The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Andres Wiemken - One of the best experts on this subject based on the ideXlab platform.
-
induction of trehalase in arabidopsis plants infected with the Trehalose producing pathogen plasmodiophora brassicae
Molecular Plant-microbe Interactions, 2002Co-Authors: David Brodmann, Roger A Aeschbacher, Astrid Schuller, Jutta Ludwigmuller, Andres Wiemken, Thomas Boller, Astrid WinglerAbstract:Various microorganisms produce the disaccharide Trehalose during their symbiotic and pathogenic interactions with plants. Trehalose has strong effects on plant metabolism and growth; therefore, we became interested to study its possible role in the interaction of Arabidopsis thaliana with Plasmodiophora brassicae, the causal agent of clubroot disease. We found that Trehalose accumulated strongly in the infected organs (i.e., the roots and hypocotyls) and, to a lesser extent, in the leaves and stems of infected plants. This accumulation pattern of Trehalose correlated with the expression of a putative Trehalose-6-phosphate synthase (EC 2.4.1.15) gene from P. brassicae, PbTPS1. Clubroot formation also resulted in an induction of the Arabidopsis trehalase gene, ATTRE1, and in a concomitant increase in trehalase (EC 3.2.1.28) activity in the roots and hypocotyls, but not in the leaves and stems of infected plants. Thus, induction of ATTRE1 expression was probably responsible for the increased trehalase activity. Trehalase activity increased before Trehalose accumulated; therefore, it is unlikely that trehalase was induced by its substrate. The induction of trehalase may be part of the plant's defense response and may prevent excess accumulation of Trehalose in the plant cells, where it could interfere with the regulation of carbon metabolism.
-
Trehalose and trehalase in arabidopsis
Plant Physiology, 2001Co-Authors: Joachim Muller, Roger A Aeschbacher, Astrid Wingler, Thomas Boller, Andres WiemkenAbstract:Trehalase is ubiquitous in higher plants. So far, indications concerning its function are scarce, although it has been implicated in the detoxification of exogenous Trehalose. A putative trehalase gene, T19F6.15 , has been identified in the genome sequencing effort in Arabidopsis. Here we show that this gene encodes a functional trehalase when its cDNA is expressed in yeast, and that it is expressed in various plant organs. Furthermore, we present results on the distribution and activity of trehalase in Arabidopsis and we describe how inhibition of trehalase by validamycin A affects the plants response to exogenous Trehalose (α-d-glucopyranosyl-[1, 1]-α-d-glucopyranoside). Trehalase activity was highest in floral organs, particularly in the anthers (approximately 700 nkat g −1 protein) and maturing siliques (approximately 250 nkat g −1 protein) and much lower in leaves, stems, and roots (less than 50 nkat g −1 protein). Inhibition of trehalase in vivo by validamycin A led to the accumulation of an endogenous substance that had all the properties of Trehalose, and to a strong reduction in sucrose and starch contents in flowers, leaves, and stems. Thus, Trehalose appears to be an endogenous substance in Arabidopsis, and Trehalose and trehalase may play a role in regulating the carbohydrate allocation in plants.
-
purification of the trehalase gmtre1 from soybean nodules and cloning of its cdna gmtre1 is expressed at a low level in multiple tissues
Plant Physiology, 1999Co-Authors: Roger A Aeschbacher, Thomas Boller, Joachim Muller, Andres WiemkenAbstract:Trehalose (α-d-glucopyranosyl-1,1-α-d-glucopyranoside), a disaccharide widespread among microbes and lower invertebrates, is generally believed to be nonexistent in higher plants. However, the recent discovery of Arabidopsis genes whose products are involved in Trehalose synthesis has renewed interest in the possibility of a function of Trehalose in higher plants. We previously showed that trehalase, the enzyme that degrades Trehalose, is present in nodules of soybean ( Glycine max [L.] Merr.), and we characterized the enzyme as an apoplastic glycoprotein. Here we describe the purification of this trehalase to homogeneity and the cloning of a full-length cDNA encoding this enzyme, named GMTRE1 ( G. max trehalase1). The amino acid sequence derived from the open reading frame of GMTRE1 shows strong homology to known trehalases from bacteria, fungi, and animals. GMTRE1 is a single-copy gene and is expressed at a low but constant level in many tissues.
