Light induces oxidative damage and protein stability in the fungal photoreceptor Vivid

"Flavin-binding photoreceptor proteins sense blue-light (BL) in diverse organisms and have become core elements in recent optogenetic applications. The light-oxygen-voltage (LOV) protein Vivid (VVD) from the filamentous fungus Neurospora crassa is a classic BL photoreceptor, characterized by effecting a photocycle based on light-driven formation and subsequent spontaneous decay of a flavin-cysteinyl adduct. Here we report that VVD presents alternative outcomes to light exposure that result in protein self-oxidation and, unexpectedly, rise of stability through kinetic control. Using optical absorbance and mass spectrometry we show that purified VVD develops amorphous aggregates with the presence of oxidized residues located at the cofactor binding pocket. Light exposure increases oxidative levels in VVD and specific probe analysis identifies singlet oxygen production by the flavin. These results indicate that VVD acts alternatively as a photosensitizer, inducing self-oxidative damage and subsequent aggregation. Surprisingly, BL illumination has an additional, opposite effect in VVD. We show that light-induced adduct formation establishes a stable state, delaying protein aggregation until photoadduct decay occurs. In accordance, repeated BL illumination suppresses VVD aggregation altogether. Furthermore, photoadduct formation confers VVD stability against chemical denaturation. Analysis of the aggregation kinetics and testing of stabilizers against aggregation reveal that aggregation in VVD proceeds through light-dependent kinetic control and dimer formation. These results uncover the aggregation pathway of a photosensor, where light induces a remarkable interplay between protein damage and stability.

Community of thermoacidophilic and arsenic resistant microorganisms isolated from a deep profile of mine heaps

"Soluble arsenic (As) in acidic feed solution may inhibit the copper (Cu) bioleaching process within mine heaps. To clarify the effect of soluble arsenic on the live biomass and bioxidative activity in heaps, toxicological assays were performed using a synthetic feed solution given by a mine company. The microorganisms had previously been isolated from two heap samples at up to 66 m depth, and cultured using specific media for chemolithotrophic acidophiles (pH 1-2) and moderate thermophiles (48 degrees C), for arsenic tolerance assay. The four media with the highest biomass were selected to assay As-resistance; one culture (Q63h) was chosen to assay biooxidative activity, using a heap sample that contained chalcopyrite and covellite. We found that 0.5 g/L of As does not affect living biomass or biooxidative activity on Cu sulfides, but it dissolves Cu, while As precipitates as arsenic acid (H3AsO4 center dot 1/2H(2)O). The arsenic tolerant community, as identified by 16S rDNA gene sequence analysis, was composed of three main metabolic groups: chemolithotrophs (Leptospirillum, Sulfobacillus); chemolithoheterotrophs and organoheterotrophs as Acidovorax temperans, Pseudomonas alcaligenes, P. mendocina and Sphingomonas spp. Leptospirillum spp. and S. thermosulfidooxidans were the dominant taxa in the Q63-66 cultures from the deepest sample of the oldest, highest-temperature heap. The results indicated arsenic resistance in the microbial community, therefore specific primers were used to amplify ars (arsenic resistance system), aio (arsenite oxidase), or arr (arsenate respiratory reduction) genes from total sample DNA. Presence of arsB genes in S. thermosulfidooxidans in the Q63-66 cultures permits H3AsO4-As(V) detoxification and strengthens the community's response to As.

