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En aquest treball es descriuen algunes de funcions matemàtiques que tracten de descriure, d'una manera el més acurada possible, les propietats de forma i simetria no d'una forma discreta, sinó com una propietat contínua dels objectes. D'aquesta manera, un cop descrit l'objectiu d'aquest conjunt d'eines, que anomenem mesures de semblança (o dissemblança) es presenta el marc general que les descriu i que alhora ens permet classificar-les. També es fa un repàs històric de les mesures existents més rellevants.A partir d'aquest punt el treball se centra en algunes d'aquestes funcions. Primerament, es descriuen les mesures contínues de forma (CShM), introduïdes per Avnir et al., conjuntament amb la metodologia que se'n despren. S'han utilitzat les CShM per l'anàlisi estructural de compostos químics associats a poliedres de set i vuit vèrtexs, especialment pel que fa als compostos de metalls de transició hepta i octacoordinats, respectivament. Les CShM també s'han emprat per l'estudi estereoquímic al llarg de la reacció entre l'anió [Co(CO)4]- i el catió amoni.També s'han analitzat les mesures contínues de simetria (CSM) i s'ha introduït una nova mesura per a l'estudi de les propietats de simetria, l'índex de simetria (SI). Un cop explicada la metodologia per cadascuna, s'han mostrat algunes aplicacions per aquestes.Finalment es fa una anàlisi de les propietats de simetria de densitats electròniques moleculars amb l'índex de simetria electrònica (ESI). S'han indicat els aspectes teòrics associats a la metodologia així com les motivacions que han portat a la introducció d'aquesta nova mesura. També s'han mostrat alguns exemples de l'aplicació de l'ESI a l'estudi de la simetria d'inversió comparant aquesta amb algunes propietats moleculars., This work describes the mathematical functions necessary to describe, in an accurate way, the shape and symmetry properties from a non-discrete point of view, but as a continuous property. This set of tools called similarity (or dissimilarity) measures, have been classified in a general framework in order to understand the relationships between them.The central part of the work is the description and the study of some of these tools. First of all, the Continuous Shape Measures (CShM) introduced by Avnir and co-workers have been described with the associated methodology. The CShM have been used in the structural analysis of the chemical compounds associated to seven and eight vertices polyhedra, specially the hepta and octacoordinated transition metal compounds. The CShM have been used in the stereochemical study along the chemical reaction between the [Co(CO)4]- anion and the amonium cation.The Continuous Symmetry Measures (CSM) have been analysed and a new measure, the Symmetry Index (SI) have been introduced in order to improve the symmetry properties study. Finally, there is an analysis of the symmetry properties of the molecular electronic density using the Electronic Symmetry Index (ESI). The theoretical aspects associated with the ESI methodology and the motivations to introduce this new tool have been developed. Some examples of the ESI applications in the inversion symmetry analysis of the electron densities have been done, trying to compare these properties with some molecular properties.

This Ph.D. Thesis has been devoted to the preparation and characterisation of bulk Gd5(SixGe1-x)4 alloys and to the study of the magnetocaloric effect at the first-order magnetostructural transition appearing in these compounds. We summarise the most relevant results from this research:- Bulk Gd5(SixGe1-x)4 samples with 0¡Âx ¡Â0.5 have been prepared by using our home-made arc-melting furnace. Characterisation techniques (SEM, microprobe, XRD, DSC, magnetisation, ac susceptibility) show that the 5:4 phase with the desired x is obtained. Some spread around the nominal value and secondary 5:3 and 1:1 phases are detected. Heat treatment favour the segregation of these secondary phases, but also reduce the spread in the x value. A treatment at 920 ¨¬C for 4 hours in a 10-5 mb vacuum furnace enables a trade-off between phase segregation and removal of x spread.