-
Trehalose and trehalase in plants recent developments
Plant Science, 1995Co-Authors: Joachim Muller, Thomas Boller, Andres WiemkenAbstract:Abstract Trehalose is a non-reducing disaccharide consisting of two α-glycosidically linked glucose units. It accumulates in many microorganisms and invertebrate animals when they are exposed to various forms of stress, and it may serve as a protectant of enzymes and membranes, particularly under conditions of heat and desiccation stress. Most vascular plants lack the capacity to produce Trehalose, except for a small number of desiccation tolerant plants, such as some ferns and the angiosperm Myrothamnus flabellifolia . In contrast, a highly specific trehalase activity has been described in many plants. The enzyme does not cleave other common α-glucosides, and it is highly sensitive to the inhibitor validamycin A. Trehalases have been found in various tissues; particularly high activities occur in pollen and legume root nodules. The possible functions of plant trehalase are discussed, focussing on its significance in the interaction of plants with Trehalose-accumulating microorganisms.
-
effects of validamycin a a potent trehalase inhibitor and phytohormones on Trehalose metabolism in roots and root nodules of soybean and cowpea
Planta, 1995Co-Authors: Joachim Muller, Thomas Boller, Andres WiemkenAbstract:Trehalose, a common microbial disaccharide, has been reported to be toxic to plants, and plant trehalase has therefore been hypothesized to function as a detoxifying enzyme. To test this, aseptically grown soybean (Glycine max L. Merr.) plantlets were supplied with Trehalose. The plants accumulated Trehalose only when validamycin A, a potent trehalase inhibitor, was added as well. Under these conditions, they accumulated Trehalose to up to 8% of the dry weight in their primary leaves without any detectable impairment of growth or health. We have previously shown that in soybean nodules, Trehalose is generated by the symbiotic bacteria, and trehalase is strongly induced. However, direct exposure of plants to Trehalose did not affect their trehalase activity, whereas a treatment with auxin strongly increased it, indicating that the enzyme level is regulated by hormones rather than by its substrate. Addition of validamycin A to nodules caused an increase in the amount of Trehalose and a decrease in the sucrose and starch pools, but nitrogen fixation was not affected. Similar results were obtained with cowpea (Vigna unguiculata L.) plantlets and nodules. These results indicate that plant trehalase is functional in metabolizing Trehalose from exogenous and endogenous sources, even though the disaccharide has no obvious toxic effects.
Solomon Nwaka - One of the best experts on this subject based on the ideXlab platform.
-
evidence for contribution of neutral trehalase in barotolerance of saccharomyces cerevisiae
Applied and Environmental Microbiology, 2000Co-Authors: Hitoshi Iwahashi, Solomon Nwaka, Kaoru ObuchiAbstract:In yeast, Trehalose accumulation and its hydrolysis, which is catalyzed by neutral trehalase, are believed to be important for thermotolerance. We have shown that Trehalose is one of the important factors for barotolerance (resistance to hydrostatic pressure); however, nothing is known about the role of neutral trehalase in barotolerance. To estimate the contribution of neutral trehalase in resisting high hydrostatic pressure, we measured the barotolerance of neutral trehalase I and/or neutral trehalase II deletion strains. Under 180 MPa of pressure for 2 h, the neutral trehalase I deletion strain showed higher barotolerance in logarithmic-phase cells and lower barotolerance in stationary-phase cells than the wild-type strain. Introduction of the neutral trehalase I gene (NTH1) into the deletion mutant restored barotolerance defects in stationary-phase cells. Furthermore, we assessed the contribution of neutral trehalase during pressure and recovery conditions by varying the expression of NTH1 or neutral trehalase activity with a galactose-inducible GAL1 promoter with either glucose or galactose. The low barotolerance observed with glucose repression of neutral trehalase from the GAL1 promoter was restored during recovery with galactose induction. Our results suggest that neutral trehalase contributes to barotolerance, especially during recovery.
