The role of trehalose and its transporter in protection against reactive oxygen species

Intracellular Protective Functions and Therapeutical Potential of Trehalose

Trehalose is a naturally occurring, non-reducing saccharide widely distributed in nature. Over the years, research on trehalose has revealed that this initially thought simple storage molecule is a multifunctional and multitasking compound protecting cells against various stress factors. This review presents data on the role of trehalose in maintaining cellular homeostasis under stress conditions and in the virulence of bacteria and fungi. Numerous studies have demonstrated that trehalose acts in the cell as an osmoprotectant, chemical chaperone, free radical scavenger, carbon source, virulence factor, and metabolic regulator. The increasingly researched medical and therapeutic applications of trehalose are also discussed.

Combined transcriptomics and metabolomics analysis reveals the molecular mechanism of heat tolerance of Le023M, a mutant in Lentinulaedodes

Lentinula edodes, one of the most highly regarded edible mushrooms in China, is susceptible to damage from high temperatures. However, a mutant strain derived from L. edodes, known as Le023M, has shown exceptional thermotolerance. Compared to the original strain Le023, Le023M exhibited accelerated mycelial recovery following heat stress. Through RNA-seq analysis, the majority of differentially expressed genes (DEGs) were found to be associated with functions such as "protein refolding", "protein unfolding", "protein folding", and "response to heat", all of which are closely linked to heat shock proteins. Furthermore, qRT-PCR results revealed significant accumulation of heat shock-related genes in Le023M under heat stress. GC-MS analysis indicated elevated levels of trehalose, aspartate, and glutamate in Le023M when subjected to heat stress. The highly expressed genes involved in these metabolic pathways were predominantly found in Le023M. Collectively, these findings highlight the following: (i) the crucial role of heat shock proteins (HSPs) in the thermo-resistant mechanisms of Le023M; (ii) the potential of trehalose accumulation in Le023M to enhance mycelium resistance to heat stress; and (iii) the induction of aspartate and glutamate accumulation in response to heat stress. These results shed light on the molecular mechanisms underlying the thermotolerance of Le023M, providing valuable insights for further understanding and improving heat stress response in L. edodes. The findings also highlight the potential applications of Le023M in the cultivation and production of L. edodes under high-temperature conditions.

A secondary function of trehalose-6-phosphate synthase is required for resistance to oxidative and desiccation stress in Fusarium verticillioides

The disaccharide trehalose has long been recognized for its role as a stress solute, but in recent years some of the protective effects previously ascribed to trehalose have been suggested to arise from a function of the trehalose biosynthesis enzyme trehalose-6-phosphate (T6P) synthase that is distinct from its catalytic activity. In this study, we use the maize pathogenic fungus Fusarium verticillioides as a model to explore the relative contributions of trehalose itself and a putative secondary function of T6P synthase in protection against stress as well as to understand why, as shown in a previous study, deletion of the TPS1 gene coding for T6P synthase reduces pathogenicity against maize. We report that a TPS1-deletion mutant of F. verticillioides is compromised in its ability to withstand exposure to oxidative stress meant to simulate the oxidative burst phase of maize defense and experiences more ROS-induced lipid damage than the wild-type strain. Eliminating T6P synthase expression also reduces resistance to desiccation, but not resistance to phenolic acids. Expression of catalytically-inactive T6P synthase in the TPS1-deletion mutant leads to a partial rescue of the oxidative and desiccation stress-sensitive phenotypes, suggesting the importance of a T6P synthase function that is independent of its role in trehalose synthesis.

Potential Properties of Natural Nutraceuticals and Antioxidants in Age-Related Eye Disorders

Eye health is crucial, and the onset of diseases can reduce vision and affect the quality of life of patients. The main causes of progressive and irreversible vision loss include various pathologies, such as cataracts, ocular atrophy, corneal opacity, age-related macular degeneration, uncorrected refractive error, posterior capsular opacification, uveitis, glaucoma, diabetic retinopathy, retinal detachment, undetermined disease and other disorders involving oxidative stress and inflammation. The eyes are constantly exposed to the external environment and, for this reason, must be protected from damage from the outside. Many drugs, including cortisonics and antinflammatory drugs have widely been used to counteract eye disorders. However, recent advances have been obtained via supplementation with natural antioxidants and nutraceuticals for patients. In particular, evidence has accumulated that polyphenols (mostly deriving from Citrus Bergamia) represent a reliable source of antioxidants able to counteract oxidative stress accompanying early stages of eye diseases. Luteolin in particular has been found to protect photoreceptors, thereby improving vision in many disease states. Moreover, a consistent anti-inflammatory response was found to occur when curcumin is used alone or in combination with other nutraceuticals. Additionally, Coenzyme Q10 has been demonstrated to produce a consistent effect in reducing ocular pressure, thereby leading to protection in patients undergoing glaucoma. Finally, both grape seed extract, rich in anthocyanosides, and polynsatured fatty acids seem to contribute to the prevention of retinal disorders. Thus, a combination of nutraceuticals and antioxidants may represent the right solution for a multi-action activity in eye protection, in association with current drug therapies, and this will be of potential interest in early stages of eye disorders.

Boar semen cryopreserved with trehalose-containing liposomes: disaccharide determination and rheological behaviour

This study aimed to detect intracellular trehalose in boar sperm that were cryopreserved with liposomes and conduct an analysis of its effects on some characteristics of thawed sperm, including rheological properties. First, soybean lecithin cholesterol-based liposomes were produced and characterized in the presence of 300 mM trehalose. Next, semen samples were frozen in two freezing media: a control medium with 300 mM trehalose and an experimental medium supplemented with 300 mM trehalose and 10% liposomes, both of which were thawed and then studied to ascertain their integrity, motility, rheological response, and trehalose quantities by testing two methods of spermatic lysis via high-performance liquid chromatography with an evaporative light-scattering detector (HPLC-ELSD). The results found spherical liposomes measuring 357 nm that were relatively stable in an aqueous medium and had an entrapment efficiency of 73%. An analysis of the cryopreserved ejaculates showed that their viability and motility did not significantly differ between groups (P > 0.05). The viscous response of the samples was influenced by the extracellular medium rather than by the freezing–thawing process, which resulted in a loss of interaction between the cells and cryoprotectants. Finally, intracellular trehalose levels were determined using HPLC-ELSD, with no differences observed (P > 0.05) when comparing both sperm lysis methods. The use of liposomes with trehalose appears to be a promising option for boar semen cryopreservation, with a marked effect on rheological properties. The proposed HPLC-ELSD method was effective for measuring trehalose in cryopreserved cell samples.

