Red Blood Cell Hexokinase in Tumor Bearing Mice

Red blood cell hexokinase of tumor-bearing BALB/c mice was found to be 35% higher than in the normal controls, whereas glucose 6-phosphate-dehydrogenase and other red blood cell glycolytic enzymes were in the normal range. This hexokinase increase cannot be explained by a mean younger red cell population because normal hematological data and normal red cell enzymes, known as red cell age-markers, have been found in tumor-bearing mice. The isozymic pattern of red cell hexokinase is not modified in the tumor-bearing mice.

Adenine and Pyridine Nucleotides in the Red Blood Cells of Subjects with Solid Tumors

The concentration of adenine (ATP, ADP, AMP) and pyridine (NADP+, NADPH, NAD+, NADH) nucleotides in the erythrocytes of subjects affected by solid tumors was evaluated using a method which allows their simultaneous extraction and reverse-phase high-performance liquid chromatographic analysis. The results showed a lower level of ATP in the erythrocytes of subjects affected by solid tumors, whereas no significant modifications were observed in the other compounds. In fact, the mean value of ATP in these subjects was 27 % lower than that of normal adults. This fact is discussed in relation to other enzymatic and metabolic modifications previously observed in red blood cells.

Relationship between Erythrocyte Hexokinase in Cancer Patients and Red Cell Age

A study of hexokinase isozymic pattern and age dependence of the enzyme was carried out on erythrocytes of 4 patients with adenocarcinoma of the gastrointestinal tract. On the basis of our results, we think that the increase in hexokinase activity previously reported and the increase in both subtypes (Ia and Ib) of the enzyme herein described are not due to a mean younger red cell population caused by secondary anemia, which is frequently present in cancer patients.

Evolution of lymphocytes. Immunoglobulin T of the teleost sea bass (Dicentrarchus labrax): Quantitation of gene expressing and immunoreactive cells

Immunoglobulin T (IgT) is one of the key effector molecules of jawed vertebrate's adaptive immune system, and in this work we describe the quantitative distribution of IgT-expressing and IgT-producing cells in tissues of the European seabass Dicentrarchus labrax by using mRNA riboprobes and a specific anti-IgT antibody. A polyclonal antiserum (pAb) was prepared by immunizing rabbits with three synthetic peptides deduced from the full length IgT cDNA sequence and located in a surface-exposed CH3 domain of IgT constant region. The obtained antiserum, named RAIgT1, was able to recognize by ELISA immunization antigens and IgT from intestinal mucus and serum. In western blots of head kidney leukocytes lysates the antiserum recognized a 180 kDa polypeptide in non-reducing, and a 75 kDa peptide in reducing conditions. Interestingly, the RAIgT1 pAb crossreacted intensely in western blots with rainbow trout IgT purified from mucus and serum. Antisense mRNA IgT oligonucleotide sequences were employed in in situ hybridization to detect IgT-expressing cells in sections from lymphoid tissues, and positive cells were observed in head kidney, spleen, intestine and gills. By employing RAIgT1 in quantitative immunohistochemistry, the highest number of IgT-producing cells was observed in the gills (9.5 ± 0.7%), followed by intestine (8.4 ± 1.2%), head kidney (6.2 ± 1.4%), and spleen (4.1 ± 0.7%). Interestingly, the number of IgT-B cells showed a regionalization in the intestine, increasing from the proximal to the terminal part. By immunofluorescence and flow cytometry of live leukocytes, the percentages of RAIgT1 stained cells were 34 ± 11% in the intestine, 22 ± 5% in head kidney, 16 ± 7% in spleen, and 9 ± 5% in gills. At the fluorescence microscope, live cells from these tissues showed a typical membrane-associated positivity and a lymphocytic morphology, and no IgT/IgM double positive cells were detected. Immunoreactive cells have been purified from head kidney using magnetic beads, and IgT-enriched cells showed by RT-PCR an enhanced expression of the IgT gene, whereas IgT-depleted cells had an highest expression of IgM and TRβ genes. These data describe for the first time a quantitative panel of IgT-expressing and IgT-immunoreactive cells in tissues of a teleost fish species.

Engineered nanoparticles of titanium dioxide (TIO2): Uptake and biological effects in a sea bass cell line

With the rapid development of nanotechnology there has been a corresponding increase in the application of titanium dioxide nanoparticles (TiO₂-NPs) in various consumer and industrial products, consequently their potential health hazards and environmental effects are considered an aspect of great concern. In the present study, in order to assess the impact of TiO₂-NPs in the marine environment, the biological effects of TiO₂-NPs on a sea bass cell line (DLEC) were investigated. Cells were exposed for 24 h to different concentrations of TiO₂-NPs (1, 8, 40, 200 and 1000 μg/ml) or co-exposed with CdCl₂ (Cd). The effects of UV light irradiation were also investigated in cells treated with TiO₂-NPs and/or Cd. The internalization of TiO₂-NPs and the morphological cell modifications induced by the treatments were examined by transmission and scanning electron microscopy, this latter coupled with energy dispersive X-ray spectroscopy (EDS) for particle element detection. In addition, the effects of controlled exposures were studied evaluating the cytotoxicity, the DNA damage and the expression of inflammatory genes. Our study indicates that TiO₂-NPs were localized on the cell surface mainly as agglomerates revealed by EDS analysis and that they were uptaken by the cells inducing morphological changes. Photoactivation of TiO₂-NPs and/or co-exposure with Cd affects ATP levels and it contributes to induce acute cellular toxicity in DLEC cells dependent on Ti concentration. The inflammatory potential and the DNA damage, this latter displayed through a caspase-3 independent apoptotic process, were also demonstrated. Overall our data suggest that the interaction of TiO₂-NPs with marine water contaminants, such as cadmium, and the UV irradiation, may be an additional threat to marine organisms.

