoprotectant macromolecules play a pivotal role during the thermal stress management in the fission yeast.

Responses of yeast biocontrol agents to environmental stress

Biological control of postharvest diseases, utilizing wild species and strains of antagonistic yeast species, is a research topic that has received considerable attention in the literature over the past 30 years. In principle, it represents a promising alternative to chemical fungicides for the management of postharvest decay of fruits, vegetables, and grains. A yeast-based biocontrol system is composed of a tritrophic interaction between a host (commodity), a pathogen, and a yeast species, all of which are affected by environmental factors such as temperature, pH, and UV light as well as osmotic and oxidative stresses. Additionally, during the production process, biocontrol agents encounter various severe abiotic stresses that also impact their viability. Therefore, understanding the ecological fitness of the potential yeast biocontrol agents and developing strategies to enhance their stress tolerance are essential to their efficacy and commercial application. The current review provides an overview of the responses of antagonistic yeast species to various environmental stresses, the methods that can be used to improve stress tolerance and efficacy, and the related mechanisms associated with improved stress tolerance.

Characterization of protein kinase PsSRPKL, a novel pathogenicity factor in the wheat stripe rust fungus

As in other eukaryotes, protein kinases (PKs) are generally evolutionarily conserved and play major regulatory roles in plant pathogenic fungi. Many PKs have been proven to be important for pathogenesis in model fungal plant pathogens, but little is currently known about their roles in the pathogenesis of cereal rust fungi, devastating pathogens in agriculture worldwide. Here, we report on an in planta highly induced PK gene PsSRPKL from the wheat stripe rust fungus Puccinia striiformis f. sp. tritici (Pst), one of the most important cereal rust fungi. PsSRPKL belongs to a group of PKs that are evolutionarily specific to cereal rust fungi. It shows a high level of intraspecies polymorphism in the kinase domains and directed green fluorescent protein chimers to plant nuclei. Overexpression of PsSRPKL in fission yeast induces aberrant cell morphology and a decreased resistance to environmental stresses. Most importantly, PsSRPKL is proven to be an important pathogenicity factor responsible for fungal growth and responses to environmental stresses, therefore contributing significantly to Pst virulence in wheat. We hypothesize that cereal rust fungi have developed specific PKs as pathogenicity factors for adaptation to their host species during evolution. Thus, our findings provide significant insights into pathogenicity and virulence evolution in cereal rust fungi.

Relationship of trehalose accumulation with ethanol fermentation in industrial Saccharomyces cerevisiae yeast strains

The protective effect and the mechanisms of trehalose accumulation in industrial Saccharomyces cerevisiae strains were investigated during ethanol fermentation. The engineered strains with more intercellular trehalose achieved significantly higher fermentation rates and ethanol yields than their wild strain ZS during very high gravity (VHG) fermentation, while their performances were not different during regular fermentation. The VHG fermentation performances of these strains were consistent with their growth capacity under osmotic stress and ethanol stress, the key stress factors during VHG fermentation. These results suggest that trehalose accumulation is more important for VHG fermentation of industrial yeast strains than regular one. The differences in membrane integrity and antioxidative capacity of these strains indicated the possible mechanisms of trehalose as a protectant under VHG condition. Therefore, trehalose metabolic engineering may be a useful strategy for improving the VHG fermentation performance of industrial yeast strains.

High hydrostatic pressure induces synthesis of heat-shock proteins and trehalose-6-phosphate synthase in Anastrepha ludens larvae

The Mexican fruit fly (Anastrepha ludens) is responsible for losses of up to 25% of crops such as mango and citrus fruits in Central America and México. The larval life cycle of A. ludens comprises three stages with a duration ranging from 3 to 8 days. Because of the damage caused by A. ludens, several methods of control have been studied and implemented. High hydrostatic pressures (HHP) are currently applied to foods and it is now proposed to be employed to inactivate eggs and larvae of A. ludens. Originally HHP was designed to inactivate microorganisms, since it exerts marked effects on cell morphology, and can affect enzymatic reactions and genetic mechanisms of microbial cells, with no major changes altering the sensory or nutritional quality of the foodstuff. In this study, A. ludens in two larval stages (5- and 8-day-old) were subjected to HHP treatments. The biochemical response of the larvae of A. ludens was dependent on their stage of development. The third larval stage (L3) developed a better protection mechanism based on the synthesis of stress proteins or heat-shock proteins (HSPs) and the enzyme trehalose-6-phosphate synthase, which are linked and possibly act together to achieve greater survivability to stress caused by hydrostatic pressure.