Kveik Brewing Yeasts Demonstrate Wide Flexibility in Beer Fermentation Temperature Tolerance and Exhibit Enhanced Trehalose Accumulation

Traditional Norwegian Farmhouse ale yeasts, also known as kveik, have captured the attention of the brewing community in recent years. Kveik were recently reported as fast fermenting thermo- and ethanol tolerant yeasts with the capacity to produce a variety of interesting flavor metabolites. They are a genetically distinct group of domesticated beer yeasts of admixed origin with one parent from the “Beer 1” clade and the other unknown. While kveik are known to ferment wort efficiently at warmer temperatures, their range of fermentation temperatures and corresponding fermentation efficiencies, remain uncharacterized. In addition, the characteristics responsible for their increased thermotolerance remain largely unknown. Here we demonstrate variation in kveik strains at a wide range of fermentation temperatures and show not all kveik strains are equal in fermentation performance and stress tolerance. Furthermore, we uncovered an increased capacity of kveik strains to accumulate intracellular trehalose, which likely contributes to their increased thermo- and ethanol tolerances. Taken together our results present a clearer picture of the future opportunities presented by Norwegian kveik yeasts and offer further insight into their applications in brewing.

Genomic Characterization of Potential Plant Growth-Promoting Features of Sphingomonas Strains Isolated from the International Space Station

In an ongoing microbial tracking investigation of the International Space Station (ISS), several Sphingomonas strains were isolated. Based on the 16S rRNA gene sequence, phylogenetic analysis identified the ISS strains as Sphingomonas sanguinis (n = 2) and one strain isolated from the Kennedy Space Center cleanroom (used to assemble various Mars mission spacecraft components) as Sphingomonas paucimobilis. Metagenomic sequence analyses of different ISS locations identified 23 Sphingomonas species. An abundance of shotgun metagenomic reads were detected for S. sanguinis in the location from where the ISS strains were isolated. A complete metagenome-assembled genome was generated from the shotgun reads metagenome, and its comparison with the whole-genome sequences (WGS) of the ISS S. sanguinis isolates revealed that they were highly similar. In addition to the phylogeny, the WGS of these Sphingomonas strains were compared with the WGS of the type strains to elucidate genes that can potentially aid in plant growth promotion. Furthermore, the WGS comparison of these strains with the well-characterized Sphingomonas sp. LK11, an arid desert strain, identified several genes responsible for the production of phytohormones and for stress tolerance. Production of one of the phytohormones, indole-3-acetic acid, was further confirmed in the ISS strains using liquid chromatography-mass spectrometry. Pathways associated with phosphate uptake, metabolism, and solubilization in soil were conserved across all the S. sanguinis and S. paucimobilis strains tested. Furthermore, genes thought to promote plant resistance to abiotic stress, including heat/cold shock response, heavy metal resistance, and oxidative and osmotic stress resistance, appear to be present in these space-related S. sanguinis and S. paucimobilis strains. Characterizing these biotechnologically important microorganisms found on the ISS and harnessing their key features will aid in the development of self-sustainable long-term space missions in the future. IMPORTANCESphingomonas is ubiquitous in nature, including the anthropogenically contaminated extreme environments. Members of the Sphingomonas genus have been identified as potential candidates for space biomining beyond earth. This study describes the isolation and identification of Sphingomonas members from the ISS, which are capable of producing the phytohormone indole-3-acetic acid. Microbial production of phytohormones will help future in situ studies, grow plants beyond low earth orbit, and establish self-sustainable life support systems. Beyond phytohormone production, stable genomic elements of abiotic stress resistance, heavy metal resistance, and oxidative and osmotic stress resistance were identified, rendering the ISS Sphingomonas isolate a strong candidate for biotechnology-related applications.

The integration of leaf-derived signals sets the timing of vegetative phase change in maize, a process coordinated by epigenetic remodeling

After germination, the maize shoot proceeds through a series of developmental stages before flowering. The first transition occurs during the vegetative phase where the shoot matures from the juvenile to the adult phase, called vegetative phase change (VPC). In maize, both phases exhibit easily-scored morphological characteristics, facilitating the elucidation of molecular mechanisms directing the characteristic gene expression patterns and resulting physiological features of each phase. miR156 expression is high during the juvenile phase, suppressing expression of squamosa promoter binding proteins/SBP-like transcription factors and miR172. The decline in miR156 and subsequent increase in miR172 expression marks the transition into the adult phase, where miR172 represses transcripts that confer juvenile traits. Leaf-derived signals attenuate miR156 expression and thus the duration of the juvenile phase. As found in other species, VPC in maize utilizes signals that consist of hormones, stress, and sugar to direct epigenetic modifiers. In this review we identify the intersection of leaf-derived signaling with components that contribute to the epigenetic changes which may, in turn, manage the distinct global gene expression patterns of each phase. In maize, published research regarding chromatin remodeling during VPC is minimal. Therefore, we identified epigenetic regulators in the maize genome and, using published gene expression data and research from other plant species, identify VPC candidates.