- A new differential scanning calorimeter (DSC), which operates under applied magnetic fields of up to 5 T and within the temperature range 10-300 K, has been developed. This calorimeter enables an accurate determination of the entropy change associated with a magnetostructural phase transition. The transition can be induced by sweeping either T or H. - It has been shown that the Clausius-Clapeyron equation and DSC measurements yield the entropy change associated with the first-order magnetostructural transition, ∆S. If the Maxwell relation is evaluated only within the field range over which the transition takes place, the same value is obtained. When the Maxwell relation is evaluated over the whole field range, the T and H dependences of the magnetisation in each phase outside the transition region yield an additional entropy change to that associated with that of the actual first-order transition. The transition temperature Tt must significantly shift with the applied field, in order to achieve a large MCE taking advantage of ∆S.- DSC under H has been used to measure ∆S for Gd5(SixGe1-x)4, x ¡Â0.5. ∆S scales with Tt, which is a direct consequence of the fact that Tt is tuned by x and H and it is thus expected to be universal for any material showing a field-induced transition. The specific shape of ∆S vs. Tt will depend on the details of the phase diagram, Tt(x). The scaling of ∆S shows the equivalence of magnetovolume and substitution-related effects in Gd5(SixGe1-x)4 alloys.- The variation of the transition field with the transition temperature, dHt/dTt, has been studied in Gd5(SixGe1-x)4 for 0¡Âx ¡Â0.5. It is shown that dHt/dTt governs the scaling of ∆S with Tt. Two distinct behaviours for dHt/dTt have been found on the two compositional ranges where the magnetostructural transition occurs, showing the difference in the strength of the magnetoelastic coupling in this system.- It has been shown that an unreported field-induced magnetic phase transition exists from the AFM phase to a phase which presents short-range correlations (SRAFM). The results suggest that the transition results from the breaking of the long-range AFM correlations when a magnetic field is applied, which leads to competing FM and AFM short-range correlations. FM correlations are also relevant in the whole long-range AFM phase. The expected transition from the SRAFM to the PM phase takes place at ~240 K at zero field, being widened and smoothed under applied field. This finding in the Ge-rich Gd5(SixGe1-x)4 alloys arises from the competition between the intraslab FM interactions and the interslab AFM interactions.- The dynamics of the first-order transition in Gd5(SixGe1-x)4 alloys has been studied by cycling virgin samples. The field-induced entropy change increases during the first cycles, then reaching a stationary value. This behaviour is related to the avalanche distribution, which also evolves with cycling. The structure of avalanches becomes repetitive after a few cycles tending towards a power-law distribution, unveiling the athermal character of the transition.

[eng] The principal aim of this thesis is the understanding of the electronic structure of organic diradical and polyradical molecules. Unveiling the properties that give them the electronic, magnetic, and optical properties to be applied as main components in optoelectronic devices. Specifically, the objectives that have been achieved are i) the characterization of organic compounds with diradical and polyradical character, and their electronic, magnetic, and spectroscopic properties; ii) the detailed description of the singlet fission mechanism, as well as the proposal of a new system that, theoretically, is able of carrying out efficiently the singlet fission process; and iii) the use of quantum mechanical methods (specifically RAS-SF) and computational tools to get a proper description of the electronic structure of the ground state of systems in which non-dynamic correlation plays an important role. In the first place, organic compounds whose optical and magnetic properties make them interesting in the field of optoelectronic materials were studied. The relationship between molecular structure and the radical character was found by the study of linear and cyclic acenes and small triangular fragments derivatives of graphene. While the diradical and tetraradical character increase together with the size of the linear and cyclic compounds, the triangular structures (TGNF, the acronym for Triangulene Graphene Nano Fragments) are open-shell systems with high-spin ground state multiplicity. Furthermore, a manner to tune the spin multiplicity in the ground state of TGNFs is proposed through heteroatom doping or hydrogenation, which offers a way to design larger graphene nanofragments with well-defined spin-multiplicity. Towards larger systems, the increment of the size is associated with the increase of the polyradical character. This thesis presents the rationalization of the electronic structure of organic macrocycles with high polyradical character. Concretely, from triradicals to decaradicaloids (up to 10 radical centers). The properties