The Neurospora crassa OS MAPK pathway-activated transcription factor ASL-1 contributes to circadian rhythms in pathway responsive clock-controlled genes

The OS-pathway mitogen-activated protein kinase (MAPK) cascade of Neurospora crassa is responsible for adaptation to osmotic stress. Activation of the MAPK, OS-2, leads to the transcriptional induction of many genes involved in the osmotic stress response. We previously demonstrated that there is a circadian rhythm in the phosphorylation of OS-2 under constant non-stress inducing conditions. Additionally, several osmotic stress-induced genes are known to be regulated by the circadian clock. Therefore, we investigated if rhythms in activation of OS-2 lead to circadian rhythms in other known stress responsive targets. Here we identify three more osmotic stress induced genes as rhythmic: cat-1, gcy-1, and gcy-3. These genes encode a catalase and two predicted glycerol dehydrogenases thought to be involved in the production of glycerol. Rhythms in these genes depend upon the oscillator component FRQ. To investigate how the circadian signal is propagated to these stress induced genes, we examined the role of the OS-responsive transcription factor, ASL-1, in mediating circadian gene expression. We find that while the asl-1 transcript is induced by several stresses including an osmotic shock, asl-1 mRNA accumulation is not rhythmic. However, we show that ASL-1 is required for generating normal circadian rhythms of some OS-pathway responsive transcripts (bli-3, ccg-1, cat-1, gcy-1 and gcy-3) in the absence of an osmotic stress. These data are consistent with the possibility that post-transcriptional regulation of ASL-1 by the rhythmically activated OS-2 MAPK could play a role in generating rhythms in downstream targets.

Enzymatic control of anhydrobiosis-related accumulation of trehalose in the sleeping chironomid, Polypedilum vanderplanki

Larvae of an anhydrobiotic insect, Polypedilum vanderplanki, accumulate very large amounts of trehalose as a compatible solute on desiccation, but the molecular mechanisms underlying this accumulation are unclear. We therefore isolated the genes coding for trehalose metabolism enzymes, i.e. trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP) for the synthesis step, and trehalase (TREH) for the degradation step. Although computational prediction indicated that the alternative splicing variants (PvTpsα/β) obtained encoded probable functional motifs consisting of a typical consensus domain of TPS and a conserved sequence of TPP, PvTpsα did not exert activity as TPP, but only as TPS. Instead, a distinct gene (PvTpp) obtained expressed TPP activity. Previous reports have suggested that insect TPS is, exceptionally, a bifunctional enzyme governing both TPS and TPP. In this article, we propose that TPS and TPP activities in insects can be attributed to discrete genes. The translated product of the TREH ortholog (PvTreh) certainly degraded trehalose to glucose. Trehalose was synthesized abundantly, consistent with increased activities of TPS and TPP and suppressed TREH activity. These results show that trehalose accumulation observed during anhydrobiosis induction in desiccating larvae can be attributed to the activation of the trehalose synthetic pathway and to the depression of trehalose hydrolysis.

Expression of pigeonpea hybrid-proline-rich protein encoding gene (CcHyPRP) in yeast and Arabidopsis affords multiple abiotic stress tolerance