Preservation of non-Saccharomyces yeasts: Current technologies and challenges

There is a recent and growing interest in the study and application of non-Saccharomyces yeasts, mainly in fermented foods. Numerous publications and patents show the importance of these yeasts. However, a fundamental issue in studying and applying them is to ensure an appropriate preservation scheme that allows to the non-Saccharomyces yeasts conserve their characteristics and fermentative capabilities by long periods of time. The main objective of this review is to present and analyze the techniques available to preserve these yeasts (by conventional and non-conventional methods), in small or large quantities for laboratory or industrial applications, respectively. Wine fermentation is one of the few industrial applications of non-Saccharomyces yeasts, but the preservation stage has been a major obstacle to achieve a wider application of these yeasts. This review considers the preservation techniques, and clearly defines parameters such as culturability, viability, vitality and robustness. Several conservation strategies published in research articles as well as patents are analyzed, and the advantages and disadvantages of each technique used are discussed. Another important issue during conservation processes is the stress to which yeasts are subjected at the time of preservation (mainly oxidative stress). There is little published information on the subject for non-Saccharomyces yeast, but it is a fundamental point to consider when designing a preservation strategy.

From baker's yeast to genetically modified budding yeasts: the scientific evolution of bioethanol industry from sugarcane

The peculiarities of Brazilian fuel ethanol fermentation allow the entry of native yeasts that may dominate over the starter strains of Saccharomyces cerevisiae and persist throughout the sugarcane harvest. The switch from the use of baker's yeast as starter to selected budding yeasts obtained by a selective pressure strategy was followed by a wealth of genomic information that enabled the understanding of the superiority of selected yeast strains. This review describes how the process of yeast selection evolved in the sugarcane-based bioethanol industry, the selection criteria and recent advances in genomics that could advance the fermentation process. The prospective use of genetically modified yeast strains, specially designed for increased robustness and product yield, with special emphasis on those obtained by the CRISPR (clustered regularly interspaced palindromic repeats)-Cas9 (CRISPR-associated protein 9) genome-editing approach, is discussed as a possible solution to confer higher performance and stability to the fermentation process for fuel ethanol production.

Deinococcus terrestris sp. nov., a gamma ray- and ultraviolet-resistant bacterium isolated from soil

Strain SDU3-2^T was isolated from a soil sample collected in Shandong Province, PR China. Cells of SDU3-2^T were spherical, Gram-stain-positive, aerobic and non-motile. Cellular growth of the strain occurred at 25-45 °C, pH 5.5-8.5 and with 0-1.5 % (w/v) of NaCl. Phylogenetic analysis based on the 16S rRNA gene sequences showed that strain SDU3-2^T was closest to the type strain Deinococcus murrayi ALT-1b^T with a similarity of 95.2 %. The draft genome was 3.49 Mbp long with 69.2 mol% G+C content. Strain SDU3-2^T exhibited high resistance to gamma radiation (D₁₀ >12 kGy) and UV (D₁₀ >900 J m^-2). The strain encoded many genes for resistance to radiation and oxidative stress, which were highly conserved with other Deinococcus species, but possessed interspecific properties. The major fatty acids of SDU3-2^T cells were C_15 : 1  ω6c, C_16 : 1  ω7c/C_16 : 1  ω6c, and C_17 : 1  ω8c, the major menaquinone was menaquinone-8, and the major polar lipids were an unidentified phosphoglycolipid, four unidentified glycolipids and an unidentified phospholipid. The average nucleotide identity and DNA-DNA hybridization results further indicated that strain SDU3-2^T represents a new species in the genus Deinococcus, for which the name Deinococcus terrestris sp. nov. is proposed. The type strain is SDU3-2^T (=CGMCC 1.17147^T=KCTC 43098^T).

Yeast Viral Killer Toxin K1 Induces Specific Host Cell Adaptions via Intrinsic Selection Pressure

The killer phenomenon in yeast (Saccharomyces cerevisiae) not only provides the opportunity to study host-virus interactions in a eukaryotic model but also represents a powerful tool to analyze potential coadaptional events and the role of killer yeast in biological diversity. Although undoubtedly having a crucial impact on the abundance and expression of the killer phenotype in killer-yeast harboring communities, the influence of a particular toxin on its producing host cell has not been addressed sufficiently. In this study, we describe a model system of two K1 killer yeast strains with distinct phenotypical differences pointing to substantial selection pressure in response to the toxin secretion level. Transcriptome and lipidome analyses revealed specific and intrinsic host cell adaptions dependent on the amount of K1 toxin produced. High basal expression of genes coding for osmoprotectants and stress-responsive proteins in a killer yeast strain secreting larger amounts of active K1 toxin implies a generally increased stress tolerance. Moreover, the data suggest that immunity of the host cell against its own toxin is essential for the balanced virus-host interplay providing valuable hints to elucidate the molecular mechanisms underlying K1 immunity and implicating an evolutionarily conserved role for toxin immunity in natural yeast populations.IMPORTANCE The killer phenotype in Saccharomyces cerevisiae relies on the cytoplasmic persistence of two RNA viruses. In contrast to bacterial toxin producers, killer yeasts necessitate a specific immunity mechanism against their own toxin because they bear the same receptor populations as sensitive cells. Although the killer phenomenon is highly abundant and has a crucial impact on the structure of yeast communities, the influence of a particular toxin on its host cell has been barely addressed. In our study, we used two derivatives secreting different amount of the killer toxin K1 to analyze potential coadaptional events in this particular host/virus system. Our data underline the dependency of the host cell's ability to cope with extracellular toxin molecules and intracellular K1 molecules provided by the virus. Therefore, this research significantly advances the current understanding of the evolutionarily conserved role of this molecular machinery as an intrinsic selection pressure in yeast populations.

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.

The diversity and commonalities of the radiation-resistance mechanisms of Deinococcus and its up-to-date applications

Deinococcus is an extremophilic microorganism found in a wide range of habitats, including hot springs, radiation-contaminated areas, Antarctic soils, deserts, etc., and shows some of the highest levels of resistance to ionizing radiation known in nature. The highly efficient radiation-protection mechanisms of Deinococcus depend on a combination of passive and active defense mechanisms, including self-repair of DNA damage (homologous recombination, MMR, ER and ESDSA), efficient cellular damage clearance mechanisms (hydrolysis of damaged proteins, overexpression of repair proteins, etc.), and effective clearance of reactive oxygen species (ROS). Due to these mechanisms, Deinococcus cells are highly resistant to oxidation, radiation and desiccation, which makes them potential chassis cells for wide applications in many fields. This article summarizes the latest research on the radiation-resistance mechanisms of Deinococcus and prospects its biotechnological application potentials.