triggered by the open-shell character of the ground state are as diverse as surprising. For instance, AWA systems (annulenes-within-annulenes) have been characterized in collaboration with experimental groups for the first time. The global aromaticity exhibit by these macrocycles responds to the radical interaction in each of the annulenes and is governed by both aromaticity rules, Hückel's, and Baird's simultaneously. On the other hand, the singlet fission process (SF) was expanded from the classical model, which involves five electronic states, to a model that includes double excitations (D states), a seven-state model. Using a simple model, it is estimated that the D states can play an active role in SF, as well as the necessary conditions to maximize their participation as an initial or intermediate state in the process. The feasibility of spiro systems carrying out SF is exposed., [spa] El principal objetivo de esta tesis es poner al descubierto las propiedades químicas que permiten que procesos fotofísicos complejos tomen lugar en moléculas orgánicas, y que les permite tener aplicaciones en materiales optoelectrónicos. Puntualmente, los objetivos que se han cumplido son i) la caracterización de di y poliradicales orgánicos y sus propiedades electrónicas, magnéticas y espectroscópicas; ii) la descripción detallada del mecanismo de fisión de singuletes, así como proponer un sistema que teóricamente es capaz de realizarlo eficientemente; y iii) la utilización de métodos de la mecánica cuántica (específicamente RAS-SF) y herramientas computacionales que permiten la descripción apropiada de la estructura electrónica del estado fundamental de sistemas en los que la correlación no-dinámica representa un papel importante. En primer lugar, se estudiaron compuestos orgánicos cuyas propiedades ópticas y magnéticas los hacen interesantes en el campo de materiales optoelectrónicos. Se encontró la dependencia del carácter radical en la topología de nanoestructuras de grafeno (acenos) lineales y cíclicos, y pequeñas laminas de estructura triangular. Mientras el carácter diradical y tetraradical crece con el tamaño de los compuestos lineales y cíclicos, las estructuras triangulares (TGNF, siglas en inglés de Triangulene Graphene Nano Fragments) son compuestos de capa abierta. Además, se propone una forma de modular la multiplicidad de espín en el estado basal de los TGNF mediante el dopaje con heteroátomos. El incremento del tamaño del sistema permite obtener molecular con alto carácter poliradical. En esta tesis se presenta la racionalización de la estructura electrónica de macrociclos orgánicos con carácter triradical hasta decaradicaloide (10 centros radicalarios). Las propiedades que se derivan de estas características son tan variadas como sorprendentes, por ejemplo, se han caracterizado sistemas AWA (anulenos-dentro de-anulenos) cuya aromaticidad global responde a la suma de la aromaticidad en cada uno de los anulenos y esta regida por las reglas de aromaticidad de Hückel y Baird simultaneamente. El proceso de fisión de singuletes (SF) fue expandido del modelo clásico, que involucra cinco estados electrónicos, a un modelo que incluye excitaciones dobles (estados D), modelo de siete estados. Usando un modelo sencillo se estima que los estados D pueden jugar un papel activo en SF, así como las condiciones necesarias para maximizar su participación como estado inicial o intermediario en el proceso. Se expone la factibilidad de que los sistemas spiro lleven a cabo SF.

[eng] In this thesis, different organic and organometallic molecules with interest for optoelectronic applications have been studied from a computational standpoint. The work presented in this thesis belongs to the molecular quantum chemistry field and in particular to the investigation of the low- lying electronic excited states involved in the target photophysical processes. Chapter 1 is devoted to the study of the absorption process of several organic dyes with potential application in dye-sensitized solar cells (DSSCs). In particular, the influence of the nature of the π- bridge in donor-acceptor dyes has been investigated. The photophysical properties of the dyes are rationalized based on geometrical characteristics and their electronic structure. The charge transfer nature of the optical state has also been investigated with several computational tools. Solvent effects on the absorption of the dye have also been considered and simulated to give an explanation to experimental observations. Chapter 2 deals with phosphorescent Ir(III) complexes that have interest as triplet emitters for organic light-emitting diodes (OLEDs). All the studies