Quantitative immunoenzymatic detection of viral encephalopathy and retinopathy virus (betanodavirus) in sea bass Dicentrarchus labrax

Viral encephalopathy and retinopathy disease caused by betanodavirus, genus of the family Nodaviridae, affects marine, wild and farmed species including sea bass, one of the most important farmed species in Europe. This work describes a reliable and sensitive indirect ELISA assay to detect betanodavirus in biological samples using a polyclonal antiserum (pAb 283) against the 283/I09 virus strain, the most common red-spotted grouper nervous necrosis virus (RGNNV) genotype in the Mediterranean area, and a capture-based ELISA using a monoclonal antibody (mAb 4C3) specific to a common epitope present on the capsid protein. Using adsorbed, purified VERv preparation, the detection limit of indirect ELISA was 2 μg mL(-1) (3 × 10(5) TCID50 per mL), whereas for capture-based ELISA, the sensitivity for the antigen in solution was 17 μg mL(-1) (35 × 10(5) TCID50 per mL). The capture-based ELISA was employed to detect VERv in brain homogenates of in vivo infected sea bass and resulted positive in 22 of 32 samples, some of these with a high viral load estimates (about 1.1 × 10(8)  TCID50 per mL). The ELISA system we propose may be helpful in investigations where coupling of viral content in fish tissues with the presence of circulating VERv-specific IgM is required, or for use in samples where PCR is difficult to perform.

T cell transcripts and T cell activities in the gills of the teleost fish sea bass (Dicentrarchus labrax)

The gills of fish are a mucosal tissue that contains T cells involved in the recognition of non-self and pathogens, and in this work we describe some features of gill-associated T cells of European sea bass, a marine model species. A whole transcriptome was obtained by deep sequencing of RNA from unstimulated gills that has been analyzed for the presence of T cell-related transcripts. Of the putative expressed sequences identified in the transcriptome, around 30 were related to main functions related to T cells including Th1/Th2/Th17/Treg cell subpopulations, thus suggesting their possible presence in the branchial epithelium. The number of T cells in the gills of sea bass, measured with the specific T cell mAb DLT15 range from 10% to 20%, and IHC analysis shows their abundance and distribution in the epithelium. Leukocytes from gills are able to proliferate in the presence of lectins ConA and PHA, as measured by flow cytometry using CFSE fluorescence incorporation, and during proliferation the number of T cells counted by immunofluorescence increased. In lectin-proliferating cells the expression of T cell-related genes TRβ, TRγ, CD4, CD8α, CD45 and IL-10 increased dramatically. Our data represent a first analysis on T cell genes and on basic T cell activities of fish gills, and suggest the presence of functionally active subpopulations of T lymphocytes in this tissue.

Dietary fat differentially modulate the mRNA expression levels of oxidative mitochondrial genes in skeletal muscle of healthy subjects

BACKGROUND AND AIMS

Different types of dietary fats exert differential effects on glucose and lipid metabolism. Our aim was to evaluate the impact of different dietary fats on the expression of skeletal muscle genes regulating mitochondrial replication and function in healthy subjects.

METHODS AND RESULTS

Ten healthy subjects (age 29 ± 3 years; BMI 25.0 ± 3 kg/m(2)) received in a random order a test meal with the same energy content but different composition in macronutrients and quality of fat: Mediterranean (MED) meal, SAFA meal (Lipid 66%, saturated 36%) and MUFA meal (Lipid 63%, monounsaturated 37%). At fast and after 180 min, a fine needle aspiration was performed from the vastus lateralis for determination of mitochondrial gene expression by quantitative PCR. No difference in glucose and triglyceride response was observed between the three meals, while NEFA levels were significantly higher following fat-rich meals compared to MED meal (p < 0.002-0.0001). MED meal was associated with an increased expression, albeit not statistically significant, of some genes regulating both replication and function. Following MUFA meal, a significant increase in the expression of PGC1β (p = 0.02) and a reduction in the transcription factor PPARδ (p = 0.006) occurred with no change in the expression of COX and GLUT4 genes. In contrast, SAFA meal was associated with a marked reduction in the expression of COX (p < 0.001) PFK (p < 0.003), LPL (p = 0.002) and GLUT4 (p = 0.009) genes.

CONCLUSION

Dietary fats differentially modulate gene transcriptional profile since saturated, but not monounsaturated fat, downregulate the expression of genes regulating muscle glucose transport and oxidation.

Exercise as a new physiological stimulus for brown adipose tissue activity

BACKGROUND AND AIM

Brown adipose tissue (BAT) plays a major role in body energy expenditure counteracting obesity and obesity-associated morbidities. BAT activity is sustained by the sympathetic nervous system (SNS). Since a massive activation of the SNS was described during physical activity, we investigated the effect of endurance running training on BAT of young rats to clarify the role of exercise training on the activity and recruitment state of brown cells.

METHODS AND RESULTS

Male, 10-week-old Sprague Dawley rats were trained on a motor treadmill (approximately 60% of VO2max), 5 days/week, both for 1 and 6 weeks. The effect of endurance training was valuated using morphological and molecular approaches. Running training affected on the morphology, sympathetic tone and vascularization of BAT, independently of the duration of the stimulus. Functionally, the weak increase in the thermogenesis (no difference in UCP-1), the increased expression of PGC-1α and the membrane localization of MCT-1 suggest a new function of BAT. Visceral fat increased the expression of the FOXC2, 48 h after last training session and some clusters of UCP-1 paucilocular and multilocular adipocytes appeared.

CONCLUSION

Exercise seemed a weakly effective stimulus for BAT thermogenesis, but surprisingly, without the supposed metabolically hypoactive effects. The observed browning of the visceral fat, by a supposed white-to-brown transdifferentiation phenomena suggested that exercise could be a new physiological stimulus to counteract obesity by an adrenergic-regulated brown recruitment of adipocytes.