Ssd1 and the cell wall integrity pathway promote entry, maintenance, and recovery from quiescence in budding yeast

Wild Saccharomyces cerevisiae strains are typically diploid. When faced with glucose and nitrogen limitation they can undergo meiosis and sporulate. Diploids can also enter a protective, nondividing cellular state or quiescence. The ability to enter quiescence is highly reproducible but shows broad natural variation. Some wild diploids can only enter cellular quiescence, which indicates that there are conditions in which sporulation is lost or selected against. Others only sporulate, but if sporulation is disabled by heterozygosity at the IME1 locus, those diploids can enter quiescence. W303 haploids can enter quiescence, but their diploid counterparts cannot. This is the result of diploidy, not mating type regulation. Introduction of SSD1 to W303 diploids switches fate, in that it rescues cellular quiescence and disrupts the ability to sporulate. Ssd1 and another RNA-binding protein, Mpt5 (Puf5), have parallel roles in quiescence in haploids. The ability of these mutants to enter quiescence, and their long-term survival in the quiescent state, can be rescued by exogenously added trehalose. The cell wall integrity pathway also promotes entry, maintenance, and recovery from quiescence through the Rlm1 transcription factor.

The trehalose protective mechanism during thermal stress in Saccharomyces cerevisiae: the roles of Ath1 and Agt1

Trehalose on both sides of the bilayer is a requirement for full protection of membranes against stress. It was not known yet how trehalose, synthesized in the cytosol when dividing Saccharomyces cerevisiae cells are shifted from 28°C to 40°C, is transported to the outside and degraded when cells return to 28°C. According to our results, the lack of Agt1, a trehalose transporter, although had not affected trehalose synthesis, reduced cell tolerance to 51°C and increased lipid peroxidation. The damage was reversed when external trehalose was added during 40°C adaptation, confirming that the reason for the agt1Δ sensitivity is the absence of trehalose at the outside of the lipid bilayer. The 40-28°C condition caused cytosolic trehalase (Nth1) activation, reducing intracellular trehalose and, consequently, the survival rates after 51°C. Although lower than nth1Δ strain, cells deficient in acid trehalase (ath1Δ)  maintained increased trehalose levels after 40°C-28°C shift, which conferred protection against 51°C. Both Ath1 and Agt1 were found into vesicles near to plasma membrane in response to stress. This suggests that Agt1 containing vesicles would fuse with the membrane under 40°C to transport part of the cytosolic trehalose to the outside. By a similar mechanism, Ath1 would reach the cell surface to hydrolyze the external trehalose but only when the stress would be over. Corroborating this conclusion, Ath1 activity in soluble cell-free extracts increased after 40°C adaptation but decreased when cells returned to 28°C. During 40°C, Ath1 is confined into vesicles, avoiding the cleavage of the outside trehalose.

Transcriptome Kinetics of Saccharomyces cerevisiae in Response to Viral Killer Toxin K1

The K1 A/B toxin secreted by virus-infected Saccharomyces cerevisiae strains kills sensitive cells via disturbance of cytoplasmic membrane functions. Despite decades of research, the mechanisms underlying K1 toxicity and immunity have not been elucidated yet. In a novel approach, this study aimed to characterize transcriptome changes in K1-treated sensitive yeast cells in a time-dependent manner. Global transcriptional profiling revealed substantial cellular adaptations in target cells resulting in 1,189 differentially expressed genes in total. Killer toxin K1 induced oxidative, cell wall and hyperosmotic stress responses as well as rapid down-regulation of transcription and translation. Essential pathways regulating energy metabolism were also significantly affected by the toxin. Remarkably, a futile cycle of the osmolytes trehalose and glycogen was identified probably representing a critical feature of K1 intoxication. In silico analysis suggested several transcription factors involved in toxin-triggered signal transduction. The identified transcriptome changes provide valuable hints to illuminate the still unknown molecular events leading to K1 toxicity and immunity implicating an evolutionarily conserved response at least initially counteracting ionophoric toxin action.

Constancy of the bioactivities of propolis samples collected on the same apiary over four years

Natural products, like propolis, have been subject of interest by several industries mainly due to their biological activities. However, besides being produced in low amounts propolis has a great variability in terms of chemical composition and bioactivities' profiles, constituting a problem for the development of propolis-based products and for its acceptance by the medical community. The aim of this work relates to the study of the bioactivities, in particular the antioxidant and the antimicrobial properties, as well as the chemical characterization of Portuguese propolis samples collected in an apiary sited at Gerês (G) along four consecutive years. Ethanol extracts of the four propolis samples (G.EEs) display antimicrobial activity, especially against Gram-positive spore forming bacteria. Antioxidant activity, evaluated by three different in vitro assays, was confirmed in vivo by flow cytometry using Saccharomyces cerevisiae as eukaryotic cell model. Cells incubated with G.EEs prior to H₂O₂ incubation, or incubated with G.EEs and H₂O₂ simultaneously, display higher viability than cells incubated only with H₂O₂, suggesting that G.EEs protect yeast cells against induced oxidative stress. All tested propolis samples exhibit very similar antimicrobial and antioxidant activities. Chemical analysis of G.EEs revealed no significant differences in terms of phenolic profiles, namely in the compounds to which propolis bioactivities are ascribed, thus supporting the more constant behavior evidenced by these propolis samples. This work highlights the valuable properties of this bee product and reveals a constancy of bioactivities in a Portuguese propolis sample over four years, raising awareness to the potentialities of this natural product often regarded as a beekeeping waste.

Evolution and expression patterns of the trehalose-6-phosphate synthase gene family in drumstick tree (Moringa oleifera Lam.)

Moringa oleifera TPSs were genome-wide identified for the first time, and a phylogenetic analysis was performed to investigate evolutionary divergence. The qRT-PCR data show that MoTPS genes response to different stress treatments. The trehalose-6-phosphate synthase (TPS) family is involved in a wide range of stress-resistance processes in plants. Its direct product, trehalose-6-phosphate, acts as a specific signal of sucrose status and a regulator to modulate carbon metabolism within the plant. In this study, eight TPS genes were identified and cloned based on the M. oleifera genome; only MoTPS1 exhibited TPS activity among Group I proteins. The characteristics of the MoTPS gene family were determined by analyzing phylogenetic relationships, gene structures, conserved motifs, selective forces, and expression patterns. The Group II MoTPS genes were under relaxed purifying selection or positive selection. The glycosyltransferase family 20 domains generally had lower Ka/Ks ratios and nonsynonymous (Ka) changes compared with those of trehalose-phosphatase domains, which is consistent with stronger purifying selection due to functional constraints in performing TPS enzyme activity. Phylogenetic analyses of TPS proteins from M. oleifera and 17 other plant species indicated that TPS were present before the monocot-dicot split, whereas Group II TPSs were duplicated after the separation of dicots and monocots. Quantitative real-time PCR analysis showed that the expression patterns of TPSs displayed group specificities in M. oleifera. Particularly, Group I MoTPS genes closely relate to reproductive development and Group II MoTPS genes closely relate to high temperature resistance in leaves, stem, stem tip and roots. This work provides a scientific classification of plant TPSs, dissects the internal relationships between their evolution and expressions, and promotes functional researches.

Trehalose Contributes to Gamma-Linolenic Acid Accumulation in Cunninghamella echinulata Based on de Novo Transcriptomic and Lipidomic Analyses

Gamma-linolenic acid (GLA) is essential for the well-being of humans and other animals. People may lack GLA because of aging or diseases, and thus, dietary supplements or medical reagents containing GLA-enriched lipids are in demand. Cunninghamella echinulata is a potential GLA-producing strain. Interestingly, we found that the GLA content of C. echinulata FR3 was up to 21% (proportion of total lipids) when trehalose was used as a carbon source, significantly higher than the 13% found when glucose was used. Trehalose is quite common and can be accumulated in microorganisms under stress conditions. However, little information is available regarding the role of trehalose in GLA synthesis and accumulation. Our study aimed to understand how the metabolism of C. echinulata responds to trehalose as a carbon source for GLA and lipid biosynthesis. We profiled the major sugars, fatty acids, phospholipids, and gene transcripts of C. echinulata FR3 grown in trehalose medium with glucose as a control by de novo transcriptomics, lipidomics, and other methods. The results showed that trehalose could influence the expression of desaturases and that the GLA proportion increased because of delta-6 desaturase upregulation. The increased GLA was transferred to the extracellular environment through the active PI ion channel, which prefers polyunsaturated acyl chains. At the same time, trehalose might prevent GLA from peroxidation by forming a trehalose-polyunsaturated fatty acid (PUFA) complex. Our study provides new insights into the functions of trehalose in GLA accumulation.

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.

The Antioxidant System in the Anhydrobiotic Midge as an Essential, Adaptive Mechanism for Desiccation Survival

One of the major damaging factors for living organisms experiencing water insufficiency is oxidative stress. Loss of water causes a dramatic increase in the production of reactive oxygen species (ROS). Thus, the ability for some organisms to survive almost complete desiccation (called anhydrobiosis) is tightly related to the ability to overcome extraordinary oxidative stress. The most complex anhydrobiotic organism known is the larva of the chironomid Polypedilum vanderplanki. Its antioxidant system shows remarkable features, such as an expansion of antioxidant genes, their overexpression, as well as the absence or low expression of enzymes required for the synthesis of ascorbate and glutathione and their antioxidant function. In this chapter, we summarize existing data about the antioxidant system of this insect, which is able to cope with substantial oxidative damage, even in an intracellular environment that is severely disturbed due to water loss.

Tailoring Trehalose for Biomedical and Biotechnological Applications

Trehalose is a non-reducing sugar whose ability to stabilize biomolecules has brought about its widespread use in biological preservation applications. Trehalose is also an essential metabolite in a number of pathogens, most significantly the global pathogen Mycobacterium tuberculosis, though it is absent in humans and other mammals. Recently, there has been a surge of interest in modifying the structure of trehalose to generate analogues that have applications in biomedical research and biotechnology. Non-degradable trehalose analogues could have a number of advantages as bioprotectants and food additives. Trehalose-based imaging probes and inhibitors are already useful as research tools and may have future value in the diagnosis and treatment of tuberculosis, among other uses. Underlying the advancements made in these areas are novel synthetic methods that facilitate access to and evaluation of trehalose analogues. In this review, we focus on both aspects of the development of this class of molecules. First, we consider the chemical and chemoenzymatic methods that have been used to prepare trehalose analogues and discuss their prospects for synthesis on commercially relevant scales. Second, we describe ongoing efforts to develop and deploy detectable trehalose analogues, trehalose-based inhibitors, and non-digestible trehalose analogues. The current and potential future uses of these compounds are discussed, with an emphasis on their roles in understanding and combatting mycobacterial infection.