presented in this chapter have been done in collaboration with the experimental group of Prof. Inamur Rahman Laskar at the Birla Institute of Technology and Science (BITS) in Pilani, India, and his coworkers. After our first collaborations, we became interested in Ir(III) complexes exhibiting aggregation induced emission (AIE). This is a very interesting phenomenon where the emission intensity is enhanced in the solid state compared to dilute solution. Systems presenting the AIE are very attractive for a wide range of applications other than OLEDs. In this chapter, a section is devoted exclusively to analyze the evolution of this field and the principal mechanisms proposed to explain this phenomenon. It does not pretend to be a complete review from the literature, but rather a critical assessment with personal thoughts on the subject. As for the results, we were interested to understand how the photophysical properties are influenced by the presence of different ligands on the Ir(III) complexes and by the presence of intermolecular interactions. The absorption and emission of the studied complexes has been characterized and different approaches have been taken to give an explanation to experimental observations from our partners. In Chapter 3 a study on the photophysics of sulfur bridged naphthalene dimers is presented. This work was partially done during a research stay in the group of Prof. Mario Barbatti at the Institut de Chimie Radicalaire in Marseille (France). Herein we were interested in explaining the dependence of the photoluminescence of the aforementioned dimers on the oxidation state of the sulfur atom at the bridge. Experimental work on these compounds and related ones had been previously reported. An explanation for the different luminescence however was not given for the naphthalene dimers. In this chaper we have tackled this problem by characterizing the excited states and crossings between the ground and first excited state PESs., [cat] En aquesta tesi s’han aplicat els mètodes de la química quàntica molecular per estudiar des del punt de vista de la fotofísica, les característiques principals de l’estructura electrònica d’un conjunt de molècules orgàniques i organometàl·liques amb interès per aplicacions optoelectròniques. En particular, s’han estudiat per una part colorants orgànics amb propietats òptiques adients per ser emprats com a sensibilitzadors en cel·les solars sensibilitzades amb colorant (DSSCs en anglès). En una altra direcció, s’han investigat una sèrie de complexos d’Ir(III) amb potencial aplicació com a compostos emissors en díodes orgànics emissors de llum (OLEDs en anglès). Aquests complexos també presenten el fenomen d’emissió induïda per agregació (AIE en anglès), en el que la intensitat d’emissió augmenta en l’estat sòlid en comparació a la feble o inexistent luminiscència mesurada en dissolucions diluïdes. Els sistemes que presenten AIE son molt atractius per un gran varietat d'aplicacions. En aquesta tesi, una secció s’ha dedicat exclusivament a analitzar l’evolució d’aquest camp i dels principals mecanismes proposats per explicar el fenomen de l’AIE, aportant una valoració crítica amb opinions personals sobre el tema en qüestió. Finalment, aquest treball inclou també la investigació computacional de les propietats fotofísiques de dímers de naftalè enllaçats per un pont basat en sofre, amb potencial aplicació en dispositius orgànics fotovoltaics (OPVs en anglès) i OLEDs. En aquest cas estàvem interessats en explicar la dependència de la fotoluminescència dels dímers estudiats amb l’estat d’oxidació de l’àtom de sofre del pont que connecta els monòmers de naftalè. Aquesta qüestió s’ha abordat caracteritzant els estats excitats i els encreuaments entre l’estat fonamental i el primer estat excitat.

The establishment of the embryonic axis in the Drosophila embryo relies on four maternal systems. Anterior and posterior axes rely on morphogens located at the poles that will generate a gradient of activity along the embryo. In contrast, terminal and dorsoventral system rely on cues that are generated by follicle cells in the egg chamber to induce the restricted activation of their receptors, Torso and Toll respectively. In the case of the terminal signaling, the torso (tor) gene encodes for a tyrosine kinase receptor uniformly localised all around the membrane of the embryo but exclusively activated at the poles upon the activity of the Torso-like (Tsl) protein. Restricted activation of the Torso receptor at the embryonic poles relies on the tsl gene. Indeed, Tsl is expressed at the poles of the egg chamber during oogenesis and, in embryogenesis, accumulates at both poles of