-
opposite roles of trehalase activity in heat shock recovery and heat shock survival in saccharomyces cerevisiae
Biochemical Journal, 1999Co-Authors: Stefaan Wera, Ilse Geyskens, Ellen De Schrijver, Solomon Nwaka, Johan M TheveleinAbstract:A variety of results has been obtained consistent with activation of neutral trehalase in Saccharomyces cerevisiae through direct phosphorylation by cAMP-dependent protein kinase (PKA). A series of neutral trehalase mutant alleles, in which all evolutionarily conserved putative phosphorylation sites were changed into alanine, was tested for activation in vitro (by PKA) and in vivo (by glucose addition). None of the mutations alone affected the activation ratio, whereas all mutations combined resulted in an inactive enzyme. All mutant alleles were expressed to similar levels, as shown by Western blotting. Several of the point mutations significantly lowered the specific activity. Using this series of mutants with different activity levels we show an inverse relationship between trehalase activity and heat-shock survival during glucose-induced Trehalose mobilization. This is consistent with a stress-protective function of Trehalose. On the other hand, reduction of trehalase activity below a certain threshold level impaired recovery from a sublethal heat shock. This suggests that Trehalose breakdown is required for efficient recovery from heat shock, and that the presence of trehalase protein alone is not sufficient for efficient heat-stress recovery.
-
neutral trehalase nth1p of saccharomyces cerevisiae encoded by the nth1 gene is a multiple stress responsive protein
FEBS Letters, 1997Co-Authors: Harald Zahringer, Mark Us Burgert, Helmut Holzer, Solomon NwakaAbstract:We have shown previously that expression of the NTH1 gene is increased at heat stress (40°C) both at the mRNA and enzymatic activity levels. This increased expression was correlated to the requirement of the NTH1 gene for recovery after heat shock at 50°C and the presence of stress responsive elements STRE (CCCCT) 3 times in its promoter region [S. Nwaka et al., FEBS Lett. 360 (1995) 286–290; S. Nwaka et al., J. Biol. Chem. 270 (1995) 10193–10198]. We show here that expression of the NTH1 gene and its product, neutral trehalase (Nth1p), are also induced by other stressors such as H 2 O 2 , CuSO 4 , NaAsO 2 , and cycloheximide (CHX). Heat-induced expression of the NTH1 gene is shown to be accompanied by accumulation of Trehalose. In contrast, the chemical stressors which also induce the expression of NTH1 did not lead to accumulation of Trehalose under similar conditions. Our data suggest that: (1) heat- and chemical stress-induced expression of neutral trehalase is largely due to de novo protein synthesis, and (2) different mechanisms may control the heat- and chemical stress-induced expression of NTH1 at the transcriptional level. Participation of neutral trehalase (Nth1p) in multiple stress response dependent and independent on Trehalose is discussed.