Comparative genomics of the tardigrades Hypsibius dujardini and Ramazzottius varieornatus

Tardigrada, a phylum of meiofaunal organisms, have been at the center of discussions of the evolution of Metazoa, the biology of survival in extreme environments, and the role of horizontal gene transfer in animal evolution. Tardigrada are placed as sisters to Arthropoda and Onychophora (velvet worms) in the superphylum Panarthropoda by morphological analyses, but many molecular phylogenies fail to recover this relationship. This tension between molecular and morphological understanding may be very revealing of the mode and patterns of evolution of major groups. Limnoterrestrial tardigrades display extreme cryptobiotic abilities, including anhydrobiosis and cryobiosis, as do bdelloid rotifers, nematodes, and other animals of the water film. These extremophile behaviors challenge understanding of normal, aqueous physiology: how does a multicellular organism avoid lethal cellular collapse in the absence of liquid water? Meiofaunal species have been reported to have elevated levels of horizontal gene transfer (HGT) events, but how important this is in evolution, and particularly in the evolution of extremophile physiology, is unclear. To address these questions, we resequenced and reassembled the genome of H. dujardini, a limnoterrestrial tardigrade that can undergo anhydrobiosis only after extensive pre-exposure to drying conditions, and compared it to the genome of R. varieornatus, a related species with tolerance to rapid desiccation. The 2 species had contrasting gene expression responses to anhydrobiosis, with major transcriptional change in H. dujardini but limited regulation in R. varieornatus. We identified few horizontally transferred genes, but some of these were shown to be involved in entry into anhydrobiosis. Whole-genome molecular phylogenies supported a Tardigrada+Nematoda relationship over Tardigrada+Arthropoda, but rare genomic changes tended to support Tardigrada+Arthropoda.

Central Role of the Trehalose Biosynthesis Pathway in the Pathogenesis of Human Fungal Infections: Opportunities and Challenges for Therapeutic Development

Invasive fungal infections cause significant morbidity and mortality in part due to a limited antifungal drug arsenal. One therapeutic challenge faced by clinicians is the significant host toxicity associated with antifungal drugs. Another challenge is the fungistatic mechanism of action of some drugs. Consequently, the identification of fungus-specific drug targets essential for fitness in vivo remains a significant goal of medical mycology research. The trehalose biosynthetic pathway is found in a wide variety of organisms, including human-pathogenic fungi, but not in humans. Genes encoding proteins involved in trehalose biosynthesis are mechanistically linked to the metabolism, cell wall homeostasis, stress responses, and virulence of Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus. While there are a number of pathways for trehalose production across the tree of life, the TPS/TPP (trehalose-6-phosphate synthase/trehalose-6-phosphate phosphatase) pathway is the canonical pathway found in human-pathogenic fungi. Importantly, data suggest that proteins involved in trehalose biosynthesis play other critical roles in fungal metabolism and in vivo fitness that remain to be fully elucidated. By further defining the biology and functions of trehalose and its biosynthetic pathway components in pathogenic fungi, an opportunity exists to leverage this pathway as a potent antifungal drug target. The goal of this review is to cover the known roles of this important molecule and its associated biosynthesis-encoding genes in the human-pathogenic fungi studied to date and to employ these data to critically assess the opportunities and challenges facing development of this pathway as a therapeutic target.

Trehalose-6-Phosphate as a Potential Lead Candidate for the Development of Tps1 Inhibitors: Insights from the Trehalose Biosynthesis Pathway in Diverse Yeast Species

In some pathogens, trehalose biosynthesis is induced in response to stress as a protection mechanism. This pathway is an attractive target for antimicrobials as neither the enzymes, Tps1, and Tps2, nor is trehalose present in humans. Accumulation of T6P in Candida albicans, achieved by deletion of TPS2, resulted in strong reduction of fungal virulence. In this work, the effect of T6P on Tps1 activity was evaluated. Saccharomyces cerevisiae, C. albicans, and Candida tropicalis were used as experimental models. As expected, a heat stress induced both trehalose accumulation and increased Tps1 activity. However, the addition of 125 μM T6P to extracts obtained from stressed cells totally abolished or reduced in 50 and 60 % the induction of Tps1 activity in S. cerevisiae, C. tropicalis, and C. albicans, respectively. According to our results, T6P is an uncompetitive inhibitor of S. cerevisiae Tps1. This kind of inhibitor is able to decrease the rate of reaction to zero at increased concentrations. Based on the similarities found in sequence and function between Tps1 of S. cerevisiae and some pathogens and on the inhibitory effect of T6P on Tps1 activity observed in vitro, novel drugs can be developed for the treatment of infectious diseases caused by organisms whose infectivity and survival on the host depend on trehalose.

Trehalose is required for stress resistance and virulence of the Basidiomycota plant pathogen Ustilago maydis

Trehalose is an important disaccharide that can be found in bacteria, fungi, invertebrates and plants. In some Ascomycota fungal plant pathogens, the role of trehalose was recently studied and shown to be important for conferring protection against several environmental stresses and for virulence. In most of the fungi studied, two enzymes are involved in the synthesis of trehalose: trehalose-6-phosphate synthase (Tps1) and trehalose-6-phosphate phosphatase (Tps2). To study the role of trehalose in virulence and stress response in the Basidiomycota maize pathogen Ustilago maydis, Δtps2 deletion mutants were constructed. These mutants did not produce trehalose as confirmed by HPLC analysis, showing that the single gene disruption impaired its biosynthesis. The mutants displayed increased sensitivity to oxidative, heat, acid, ionic and osmotic stresses as compared to the wild-type strains. Virulence of Δtps2 mutants to maize plants was extremely reduced compared to wild-type strains, possibly due to reduced capability to deal with the hostile host environment. The phenotypic traits displayed by Δtps2 strains were fully restored to wild-type levels when complemented with the endogenous UmTPS2 gene, or a chimeric construct having the Saccharomyces cerevisiae TPS2 ORF. This report demonstrates the presence of a single biosynthetic pathway for trehalose, and its importance for virulence in this model Basidiomycota plant pathogen.

Chaotropicity: a key factor in product tolerance of biofuel-producing microorganisms

Fermentation products can chaotropically disorder macromolecular systems and induce oxidative stress, thus inhibiting biofuel production. Recently, the chaotropic activities of ethanol, butanol and vanillin have been quantified (5.93, 37.4, 174kJ kg(-1)m(-1) respectively). Use of low temperatures and/or stabilizing (kosmotropic) substances, and other approaches, can reduce, neutralize or circumvent product-chaotropicity. However, there may be limits to the alcohol concentrations that cells can tolerate; e.g. for ethanol tolerance in the most robust Saccharomyces cerevisiae strains, these are close to both the solubility limit (<25%, w/v ethanol) and the water-activity limit of the most xerotolerant strains (0.880). Nevertheless, knowledge-based strategies to mitigate or neutralize chaotropicity could lead to major improvements in rates of product formation and yields, and also therefore in the economics of biofuel production.