the inner side of the vitelline membrane, the innermost eggshell layer, by means of three protein encoded by the Nasrat (f(s) N), Polehole (f(s) Ph) and Closca (clos) genes. f(s) N, f(s) Ph and clos encode for proteins that localise in the vitelline membrane and are involved in the crosslinking of the vitelline membrane converting the eggshell into a stiff and insoluble layer. Indeed, females bearing mutations in any of these genes produce collapsed eggs due to defects in their eggshell. fs(1)N12, fs(1)ph1901 and clos1 are the only point mutation alleles which do not abolish the integrity of the vitelline membrane but cause the lack of terminal structures. The main objective of this work was to shed light on the role of Tsl, Nasrat, Polehole and Closca in ensuring restricted of Tor activation at the embryonic poles. In the case of Tsl, we found that, during oogenesis, it accumulates at the vitelline membrane while, in embryogenesis it localises at both ends of the embryonic plasma membrane probably at egg activation. These results suggest a a mechanism to transfer the Tsl from the egg chamber to the early embryo. This mechanism relies on the initial anchoring of Tsl at the vitelline membrane as it is secreted by the follicle cells, followed by its later translocation to the egg plasma membrane. In the case of Nasrat, Polehole and Closca,we found that embryo laid by fs(1)N12, fs(1)ph1901 and clos1 mutant females display defects in dorsoventral patterning specification besides their terminal phenotype. Nasrat, Polehole and Closca, are required for proper anchorage and activity of Nudel, a protease acting both in embryonic dorsoventral patterning and vitelline membrane integrity, thus providing a mechanism for the role of Nasrat, Polehole and Closca in vitelline membrane cross linking and dorsoventral patterning. Therefore, the dorsoventral and terminal systems, hitherto considered independent, share a common extracellular mechanism constituted by the Nasrat, Polehole and Closca proteins. Moreover, we found that these proteins have a new Tsl-independent role in terminal signaling. In the embryonic terminal system, Tor is activated only at the poles by its ligand Trunk while, in Drosophila larvae, Tor is also expressed and activated by another ligand called Prothoracicotropic hormone (PTTH) in the Prothoracic Gland. Ectopic expression of PTTH in the embryo is able to activate Tor ectopically even in the absence of Tsl but requires Nasrat, Polehole and Closca. From these results, we propose that a Nasrat/Polehole/Closca complex acts as a multifunctional hub to anchor various proteins synthesized at oogenesis, ensuring their spatial and temporal restricted function. These findings shed light on the eggshell not just as protective layer but as a specialised extracellular matrix that regulates the spatial and temporal control of early embryonic developmental processes., El eje antero-posterior del embrión de Drosophila se especifica por acción de tres sistemas maternos: el sistema anterior, el sistema posterior y el sistema terminal. En el sistema terminal el receptor tirosina quinasa Torso (Tor) está localizado uniformemente en la membrana del embrión temprano pero se activa sólo en los polos por acción de la proteína Torso-like (Tsl). Aunque el papel de Tsl en la activación de Tor no está del todo claro, se ha descrito que Tsl es la única proteína de todo el sistema terminal localizada en los polos. De hecho, Tsl se acumula en la cara interna de la membrana vitelina (MV), anclado a las proteínas Nasrat, Polehole y Closca. El papel molecular de estas proteínas es poco conocido, pero análisis genéticos han demostrado que se necesitan para una correcta estructura de la MV y también para la activación de Tor. En esta tesis, nos hemos focalizado en la función de las proteínas Tsl, Nasrat, Polehole y Closca y su papel en la activación de Tor en los polos. Respecto a Tsl, descubrimos que esta proteína se acumula en la MV durante la oogénesis y, al principio de la embriogénesis, transloca de la MV a la membrana plasmática del embrión. En cuanto a Nasrat, Polehole y Closca descubrimos que estas proteínas se necesitan también para la correcta localización y función de Nudel, una proteína involucrada en la especificación del eje dorso ventral del embrión. Además encontramos que Nasrat, Polehole y Closca tienen una función adicional en el sistema terminal independiente de Tsl. De los resultados aquí descritos proponemos que un complejo formado por las proteínas Nasrat, Polehole y Closca podría funcionar en la MV como un centro multifuncional para anclar proteínas importantes por la especificación de los ejes del embrión.