A hybrid-proline-rich protein encoding gene (CcHyPRP) has been isolated and characterized, for the first time, from the subtracted cDNA library of pigeonpea (Cajanus cajan L.) plants subjected to drought stress. Functionality of CcHyPRP has been validated for abiotic stress tolerance using the heterologous yeast and Arabidopsis systems. The CcHyPRP contained a repetitive proline-rich (PR) N-terminal domain and a conserved eight cysteine motif (8CM) at the C-terminus. Southern analysis disclosed single-copy nature of CcHyPRP gene in the pigeonpea genome. Northern analysis revealed higher levels of CcHyPRP transcripts in PEG, NaCl, heat (42 degrees C), cold and ABA-treated plants compared with the weak signals observed in the untreated plants, suggesting stress-responsive nature of the CcHyPRP gene. In yeast, expression of CcHyPRP imparted marked tolerance against abiotic stresses exerted by PEG, high temperature, NaCl and LiCl. Transgenic Arabidopsis lines, expressing CcHyPRP under the control of CaMV35S and rd29A promoters, when subjected to PEG, mannitol, NaCl, LiCl and heat (42 degrees C) stress, developed into healthy plants with profuse root system and increased biomass in contrast to the weak-stunted wild-type plants. The CcHyPRP-transgenics driven by stress-inducible rd29A exhibited similar stress-tolerance as that of CaMV35S-lines without any negative effects on plant morphology, implying that stress-inducible promoters are preferable for production of stress tolerant transgenics. The overall results amply demonstrate the profound effect of CcHyPRP in bestowing multiple abiotic stress tolerance at cellular and whole plant levels. Accordingly, the multipotent CcHyPRP seems promising as a prime candidate gene to fortify crop plants with abiotic stress tolerance.

Trehalose-6-phosphate synthase 1 from Metarhizium anisopliae: clone, expression and properties of the recombinant

Trehalose, an important component in fungal spores, is a disaccharide which protects against several environmental stresses, such as heat, desiccation, salt. Trehalose-6-phosphate synthase 1 (TPS1) is a subunit of trehalose synthase complex in fungi; it plays a key role in the biosynthesis of trehalose. In this study, a full-length cDNA from Metarhizium anisopliae encoding TPS1 (designated as MaTPS1) was isolated. The MaTPS1 cDNA is composed of 1836 nucleotides encoding a protein of 517 amino acids with a molecular mass of 58 kDa. The amino acid sequence has a relatively high homology with the TPS1s in several other filamentous fungi. Southern blot analysis showed that MaTPS1 gene occurs as a single copy in the M. anisopliae genome. And MaTPS1 was cloned into Pichia pastoris KM71 and secretively expressed with a histamine tag to facilitate a rapid purification of recombinant MaTPS1 (designated reTPS1). The properties of reTPS1 were examined. The K(m) value of reTPS1 for UDP-glucose and glucose-6-phosphate was 9.6 mM and 3.9 mM, respectively, and the optimal pH and temperature were about 6.5 and 40 degrees C. The enzyme was highly specific to glucose-6-phosphate for glucosyl acceptor, and its activity decreased rapidly as the concentrations of phosphate increased. The expression system will provide sufficient amounts of reTPS1 for future structural characterization of the protein and use for further investigation of MaTPS1's function.

Effect of intracellular trehalose in Cryptococcus laurentii and exogenous lyoprotectants on its viability and biocontrol efficacy on Penicillium expansum in apple fruit

AIMS

To improve viability and biocontrol efficacy of Cryptococcus laurentii after freeze drying and in subsequent storage.

METHODS AND RESULTS

Viability of C. laurentii was improved after freeze drying and in subsequent storage at 4 or 25 degrees C by using skimmed milk (SM) and sugars (glucose, galactose, sucrose and trehalose) as protectants. Sugars and SM mixed together showed better protection than when they were used separately. Citric acid used as carbon source could induce accumulation of intracellular trehalose in the yeast. The yeast cells with high trehalose level (HT cells) had higher viability than those with low trehalose level (LT cells) after freeze drying and storage for 90 days. After storage for 90 days at 4 degrees C, the HT cells plus SM and sugars as protectant showed a similar biocontrol effect against blue mould rot in apple fruit caused by Penicillium expansum as fresh cells.

CONCLUSIONS

Increasing intracellular trehalose content of C. laurentii and adding exogenous protectant (sugars + SM) could improve its viability and maintain its biocontrol efficacy.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results have a potential value for commercial application of C. laurentii.