-
Molecular Biology of Trehalose and the Trehalases in the Yeast Saccharomyces cerevisiae
Progress in Nucleic Acid Research and Molecular Biology, 1997Co-Authors: Solomon Nwaka, Helmut HolzerAbstract:The present state of knowledge of the role of Trehalose and Trehalose hydrolysis catalyzed by trehalase (EC 3.2.1.28) in the yeast Saccharomyces cerevisiae is reviewed. Trehalose is believed to function as a storage carbohydrate because its concentration is high during nutrient limitations and in resting cells. It is also believed to function as a stress metabolite because its concentration increases during certain adverse environmental conditions, such as heat and toxic chemicals. The exact way Trehalose may perform the stress function is not understood, and conditions exist under which Trehalose accumulation and tolerance to certain stress situations cannot be correlated. Three trehalases have been described in S. cerevisiae: 1) the cytosolic neutral trehalase encoded by the NTH1 gene, and regulated by cAMP-dependent phosphorylation process, nutrients, and temperature; 2) the vacuolar acid trehalase encoded by the ATH1 gene, and regulated by nutrients; and 3) a putative trehalase Nth1p encoded by the NTH2 gene (homolog of the NTH1 gene) and regulated by nutrients and temperature. The neutral trehalase is responsible for intracellular hydrolysis of Trehalose, in contrast to the acid trehalase, which is responsible for utilization of extracellular Trehalose. The role of the putative trehalase Nth2p in Trehalose metabolism is not known. The NTH1 and NTH2 genes are required for recovery of cells after heat shock at 50 °C, consistent with their heat inducibility and sequence similarity. Other stressors, such as toxic chemicals, also induce the expression of these genes. We therefore propose that the NTH1 and NTH2 genes have stress-related (unction and the gene products may be called stress proteins. Whether the stress function of the trehalase genes is linked to Trehalose is not clear, and possible mechanisms of stress protective function of the trehalases are discussed. © 1998 Academic Press
-
expression and function of the trehalase genes nth1 and ybr0106 in saccharomyces cerevisiae
Journal of Biological Chemistry, 1995Co-Authors: Solomon Nwaka, Meinrad Kopp, Helmut HolzerAbstract:Abstract The biological function of the Trehalose-degrading yeast enzyme neutral trehalase consists of the control of the concentration of Trehalose, which is assumed to play a role in thermotolerance, in germination of spores, and in other life functions of yeast. Resequencing of the neutral trehalase gene NTH1 on chromosome IV resulted in the observation of two possible start codons (Kopp, M., Nwaka, S., and Holzer, H. (1994) Gene (Amst.) 150, 403-404). We show here that only the most upstream start codon which initiates translation of the longest possible ORF is used for expression of NTH1 in vivo. A gene with 77% identity with NTH1, YBR0106, which was discovered during sequencing of chromosome II (Wolfe, K. H., and Lohan, A. J. E. (1994) Yeast 10, S41-S46), is shown here to be expressed into mRNA. Experiments with a mutant disrupted in the YBR0106 ORF showed, in contrast to a NTH1 deletion mutant, no changes in trehalase activity and in Trehalose concentration. However, similar to the NTH1 gene a requirement of the intact YBR0106 gene for thermotolerance is demonstrated in experiments with the respective mutants. This indicates that the products of the likely duplicated YBR0106 gene and the NTH1 gene serve a heat shock protein function. In case of the YBR0106 gene, this is the only phenotypic feature found at present.
Helmut Holzer - One of the best experts on this subject based on the ideXlab platform.
-
neutral trehalase nth1p of saccharomyces cerevisiae encoded by the nth1 gene is a multiple stress responsive protein
FEBS Letters, 1997Co-Authors: Harald Zahringer, Mark Us Burgert, Helmut Holzer, Solomon NwakaAbstract:We have shown previously that expression of the NTH1 gene is increased at heat stress (40°C) both at the mRNA and enzymatic activity levels. This increased expression was correlated to the requirement of the NTH1 gene for recovery after heat shock at 50°C and the presence of stress responsive elements STRE (CCCCT) 3 times in its promoter region [S. Nwaka et al., FEBS Lett. 360 (1995) 286–290; S. Nwaka et al., J. Biol. Chem. 270 (1995) 10193–10198]. We show here that expression of the NTH1 gene and its product, neutral trehalase (Nth1p), are also induced by other stressors such as H 2 O 2 , CuSO 4 , NaAsO 2 , and cycloheximide (CHX). Heat-induced expression of the NTH1 gene is shown to be accompanied by accumulation of Trehalose. In contrast, the chemical stressors which also induce the expression of NTH1 did not lead to accumulation of Trehalose under similar conditions. Our data suggest that: (1) heat- and chemical stress-induced expression of neutral trehalase is largely due to de novo protein synthesis, and (2) different mechanisms may control the heat- and chemical stress-induced expression of NTH1 at the transcriptional level. Participation of neutral trehalase (Nth1p) in multiple stress response dependent and independent on Trehalose is discussed.