[spa] Uno de los temas fundamentales en el estudio de la evolución es el papel que desempeña la modificación de la actividad genética en la aparición de nuevas morfologías. Con el fin de comprender dicha relación, hemos comparado el sistema respiratorio altamente derivado del díptero Drosophila melanogaster con el del coleóptero Tribolium castaneum, menos derivado. A diferencia de Drosophila, el sistema traqueal de Tribolium no ha sido prácticamente descrito, por lo que ha sido necesario definirlo previamente, tanto a nivel morfológico como molecular. Así, hemos comprobado que en ambos casos el sistema traqueal se origina a partir de 10 placodas de origen ectodérmico a cada lado del embrión, llamadas primordios traqueales (Manning and Krasnow, 1993). Una vez las células traqueales han sido determinadas, invaginan y comienzan a migrar hacia las zonas dorsal y ventral. Durante este proceso las células se alargan e intercalan, formando las futuras ramas traqueales. Por último, cada metámero traqueal acaba uniéndose al adyacente por medio de la fusión de las ramas laterales. Sin embargo, ambos sistemas presentan un diferente grado de organización durante sus etapas larvadas, adaptada al medio que habitan. Este se diferencia principalmente en la presencia en Drosophila y ausencia en Tribolium de dos tubos longitudinales llamados troncos dorsales (TD), así como en la diferente disposición a lo largo del cuerpo de los espiráculos, las estructuras a través de las cuales se conecta la tráquea con el exterior. En Tribolium las tráqueas conectan con el exterior en cada uno de los metámeros a través de los espiráculos laterales. En cambio en Drosophila, estos espiráculos laterales no se desarrollan y el sistema traqueal conecta con el exterior mediante los espiráculos anteriores y posteriores, que están conectados a los tubos dorsales. A continuación investigamos los mecanismos moleculares responsables de las citadas diferencias morfológicas. Así, durante nuestro estudio hemos comprobado que el factor de transcripción Spalt (Sal) no mantienen el mismo patrón de expresión en las células traqueales de ambas especies. De hecho sal, responsable de la formación del tronco dorsal en Drosophila, no se expresa en las células traqueales de Tribolium, sugiriendo que esta diferente expresión de sal en las células traqueales de Drosophila podría ser la responsable de la adquisición de los troncos dorsales en esta especie. Así mismo hemos descubierto que el factor de transcripción Cut es necesario para el desarrollo de los espiráculos. Sin embargo su activación es diferente en las dos especies. Mientras que en Drosophila cut únicamente se expresa en el último segmento abdominal, en Tribolium se expresa en todos los segmentos laterales. Además, hemos visto que Cut reprime la expresión de sal en Drosophila. Esta diferencia de expresión del gen cut en Drosophilla podría deberse a la separación de los primordios traqueal y espiracular en Drosophila. Los sistemas traqueal y espiracular de Drosophila se originan a partir de diferentes poblaciones celulares bajo el control de diferentes mecanismos génicos, la vía de JAK/STAT y el gen homeótico Abdominal-B, respectivamente., [eng] Evolution, through modification of morphogenesis, led animals to acquire the body shapes and organ systems that enabled them to enter, survive and reproduce in a vast number of different habitats. While it is undisputed that evolving genomes are ultimately responsible for morphological modifications, little is known about how major innovations can be conveyed by small genetic changes. We have addressed this issue by analyzing expression and function of regulatory genes in the developing tracheal systems of two insect species. The tracheal system of Drosophila is distinguished from the less derived tracheal system of the beetle Tribolium by two main features: First, the lateral spiracles, which in Tribolium connect the tracheal branches to the exterior in each segment, are not present in Drosophila. Instead it has only one pair of heavily derived posterior spiracles. Second, the dorsal trunks, two prominent branches that distribute air from the posterior spiracles and span longitudinally through the larvae, do not exist in Tribolium. Both innovations, while considered independent structures, are functionally dependent on each other and linked to habitat occupancy: half-buried Drosophila larvae in semi-liquid environments keep their posterior spiracles above the surface and distribute the gas to the body through the dorsal trunks. Conversely, the lateral spiracles of free-living Tribolium larvae provide sufficient airflow to all segments, so that no thick dorsal trunks are needed to distribute the oxygen. Here we show that changes in the domains of spalt and cut expression are associated with the acquisition of each innovation. Moreover, we show these two genetic modifications to be not only functionally but also genetically connected, providing an evolutionary scenario by which a single genetic event can contribute to the joint evolution of functionally inter-related organs.