Isoforms of trehalase and invertase of Fusarium oxysporum

Enzymatic assays and native PAGE were used to study trehalase and invertase activities, depending on culture age and different sugar conditions, in cell-free extracts, culture filtrates and ribosomal wash of Fusarium oxysporum. The activity of invertase preceded that of trehalase; in the exponential phase of growth, mainly invertase activity was produced, whereas trehalase activity was high in the stationary phase. In this last phase of growth, the activity of intracellular trehalase was repressed by monosaccharides, whereas disaccharides, especially lactose and starch, enhanced the activity of intracellular and extracellular trehalase. However, invertase activity was not repressed under these conditions and had the maximal activity in the presence of saccharose. Intracellular trehalase appeared in a single, high-molecular weight (120 kDa) form, whereas the extracellular enzyme appeared in a single, low-molecular weight (60 kDa) form. The activity pattern of invertase isoforms indicated the occurrence of three forms of intracellular enzyme with the main activity band at 120 kDa and two isoforms of extracellular enzyme. In the ribosomal wash, high-molecular weight isoforms of both trehalase and invertase were identified. A possible role of trehalase and invertase in carbohydrate metabolism of fungal pathogens is also discussed.

Trehalose accumulation in a high-trehalose-accumulating mutant of Saccharomycopsis fibuligera sdu does not respond to stress treatments

The isolation of high-trehalose-accumulating mutant A11 from Saccharomycopsis fibuligera sdu has been previously described. In this paper, accumulation of trehalose under various stress conditions in S. fibuligera A11 was investigated. Neither activation of trehalose-6-phosphate synthase (SfTps1) nor change in trehalose content was observed under stress exposure of S. fibuligera A11 cells. A fragment of the Sftps1 gene in this strain was also cloned by degenerate PCR using the CoDeHOP strategy and multiply-aligned Tps1 sequences. This sequence allowed us to investigate the expression of the Sftps1 gene, which was also kept constant under the various stress conditions. Altogether, these results indicate that trehalose metabolism in S. fibuligera A11 in response to stress conditions clearly differs from that of Saccharomyces cerevisiae and most other fungi. The expression of the Sftps1 gene was not responsive to different stress treatments.

Stress tolerance in fungi — to kill a spoilage yeast

The fungal spoilage of ingredients of food manufacture is an economic problem, often causes product loss and may constitute a health hazard. To effectively combat fungal food spoilage, a mechanistic understanding of tolerance for, and adaptation to, the preservation method used is crucial. Both are dependent on the genetic make-up and growth history of the organism. In the post-genomic era we are arriving at a situation in which, in the model organism Saccharomyces cerevisiae, physiological data, classical molecular biology and whole-genome responses can be combined to obtain explanatory and predictive models for growth. For food spoilage fungi we have not yet reached such a level of understanding, but we may use the knowledge gained for S. cerevisiae for the prevention of spoilage.

Homozygous diploid deletion strains of Saccharomyces cerevisiae that determine lag phase and dehydration tolerance

This study identifies genes that determine length of lag phase, using the model eukaryotic organism, Saccharomyces cerevisiae. We report growth of a yeast deletion series following variations in the lag phase induced by variable storage times after drying-down yeast on filters. Using a homozygous diploid deletion pool, lag times ranging from 0 h to 90 h were associated with increased drop-out of mitochondrial genes and increased survival of nuclear genes. Simple linear regression (R2 analysis) shows that there are over 500 genes for which > 70% of the variation can be explained by lag alone. In the genes with a positive correlation, such that the gene abundance increases with lag and hence the deletion strain is suitable for survival during prolonged storage, there is a strong predominance of nucleonic genes. In the genes with a negative correlation, such that the gene abundance decreases with lag and hence the strain may be critical for getting yeast out of the lag phase, there is a strong predominance of glycoproteins and transmembrane proteins. This study identifies yeast deletion strains with survival advantage on prolonged storage and amplifies our understanding of the genes critical for getting out of the lag phase.