Aspects on the integrative actions of the brain from neural networks to "brain-body medicine"

"Integration" is a key term in describing how nervous system can perform high level functions. A first condition to have "integration" is obviously the presence of efficient "communication processes" among the parts that have to be combined into the harmonious whole. In this respect, two types of communication processes, called wiring transmission (WT) and volume transmission (VT), respectively, were found to play a major role in the nervous system, allowing the exchange of signals not only between neurons, but rather among all cell types present in the central nervous system (CNS). A second fundamental aspect of a communication process is obviously the recognition/decoding process at target level. As far as this point is concerned, increasing evidence emphasizes the importance of supramolecular complexes of receptors (the so called receptor mosaics) generated by direct receptor-receptor interactions. Their assemblage would allow a first integration of the incoming information already at the plasma membrane level. Recently, evidence of two new subtypes of WT and VT has been obtained, namely the tunnelling nanotubes mediated WT and the microvesicle (in particular exosomes) mediated VT allowing the horizontal transfer of bioactive molecules, including receptors, RNAs and micro-RNAs. The physiological and pathological implications of these types of communication have opened up a new field that is largely still unexplored. In fact, likely unsuspected integrative actions of the nervous system could occur. In this context, a holistic approach to the brain-body complex as an indissoluble system has been proposed. Thus, the hypothesis has been introduced on the existence of a brain-body integrative structure formed by the "area postrema/nucleus tractus solitarius" (AP/NTS) and the "anteroventral third ventricle region/basal hypothalamus with the median eminence" (AV3V-BH). These highly interconnected regions operate as specialized interfaces between the brain and the body integrating brain-borne and body-borne neural and humoral signals.

Proteomics-based investigation in C2C12 myoblast differentiation

Skeletal muscle cell differentiation is a multistage process extensively studied over the years. Even if great improvements have been achieved in defining biological process underlying myogenesis, many molecular mechanisms need still to be clarified.

To further highlight this process, we studied cells at undifferentiated, intermediate and highly differentiated stages, and we analyzed, for each condition, morphological and proteomic changes. We also identified the proteins that showed statistical significant changes by a ESI-Q-TOF mass spectrometer. This work provides further evidence of the involvement of particular proteins in skeletal muscle development. Furthermore, the high level of expression of many heat shock proteins, suggests a relationship between differentiation and cellular stress. Intriguingly, the discovery of myogenesis-correlated proteins, known to play a role in apoptosis, suggests a link between differentiation and this type of cell death.

Genomic profiling of carbohydrate metabolism in the ectomycorrhizal fungus Tuber melanosporum

• Primary carbohydrate metabolism plays a special role related to carbon/nitrogen exchange, as well as metabolic support of fruiting body development, in ectomycorrhizal macrofungi. In this study, we used information retrieved from the recently sequenced Tuber melanosporum genome, together with transcriptome analysis data and targeted validation experiments, to construct the first genome-wide catalogue of the proteins supporting carbohydrate metabolism in a plant-symbiotic ascomycete. • More than 100 genes coding for enzymes of the glycolysis, pentose phosphate, tricarboxylic acid, glyoxylate and methylcitrate pathways, glycogen, trehalose and mannitol metabolism and cell wall precursor were annotated. Transcriptional regulation of these pathways in different stages of the T. melanosporum lifecycle was investigated using whole-genome oligoarray expression data together with real-time reverse transcription-polymerase chain reaction analysis of selected genes. • The most significant results were the identification of methylcitrate cycle genes and of an acid invertase, the first enzyme of this kind to be described in a plant-symbiotic filamentous fungus. • A subset of transcripts coding for trehalose, glyoxylate and methylcitrate enzymes was up-regulated in fruiting bodies, whereas genes involved in mannitol and glycogen metabolism were preferentially expressed in mycelia and ectomycorrhizas, respectively. These data indicate a high degree of lifecycle stage specialization for particular branches of carbohydrate metabolism in T. melanosporum.

Two weekly sessions of combined aerobic and resistance exercise are sufficient to provide beneficial effects in subjects with Type 2 diabetes mellitus and metabolic syndrome

This study was performed to establish whether only 2 sessions per week of combined aerobic and resistance exercise are enough to reduce glycated hemoglobin (HbA(1c)) and to induce changes in skeletal muscle gene expression in Type 2 diabetes mellitus (DM2) subjects with metabolic syndrome. Eight DM2 subjects underwent a 1-yr exercise program consisting of 2 weekly sessions of 140 min that combined aerobic [at 55-70% of maximal oxygen uptake (VO(2max))] and resistance circuit training [at 60-80% of 1 repetition maximum (RM)]. The training significantly improved VO(2max) (from 33.5+/-3.8 ml/kg/min to 38.2+/-3.5 ml/kg/min, p=0.0085) and muscle strength (p<0.05). Changes over baseline were significant for HbA(1c), reduced by 0.45% (p=0.0084), fasting blood glucose (from 8.8+/-1.5 to 6.9+/-2.2 mmol/l, p=0.0132), waist circumference (from 98.9+/-4.8 to 95.9+/-4.6 cm, p=0.0054), body weight (from 87.5+/-10.7 to 85.7+/-10.1 kg, p=0.0375), systolic blood pressure (from 137+/-15 to 126+/-8 mmHg, p=0.0455), total cholesterol (from 220+/-24 to 184+/-13 mg/dl, p=0.0057), and LDL-cholesterol (from 150+/-16 to 105+/-15 mg/dl, p=0.0004). Mitochondrial DNA/nuclear DNA ratio at 6 and 12 months did not change. There was a significant increase of mRNA of peroxisome proliferator- activated receptor (PPAR)-gamma after 6 months of train - ing (p=0.024); PPARalpha mRNA levels were significantly increased at 6 (p=0.035) and 12 months (p=0.044). The mRNA quantification of other genes measured [mitochondrially encoded cytochrome c oxidase subunit II (MTCO2), cytochrome c oxidase subunit Vb (COX5b), PPARgamma coactivator 1alpha (PGC- 1alpha), glucose transporter 4 (GLUT 4), forkhead transcription factor BOX O1 (FOXO-1), carnitine palmitoyltransferase 1 (CPT-1), lipoprotein lipase (LPL), and insulin receptor substrate 1 (IRS-1)] did not show significant changes at 6 and 12 months. This study suggests that a twice-per-week frequency of exercise is sufficient to improve glucose control and the expression of skeletal muscle PPARgamma and PPARalpha in DM2 subjects with metabolic syndrome.