The influence of phosphate limitation on conidiation in Trichoderma atroviride and light blind mutants

"Los eventos moleculares asociados a la conidiación inducida por luz en Trichoderma están regulados por el complejo formado por las proteínas BLR-1 y BLR-2, donde la primera actúa como fotorreceptor y ambas tienen actividad como factor de transcripción. Las cepas mutantes nulas en los genes blr de T. atroviride pierden la capacidad de responder al estímulo luminoso y son consideradas "mutantes ciegas". La limitación de algunos nutrientes esenciales también desencadenan la conidiación en T. atroviride. La influencia de bajas concentraciones de fosfato inorgánico (Pi) en el medio de cultivo sobre la fotoconidiación de la cepa silvestre y las mutantes blr de T. atroviride fue probada. Todas las cepas utilizadas mostraron el desarrollo de conidias bajo concentraciones limitantes de Pi (hasta 0.1 mM) en ausencia de la luz. Los resultados indican que la limitación de Pi es un factor desencadenante del proceso de conidiación a través de una vía independiente a la mediada por las proteínas BLR.""Molecular events associated with photoconidiation of Trichoderma are regulated by the BLR-1 and BLR-2 protein complex, where the first plays an essential role as sensor, and both function as a transcriptional factor. Null mutant strains of blr genes in T. atroviride are unable to respond to light stimulation and are then considered blind mutants. Limited concentration of essential nutrients in the media is a condition that triggers conidiation in T. atroviride. In the present study we show the influence of limited concentration of inorganic phosphate (Pi) in the media on photoconidiation in T. atroviride and two blr null mutants. All strains tested showed the development of conidial structures when low levels of Pi (0.1 mM) were present in the absence of light. The data showed that sensing environmental cues such as phosphate limitation is independent of BLR proteins pathway.

Matas de microalgas termófilas que crecen sobre la estructura de madera de una torre de enfriamiento de una central termoeléctrica en el centro de México

"The aims of this research are to identify and describe a periphyton community of thermophilic microalgae in order to expand our knowledge on biodiversity of a particular environment. Conspicuous biomass of thermophilic microalgae (48 °C) inhabits the cooling towers of the thermoelectric power plant of Villa de Reyes (Central Mexico). Aggregate samples or microalgal mats were taken in three different areas of the top of a cooling tower, for identification. According to the sequencing analysis of 16S and 18S rDNA genes, the community is dominated by 3 species of Cyanoprokaryota: Chlorogloeopsis fritschii, Arthronema africanum and Chroococcidiopsis sp., previously reported as thermophiles. Also, 2 species of the Chlorophyte or green algae Scenedesmus. Finally, 12 species of diatoms comprise the microalgal community; diatoms were only microscopically identified within the mats, suggesting that the mats constitute a suitable microenvironment in thermal ambiences. The identified species are of particular interest because their habitat represents an extreme and an artificial biotope. To the best of our knowledge, this is the first report of thermophilic communities of microalgae in Mexico from a power plant; also, this is the first report of A. africanum for the country.""Esta investigación tiene por objetivo identificar y describir la comunidad perifítica de microalgas termófilas, para expandir nuestro conocimiento de la biodiversidad en ambientes particulares, como las microalgas termófilas (48 °C) que crecen de manera conspicua en la zona superior de la torre de enfriamiento de la central termoeléctrica de Villa de Reyes (centro de México). Se tomaron muestras de agregados o tapetes microalgales en 3 zonas distintas de la parte superior de una torre de enfriamiento, para su identificación. Una vez realizada la amplificación, la clonación y el análisis de los genes que codifican para las subunidades 16S y 18S del rDNA, se observó el predominio de 3 especies de Cyanoprokaryota: Chlorogloeopsis fritschii, Arthronema africanum y Chroococcidiopsis sp., especies descritas como termófilas en trabajos previos. Además, se identificaron 2 especies de Chlorophyta (algas verdes) del género Scenedesmus y 12 especies de diatomeas; la identificación de diatomeas se realizó a partir de observaciones por microscopia electrónica de barrido. Característicamente, las diatomeas solo se observaron dentro los densos tapetes algales que se conforman, sugiriendo que estos tapetes constituyen un microambiente conveniente en ambientes térmicos. Las especies identificadas son de particular interés, ya que su hábitat representa un biotopo extremo y artificial. Por lo que sabemos, este trabajo constituye el primer registro de microalgas termófilas que habitan en torres de enfriamiento y Arthronema africanum se documenta por primera vez para México.