Role of trehalose phosphate synthase and trehalose during hypoxia: from flies to mammals

Trehalose is a nonreducing disaccharide in which the two glucose units are linked in an α,α-1,1-glycosidic linkage. The best known and most widely distributed pathway of trehalose synthesis involves the transfer of glucose from UDP-glucose to glucose 6-phosphate to form trehalose-6-phosphate and UDP via the trehalose-6-phosphate synthase (TPS1). Trehalose-6-phosphate phosphatase (TPS2) then converts trehalose-6-phosphate to free trehalose. This sugar is present in a wide variety of organisms,including bacteria, yeast, fungi, insects, invertebrates and plants, and because of its particular physical features, trehalose is able to protect the integrity of cells against a variety of environmental stresses such as desiccation, dehydration, heat, cold and oxidation. Our current studies described here indicate that trehalose protects Drosophila and mammalian cells from hypoxic and anoxic injury. The mechanism of this protection is probably related to a decrease in protein denaturation through protein–trehalose interactions.

Effect of adaptation to ethanol on cytoplasmic and membrane protein profiles of Oenococcus oeni

The practical application of commercial malolactic starter cultures of Oenococcus oeni surviving direct inoculation in wine requires insight into mechanisms of ethanol toxicity and of acquired ethanol tolerance in this organism. Therefore, the site-specific location of proteins involved in ethanol adaptation, including cytoplasmic, membrane-associated, and integral membrane proteins, was investigated. Ethanol triggers alterations in protein patterns of O. oeni cells stressed with 12% ethanol for 1 h and those of cells grown in the presence of 8% ethanol. Levels of inosine-5'-monophosphate dehydrogenase and phosphogluconate dehydrogenase, which generate reduced nicotinamide nucleotides, were decreased during growth in the presence of ethanol, while glutathione reductase, which consumes NADPH, was induced, suggesting that maintenance of the redox balance plays an important role in ethanol adaptation. Phosphoenolpyruvate:mannose phosphotransferase system (PTS) components of mannose PTS, including the phosphocarrier protein HPr and EII(Man), were lacking in ethanol-adapted cells, providing strong evidence that mannose PTS is absent in ethanol-adapted cells, and this represents a metabolic advantage to O. oeni cells during malolactic fermentation. In cells grown in the presence of ethanol, a large increase in the number of membrane-associated proteins was observed. Interestingly, two of these proteins, dTDT-glucose-4,6-dehydratase and D-alanine:D-alanine ligase, are known to be involved in cell wall biosynthesis. Using a proteomic approach, we provide evidence for an active ethanol adaptation response of O. oeni at the cytoplasmic and membrane protein levels.

Yeast Adapt to Near-Freezing Temperatures by STRE/Msn2,4-Dependent Induction of Trehalose Synthesis and Certain Molecular Chaperones

Virtually nothing is known about the biochemical adaptations in eukaryotic cells that may enhance survival at low temperatures or upon freezing. Here we demonstrate an adaptive response in yeast that is activated below 10 degrees C and increases tolerance to low temperatures and freezing. This response involves a dramatic accumulation of the chemical chaperone trehalose and induction of trehalose-synthesizing enzymes (Tps1, Tps2) and certain heat shock proteins (Hsp104, Hsp42, Hsp12, Ssa4). mRNAs for these proteins increase dramatically below 10 degrees C and even at 0 degrees C. Their expression requires Msn2,4 transcription factors but also involves marked mRNA stabilization. Upon return to 30 degrees C, TPS1, TPS2, and HSP104 mRNAs, trehalose levels and tolerance to freezing fall dramatically within minutes. Mutants lacking trehalose or Msn2,4 die more rapidly at 0 degrees C and upon freezing. Thus, below 10 degrees C, yeast show an adaptive response that sustains viability at low or freezing temperatures, which are commonly encountered in natural environments and laboratory refrigerators.