-
Molecular Biology of Trehalose and the Trehalases in the Yeast Saccharomyces cerevisiae
Progress in Nucleic Acid Research and Molecular Biology, 1997Co-Authors: Solomon Nwaka, Helmut HolzerAbstract:The present state of knowledge of the role of Trehalose and Trehalose hydrolysis catalyzed by trehalase (EC 3.2.1.28) in the yeast Saccharomyces cerevisiae is reviewed. Trehalose is believed to function as a storage carbohydrate because its concentration is high during nutrient limitations and in resting cells. It is also believed to function as a stress metabolite because its concentration increases during certain adverse environmental conditions, such as heat and toxic chemicals. The exact way Trehalose may perform the stress function is not understood, and conditions exist under which Trehalose accumulation and tolerance to certain stress situations cannot be correlated. Three trehalases have been described in S. cerevisiae: 1) the cytosolic neutral trehalase encoded by the NTH1 gene, and regulated by cAMP-dependent phosphorylation process, nutrients, and temperature; 2) the vacuolar acid trehalase encoded by the ATH1 gene, and regulated by nutrients; and 3) a putative trehalase Nth1p encoded by the NTH2 gene (homolog of the NTH1 gene) and regulated by nutrients and temperature. The neutral trehalase is responsible for intracellular hydrolysis of Trehalose, in contrast to the acid trehalase, which is responsible for utilization of extracellular Trehalose. The role of the putative trehalase Nth2p in Trehalose metabolism is not known. The NTH1 and NTH2 genes are required for recovery of cells after heat shock at 50 °C, consistent with their heat inducibility and sequence similarity. Other stressors, such as toxic chemicals, also induce the expression of these genes. We therefore propose that the NTH1 and NTH2 genes have stress-related (unction and the gene products may be called stress proteins. Whether the stress function of the trehalase genes is linked to Trehalose is not clear, and possible mechanisms of stress protective function of the trehalases are discussed. © 1998 Academic Press
-
expression and function of the trehalase genes nth1 and ybr0106 in saccharomyces cerevisiae
Journal of Biological Chemistry, 1995Co-Authors: Solomon Nwaka, Meinrad Kopp, Helmut HolzerAbstract:Abstract The biological function of the Trehalose-degrading yeast enzyme neutral trehalase consists of the control of the concentration of Trehalose, which is assumed to play a role in thermotolerance, in germination of spores, and in other life functions of yeast. Resequencing of the neutral trehalase gene NTH1 on chromosome IV resulted in the observation of two possible start codons (Kopp, M., Nwaka, S., and Holzer, H. (1994) Gene (Amst.) 150, 403-404). We show here that only the most upstream start codon which initiates translation of the longest possible ORF is used for expression of NTH1 in vivo. A gene with 77% identity with NTH1, YBR0106, which was discovered during sequencing of chromosome II (Wolfe, K. H., and Lohan, A. J. E. (1994) Yeast 10, S41-S46), is shown here to be expressed into mRNA. Experiments with a mutant disrupted in the YBR0106 ORF showed, in contrast to a NTH1 deletion mutant, no changes in trehalase activity and in Trehalose concentration. However, similar to the NTH1 gene a requirement of the intact YBR0106 gene for thermotolerance is demonstrated in experiments with the respective mutants. This indicates that the products of the likely duplicated YBR0106 gene and the NTH1 gene serve a heat shock protein function. In case of the YBR0106 gene, this is the only phenotypic feature found at present.
-
phenotypic features of trehalase mutants in saccharomyces cerevisiae
FEBS Letters, 1995Co-Authors: Solomon Nwaka, Bernd Mechler, Monika Destruelle, Helmut HolzerAbstract:Abstract In the yeast Saccharomyces cerevisiae , some studies have shown that Trehalose and its hydrolysis may play an important physiological role during the life cycle of the cell. Recently, other studies demonstrated a close correlation between Trehalose levels and tolerance to heat stress, suggesting that Trehalose may be a protectant which contributes to thermotolerance. We had reported lack of correlation between Trehalose accumulation and increase in thermotolerance under certain conditions, suggesting that Trehalose may not mediate thermotolerance [Nwaka, S., et al. (1994) FEBS Lett. 344, 225–228]. Using mutants of the trehalase genes, NTH1 and YBR0106 , we have demonstrated the necessity of these genes in recovery of yeast cells after heat shock, suggesting a role of these genes in thermotolerance (Nwaka, S., Kopp, M., and Holzer, H., submitted for publication). In the present paper, we have analysed the expression of the trehalase genes under heat stress conditions and present genetic evidence for the ‘poor-heat-shock-recovery’ phenotype associated with NTH1 and YBR0106 mutants. Furthermore, we show a growth defect of neutral and acid trehalase-deficient mutants during transition from glucose to glycerol, which is probably related to the ‘poor-heat-shock-recovery’ phenomenon.
