La tierra y el hombre: ¿dos biosistemas incompatibles?

Depto. de Biodiversidad, Ecología y EvoluciónFac. de Ciencias BiológicasTRUEpu

Reflexiones sobre posibles nuevas estrategias en materia de Educación Ambiental.

Sin resume

Reflexiones sobre posibles nuevas estrategias en materia de Educación Ambiental.

Sin resume

Genética y epigenética: yo soy yo y mi circunstancia

En 1914 publicaba D. José Ortega y Gasset su libro “Meditaciones del Quijote” en el cual afirmaba: “Yo soy yo y mi circunstancia y si no la salvo a ella no me salvo yo”. El fondo científico del “yo soy yo y mi circunstancia” fue definido por Waddington al definir la Epigenética como el estudio de las interacciones causales entre los genes y sus productos que dan lugar al fenotipo. Dicho de otra forma, durante el desarrollo y el ciclo vital de cada individuo pueden darse cambios heredables en la función génica que se producen sin un cambio en la secuencia del DNA. Estos cambios consisten en modificaciones del DNA, modificaciones de las histonas y producción de RNAs no mensajeros y, por tanto, no codificantes. Las modificaciones del DNA consisten en la metilación en el C5 de la citosina en las llamadas islas CpG, regiones genómicas de entre 300 y 3.000 pares de bases con alto contenido en citosina (C) y guanina (G) contiguas. Las islas metiladas, si permanecen, reclutan represores de la transcripción que, al unirse a ellas, impiden la transcripción del gen en anexo. Las islas metiladas también reclutan desacetilasas y metilasas de histonas, las cuales pueden regular a su vez la expresión genética. Las histonas que recubre el DNA pueden también sufrir modificaciones post-traduccionales consistentes en acetilación, metilación y fosforilación de histona H3 en su grupo -amino (no involucrado en el enlace peptídico) de un resto lisina localizado en las colas amino terminales. En este estado conformacional, la histona recubre al DNA haciéndolo inaccesible a la maquinaria de la transcripción. Por último, los sRNAs (“small RNA”) son pequeños RNAs no codificantes (ncRNAs) que actúan como RNAs de interferencia, silenciando la traducción de proteínas específicas. Estas modificaciones, condicionadas por factores ambientales, son perdurables y transmisibles, y afectan al desarrollo emocional del individuo, al desarrollo de los centros cerebrales encargados de la percepción, la memoria, las relaciones causa-efecto y la gestión de las emociones. Por ello, la personalidad final de un individuo viene condicionada, no solo por su genoma, lo que anularía el libre albedrío, sino por las modificaciones epigenéticas de su genoma que acumula durante toda su vida. Hoy día se conocen muchos genes, implicados en el desarrollo del cerebro, sometidos a regulación epigenética, como los implicados en el tamaño de la corteza cerebral, en la vía apoptótica durante la proliferación neural, en las vías de señalización WNT, en la codificación para una proteína esencial en la organización de las estructuras anteriores durante el desarrollo cerebral, en el control del tamaño cerebral, y en la especificidad de las estructuras ventrales del sistema nervioso central, directamente implicadas en las gestión de la experiencia acumulada

Microfilament-coordinated adhesion dynamics drives single cell migration and shapes whole tissues [version 1; Referees:4:approved]

Cell adhesion to the substratum and/or other cells is a crucial step of cell migration. While essential in the case of solitary migrating cells (for example, immune cells), it becomes particularly important in collective cell migration, in which cells maintain contact with their neighbors while moving directionally. Adhesive coordination is paramount in physiological contexts (for example, during organogenesis) but also in pathology (for example, tumor metastasis). In this review, we address the need for a coordinated regulation of cell-cell and cell-matrix adhesions during collective cell migration. We emphasize the role of the actin cytoskeleton as an intracellular integrator of cadherin- and integrin-based adhesions and the emerging role of mechanics in the maintenance, reinforcement, and turnover of adhesive contacts. Recent advances in understanding the mechanical regulation of several components of cadherin and integrin adhesions allow us to revisit the adhesive clutch hypothesis that controls the degree of adhesive engagement during protrusion. Finally, we provide a brief overview of the major impact of these discoveries when using more physiological three-dimensional models of single and collective cell migration

