Epulorhiza epiphytica sp. nov. isolated from mycorrhizal roots of epiphytic orchids in Brazil

 Epulorhiza epiphytica sp. nov. isolated from the roots of two Brazilian native epiphytic orchid species is described. In culture, it differs from the known species of Epulorhiza in the minute size of monilioid cells with foveate surfaces. This is the first report of an orchid mycorrhizal fungus from Brazil

Small heat shock proteins in the development of thermotolerance in Pisolithus sp.

Small heat shock proteins (HSPs) have been shown to confer thermotolerance in many organisms. Here, we demonstrate that small HSPs (sHSPs) can also be involved in development of thermotolerance in Pisolithus sp. In heat shock response, Pisolithus isolate RV82 synthesized proteins of molecular mass 28, 26 and 15–18 kDa. These group of proteins are synthesized when mycelial mass are exposed to heat shock temperature (42 °C) for short period (30 min) and incubated back at 28 °C, the optimal temperature for growth. Our results show sHSPs are an important biochemical alteration in ectomycorrhizal fungi under thermal stress

In vivo bioavailability of selenium in enriched Pleurotus ostreatus mushrooms

The in vivo bioavailability of Se was investigated in enriched Pleurotus ostreatus mushrooms. A bioavailability study was performed using 64 Wistar male rats separated in 8 groups and fed with different diets: without Se, with mushrooms without Se, with enriched mushrooms containing 0.15, 0.30 or 0.45 mg kg(-1) Se and a normal diet containing 0.15 mg kg(-1) of Se using sodium selenate. The experiment was performed in two periods: depletion (14 days) and repletion (21 days), according to the Association of Official Analytical Chemists. After five weeks, the rats were sacrificed under carbon dioxide, and blood was drawn by heart puncture. Blood plasma was separated by centrifugation. The total Se concentration in the plasma of rats fed with enriched mushrooms was higher than in rats fed with a normal diet containing sodium selenate. The plasma protein profiles were obtained using size exclusion chromatography (SEC) and UV detectors. Aliquots of effluents (0.5 mL per minute) were collected throughout in the end of the chomatographic column. However, Se was determined by graphite furnace atomic absorption spectrometry (GF AAS) only in the aliquots where proteins were detected by SEC-UV. The plasma protein pro. le of rats fed with different diets was similar. The highest Se concentration was observed in a peptide presenting 8 kDa. Furthermore, the higher Se concentration in this peptide was obtained for rats fed with a diet using enriched mushrooms (7 mu g L(-1) Se) compared to other diets (2-5 mu g L(-1) Se). These results showed that Se-enriched mushrooms can be considered as an alternative Se food source for humans, due to their high bioavailability

A pH signaling mechanism involved in the spatial distribution of calcium and anion fluxes in ectomycorrhizal roots

Mycorrhization is a typical example of a host–pathogen symbiotic interaction where the pathogen cell biology and the host immune response coevolved several functional links. Here, the role played by ion fluxes across the root concerning nutrient uptake, osmoregulation, growth and signaling events is addressed. An ion‐selective vibrating probe system was used to determine the net fluxes of protons (H+), calcium (Ca2+) and anions (A−) along nonmycorrhizal and ectomycorrhizal (ECM) roots of Eucalyptus globulus colonized by Pisolithus sp. These data show that, from five root zones analyzed, the main effect of fungal colonization was localized to the elongation zone. Here, strong changes in ion dynamics and rhizosphere acidification capacity were observed. Additionally, ion fluxes exhibited periodic fluctuations. To verify whether these fluctuations corresponded to sustained oscillations, continuous wavelet time spectrum analysis was applied and it was determined that H+ and A− fluxes from ECM roots had longer periods than nonmycorrhizal roots. By contrast, Ca2+ oscillations were completely abolished following fungal interaction. These results are interpreted in the light of a working model in which nutrient uptake and stimulation of growth are mediated by ECM fungi and may be pH‐dependent. Furthermore, the variations detected in ECM roots for H+ and A− fluxes suggest a main contribution from the plant, while the results obtained for Ca2+ point to a significant involvement of the fungus

Enrichment of Pleurotus ostreatus mushrooms with selenium in coffee husks

Pleurotus ostreatus fungus forms an edible mushroom that possesses important nutritional and medicinal properties. Selenium (Se) is essential to human diets and it is in low concentration in the soil, and consequently in food. P. ostreatus was grown in coffee husks enriched with various concentrations of sodium selenite. The biological efficiency of P. ostreatus was affected by the addition of high concentrations of Se. The highest level of Se absorption was obtained by adding 51 mg kg(1) of sodium selenite. The mushrooms from first flush contained more Se than the further flushes. These results demonstrate the great potential of coffee husks in the production of Se-enriched mushrooms and show the ability of this fungus to absorb and biomagnify Se. (C) 2011 Elsevier Ltd. All rights reserved.Brazilian Agency: CNPqBrazilian agency CAPESBrazilian agency FAPEMI

Polymorphism in the internal transcribed spacer (ITS) of the ribosomal DNA of 26 isolates of ectomycorrhizal fungi

Inter- and intraspecific variation among 26 isolates of ectomycorrhizal fungi belonging to 8 genera and 19 species were evaluated by analysis of the internal transcribed sequence (ITS) of the rDNA region using restriction fragment length polymorphism (RFLP). The ITS region was first amplified by polymerase chain reaction (PCR) with specific primers and then cleaved with different restriction enzymes. Amplification products, which ranged between 560 and 750 base pairs (bp), were obtained for all the isolates analyzed. The degree of polymorphism observed did not allow proper identification of most of the isolates. Cleavage of amplified fragments with the restriction enzymes Alu I, Hae III, Hinf I, and Hpa II revealed extensive polymorphism. All eight genera and most species presented specific restriction patterns. Species not identifiable by a specific pattern belonged to two genera: Rhizopogon (R. nigrescens, R. reaii, R. roseolus, R. rubescens and Rhizopogon sp.), and Laccaria (L. bicolor and L. amethystea). Our data confirm the potential of ITS region PCR-RFLP for the molecular characterization of ectomycorrhizal fungi and their identification and monitoring in artificial inoculation programs