C2C12 myoblasts release micro-vesicles containing mtDNA and proteins involved in signal transduction

Micro-vesicles can be released by different cell types and operate as 'safe containers' mediating inter-cellular communication. In this work we investigated whether cultured myoblasts could release exosomes. The reported data demonstrate, for the first time, that C2C12 myoblasts release micro-vesicles as shown by the presence of two exosome markers (Tsg101 and Alix proteins). Using real-time PCR analysis it was shown that these micro-vesicles, like other cell types, carry mtDNA. Proteomic characterization of the released micro-vesicle contents showed the presence of many proteins involved in signal transduction. The bioinformatics assessment of the Disorder Index and Aggregation Index of these proteins suggested that C2C12 micro-vesicles mainly deliver the machinery for signal transduction to target cells rather than key proteins involved in hub functions in molecular networks. The presence of IGFBP-5 in the purified micro-vesicles represents an exception, since this binding protein can play a key role in the modulation of the IGF-1 signalling pathway. In conclusion, the present findings demonstrate that skeletal muscle cells release micro-vesicles, which probably have an important role in the communication processes within skeletal muscles and between skeletal muscles and other organs. In particular, the present findings suggest possible new diagnostic approaches to skeletal muscle diseases.

Bdnf expression in rat skeletal muscle after acute or repeated exercise

Brain derived growth factor (BDNF) gene of rat has a complex structure: at least four 5' untranslated exons regulated by different promoters and one 3' exon containing the encoding region. BDNF is expressed by skeletal muscles in an activity-dependent manner. In this study, BDNF mRNA was analysed by RT-PCR in the soleus muscle following a single (acute) session of running or a training of five days of running (repetitive exercise). Moreover, the expression of the exons was quantitatively analysed by real time RT-PCR. Finally, muscle BDNF protein level was evaluated by western blotting. BDNF mRNA was found to increase over the second day after acute exercise; on the other hand, two peaks (2 and 24 hours after the last session, respectively) in BDNF mRNA level were found after repetitive exercise, but it was similar to that of controls 6 hours after the last session. BDNF protein level progressively increased also after the mRNA went back to the basal level, so suggesting that it cumulates within the cell after acute exercise, whereas it followed the mRNA level time course after repetitive exercise. These results point to the following conclusions: BDNF mRNA is up-regulated by activity, but this response is delayed to the second day after acute exercise; repetitive exercise transiently depresses the expression of BDNF mRNA, so that the over-expression due to the previous day's exercise completely disappears 6 hours after the last exercise session.

Characterization and biological activity of the main flavonoids from Swiss Chard (Beta vulgaris subspecies cycla)

The molecular components of a phenolic fraction (P2), obtained from liquid chromatography of a Swiss Chard (Beta vulgaris subsp. cycla) extract, were identified using HPLC-ESI-MS/MS. The primary P2 components were: vitexin-2''O-rhamnoside, its demethylated form 2''-xylosylvitexin, isorhamnetin 3-gentiobioside, and rutin. P2 "in toto" and the single components were characterized for antioxidant capacity, antimitotic activity on MCF-7 human breast cancer cells and for toxicity to human lymphocytes and macrophages. P2 inhibited MCF-7 cell proliferation (IC(50) value = 9 microg/ml) without inducing apoptosis, showed no toxicity to human lymphocytes and slight toxicity to macrophages. Vitexin-2''O-rhamnoside strongly inhibited DNA synthesis in MCF-7 cells, whereas 2''-xylosylvitexin and isorhamnetin 3-gentiobioside were activators; combinations of activators and inhibitors maintained the over-all inhibitory effect.

Molecular characterisation of the small GTPase CDC42 in the ectomycorrhizal fungus Tuber borchii Vittad

The small GTPase CDC42 is ubiquitously expressed in eukaryotes, where it participates in the regulation of the cytoskeleton and a wide range of cellular processes, including cytokinesis, gene expression, cell cycle progression, apoptosis, and tumorigenesis. As very little is known on the molecular level about mycorrhizal morphogenesis and development and these events depend on a tightly regulated reorganisation of the cytoskeleton network in filamentous fungi, we focused on the molecular characterisation of the cdc42 gene in Tuber borchii Vittad., an ascomycetous hypogeous fungus forming ectomycorrhizae. The entire gene was isolated from a T. borchii cDNA library and Southern blot analyses showed that only one copy of cdc42 is present in the T. borchii genome. The predicted amino acid sequence is very similar to those of other known small GTPases and the similar domain structures suggest a similar function. Real-time PCR analyses revealed an increased expression of Tbcdc42 during the phase preparative to the instauration of symbiosis, in particular after stimulation with root exudate extracts. Immunolocalisation experiments revealed an accumulation of CDC42 in the apical tips of the growing hyphae. When a constitutively active Tbcdc42 mutant was expressed in Saccharomyces cerevisiae, morphological changes typical of pseudohyphal growth were observed. Our results suggest a fundamental role of CDC42 in cell polarity development in T. borchii.

The expression profile of the Tuber borchii nitrite reductase suggests its positive contribution to host plant nitrogen nutrition

Ectomycorrhizal symbiosis is a ubiquitous association between plant roots and numerous fungal species. One of the main aspects of the ectomycorrhizal association are the regulation mechanisms of fungal genes involved in nitrogen acquisition. We report on the genomic organisation of the nitrate gene cluster and functional regulation of tbnir1, the nitrite reductase gene of the ectomycorrhizal ascomycete Tuber borchii. The sequence data demonstrate that clustering also occurs in this ectomycorrhizal fungus. Within the TBNIR1 protein sequence, we identified three functional domains at conserved positions: the FAD box, the NADPH box and the two (Fe/S)-siroheme binding site signatures. We demonstrated that tbnir1 presents an expression pattern comparable to that of nitrate transporter. In fact, we found a strong down-regulation in the presence of primary nitrogen sources and a marked tbnir1 mRNA accumulation following transfer to either nitrate or nitrogen limited conditions. The real-time PCR assays of tbnir1 and nitrate transporter revealed that both nitrate transporter and nitrite reductase expression levels are about 15-fold and 10-fold higher in ectomycorrhizal tissues than in control mycelia, respectively. The results reported herein suggest that the symbiotic fungus Tuber borchii contributes to improving the host plant's ability to make use of nitrate/nitrite in its nitrogen nutrition.