The role of lichenized algae in the production of Cladonia verticillaris depsidones, revealed by using alginate-immobilized cells

The mycobiont of the lichen Cladonia verticillaris produces two depsidones, protocetraric and fumarprotocetraric acids, in the nature. This last compound is produced from the former depsidone. To study the role of the algal partner in the production of these depsidones in the lichen thallus, fungal and algal partners were separated and immobilized in calcium alginate. The fungal immobilizates, as lichenized or isolated mycobiont, produced both depsidones, preferently fumarporotocetraric acid from acetate as a precursor. However, when algal immobilizates were co-incubated on acetate with the fungal ones, protocetraric acid was over-produced during the first 11 days of incubation to be later converted into fumarprotocetraric acid. We hypothesized about the algal production of a diffusible metabolite that inhibits the transformation of a depsidone into the other one

La ciencia de las plantas aprendida en jardines, casas, patios y azoteas

La ciencia impregna prácticamente todos los aspectos de nuestra vida gracias a la rapidez con la que se genera el conocimiento científico, la velocidad con la que dicho conocimiento se transmite y la profunda tecnificación de nuestra vida cotidiana. Velocidad que muchas veces no permite ese instante de reflexión que es necesario para que el concepto se comprenda correctamente y se incorpore al acervo cultural de nuestra persona. En este trabajo se analizan las fuentes de información, su credibilidad y la disponibilidad de fuentes de conocimiento que nuestra vida diaria pone a nuestra disposición en relación con la ciencia de las plantas

Effects of concanavalin A on the germination of smut teliospores and on the hyphal growth

Sporisorium scitamineum cells, that causes smut disease in sugar cane, respond to Concanavalin A (ConA). This lectin stimulates the cytoagglutination of teliospores, an excessive elongation of germinative tubes and induces morphological changes in hyphae, in the same way that it occurs in other cellular types. These events seem to play a defensive role in plants against pathogenic infections. In fact, ConA prevents S. scitamineum germination. Binding assays reveal that the distribution of ConA specific receptors is heterogeneous in both location and stage of cycle. Generally, it seems that the lectin activates mitotic events during the life cycle of cells that have been previously able to germinate. For example, increased cell budding is observed in released sporidia after contact with high concentration of the lectin. Moreover, desorption assays indicate that bound ConA is partially desorbed by methyl-mannose and by sugar cane glycoproteins, suggesting that important polysaccharide ligands involved in the defensive response against smut disease could be contained in sugar cane juice produced by resistant varieties

Algal-fungal mutualism: cell recognition and maintenance of the symbiotic status of lichens

Lichens are specific symbiotic associations between photosynthetic algae or cyanobacteria and heterotrophic fungi forming a double entity in which both components coexist. Specificity required for the lichen establishment can be defined in this context as the preferential, but not exclusive, association of a biont with another, since the algal factor susceptible to be recognized is an inducible protein. Recognition of compatible algal cells is performed by specific lectins produced and secreted by the potential mycobiont. Some lectins from phycolichens and cyanolichens are glycosylated arginases which bind to an algal cell wall receptor, identified as a a-1, 4-polygalactosylated urease. However, other ligands exist which bind other lectins specific for mannose or glucose. This implies that, after recognition of a potential, compatible partner, other fungal lectins could determine the final success of the association. Since the fungus can parasitize non - recognized partners during the development of the association, the success after the first contact needs of a set of algal cells, the number of which was sufficient to prevent that the death of a certain number of them makes fail the symbiosis. Fungal lectins act as chemo tactic factors in such a way that algae and cyanobacteria move towards the hyphae, to acquire that critical size of the colony, by means of successive contractions and relaxation of the actomyosin cytoskeleton in absence of any motile appendages

Physiological basis of smut infectivity in the early stages of sugar cane colonization

Sugar cane smut (Sporisorium scitamineum) interactions have been traditionally considered from the plant’s point of view: How can resistant sugar cane plants defend themselves against smut disease? Resistant plants induce several defensive mechanisms that oppose fungal attacks. Herein, an overall view of Sporisorium scitamineum’s mechanisms of infection and the defense mechanisms of plants are presented. Quorum sensing effects and a continuous reorganization of cytoskeletal components, where actin, myosin, and microtubules are required to work together, seem to be some of the keys to a successful attack