Browsing by Author "Mancilla, Rodrigo A."

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    Effect of manganese on the secretion of manganese-peroxidase by the basidiomycete Ceriporiopsis subvermispora
    (2010) Mancilla, Rodrigo A.; Canessa, Paulo; Manubens, Augusto; Vicuna, Rafael
    The ligninolytic machinery of the widely used model fungus Ceriporiopsis subvermispora includes the enzymes manganese-peroxidase (MnP) and laccase (Lcs). In this work the effect of Mn(II) on the secretion of MnP was studied. Cultures grown in the absence of Mn(II) showed high levels of mnp transcripts. However, almost no MnP enzyme was detected in the extracellular medium, either by enzymatic activity assays or Western blot hybridizations. In the corresponding mycelia, immuno-electron microscopy experiments showed high levels of MnP enzyme within intracellular compartments. These results suggest that in addition to its well-known effect on transcription regulation of mnp genes, manganese influences secretion of MnP to the extracellular medium. Experiments carried out in the presence of cycloheximide confirmed that the metal is required to secrete MnP already synthesized and retained within the cell. (C) 2010 Elsevier Inc. All rights reserved.
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    Expression of genes encoding laccase and manganese-dependent peroxidase in the fungus Ceriporiopsis subvermispora is mediated by an ACE1-like copper-fist transcription factor
    (2009) Miguel Alvarez, Jose; Canessa, Paulo; Mancilla, Rodrigo A.; Polanco, Ruben; Santibanez, Paulina A.; Vicuna, Rafael
    The effect of copper on the expression of genes encoding the ligninolytic enzymes laccase (ICS) and manganese peroxidase (mnp) in Ceriporiopsis subvermispora was evaluated. This metal increased transcript levels of lcs, mnp1 and mnp2. This finding was not unexpected in the case of lcs, since its promoter contains a putative ACE element. Originally characterized in the yeast Saccharomyces cerevisiae, ACE is the target sequence of the ACE1 copper-responsive transcription factor in this microorganism. Analysis of the promoter regions of mnp genes revealed the presence of formerly unnoticed ACE elements. Based on the ace1 gene from Phanerochaete chrysosporium, we isolated and characterized an ACE1-like transcription factor from C. subvermispora (Cs-ACE1) through complementation of a S. cerevisiae ace1 Delta strain. Surprisingly, ACE1 factors from both basidiomycetes exhibit substantial differences, not only structurally but also in their ability to complement the aforementioned yeast strain. Specific binding of Cs-ACE1 to its cognate DNA sequence was confirmed by electrophoretic mobility-shift assays. (C) 2008 Elsevier Inc. All rights reserved.
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    Hydroquinone and H2O2 differentially affect the ultrastructure and expression of ligninolytic genes in the basidiomycete Ceriporiopsis subvermispora
    (2009) Amoroso, Alejandro; Mancilla, Rodrigo A.; Gonzalez, Bernardo; Vicuna, Rafael
    The biodegradation of lignin is a highly oxidative process in which various oxidases and peroxidases play a major role. During lignin decay, the generation of aromatic compounds and reactive oxygen species leads to oxidative stress. In this work, the effect of the oxidative compounds H2O2 and hydroquinone in the ligninolytic fungus Ceriporiopsis subvermispora was studied, both at the ultrastructural and at the transcriptional level. Transmission electron microscopy revealed the presence of microvesicles and extensive cytoplasm degeneration after incubation with hydroquinone, but not with H2O2. Studies of the intracellular redox state of the fungus showed that hydroquinone causes a transient decrease in the reduced glutathione/oxidized glutathione (GSH/GSSG) ratio and an increase in the glutathione-S-transferase mRNA levels. These results suggest that hydroquinone produces oxidative stress in this microorganism. On the other hand, it was observed that hydroquinone, but not H2O2, affects Mn-dependent peroxide and laccase transcripts levels. We propose that the mechanism by which the fungus reacts against oxidative stress contributes to its selectivity toward lignin during wood decay.
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    Hypolithic Cyanobacteria Supported Mainly by Fog in the Coastal Range of the Atacama Desert
    (2011) Azua-Bustos, Armando; Gonzalez-Silva, Carlos; Mancilla, Rodrigo A.; Salas, Loreto; Gomez-Silva, Benito; McKay, Christopher P.; Vicuna, Rafael
    The Atacama Desert is one of the driest places on Earth, with an arid core highly adverse to the development of hypolithic cyanobacteria. Previous work has shown that when rain levels fall below similar to 1 mm per year, colonization of suitable quartz stones falls to virtually zero. Here, we report that along the coast in these arid regions, complex associations of cyanobacteria, archaea, and heterotrophic bacteria inhabit the undersides of translucent quartz stones. Colonization rates in these areas, which receive virtually no rain but mainly fog, are significantly higher than those reported inland in the hyperarid zone at the same latitude. Here, hypolithic colonization rates can be up to 80%, with all quartz rocks over 20 g being colonized. This finding strongly suggests that hypolithic microbial communities thriving in the seaward face of the Coastal Range can survive with fog as the main regular source of moisture. A model is advanced where the development of the hypolithic communities under quartz stones relies on a positive feedback between fog availability and the higher thermal conductivity of the quartz rocks, which results in lower daytime temperatures at the quartz-soil interface microenvironment.