The isoprenoid pathway in the ectomycorrhizal fungus Tuber borchii Vittad.: cloning and characterisation of the tbhmgr, tbfpps and tbsqs genes

The isoprenoid pathway of the ectomycorrhizal fungus Tuber borchii Vittad is investigated to better understand the molecular mechanisms at work, in particular during the maturation of the complex ascomata (the so-called "truffles"). Three T. borchii genes coding for the most important regulatory enzymes of the isoprenoid biosynthesis, 3-hydroxy-3-methylglutaryl-CoA reductase, farnesyl-diphosphate synthase (FPPS) and squalene synthase (SQS), were cloned and characterised. The analyses of their nucleotide and deduced amino acid sequences led us to identify the typical domains shown in homologous proteins. By using a quantitative real-time PCR the expression pattern of the three genes was analysed in the vegetative phase and during the complex ascoma maturation process, revealing an over-expression in the mature ascomata. The enzymatic activity of the T. borchii 3-hydroxy-3-methylglutaril-CoA reductase (HMGR) was investigated with a HPLC method, confirming that the significant isoprenoid biosynthesis in ripe ascomata proceeds not only via a transcriptional activation, but also via an enzyme activity control. These findings imply that isoprenoids play a fundamental role in Tuber ascomata, particularly in the last phases of their maturation, when they could be involved in antifungal or/and antimicrobial processes and contribute to the famous flavour of the truffle ascomata.

Molecular characterisation of a Tuber borchii Smt3 gene

Tbsmt3 gene from the ectomychorrizal fungus Tuber borchii was identified and sequenced. The Tbsmt3 gene encodes for a protein sharing significant amino acid homology with the yeast SMT3, a ubiquitin-like protein that is post-translationally attached to several proteins involved in many cellular processes. The comparison between the Tbsmt3 genomic and cDNA sequences established that the encoding sequence is interrupted by an intron of 312 bp. Southern blot analysis revealed only one copy of Tbsmt3 gene in the T. borchii genome. Tbsmt3 is expressed in all phases of T. borchii life cycle: mycelium, ectomycorrhiza and ascoma. However, the Tbsmt3 mRNA decreased during fruit body maturation.

Characterization and complementation of a Fus3/Kss1 type MAPK from Tuber borchii, TBMK

Mitogen-activated protein kinases (MAPK) are used by organisms to transduce extra cellular signals from the environment in cellular events such as proliferation and differentiation. In the present study, we have characterized the first MAPK from the ectomycorrhizal fungus Tuber borchii (TBMK) which belongs to the YERK1 (yeast extra cellular regulated kinase) subfamily. TBMK is present as a single copy in the genome and the codified protein was phosphorylated during the interaction with the host plant, Tilia americana. Complementation studies showed that TBMK restores pheromone signaling in Saccharomyces cerevisiae and partially restores invasive growth of Fusarium oxysporum that lack the fmk1 gene. This suggests a protein kinase activity and its involvement in the infection processes. Hence, TBMK could play an important role during the pre-symbiotic phase of T. borchii with its host plant in the modulation of genes necessary for the establishment of symbiosis leading to the synthesis of functional ectomycorrhizae.

Determination of microbial volatile organic compounds from Staphylococcus pasteuri against Tuber borchii using solid-phase microextraction and gas chromatography/ion trap mass spectrometry

The mycelium of Tuber borchii Vittad., a commercial truffle species, is used as a model system for in vitro ectomycorrhizal synthesis, infected seedling production and biotechnological applications. Our fungal cultures were accidentally contaminated with a Staphylococcus pasteuri strain, showing a strong antifungal activity against T. borchii mycelium. In order to identify the antifungal volatile agents produced by S. pasteuri, solid-phase microextraction (SPME) with gas chromatography and mass spectrometry (GC/MS) was used. Using this method 65 microbial volatile organic compounds (MVOCs), synthesized by this bacterium in either single or in fungal-bacterial dual culture, were identified. SPME combined with GC/MS may be a useful method for the determination of MVOCs involved in the antifungal activity. These results showed that bacteria with unusual biological activities could be a major problem during large-scale production of inoculum for truffle-infected seedling.

Differential gene expression during pre-symbiotic interaction between Tuber borchii Vittad. and Tilia americana L

Ectomycorrhizal formation is a highly regulated process involving the molecular reorganization of both partners during symbiosis. An analogous molecular process also occurs during the pre-symbiotic phase, when the partners exchange molecular signals in order to position and prepare both organisms for the establishment of symbiosis. To gain insight into genetic reorganization in Tuber borchii during its interaction with its symbiotic partner Tilia americana, we set up a culture system in which the mycelium interacts with the plant, even though there is no actual physical contact between the two organisms. The selected strategies, suppressive subtractive hybridisation and reverse Northern blots, allowed us to identify, for the first time, 58 cDNA clones differentially expressed in the pre-symbiotic phase. Sequence analysis of the expressed sequence tags showed that the expressed genes are involved in several biochemical pathways: secretion and apical growth, cellular detoxification, general metabolism and both mutualistic and symbiotic features.

A putative mitochondrial fission gene from the ectomycorrhizal ascomycete Tuber borchii Vittad.: cloning, characterisation and phylogeny

Mitochondrial binary division is a complex process occurring in multiple steps, mediated by several proteins. In Saccharomyces cerevisiae, a mitochondrial membrane protein, Fis1p, is required for the proper assembly of the mitochondrial division apparatus. In this study, we report the cloning, characterisation and phylogenetic analysis of Tbfis1, a gene from the ectomycorrhizal ascomycetous truffle Tuber borchii, encoding for an orthologue of S. cerevisiae Fis1p. The Tbfis1 coding region consists of a 468-nucleotide open reading frame interrupted by four introns, which encodes for a polypeptide of 155 amino acids, having a predicted transmembrane domain structure typical of the Fis1p Family. Southern blot analysis revealed that Tbfis1 is a single-copy gene in the T. borchii genome. Tbfis1 is highly expressed during the first stages of T. borchii fruit body ripening, while its expression decreases during T. borchii mycelium ageing. Also, Virtual Northern blot analysis revealed Tbfis1 expression in the symbiotic phase of the fungus life cycle. Phylogenetic analysis allowed the identification of Tbfis1 orthologues in filamentous fungi, yeasts, plants, worms, flies and mammals, indicating that the function of the protein coded by this gene has been conserved during evolution.

Characterization of the Tuber borchii nitrate reductase gene and its role in ectomycorrhizae

The nitrate assimilation pathway represents a useful model system in which to study the contribution of a mycorrhizal fungus to the nitrogen nutrition of its host plant. In the present work we cloned and characterized the nitrate reductase gene (tbnr1) from Tuber borchii. The coding region of tbnr1 is 2,787 nt in length, and it encodes a protein of 929 amino acids. Biochemical and Northern-blot analyses revealed that nitrate assimilation in T. borchii is an inducible system that responds mainly to nitrate. Furthermore, we cloned a nitrate reductase cDNA (tpnr1) from Tilia platyphyllos to set up a quantitative real-time PCR assay that would allow us to determine the fungal contribution to nitrate assimilation in ectomycorrhizal tissue. Using this approach we demonstrated that the level of tbnr1 expression in ectomycorhizae is eight times higher than in free-living mycelia, whereas tpnr1 transcription was found to be down-regulated after the establishment of the symbiosis. Enzymatic assays showed that NADPH-dependent nitrite formation markedly increases in ectomycorrhizae. These findings imply that the fungal partner plays a fundamental role in nitrate assimilation by ectomycorrhizae. Amino acid determination by HPLC revealed higher levels of glutamate, glutamine and asparagine in symbiotic tissues compared with mycelial controls, thus suggesting that these amino acids may represent the compounds that serve to transfer nitrogen to the host plant.

Solid-phase microextraction gas chromatography/ion trap mass spectrometry and multistage mass spectrometry experiments in the characterization of germacrene D

Germacrene D is a vegetable pheromone utilized in interactions among organisms belonging to different species. For the first time, using solid-phase microextraction/gas chromatography/ion trap mass spectrometry, the presence of this compound was detected in an in vitro mycorrhizal synthesis system where the mycelium of the ectomycorrhizal fungus Tuber borchii Vittad. interacts with the plant Tilia Americana L. From this symbiosis, a new structure, called ectomycorrhiza, is formed where the two symbionts exchange nutrients and metabolites. It seems that only after this interaction can the mycelium develop the fruitbody, commonly known as truffle. The results obtained allowed us to ascertain that germacrene D was synthesized by the plant exclusively in the presence of T. borchii. The originality of these data prompted us to hypothesize that this compound could be involved in the first step of ectomycorrhiza formation, as it is able to stimulate specific fungi receptors. In fact, plants release hundreds of secondary metabolites that are important in their interactions with other organisms.

Comparative study and molecular characterization of ectomycorrhizas in Tilia americana and Quercus pubescens with Tuber brumale

Mycorrhizas of Tuber brumale on Quercus pubescens and Tilia americana were obtained in vitro using micropropagated plantlets. Mycelium pure cultures were used for inoculation. Both the mycelium used for the inoculations, as well as the mycorrhizas which were obtained, were identified using several molecular approaches: analysis of the ITS region, polymerase chain reaction (PCR) specific primers and sequencing. The mycorrhizas were described from a morphological standpoint. Some of their biometric characteristics were different in bass-wood than they were in oak, thus showing the influence of the host plant on several of the morphological features believed to be necessary for the identification of the species. Considering the variability of their morphological characteristics, molecular analysis proved to be a necessary tool for the recognition of the mycorrhizas of Tuber spp.

Morphological and molecular characterization of mycelia of some Tuber species in pure culture

•  Pure cultures of Tuber maculatum , Tuber melanosporum , Tuber aestivum , Tuber macrosporum , Tuber rufum and Tuber brumale were isolated and characterized by morphological and molecular methods. •  The Tuber mycelia were isolated from fruit bodies and molecular identification was performed using specific primers, restriction fragment length polymorphism and/or sequence analyses of the ITS region. •  The species grew between 1.1 mm wk ^-1 and 14 mm wk ^-1 on the selected medium. The mycelium of different Tuber species showed several common morphological features such as hyphal anastomoses, vesicle formation and hyphal aggregation. Differences were found in the frequency of these morphological features and in the hyphal pattern. The isolated mycelia also showed differences in the hyphal branch angle, septal distance, hyphal diameter and rate of growth of the hyphae. •  This result opens the possibility of using pure mycelial cultures of Tuber spp. for experimental purposes and for the commercial production of infected truffle plants.

Identification of differentially expressed cDNA clones in Tilia platyphyllos-Tuber borchii ectomycorrhizae using a differential screening approach

No information is presently available on the molecular mechanisms that control the morphogenesis of the truffle, an ectomycorrhizal ascomycetous fungus of great economic interest not only for forestry and agronomy but also for the organoleptic properties of its hypogeous fruitbodies. A Tilia platyphyllos- Tuber borchii model system was used in order to identify genes induced or up-regulated during symbiosis, since their isolation is a prerequisite for the understanding of the molecular bases of mycorrhizal development and regulation. The strategy applied involved the construction of an ectomycorrhizal cDNA library and random selection of clones, followed by a differential screening procedure to analyse cDNA expression in uninfected roots, ectomycorrhizae and free-living mycelia. The results revealed that many genes - and more plant genes than fungal genes - are expressed at higher levels during the symbiotic phase. Several clones were also investigated in order to understand their biological function. This study represents the first attempt to extend our knowledge of the molecular mechanisms underlying the establishment of ectomycorrhiza in Tuber species.