A role for calcium in the regulation of neutral trehalase activity in the fission yeast Schizosaccharomyces pombe

Neutral trehalases mobilize trehalose accumulated by fungal cells as a protective and storage carbohydrate. A structural feature of these enzymes is the presence of an EF-like motif similar to that shown by many Ca2+-binding proteins. In this study we provide direct evidence for physical binding of Ca2+ to neutral trehalase (Ntp1p) of the fission yeast Schizosaccharomyces pombe, and show that aspartic residues at positions 97 and 108 in the conserved putative Ca2+-binding motif of Ntp1p appear to be responsible for this interaction. Mutations in these residues do not interfere with the ability of Ntp1p to associate in vivo with trehalose-6-phosphate synthase, but prevent activation of neutral trehalase triggered by the addition of glucose or by subjecting cells to stressing conditions. Strains expressing Ntp1p variants that are unable to bind Ca2+ partially resemble those devoid of the ntp1+ gene in terms of trehalose hyperaccumulation. Gel filtration of cell extracts from wild-type cells after EDTA treatment or from cells containing Ntp1p with mutations in aspartic acid residues within the Ca2+-binding site revealed that Ntp1p eluted mainly in an inactive conformation instead of the dimeric or trimeric active form of the enzyme. These results suggest that activation of S. pombe Ntp1p under different conditions depends upon Ca2+ binding through the Ca2+-binding motif as a prerequisite for correct enzyme oligomerization to its active form. Given the high degree of conservation of the Ca2+ accommodation site, this might be a general mechanism regulating neutral trehalase activity in other yeasts and filamentous fungi.

Ethanol and thermotolerance in the bioconversion of xylose by yeasts

The mechanisms underlying ethanol and heat tolerance are complex. Many different genes are involved, and the exact basis is not fully understood. The integrity of cytoplasmic and mitochondrial membranes is critical to maintain proton gradients for metabolic energy and nutrient uptake. Heat and ethanol stress adversely affect membrane integrity. These factors are particularly detrimental to xylose-fermenting yeasts because they require oxygen for biosynthesis of essential cell membrane and nucleic acid constituents, and they depend on respiration for the generation of ATP. Physiological responses to ethanol and heat shock have been studied most extensively in S. cerevisiae. However, comparative biochemical studies with other organisms suggest that similar mechanisms will be important in xylose-fermenting yeasts. The composition of a cell's membrane lipids shifts with temperature, ethanol concentration, and stage of cultivation. Levels of unsaturated fatty acids and ergosterol increase in response to temperature and ethanol stress. Inositol is involved in phospholipid biosynthesis, and it can increase ethanol tolerance when provided as a supplement. Membrane integrity determines the cell's ability to maintain proton gradients for nutrient uptake. Plasma membrane ATPase generates the proton gradient, and the biochemical characteristics of this enzyme contribute to ethanol tolerance. Organisms with higher ethanol tolerance have ATPase activities with low pH optima and high affinity for ATP. Likewise, organisms with ATPase activities that resist ethanol inhibition also function better at high ethanol concentrations. ATPase consumes a significant fraction of the total cellular ATP, and under stress conditions when membrane gradients are compromised the activity of ATPase is regulated. In xylose-fermenting yeasts, the carbon source used for growth affects both ATPase activity and ethanol tolerance. Cells can adapt to heat and ethanol stress by synthesizing trehalose and heat-shock proteins, which stabilize and repair denatured proteins. The capacity of cells to produce trehalose and induce HSPs correlate with their thermotolerance. Both heat and ethanol increase the frequency of petite mutations and kill cells. This might be attributable to membrane effects, but it could also arise from oxidative damage. Cytoplasmic and mitochondrial superoxide dismutases can destroy oxidative radicals and thereby maintain cell viability. Improved knowledge of the mechanisms underlying ethanol and thermotolerance in S. cerevisiae should enable the genetic engineering of these traits in xylose-fermenting yeasts.