The separation between the 5′-3′ ends in long RNA molecules is short and nearly constant

"RNA molecules play different roles in coding, decoding and gene expression regulation. Such roles are often associated to the RNA secondary or tertiary structures. The folding dynamics lead to multiple secondary structures of long RNA molecules, since an RNA molecule might fold into multiple distinct native states. Despite an ensemble of different structures, it has been theoretically proposed that the separation between the 5 ' and 3 ' ends of long single-stranded RNA molecules (ssRNA) remains constant, independent of their base content and length. Here, we present the first experimental measurements of the end-to-end separation in long ssRNA molecules. To determine this separation, we use single molecule Fluorescence Resonance Energy Transfer of fluorescently end-labeled ssRNA molecules ranging from 500 to 5500 nucleotides in length, obtained from two viruses and a fungus. We found that the end-to-end separation is indeed short, within 5-9 nm. It is remarkable that the separation of the ends of all RNA molecules studied remains small and similar, despite the origin, length and differences in their secondary structure. This implies that the ssRNA molecules are 'effectively circularized' something that might be a general feature of RNAs, and could result in finetuning for translation and gene expression regulation.

Antifungal Nanocomposites Inspired by Titanate Nanotubes for Complete Inactivation of Botrytis cinerea Isolated from Tomato Infection

"Antifungal silver nanocomposites inspired by titanate nanotubes (AgTNTs) were successfully evaluated for the effective inactivation of the phytopathogenic fungus Botrytis cinerea within 20 min. One-dimensional H2Ti3O7 nanotubes functionalized with silver nanoparticles (AgNPs) exhibit unique surface and antifungal properties for the photoinactivation of B. cinerea. Nanostructured titanates were synthesized by the eco-friendly, practical, microwave-induced, hydrothermal method followed by a highly monodispersive AgNP UV-photodeposition. Protonated nanotubes of ∼11 nm in diameter and four-layers displayed high surface areas, 300 m2/g, with a size functionalization of 5 nm for the AgNPs. UV–vis DRS and XPS allowed the characterization and/or quantification of surface reactive species and cytotoxic silver species such as Ag°, Ag+. The effective biocidal properties of the nanocomposites were confirmed by using the well-known Gram-negative bacteria Escherichia coli, and then proceeding to the effective inactivation of the phytopathogenic fungus under visible light. The photoassisted inactivation mechanism was examined by HAADF-STEM, HRTEM, and FESEM electronic microscopies. A plasmalemma invagination due to oxidative stress caused by reactive oxygen, silver cytotoxicity species, and AgTNT sharp morphology damage expands the conidia to induce the cell death. The impact of the eco-friendly inactivation is significant because of the ease with which it is carried out and the possibility of being performed in situ with plants like tomato and grapes, which are ranked among the most valuable agricultural products worldwide.

Trichoderma as a Model to Study Effector-Like Molecules

Plants are capable of perceiving microorganisms by coordinating processes to establish different forms of plant–microbe relationships. Plant colonization is governed in fungal and bacterial systems by secreted effector molecules, suppressing plant defense responses and modulating plant physiology to promote either virulence or compatibility. Proteins, secondary metabolites, and small RNAs have been described as effector molecules that use different mechanisms to establish the interaction. Effector molecules have been studied in more detail due to their involvement in harmful interactions, leading to a negative impact on agriculture. Recently, research groups have started to study the effectors in symbiotic interactions. Interestingly, most symbiotic effectors are members of the same families present in phytopathogens. Nevertheless, the quantity and ratio of secreted effectors depends on the microorganism and the host, suggesting a complex mechanism of recognition between the plant and their associated microorganisms. Fungi belonging to Trichoderma genus interact with plants by inducing their defense system and promoting plant growth. Research suggests that some of these effects are associated with effector molecules that Trichoderma delivers during the association with the plant. In this review, we will focus on the main findings concerning the effector molecules reported in Trichoderma spp. and their role during the interaction with plants, mainly in the molecular dialogue that takes place between them