Cloning and characterisation of a polyubiquitin gene from the ectomycorrhizal fungus Tuber borchii vittad

Ubiquitin is a highly conserved 76-amino acid protein implicated in the function of quite different vital cellular processes. In the present study, we cloned and sequenced a polyubiquitin gene from Tuber borchii (Ubil) that is organised in four tandem repeats, with two C-terminal extension amino acids, serine and leucine. Two introns of 116 bp and 55 bp in length were detected in the first and second repeats, respectively. The Ubil gene is highly expressed in mycelium and is less expressed in the ripe fruiting body. Southern and Northern blot analyses revealed a second form of the ubiquitin gene.

Cloning, expression, and characterization of the hxk-1 Gene from the white truffle Tuber borchii vittad.: A first step toward understanding sugar metabolism

Recent biochemical investigations of Tuber borchii Vittad. mycelium have demonstrated the presence of three distinct forms of hexokinase (HK(M1), HK(M2), and HKM3). In the investigation described here, a gene coding for hexokinase (hxk-1) from T. borchii was isolated and characterized. The hxk-1 gene is characterized by an ORF of 1494 nucleotides and codes for a polypeptide of 497 aa. The gene was overexpressed in Escherichia coli, and the recombinant protein was kinetically characterized. The K(cat) value for fructose is in agreement with the data reported for the hexokinase of Yarrowia lipolytica, the Km for ATP is not dependent on the sugar used, and the enzyme is not inhibited by trehalose 6-phosphate or glucose 6-phosphate. The biochemical characteristics confirm that this enzyme is a hexokinase, as suggested by the Pileup results, and it corresponds to the HKM1 isoform. This work represents the first characterization of the key enzyme of the glycolytic pathway and the related gene in a Tuber species.

One-step purification of a fully active hexahistidine-tagged human hexokinase type I overexpressed in Escherichia coli

The conversion of glucose into glucose 6-phosphate (Glc 6-P)1 traps glucose in a chemical state in which it cannot leave the cell and hence commits glucose to metabolism. In human tissues there are at least three hexokinase isoenzymes responsible for hexose phosphorylation. These enzymes are constituted by a single polypeptide chain with a molecular weight of approximately 100 kDa. Among these isoenzymes, hexokinase type I is the most widely expressed in mammalian tissues and shows reversion of Glc 6-P inhibition by physiological levels of inorganic phosphate. In this work the hexokinase I from human brain was overexpressed in Escherichia coli, as a hexahistidine-tagged protein with the tag extending the C-terminal end. An average of 900 U per liter of culture was obtained. The expressed protein was one-step purified by metal chelate affinity chromatography performed in NTA-agarose column charged with Ni(2+) ions. In order to stabilize the enzymatic activity 0.5 M ammonium sulfate was added to elution buffer. The specific activity of purified hexokinase I was 67.8 U/mg. The recombinant enzyme shows kinetic properties in agreement with those described for the native enzyme, and thus it can be used for biophysical and biochemical investigation.

Possible involvement of Pseudomonas fluorescens and Bacillaceae in structural modifications of Tuber borchii fruit bodies

Previous studies on Tuber borchii fruit bodies in early maturation stages suggested a role of bacteria in sporocarp structural modifications. In order to verify this hypothesis, in the present study we investigated by means of microbial and ultrastructural approaches, the bacterial population of T. borchii sporocarps from intermediate maturation phases to advanced decomposition stages, paying particular attention to chitinolytic and cellulolytic bacteria and to their relationships with ascii and ascospores. We found that Pseudomonas fluorescens and spore-forming Bacillaceae, both able to degrade cellulose and chitin, are present inside the sporocarps in all maturation stages investigated. Moreover, rod-shaped bacteria seem able to erode ascus walls and colonize the interior of ascii containing mature spores. These results suggest a possible role of these bacteria in the process of ascus opening. Moreover, the presence of P. fluorescens and Bacillaceae on isolated mature spores after decontamination suggests an intimate association between these bacteria and the ascospores.

Effects of different carbohydrate sources on the growth of Tuber borchii Vittad. mycelium strains in pure culture

The influence of carbohydrate utilisation on the growth of three strains of Tuber borchii Vittad. mycelium (1BO, 17BO and 10RA) in culture was assessed using culture media containing glucose (control), mannose or mannitol. Mannose was the best substrate for growth of the strains and this was particularly evident for strain 17BO. Mannitol instead was metabolized only by 10RA and 1BO. In order to explain the different growth trends, analyses of enzyme levels, kinetic parameters, protein patterns and the morphology of the three strains were carried out. Our results show that these strains of T. borchii mycelium were affected by the substrates used in the media. The aim of the present work was to optimise the in vitro production of T. borchii mycelium for use in experiments which require the fungus in precise and reproducible conditions, such as mycorrhizal synthesis or protein and nucleic acid extractions.

Morphological and molecular characterisation of Pulvinula constellatio ectomycorrhizae

The ascomycete Pulvinula constellatio was found to form competing ectomycorrhizal relationships with plants that had been inoculated with Tuber spp. and other edible ectomycorrhizal fungi. In order to be able to distinguish P. constellatio mycorrhizae from those of the Tuber spp., we determined the morphological and bio-molecular characteristics of P. constellatio. The complete sequence of the ITS regions was determined, in order to select specific primers. The ITS region was also studied using restriction fragment length polymorphism analyses with several restriction enzymes that allowed an unambiguous identification of the species.