Different roles for the stress-activated protein kinase pathway in the regulation of trehalose metabolism in Schizosaccharomyces pombe

The Wis1p-Sty1p mitogen-activated protein kinase cascade is a major signalling system in the fission yeast Schizosaccharomyces pombe for a wide range of stress responses. It is known that trehalose functions as a protective metabolite to counteract deleterious effects of environmental stresses. Herein it is reported that the expression of genes related to trehalose metabolism in S. pombe, ntp1(+) (neutral trehalase) and tps1(+) [trehalose-6-phosphate (T6P) synthase], is partially regulated by the Sty1p kinase under salt-induced osmotic stress and conditions of slight oxidative stress and is fully dependent on this kinase under severe oxidative stress. This control is carried out through transcription factors Atf1p/Pcr1p during osmotic stress and through Pap1p during exposure to low levels of oxidative stress. However, all three transcription factors are needed for gene expression under conditions of extreme oxidative stress. In addition, a role for Sty1p in the modulation of post-transcriptional activation of trehalase mediated by Pka1p/Sck1p kinases, as well as in the activity of T6P synthase under such stressful conditions has been demonstrated. These results reveal a novel dual action of the Wis1p-Sty1p pathway in the regulation of trehalose metabolism in fission yeast.

Chronic myelogenous leukemia molecular signature

To obtain comprehensive information about the genes involved in BCR/ABL-dependent leukemogenesis, samples from 15 chronic myelogenous leukemia (CML) patients and seven normal donors were analysed using a cDNA microarray assay. After subtraction of the artificial, random or cross-hybridization signals, data about 5315 genes have been effectively analysed in all samples. The assay revealed >/=4-fold difference in the average expression of 263 genes in all CML samples when compared to normal counterparts, with 148 genes being upregulated and 115 being downregulated. Differentially expressed genes include those associated with BCR/ABL-induced abnormalities in signal transduction, gene transactivation, cell cycle, apoptosis, adhesion, DNA repair, differentiation, metabolism and malignant progression. Interestingly, CML-blast crisis cells in peripheral blood differ from those from bone marrow, indicating major changes in gene expression profiles upon entering into the bloodstream. Moreover, BCR/ABL modulates expression of genes, which are involved in regulation of chromosome/chromatin/DNA dynamics during S and M cell cycle phase. Moreover, the ability of CML cells to recognize and respond to a pathogen infection may be compromised. Altogether, this work provides a large body of information regarding gene expression profiles associated with CML and also represents a source of potential targets for CML therapeutics.

Cloning and characterization of genes encoding trehalose-6-phosphate synthase (TPS1) and trehalose-6-phosphate phosphatase (TPS2) from Zygosaccharomyces rouxii

In many organisms, trehalose protects against several environmental stresses, such as heat, desiccation, and salt, probably by stabilizing protein structures and lipid membranes. Trehalose synthesis in yeast is mediated by a complex of trehalose-6-phosphate synthase (TPS1) and trehalose-6-phosphate phosphatase (TPS2). In this study, genes encoding TPS1 and TPS2 were isolated from Zygosaccharomyces rouxii (designated ZrTPS1 and ZrTPS2, respectively). They were functionally identified by their complementation of the tps1 and tps2 yeast deletion mutants, which are unable to grow on glucose medium and with heat, respectively. Full-length ZrTPS1 cDNA is composed of 1476 nucleotides encoding a protein of 492 amino acids with a molecular mass of 56 kDa. ZrTPS2 cDNA consists of 2843 nucleotides with an open reading frame of 2700 bp, which encodes a polypeptide of 900 amino acids with a molecular mass of 104 kDa. The amino acid sequence encoded by ZrTPS1 has relatively high homology with TPS1 of Saccharomyces cerevisiae and Schizosaccharomyces pombe, compared with TPS2. Western blot analysis showed that the antibody against S. cerevisiae TPS1 recognizes ZrTPS1. Under normal growth conditions, ZrTPS1 and ZrTPS2 were highly and constitutively expressed, unlike S. cerevisiae TPS1 and TPS2. Salt stress and heat stress reduced the expression of the ZrTPS1 and ZrTPS2 genes, respectively.