-
assay of Trehalose with acid trehalase purified from saccharomyces cerevisiae
Yeast, 1993Co-Authors: Iris Kienle, Mark Us Burgert, Helmut HolzerAbstract:An enzymatic end-point assay of Trehalose using acid trehalase from yeast is described. After quantitative hydrolysis of Trehalose by acid trehalase, the resulting glucose is assayed with the commercially available glucose oxidase/peroxidase dye system. Pre-existing glucose is determined in a control reaction from which acid trehalase is omitted. When intact cells are analysed for Trehalose, pre-existing glucose can be washed out with ice-cold water without reducing the Trehalose content of the cells. A convenient method for extraction of Trehalose from intact yeast cells is heating for 20 min at 95°C followed by centrifugation. The specificity of the assay is determined by the specificity of the acid trehalase preparation used. As described previously (Mittenbuhler, K. and Holzer, H., 1988, J. Biol. Chem.263, 8537–8543; Mittenbuhler, K., 1988, Thesis, University of Freiburg), the following sugars and sugar derivatives do not form glucose when incubated with purified acid trehalase: sucrose, cellobiose, mellobiose, raffinose, maltose, lactose, glucose-6-phosphate, glucose-1-phosphate, galactose. The application of the new Trehalose assay to yeast cells grown to different growth stages and at various temperatures is presented.
Jean Luc Parrou - One of the best experts on this subject based on the ideXlab platform.
-
new insights into Trehalose metabolism by saccharomyces cerevisiae nth2 encodes a functional cytosolic trehalase and deletion of tps1 reveals ath1p dependent Trehalose mobilization
Applied and Environmental Microbiology, 2008Co-Authors: Matthieu Jules, Jean Marie François, Gemma Beltran, Jean Luc ParrouAbstract:In the yeast Saccharomyces cerevisiae, the synthesis of endogenous Trehalose is catalyzed by a Trehalose synthase complex, TPS, and its hydrolysis relies on a cytosolic/neutral trehalase encoded by NTH1. In this work, we showed that NTH2, a paralog of NTH1, encodes a functional trehalase that is implicated in Trehalose mobilization. Yeast is also endowed with an acid trehalase encoded by ATH1 and an H+/Trehalose transporter encoded by AGT1, which can together sustain assimilation of exogenous Trehalose. We showed that a tps1 mutant defective in the TPS catalytic subunit cultivated on Trehalose, or on a dual source of carbon made of galactose and Trehalose, accumulated high levels of intracellular Trehalose by its Agt1p-mediated transport. The accumulated disaccharide was mobilized as soon as cells entered the stationary phase by a process requiring a coupling between its export and immediate extracellular hydrolysis by Ath1p. Compared to what is seen for classical growth conditions on glucose, this mobilization was rather unique, since it took place prior to that of glycogen, which was postponed until the late stationary phase. However, when the Ath1p-dependent mobilization of Trehalose identified in this study was impaired, glycogen was mobilized earlier and faster, indicating a fine-tuning control in carbon storage management during periods of carbon and energy restriction.