Immunolocalization of hydrophobin HYDPt-1 from the ectomycorrhizal basidiomycete Pisolithus tinctorius during colonization of Eucalyptus globulus roots

•  The immunolocalization of one of the hydrophobins of Pisolithustinctorius (HYDPt-1) is reported. Hydrophobin proteins play key roles in adhesion and aggregation of fungal hyphae, and it is already known that formation of ectomycorrhizas on eucalypt roots enhances the accumulation of hydrophobin mRNAs in the mycelium of Pisolithus tinctorius. •  Purification of SDS-insoluble proteins from the mycelium of P. tinctorius showed the presence of a 13 kDa polypeptide with properties of class I hydrophobin. •  Polyconal antibodies were raised against a recombinant HYDPt-1 polypeptide, and these were used for immunofluorescence-coupled transmission electron microscopy. •  HYDPt-1 is a cell wall protein located at the surface of the hyphae with no preferential accumulation in the fungal cells of the different tissues of the ectomycorrhiza (i.e. extraradical hyphae, mantle or Hartig net).

Phylogenetic characterization and in situ detection of a Cytophaga-Flexibacter-Bacteroides phylogroup bacterium in Tuber borchii vittad. Ectomycorrhizal mycelium

Mycorrhizal ascomycetous fungi are obligate ectosymbionts that colonize the roots of gymnosperms and angiosperms. In this paper we describe a straightforward approach in which a combination of morphological and molecular methods was used to survey the presence of potentially endo- and epiphytic bacteria associated with the ascomycetous ectomycorrhizal fungus Tuber borchii Vittad. Universal eubacterial primers specific for the 5' and 3' ends of the 16S rRNA gene (16S rDNA) were used for PCR amplification, direct sequencing, and phylogenetic analyses. The 16S rDNA was amplified directly from four pure cultures of T. borchii Vittad. mycelium. A nearly full-length sequence of the gene coding for the prokaryotic small-subunit rRNA was obtained from each T. borchii mycelium studied. The 16S rDNA sequences were almost identical (98 to 99% similarity), and phylogenetic analysis placed them in a single unique rRNA branch belonging to the Cytophaga-Flexibacter-Bacteroides (CFB) phylogroup which had not been described previously. In situ detection of the CFB bacterium in the hyphal tissue of the fungus T. borchii was carried out by using 16S rRNA-targeted oligonucleotide probes for the eubacterial domain and the Cytophaga-Flexibacter phylum, as well as a probe specifically designed for the detection of this mycelium-associated bacterium. Fluorescent in situ hybridization showed that all three of the probes used bound to the mycelium tissue. This study provides the first direct visual evidence of a not-yet-cultured CFB bacterium associated with a mycorrhizal fungus of the genus Tuber.

Identification of Tuber borchii Vittad. mycelium proteins separated by two-dimensional polyacrylamide gel electrophoresis using amino acid analysis and sequence tagging

This paper reports the first results in the proteome analysis of Tuber borchii Vittad. mycelium, an ectomycorrhizal fungus poorly defined genetically, but known for its generation of edible fruit bodies known as white truffles. Employing isoelectric focusing on immobilized pH gradients, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, we obtained an electropherogram presenting over 800 spots within the window of isoelectric points (pI) 3.5-9 and a molecular mass of 10-200 kDa. Different reducing agents were tested in the sample preparation buffers, and the standard lysis buffer plus 2% w/v polyvinylpolypyrrolidone allowed the best solubilization and resolution of the proteins. The T. borchii proteins separated in micropreparative gels were electroblotted onto polyvinylidene difluoride membranes and visualized by Coomassie staining. Twenty-three proteins were excised and analyzed by the combination of amino acid and N-terminal analysis. One protein was identified by matching its amino acid composition, estimated isoelectric point and molecular mass against the SWISS-PROT and EMBL databases. Four spots were successfully tagged by Edman microsequencing but no homologous sequences were found in databases.

Multiplex PCR for the identification of white Tuber species

Species-specific primers selected from the internal transcribed spacer region sequence were used to set up a multiplex polymerase chain reaction (PCR) able to simultaneously identify the white truffle species Tuber magnatum, Tuber borchii, Tuber maculatum and Tuber puberulum. Furthermore, a primer specific for the competitive fungus Sphaerosporella brunnea was designed and added to the multiplex PCR set, allowing the detection of the Tuber species and the contaminant fungus in a one-step reaction.

Estimation of fungal biomass and transcript levels in Tilia platyphyllos-Tuber borchii ectomycorrhizae

Very little information is available to date about the complex truffle life cycle which involves the succession of three developmental phases. In order to gain more knowledge about ectomycorrhizal formation and fruit body development an ectomycorrhizal model system was used to study fungal biomass and plant and fungal transcript levels. They were evaluated in ectomycorrhizal development using the ergosterol assay and the internal transcribed spacer-5.8S ribosomal DNA from Tilia platyphyllos and Tuber borchii as molecular probes respectively. The results obtained from different approaches revealed a decrease in fungal biomass, transcript and protein levels during ectomycorrhizal development.

In vitro effects of 50 Hz magnetic fields on oxidatively damaged rabbit red blood cells

The aim of this study was to investigate the effects of 50 Hz magnetic fields (0.2-0.5 mT) on rabbit red blood cells (RBCs) that were exposed simultaneously to the action of an oxygen radical-generating system, Fe(II)/ascorbate. Previous data obtained in our laboratory showed at the exposure of rabbit erythrocytes or reticulocytes to Fe(II)/ascorbate hexokinase inactivation, whereas the other glycolytic enzymes do not show any decay. We also observed depletion of reduced glutathione (GSH) content with a concomitant intracellular and extracellular increase in oxidized glutathione (GSSG) and a decrease in energy charge. In this work we investigated whether 50 Hz magnetic fields could influence the intracellular impairments that occur when erythrocytes or reticulocytes are exposed to this oxidant system, namely, inactivation of hexokinase activity, GSH depletion, a change in energy charge, and hemoglobin oxidation. The results obtained indicate the a 0.5 mT magnetic field had no effect on intact RBCs, whereas it increased the damage with Fe(II)/ascorbate to a 0.5 mT magnetic field induced a significant further decay in hexokinase activity (about 20%) as well as a twofold increase in methemoglobin production compared with RBCs that were exposed to the oxidant system alone. Although further studies will be needed to determine the physiological implications of these data, the results reported in this study demonstrate that the effects of the magnetic fields investigated are able to potentiate the cellular damage induced in vitro by oxidizing agents.