Lack of intracellular trehalose affects formation of Escherichia coli persister cells

Persisters are dormant antibiotic-tolerant cells that usually compose a small fraction of bacterial populations. In this work, we focused on the role of trehalose in persister formation. We found that the ΔotsA mutant, which is unable to synthesize trehalose, produced increased levels of persisters in the early stationary phase and under heat stress conditions. The lack of trehalose in the ΔotsA mutant resulted in oxidative stress, manifested by increased membrane lipid peroxidation after heat shock. Stationary ΔotsA cells additionally exhibited increased levels of oxidized proteins and apurinic/apyrimidinic sites in DNA as compared to WT cells. Oxidative stress caused by the lack of trehalose was accompanied by the overproduction of extracellular indole, a signal molecule that has been shown to stimulate persister formation. Our major conclusion is that intracellular trehalose protects E. coli cells against oxidative stress and limits indole synthesis, which in turn inhibits the formation of persisters.

Delineating the relationships among the formation of reactive oxygen species, cell membrane instability and innate autoimmunity in intestinal reperfusion injury

Acute intestinal ischemia is a medical emergency with a high mortality rate, attesting to the need for a better understanding of its pathogenesis and the development of effective therapies. The goal of this study was to delineate the relationships among intracellular and extracellular events in intestinal ischemia/reperfusion (I/R) injury, particularly the formation of reactive oxygen species (ROS), cell membrane instability associated with lipid peroxidation and the innate autoimmune response mediated by natural IgM and complement. A murine model of natural IgM-mediated intestinal I/R was used. Mice overexpressing anti-oxidant enzyme SOD1 were found to have significantly reduced intestinal tissue damage and complete blockage of IgM-mediated complement activation compared with WT controls. To determine if cell membrane instability was an event intermediate between ROS formation and natural IgM-mediated innate autoimmune response, the cell membrane stabilizer (trehalose) was administered to WT mice prior to the induction of intestinal ischemia. Treatment with trehalose significantly protected animals from I/R injury and inhibited IgM-mediated complement activation although it did not prevent membrane lipid peroxidation. These data indicate that in normal mice subjected to I/R injury, intracellular ROS formation is an event upstream of the lipid peroxidation which results in cell membrane instability. The membrane instability leads to an innate autoimmune response by natural IgM and complement. Trehalose, a nontoxic disaccharide tolerated well by animals and humans, has promise as a protective agent for patients with medical conditions related to acute intestinal ischemia.

Brazilian propolis protects Saccharomyces cerevisiae cells against oxidative stress

Propolis is a natural product widely used for humans. Due to its complex composition, a number of applications (antimicrobial, antiinflammatory, anesthetic, cytostatic and antioxidant) have been attributed to this substance. Using Saccharomyces cerevisiae as a eukaryotic model we investigated the mechanisms underlying the antioxidant effect of propolis from Guarapari against oxidative stress. Submitting a wild type (BY4741) and antioxidant deficient strains (ctt1Δ, sod1Δ, gsh1Δ, gtt1Δ and gtt2Δ) either to 15 mM menadione or to 2 mM hydrogen peroxide during 60 min, we observed that all strains, except the mutant sod1Δ, acquired tolerance when previously treated with 25 μg/mL of alcoholic propolis extract. Such a treatment reduced the levels of ROS generation and of lipid peroxidation, after oxidative stress. The increase in Cu/Zn-Sod activity by propolis suggests that the protection might be acting synergistically with Cu/Zn-Sod.

Improved tolerance of recombinant Escherichia coli to the toxicity of crude glycerol by overexpressing trehalose biosynthetic genes (otsBA) for the production of β-carotene

This study aims to investigate whether overexpressing the trehalose biosynthetic gene, otsBA operon, in β-carotene-producing recombinant Escherichia coli protects cells from toxic impurities in crude glycerol. The concentrations of potassium and methanol in crude glycerol were too low to inhibit cell growth. Cell growth and production in control cell culture were inhibited significantly in the presence of a small amount of crude fatty acids. Peroxides were generated in the presence of crude fatty acids during autoclaving and, thus, the inhibitory effect of crude fatty acids was caused primarily by these peroxides. Engineered cells overexpressing otsBA tolerated crude fatty acids (≤42 wet-g/L), methanol (≤7.5 g/L), and t-BuOOH (≤60 μM) in separate experiments and tolerated up to 60 g/L crude glycerol. These results demonstrate that overexpressing otsBA endowed cells with the capacity to tolerate the toxicity of crude glycerol for direct use.

Chromate reduction is expedited by bacteria engineered to produce the compatible solute trehalose

The toxicity and solubility of chromium(VI) can be decreased by certain microbes that reduce chromium(VI) to chromium(III). However, these bacteria do not escape unscathed from this process. Chromium(VI) reduction damages the essential macromolecules of living systems. Trehalose protects organisms from chemical stress but has not been tested in the context of bioremediation. We engineered bacteria to produce trehalose and found that they then reduced 1 mM chromium(VI) to chromium(III), whereas wild-type cells were only able to reduce half that amount. Thus, by providing bacteria with a biochemical defense against the side-effects of chromate reduction may be a new approach to cleaning up sites that are contaminated with high levels of chromate.