-
the arabidopsis thaliana trehalase is a plasma membrane bound enzyme with extracellular activity
FEBS Letters, 2007Co-Authors: Mathieu Frison, Jean Luc Parrou, Damien Guillaumot, Daniele Masquelier, Jean Marie François, Francois Chaumont, Henri BatokoAbstract:The lack of Trehalose accumulation in most plant species has been partly attributed to the presence of an active trehalase. Although Trehalose synthesis enzymes are thought to be cytosolic, and previous studies have indicated that trehalase activity is extracellular, the exact location of the enzyme has not yet been established in plant cell. We present evidence that the yet uncharacterised full-length Arabidopsis trehalase is a plasma membrane-bound protein, probably anchored to the membrane through a predicted N-terminal membrane spanning domain. The full-length AtTRE1, when expressed in yeast can functionally substitute for the extracellularly active trehalase Ath1p, by sustaining the growth of an ath1 null mutant strain on Trehalose and at pH 4.8. We further demonstrate that AtTRE1 expressed in yeast is plasma membrane-bound as in plant cell. In light of these findings, the regulation of plant cell endogenous Trehalose by trehalase is discussed.
-
acid trehalase in yeasts and filamentous fungi localization regulation and physiological function
Fems Yeast Research, 2005Co-Authors: Jean Luc Parrou, Matthieu Jules, Gemma Beltran, Jean Marie FrançoisAbstract:Yeasts and filamentous fungi are endowed with two different Trehalose-hydrolysing activities, termed acid and neutral trehalases according to their optimal pH for enzymatic activity. A wealth of information already exists on fungal neutral trehalases, while data on localization, regulation and function of fungal acid trehalases have remained elusive. The gene encoding the latter enzyme has now been isolated from two yeast species and two filamentous fungi, and sequences encoding putative acid trehalase can be retrieved from available public sequences. Despite weak similarities between amino acids sequences, this type of trehalase potentially harbours either a transmembrane segment or a signal peptide at the N-terminal sequence, as deduced from domain prediction algorithms. This feature, together with the demonstration that acid trehalase from yeasts and filamentous fungi is localized at the cell surface, is consistent with its main role in the utilisation of exogenous Trehalose as a carbon source. The growth on this disaccharide is in fact pretty effective in most fungi except in Saccharomyces cerevisiae. This yeast species actually exhibits a ‘Kluyver effect’ on Trehalose. Moreover, an oscillatory behaviour reminiscent of what is observed in aerobic glucose-limited continuous cultures at low dilution rate is also observed in batch growth on Trehalose. Finally, the S. cerevisiae acid trehalase may also participate in the catabolism of endogenous Trehalose by a mechanism that likely requires the export of the disaccharide, its extracellular hydrolysis, and the subsequent uptake of the glucose released. Based on these recent findings, we suggest to rename ‘acid’ and ‘neutral’ trehalases as ‘extracellular’ and ‘cytosolic’ trehalases, which is more adequate to describe their localization and function in the fungal cell.
-
effects of various types of stress on the metabolism of reserve carbohydrates in saccharomyces cerevisiae genetic evidence for a stress induced recycling of glycogen and Trehalose
Microbiology, 1997Co-Authors: Jean Luc Parrou, Marieange Teste, Jean Marie FrançoisAbstract:It is well known that glycogen and Trehalose accumulate in yeast under nutrient starvation or entering into the stationary phase of growth, and that high levels of Trehalose are found in heat-shocked cells. However, effects of various types of stress on Trehalose, and especially on glycogen, are poorly documented. Taking into account that almost all genes encoding the enzymes involved in the metabolism of these two reserve carbohydrates contain between one and several copies of the stress-responsive element (STRE), an investigation was made of the possibility of a link between the potential transcriptional induction of these genes and the accumulation of glycogen and Trehalose under different stress conditions. Using transcriptional fusions, it was found that all these genes were induced in a similar fashion, although to various extents, by temperature, osmotic and oxidative stresses. Experiments performed with an msn2/msn4 double mutant proved that the transcriptional induction of the genes encoding glycogen synthase (GSY2) and Trehalose-6-phosphate synthase (TPS1) was needed for the small increase in glycogen and Trehalose upon exposure to a mild heat stress and salt shock. However, the extent of transcriptional activation of these genes upon stresses in wild-type strains was not correlated with a proportional rise in either glycogen or Trehalose. The major explanation for this lack of correlation comes from the fact that genes encoding the enzymes of the biosynthetic and of the biodegradative pathways were almost equally induced. Hence, Trehalose and glycogen accumulated to much higher levels in cells lacking neutral trehalase or glycogen phosphoryiase exposed to stress conditions, which suggested that one of the major effects of stress in yeast is to induce a wasteful expenditure of energy by increasing the recycling of these molecules. We also found that transcriptional induction of STRE-controlled genes was abolished at temperatures above 40 °C, while induction was still observed for a heat-shock-element-regulated gene. Remarkably, Trehalose accumulated to very high levels under this condition. This can be explained by a stimulation of Trehalose synthase and inhibition of trehalase by high temperature.