[spa] En el reino animal hay numerosos ejemplos de sistemas de órganos tubulares, como los pulmones y el sistema vascular de los mamíferos. En este estudio hemos usado el sistema traqueal de Drosophila melanogaster para estudiar el desarrollo de este tipo de órganos. En particular, nos centramos en los pliegues taenidiales, estructuras de quitina que rodean el lumen tubular y dan resistencia mecánica a los tubos traqueales. Formados por la secreción de quitina en la matriz extracelular apical, estos pliegues se extienden más allá de los límites de una sola célula, abarcando múltiples células. Esto implica un alto nivel de coordinación intra e intercelular. Hay una serie de genes cuya ausencia produce perturbaciones en los pliegues taenidiales. De éstos, nuestro estudio se centra en Blimp-1 y pri. En ausencia de cada uno de estos genes, los pliegues taenidiales no se desarrollan correctamente mientras que otros aspectos del desarrollo traqueal no se ven demasiado afectados. Hemos analizado el patrón de expresión de Blimp-1 y pri, y hemos encontrado que ambos genes se expresan en las células traqueales de Drosophila durante el desarrollo embrionario. Los pliegues taenidiales todavía se forman en ausencia de Blimp-1 o pri, pero no están organizados correctamente, lo que indica que Blimp-1 y pri contribuyen a su adecuada formación. Existen varios sistemas en Drosophila en que estructuras de actina contribuyen a la organización de la quitina, como los dentículos de la epidermis y el lumen el sistema traqueal. En los mutantes Blimp-1, no se forman los anillos de actina apical, que si que lo hacen en los mutantes pri pero con una mala orientacion, lo que indica que la función de Blimp-1 y pri se requiere para el ensamblaje de la F-actina. Por otra parte, nuestros resultados indican que perturbar la síntesis de quitina o su organización, desorganiza la F-actina apical que no forma haces. Por lo tanto, durante el desarrollo del sistema traqueal se establece una interacción mútua entre la organización de la F-actina y de las estructuras de quitina. Mediante la expresión de la forma silvestre del gen en una sola célula en un fondo mutante, hemos estudiado cómo las células individuales contribuyen a generar una estructura supra-celular. Los resultados de nuestro análisis revelan que la orientación de los pliegues taenidiales no es regulada de manera autónoma y que depende en gran medida de los pliegues taenidiales formados por las células vecinas. Por último, mostramos que perturbar las uniones entre células, a través de la reducción de los niveles de α-catenina, da lugar a que las células traqueales formen su pliegues taenidiales de forma independiente a sus vecinas., [eng] Examples of tubular organ systems like the mammalian lungs and vascular system abound in the animal kingdom. In this study we used the Drosophila melanogaster tracheal system to study tubular organ development. In particular, we focused on taenidial folds, chitin structures surrounding the tubular lumen that give mechanical strength to the tracheal tubes. Formed by the secretion of chitin into the apical extracellular matrix, these folds extend beyond the limits of a single cell spanning through multiple cells. This implies a high level of intra and intercellular coordination. There are a number of genes in the absence of which taenidial folds are disturbed. Among these, we focused on Blimp-1 and pri. In the absence of each of these genes, taenidial folds are disrupted while other aspects of tracheal development are unaffected. We have analyzed the expression pattern of Blimp-1 and pri and found that both genes are expressed in Drosophila tracheal cells during embryonic development. Taenidial folds are still formed in the absence of Blimp-1 or pri but they are not organized correctly, thereby indicating that Blimp-1 and pri contribute to their proper formation. Actin structures contributing to chitin organization have been reported for many systems in Drosophila, like denticle belts at the epidermis and the lumenal structure in the tracheal system. In Blimp-1 mutants, apical actin rings fail to form whereas in pri mutants they are formed but misoriented, suggesting that the function of Blimp-1 and pri is required for F-actin assembly. Interestingly, when we impair either chitin synthesis or chitin organization the apical F-actin is disorganized and does not form bundles. For the first time, we show that during tracheal system development there is a crosstalk between F-actin organization and chitin structures. By rescuing the mutant phenotype in single cells, we studied how individual cells contribute to generate a supra-cellular structure. Results of our analysis reveal that the orientation of taenidial folds is not cell-autonomously regulated and that it depends highly on the taenidial folds formed by the neighboring cells. Finally, we show that impairing cell-cell junctions, via down-regulation of α-catenin, gives rise to tracheal cells that form their taenidial folds independently.