Hydrogen peroxide and ecdysone in the cryoprotective dehydration strategy of Megaphorura arctica (Onychiuridae: Collembola)

The Arctic springtail, Megaphorura arctica, survives sub-zero temperatures in a dehydrated state via trehalose-dependent cryoprotective dehydration. Regulation of trehalose biosynthesis is complex; based in part on studies in yeast and fungi, its connection with oxidative stress caused by exposure of cells to oxidants, such as hydrogen peroxide (H₂O₂), or dehydration, is well documented. In this respect, we measured the amount of H₂O₂ and antioxidant enzyme activities (superoxide dismutases: copper, zinc--CuZnSOD and manganese containing--MnSOD, and catalase--CAT), as the regulatory components determining H₂O₂ concentrations, in Arctic springtails incubated at 5 °C (control) versus -2 °C (threshold temperature for trehalose biosynthesis). Because ecdysone also stimulates trehalose production in insects and regulates the expression of genes involved in redox homeostasis and antioxidant protection in Drosophila, we measured the levels of the active physiological form of ecdysone--20-hydroxyecdysone (20-HE). Significantly elevated H₂O₂ and 20-HE levels were observed in M. arctica incubated at -2 °C, supporting a link between ecdysone, H₂O₂, and trehalose levels during cryoprotective dehydration. CAT activity was found to be significantly lower in M. arctica incubated at -2 °C versus 5 °C, suggesting reduced H₂O₂ breakdown. Furthermore, measurement of the free radical composition in Arctic springtails incubated at 5 °C (controls) versus -2 °C by Electron Paramagnetic Resonance spectroscopy revealed melanin-derived free radicals at -2 °C, perhaps an additional source of H₂O₂. Our results suggest that H₂O₂ and ecdysone play important roles in the cryoprotective dehydration process in M. arctica, linked with the regulation of trehalose biosynthesis.

Saccharomyces cerevisiae in the stationary phase as a model organism--characterization at cellular and proteome level

The yeast Saccharomyces cerevisiae has been used as a model organism to investigate responses to different environmental stressors. The importance of their conclusions has been expanded to human cells. The experiments were done with exponentially growing cells, which do not resemble human cells. Human and other eukaryotic cells spend the greater part of their lives in a quiescent state, known as G0 corresponding to the yeast stationary phase. Providing energy, which comes from mitochondrial respiration, is also common. Thus, in the present study S. cerevisiae was used in the stationary phase for characterization at the cellular and proteome levels. At the cellular level, optical density, cell viability, glycogen content, intracellular oxidation and cell energy metabolic activity were measured, while at the proteome level, protein profiles were analyzed using two-dimensional electrophoresis. The data obtained at both levels provide better insight into quiescence program state, which still remains poorly understood. At their base, optimal time period reflecting a stable metabolic and oxidative state of the yeast was determined. Consequently, this period is the appropriate to study changes in cell oxidant status and energy metabolic activity in response to different environmental stressors.

Trehalose and plant stress responses: friend or foe?

The disaccharide trehalose is involved in stress response in many organisms. However, in plants, its precise role remains unclear, although some data indicate that trehalose has a protective role during abiotic stresses. By contrast, some trehalose metabolism mutants exhibit growth aberrations, revealing potential negative effects on plant physiology. Contradictory effects also appear under biotic stress conditions. Specifically, trehalose is essential for the infectivity of several pathogens but at the same time elicits plant defense. Here, we argue that trehalose should not be regarded only as a protective sugar but rather like a double-faced molecule and that further investigation is required to elucidate its exact role in stress tolerance in plants.

Sugar signalling and antioxidant network connections in plant cells

Sugars play important roles as both nutrients and regulatory molecules throughout plant life. Sugar metabolism and signalling function in an intricate network with numerous hormones and reactive oxygen species (ROS) production, signalling and scavenging systems. Although hexokinase is well known to fulfil a crucial role in glucose sensing processes, a scenario is emerging in which the catalytic activity of mitochondria-associated hexokinase regulates glucose-6-phosphate and ROS levels, stimulating antioxidant defence mechanisms and the synthesis of phenolic compounds. As a new concept, it can be hypothesized that the synergistic interaction of sugars (or sugar-like compounds) and phenolic compounds forms part of an integrated redox system, quenching ROS and contributing to stress tolerance, especially in tissues or organelles with high soluble sugar concentrations.

Differential importance of trehalose accumulation in Saccharomyces cerevisiae in response to various environmental stresses

Trehalose is believed to play an important role in stress tolerance in the yeast Saccharomyces cerevisiae. In this research, the responses to various environmental stresses, such as high ethanol concentration, heat, oxidative, and freezing stresses, were investigated in a strain with deletion of the NTH1, NTH2, and ATH1 genes encoding trehalases that are involved in trehalose degradation and the triple deletion strains overexpressing TPS1 or TPS2, both of which encode trehalose biosynthesis enzymes in S. cerevisiae. The contents of trehalose constitutively accumulated in the TPS1- and TPS2-overexpressing triple deletion strains were higher than that in the original triple deletion strain. High trehalose accumulation and growth activity were observed in the TPS2-overexpressing triple deletion strain after ethanol stress induction. The same was also observed in the triple deletion and the TPS1- and TPS2-overexpressing triple deletion strains after heat stress induction. In case of freezing stress, all the recombinant strains with high constitutive trehalose content showed high tolerance. However, in case of oxidative stress, trehalose accumulation could not make the yeast cells tolerant. Our results indicated that high trehalose accumulation can make yeast cells resistant to multiple stresses, but the importance of this accumulation before or after stress induction is varied depending on the type of stress.

The induction of trehalose and glycerol in Saccharomyces cerevisiae in response to various stresses

Trehalose and glycerol have been implicated as potential stress protectants that accumulate in yeasts during various stress conditions. We investigated the levels of glycerol and trehalose and the expression profiles of genes involved in their metabolism to determine their involvement in the response of Saccharomyces cerevisiae XQ1 to thermal, sorbitol and ethanol stresses. The results showed that the genes involved in the synthesis and degradation of trehalose and glycerol were stress induced, and that trehalose and glycerol were synthesized simultaneously during the initial stages (a sensitive response period) of diverse stress treatments. Trehalose accumulated markedly under heat treatment, but not under sorbitol or ethanol stress, whereas glycerol accumulated strikingly under sorbitol stress conditions. Interestingly, extracellular trehalose seemed to be involved in protecting cells from damage under unfavorable conditions. Moreover, our results suggest that the stress-activated futile ATP cycles of trehalose and glycerol turnover are of general importance during cellular stress adaptation.