Gerhard Wegener - One of the best experts on this subject based on the ideXlab platform.
-
fate and effects of the trehalase inhibitor trehazolin in the migratory locust locusta migratoria
Journal of Insect Physiology, 2010Co-Authors: Martina P Liebl, Victoria Nelius, Gunter Kamp, Osamu Ando, Gerhard WegenerAbstract:Abstract Trehalose is the main haemolymph sugar in many insect species. To be utilized Trehalose must be hydrolysed into its glucose units by trehalase (EC 3.2.1.28). Inhibitors of trehalase have attracted interest as possible pesticides and tools for studying the regulation of Trehalose metabolism in insects. To make full use of these inhibitors requires knowledge of their fate and effects in vivo. To this end we have measured trehazolin in locusts using a method based on the specific inhibition of a trehalase preparation. After injection of 20 μg, trehazolin decreased in haemolymph with a half-life of 2.6 days and after 10 days almost 95% had disappeared. Trehazolin did not reach the intracellular water space of locust tissues, but appeared with full inhibitory potency in locust faeces, suggesting that it was not metabolized, but quantitatively eliminated via the gut. Haemolymph Trehalose increased transiently upon trehazolin injection, it was maximal after 3 days, then decreased and reached control level after 10 days. Inhibition of flight muscle trehalase by trehazolin was prolonged and still conspicuous 21 days post injection, suggesting that trehazolin inhibits trehalase activity irreversibly in vivo and that recovery requires de novo enzyme synthesis.
-
the toxic and lethal effects of the trehalase inhibitor trehazolin in locusts are caused by hypoglycaemia
The Journal of Experimental Biology, 2003Co-Authors: Gerhard Wegener, Volker Tschiedel, Paul Schloder, Osamu AndoAbstract:The main blood sugar of locusts is Trehalose, which is hydrolysed to two glucose units by trehalase. Homogenates of locust flight muscles are rich in trehalase activity, which is bound to membranes. A minor fraction of trehalase is in an overt form while the remainder is latent, i.e. active only after impairing membrane integrity. Trehazolin, an antibiotic pseudosaccharide, inhibits locust flight muscle trehalase with apparent K i - and EC 5 0 values of 10 - 8 mol l - 1 and 10 - 7 mol l - 1 , respectively. Trehazolin is insecticidal: 50 μg injected into locusts completely and selectively blocked the overt form of muscle trehalase (with little effect on latent activity) and killed 50% of the insects within 24 h. Here, it is demonstrated for the first time that trehazolin causes dramatic hypoglycaemia. Injection of 10 μg trehazolin caused glucose levels to fall by over 90% in 24 h, from 2.8 mmol l - 1 to 0.23 mmol l - 1 , while Trehalose increased from 61 mmol l - 1 to 111 mmol l - 1 . Feeding glucose to the locusts fully neutralized the effects of a potentially lethal dose of trehazolin. This indicates that hypertrehalosaemia is not acutely toxic, whereas lack of glucose causes organ failure (presumably of the nervous system), and that sufficient haemolymph glucose can only be generated from Trehalose by trehalase. The results also suggest that overt flight muscle trehalase is located in the plasma membrane with the active site accessible to the haemolymph. Trehalase inhibitors are valuable tools for studying the molecular physiology of trehalase function and sugar metabolism in insects.