Heat and osmotic stress responses of probiotic Lactobacillus rhamnosus HN001 (DR20) in relation to viability after drying

The viability of lactic acid bacteria in frozen, freeze-dried, and air-dried forms is of significant commercial interest to both the dairy and food industries. In this study we observed that when prestressed with either heat (50 degrees C) or salt (0.6 M NaCl), Lactobacillus rhamnosus HN001 (also known as DR20) showed significant (P < 0.05) improvement in viability compared with the nonstressed control culture after storage at 30 degrees C in the dried form. To investigate the mechanisms underlying this stress-related viability improvement in L. rhamnosus HN001, we analyzed protein synthesis in cultures subjected to different growth stages and stress conditions, using two-dimensional gel electrophoresis and N-terminal sequencing. Several proteins were up- or down-regulated after either heat or osmotic shock treatments. Eleven proteins were positively identified, including the classical heat shock proteins GroEL and DnaK and the glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, enolase, phosphoglycerate kinase, and triose phosphate isomerase, as well as tagatose 1,6-diphosphate aldolase of the tagatose pathway. The phosphocarrier protein HPr (histidine-containing proteins) was up-regulated in cultures after the log phase irrespective of the stress treatments used. The relative synthesis of an ABC transport-related protein was also up-regulated after shock treatments. Carbohydrate analysis of cytoplasmic contents showed higher levels (20 +/- 3 microg/mg of protein) in cell extracts (CFEs) derived from osmotically stressed cells than in the unstressed control (15 +/- 3 microg/mg of protein). Liquid chromatography of these crude carbohydrate extracts showed significantly different profiles. Electrospray mass spectrometry analysis of CFEs revealed, in addition to normal mono-, di-, tri-, and tetrasaccharides, the presence of saccharides modified with glycerol.

Physiological diversity and trehalose accumulation in Schizosaccharomyces pombe strains isolated from spontaneous fermentations during the production of the artisanal Brazilian cachaça

Twenty-seven Schizosaccharomyces pombe isolates from seven cachaça distilleries were tested for maximum temperature of growth and fermentation, osmotolerance, ethanol resistance, invertase production, and trehalose accumulation. Two isolates were selected for studies of trehalose accumulation under heat shock and ethanol stress. The S. pombe isolates were also characterized by RAPD-PCR. The isolates were able to grow and ferment at 41 degrees C, resisted concentrations of 10% ethanol, and grew on 50% glucose medium. Four isolates yielded invertase activity of more than 100 micromol of reducing sugar x mg(-1) x min(-1). The S. pombe isolates were able to accumulate trehalose during stationary phase. Two isolates, strains UFMG-A533 and UFMG-A1000, submitted to a 15 min heat shock, were able to accumulate high trehalose levels. Strain UFMG-A533 had a marked reduction in viability during heat shock, but strain UFMG-A1000 preserved a viability rate of almost 20% after 15 min at 48 degrees C. No clear correlation was observed between trehalose accumulation and cell survival during ethanol stress. Strain UFMG-A1000 had higher trehalose accumulation levels than strain UFMG-A533 under conditions of combined heat treatment and ethanol stress. Molecular analysis showed that some strains are maintained during the whole cachaça production period; using the RAPD-PCR profiles, it was possible to group the isolates according to their isolation sites.

Role of trehalose phosphate synthase in anoxia tolerance and development in Drosophila melanogaster

Recent studies have shown that trehalose plays a protective role in yeast in a variety of stresses, including heat, freezing and thawing, dehydration, hyperosmotic shock, and oxidant injury. Because (a) heat shock and anoxia share mechanisms that allow organisms to survive, (b) Drosophila melanogaster is tolerant to anoxia, and (c) trehalose is present in flies and is metabolically active, we asked whether trehalose can protect against anoxic stress. Here we report on a new role of trehalose in anoxia resistance in Drosophila. We first cloned the gene trehalose-6-phosphate synthase (tps1), which synthesizes trehalose, and examined the effect of tps1 overexpression as well as mutation on the resistance of Drosophila to anoxia. Upon induction of tps1, trehalose increased, and this was associated with increased tolerance to anoxia. Furthermore, in vitro experiments showed that trehalose reduced protein aggregation caused by anoxia. Homozygous tps1 mutant (P-element insertion into the third intron of the gene) leads to lethality at an early larval stage, and excision of the P-element rescues totally the phenotype. We conclude that trehalose contributes to anoxia tolerance in flies; this protection is likely to be due to a reduction of protein aggregation.