La utilització de composts com substrats de cultiu i/o l'ús d'agents de control biològic són una alternativa als mitjans de control de fitopatògens mitjançant fitosanitaris químics. Aquesta tesi consta de 4 capítols. En el Capítol I es va estudiar la capacitat de 5 composts procedents de residus municipals i agrícoles de suprimir la malaltia produïda pel patogen foliar Botrytis cinerea en plantes de cogombre. Els cinc composts van ser capaços de reduir la incidència i severitat de la malaltia en comparació amb els substrats de cultiu estàndard (2 torbes comercials). La reducció de la malaltia es va associar al subministrament de Ca, Mo i Si per part dels composts, a cert grau d'estrès salí produït en la planta, així com a l'alta activitat microbiològica dels composts. En el Capítol II es descriu el desenvolupament d'un mètode basat en la cromatografia líquida acoblada a detecció per espectrometria de masses en tàndem per a la quantificació simultània de les hormones àcid salicílic i àcid jasmònic en extractes vegetals. El mètode es va aplicar per a estudiar l'efecte de la colonització de l'arrel de plantes de cogombre per part de l'agent de control biològic Trichoderma asperellum T34 o la infecció per part del patogen Rhizoctonia solani. No es va observar cap efecte de T34 aplicat a l'arrel a 105 ufc/ml sobre els nivells d'aquestes hormones. R. Solani, va produir l'increment de les dues hormones, tant en arrel com en cotilèdon. En el Capítol III es va estudiar l'efecte de T34 aplicat a l'arrel de la planta de cogombre a 105, 106 i 107 ufc/ml sobre l'activitat peroxidasa, els nivells d'àcid salicílic i jasmònic i el proteoma dels cotilèdons en les primeres hores de la interacció. T34 activa l'activitat peroxidasa i eleva els nivells de les hormones estudiades de forma depenent a la concentració. A 105 no s'observen efectes. T34 aplicat a l'arrel a 107 ufc/ml és capaç de produir canvis el proteoma dels cotilèdons afectant l'expressió de proteïnes relacionades amb la defensa contra patògens. Aquest mateix tractament és capaç d'induir en la planta resistència sistèmica contra el patogen foliar Pseudomonas syringae pv. lachrymans. En el Capítol IV es va comprovar la capacitat de T34 aplicat a 105 ufc/ml per a induir resistència sistémica en Arabidopsis enfront dels patògens foliars Pseudomonas syringae pv. tomato, Hyaloperonospora parasitica i Plectosphaerella cucumerina. Aquesta resistència sistèmica és semblant a la induced systemic resistance (ISR) produïda per rizobacteris no patogènics. L'ús d'Arabidopsis mutants va permetre establir que la ISR induïda per T34 és independent d'àcid salicílic i depenent de NPR1 i MYB72. A més, la ISR induïda per T34 es basa en el priming ja que precondiciona a les plantes a expressar el gen LOX2 i el bloqueig d'espores de patògens mitjançant cal·losa de forma mes ràpida i intensa quan posteriorment responen a un atac., This thesis consists in 4 chapters. In Chapter I we checked the ability of 5 composts from municipal an agricultural wastes to suppress disease produced by the foliar pathogen Botrytis cinerea in cucumber plants. The 5 studied composts were able to reduce disease incidence and disease severity compared to standard growth media (2 commercial peats). The reduction in disease was related to the supply of Ca, Mo and Si to the plants, a certain degree of salt stress and the high microbial activity of the composts. In Chapter II we describe a method based in liquid chromatography coupled to mass spectrometry to simultaneously quantify salicylic and jasmonic acids in crude plant extracts. No effect on the hormones was found when the biological control agent Trichoderma asperellum T34 was applied to the roots at 105 cfu/ml. Rhizoctonia solani infection increased both hormones in both cotyledons and roots. In Chapter III we studied the effect of T34 applied to the roots at 105, 106 and 107 cfu/ml on peroxidase activity, salicylic and jasmonic acids levels and proteome of cucumber cotyledons during the early hours after the interaction. T34 affects peroxidase activity and hormone levels depending on the concentration. No effects at 105. T34 applied to the roots at 107 cfu/ml is able to produce changes to the proteome affecting the expression of defense related proteins. This treatment is also able to induce systemic resistance against the foliar pathogen Pseudomonas syringae pv. lachrymans. In Chapter IV we checked the ability of T34 applied at 105 cfu/ml to induce systemic resistance in Arabidopsis against the foliar pathogens Pseudomonas syringae pv. tomato, Hyaloperonospora parasitica and Plectosphaerella cucumerina. This systemic resistance is similar to induced systemic resistance (ISR) triggered by non pathogenic rhizobacteria. The use of Arabidopsis mutants allowed us to establish that ISR induced by T34 is salicylic acid independent but is dependent on NPR1 and MYB72. In addition ISR triggered by T34 is based on priming as it primes plants for enhanced LOX2 gene expression as well as callose deposition when plants face an stress.