Mango (Mangifera indica L.) cv. Kent fruit mesocarp de novo transcriptome assembly identifies gene families important for ripening

"Fruit ripening is a physiological and biochemical process genetically programmed to regulate fruit quality parameters like firmness, flavor, odor and color, as well as production of ethylene in climacteric fruit. In this study, a transcriptomic analysis of mango (Mangifera indica L.) mesocarp cv. "Kent" was done to identify key genes associated with fruit ripening. Using the Illumina sequencing platform, 67,682,269 clean reads were obtained and a transcriptome of 4.8 Gb. A total of 33,142 coding sequences were predicted and after functional annotation, 25,154 protein sequences were assigned with a product according to Swiss-Prot database and 32,560 according to non-redundant database. Differential expression analysis identified 2,306 genes with significant differences in expression between mature-green and ripe mango [1,178 up-regulated and 1,128 down-regulated (FDR <= 0.05)1. The expression of 10 genes evaluated by both gRT-PCR and RNA-seq data was highly correlated (R = 0.97), validating the differential expression data from RNA-seq alone. Gene Ontology enrichment analysis, showed significantly represented terms associated to fruit ripening like "cell wall," "carbohydrate catabolic process" and "starch and sucrose metabolic process" among others. Mango genes were assigned to 327 metabolic pathways according to Kyoto Encyclopedia of Genes and Genomes database, among them those involved in fruit ripening such as plant hormone signal transduction, starch and sucrose metabolism, galactose metabolism, terpenoid backbone, and carotenoid biosynthesis. This study provides a mango transcriptome that will be very helpful to identify genes for expression studies in early and late flowering mangos during fruit ripening.

Mioepitelioma plasmocitoide en labio.

RESUMENIntroducción: El mioepitelioma es una neoplasia benigna derivada del tejido que conforma las glándulas salivales,  su ocurrencia es baja y representa del 1 al 1.5% del total de neoplasias de este grupo. Las glándulas salivales mayores son el sitio de ocurrencia más frecuente comparativamente con las glándulas salivales menores. Su prevalencia es mayor en la cuarta década de vida y sin predilección por género.Objetivo: La finalidad de este reporte es documentar un raro caso de mioeplitelioma plasmocitoide en labio, su diagnóstico, manejo y resultados postoperatorios. Presentación del caso: Paciente masculino de 73 años de edad con un aumento de volumen en el lado derecho del labio superior con 5 años de evolución.El paciente se programó para escisión, procedimiento que se realizó bajo anestesia local infiltrativa con lidocaína y epinefrina a nivel de fondo de saco de labio superior a ambos lados de la línea media, se envió muestra para la identificación histopatológica y se recibió diagnóstico de Mioepitelioma Plasmocitoide. En el control post operatorio, a la semana se observó dehiscencia de la herida, sin infección, se retiró el material de sutura y se indicaron colutorios con clorhexidina. A la semana 2, se observó herida sana, granulando adecuadamente, con cierre todavía incompleto.Conclusiones: Podemos destacar que nuestro caso presentó crecimiento lento y sin sintomatología, que es característico de esta entidad. El diagnóstico diferencial es imprescindible contra el adenoma pleomorfo, carcinoma adenoideo quístico, mioepitelioma maligno, leiomioma. La primera opción de tratamiento es la enucleación y remoción quirúrgica total, hasta el área segura en tejido sano. De acuerdo a los reportes encontrados la mayoría de los casos manifiestan una recurrencia baja. Palabras clave: mioepitelioma, plasmocitoide, glándulas salivales menores, labio, tumor, neoplasia.     

La vida silvestre: patrimonio nacional : conferencia pronunciada en la Sociedad Científica Argentina. Sesión pública del 20 de Octubre de 1970

Fil: Navas, Jorge R.. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentin