The genetic architecture of gene expression in Caenorhabditis elegans

Most organisms are exposed to a continuously changing environment throughout their life. For instance the ambient temperature is usually not constant and many species are exposed to a diverse range of anthropogenic stressors like toxic compounds. Moreover, individuals are prone to genetic changes due to mutation and allelic recombinations. All these factors might affect particular phenotypes, while others remain unchanged. This thesis provides insight into how phenotypic traits are affected by external stress factors and allelic recombinations in the nematode Caenorhabditis elegans (Nematoda; Rhabditidae). Because phenotypes and their variation may be explained by variation in gene expression, this thesis explored the architecture of gene expression and some of the elements that contribute to gene expression. Chapters 2 and 3 focus on environmental stressors with i) a specific target (two organophosphorus pesticides) and ii) a non-target mode of action (temperature) to study their influence on gene expression. A single genotype, the canonical wild type strain Bristol (N2) was used to study the effect of interacting pesticides by exposing nematodes to a toxicant mixture at two different temperatures Analysis revealed common transcriptional responses related to detoxification, stress, innate immunity, and transport of lipids to all treatments. It was found that for both pesticides these similar processes were regulated by different gene transcripts in single and combined treatments. These results also showed that the effect of a mix of low doses of pesticides is not a summed effect of the single components. Moreover, increased temperature elevates the toxic consequences to the pesticides exposures. This toxicity gain is attributed to an elevated uptake and accumulation of the toxicants in the organisms. These results support the idea that the observed higher toxicity of pesticides with temperature might be a consequence of gene-environment interactions affecting detoxification genes. Together, thefirst part of this thesis illustrates the intense crosstalk between gene pathways in response to interacting environmental stressors in C. elegans. The second part of the thesis elaborates on the influence of different genotypes as multiple perturbations on gene expression. How the genotype-phenotype relationship progresses with age was investigated using a quantitative genetics approach (genetical genomics). We performed a genetic mapping strategy of gene transcription variation (expression-QTL, eQTL) to explore the dynamics of regulatory loci affecting genome-wide gene expression at three different ages. We used a recombinant inbred line (RIL) population generated from a cross between the C. elegans strain N2 and the wild type CB4856 in Chapter 4. Also, we investigated the influence of age to reveal a genotype-by-age effect (gxaeQTL) on gene expression. The total number of detected eQTL decreased with age whereas the variation in expression increased. In developing worms, the number of genes with increased expression variation (1282) was similar to the ones with decreased expression variation (1328). In aging worms the number of genes with increased variation (1772) was nearly 5 times higher than the number of genes with a decreased expression variation (373). Furthermore, the number of cis-acting eQTL in juveniles decreased by almost 50% in old worms whereas the number of trans-acting loci decreased by ~27%, indicating that cis-regulation becomes relatively less frequent than trans-regulation in aging worms. Our findings demonstrate that eQTL patterns are strongly affected by age and suggest that gene network integrity declines with age. To better understand the changes in the gene network with age, gene expression profiles of N2 and CB4856 were generated for Chapter 5. We explored gene expression heritability and transgression as genetic parameters for the analysis of gene expression divergence in different genotypes. The average broad sense heritability was similar in developing and aging worms; but the gene expression variance that can be attributed to genetic variance in each gene changes with age. It can be proposed that regulation became more polygenic in aging worms. These changes explain the decrease in detected eQTLs. Likewise, it explains the imbalance between highly heritable genes and eQTLs in aging worms. Chapter 6 discusses the main conclusion of this thesis in the context of the robustness theory. Robustness in biological systems provides the potential to survive severe environmental and genetic perturbations in the form of cryptic genetic variation. The variation we observed in gene transcripts due to external and internal perturbations not always translated to physiological phenotypic variation. In some cases however, the mechanisms underlying phenotypic robustness failed and phenotypic variation was observed. Such genetic cryptic variation was revealed as new molecular and physiological phenotypes. </p

Acción diferencial de dos formulaciones de azadiractina sobre los estados de desarrollo de Ceratitis Capitata (Wiedemann) (Diptera: Tephritidae)

Pruebas de toxicidad con dos formulados de azadiractina (Align y Neem-e) sobre Ceratitis capitata (Wiedemann) realizadas en laboratorio, mostraron un distinto grado de actividad dependiente del producto y del estado de desarrollo de la mosca tratado. A bajas concentraciones Neem-e no tuvo acción ovicida ni larvicida, mientras que Align inhibió la eclosión del 90% de los huevos tratados a una dosis de 4,2 mg/l y a 1 mg/l no emergieron adultos, cuando las larvas neonatas se criaron en dieta tratada. Por el contrario, Align no tuvo ningún efecto tóxico al ser suministrado en el agua de beber a adultos de la mosca, mientras que Neem-e fue moderamente activo, obteniéndose una mortalidad del 100% para una dosis de 50 mg/

Variaciones estacionales en las preferencias de hábitat de la ganga ibérica en estepas agrícolas

[EN]: We investigated habitat use and preferences of pin-tailed sandgrouse Pterocles alchata in agrarian pseudo-steppes of central Spain. We used radio-tracking to characterise habitat selection throughout the year and look for seasonal variations. Pin-tailed sandgrouses selected ploughed fields all year round, except in winter when they preferred stubble fields. Pasturelands were used more often than expected in the breeding and post-breeding seasons and fallows in winter and pre-breeding seasons. Cereal crops, olive groves and vineyards were avoided. Our results indicate that appropriate habitat management for the pin-tailed sandgrouse should take into consideration its habitat preferences during the full annual cycle.[ES]: Estudiamos el uso y las preferencias de hábitat de la ganga ibérica Pterocles alchata en el centro de España. Mediante radio-seguimiento caracterizamos el uso y selección de hábitat a lo largo de un ciclo anual, e investigamos las variaciones estacionales. Las gangas seleccionaron campos labrados durante todo el año, excepto en invierno, cuando prefirieren los rastrojos. Los pastos fueron seleccionados positivamente en la estación de cría y en la post-reproductiva, y los barbechos en la invernal y pre-reproductiva. Las siembras de cereal, olivares y viñedos fueron evitados. Un correcto manejo del hábitat de la ganga ibérica debería tener en cuenta sus preferencias de hábitat durante el ciclo anual completo.The study was financed by the Dirección General de Investigación (projects CGL2007-66322/BOS and CGL2008-04282/BOS), and the Consejería de Educación y Ciencia of Castilla-La Mancha (projects PAI08-0171-9582 and PAC06-137). The Consejería de Medio Ambiente y Desarrollo Rural of the Junta of Castilla-La Mancha allowed us to capture and radio-tag the birds. C. A. Martín holds a postdoctoral contract (I3P Programme, CSIC), and F. Casas was supported by a postdoctoral grant of the Junta de Comunidades de Castilla-La Mancha (JCCM).Peer Reviewe

Aging Uncouples Heritability and Expression-QTL in Caenorhabditis elegans

The number and distribution of gene expression QTL (eQTL) represent the genetic architecture of many complex traits, including common human diseases. We previously reported that the heritable eQTL patterns are highly dynamic with age in an N2 × CB4856 recombinant inbred population of the nematode Caenorhabditis elegans. In particular, we showed that the number of eQTL decreased with age. Here, we investigated the reason for this decrease by combining gene expression profiles at three ages in the wild types N2 and CB4856 with the reported expression profiles of the RIL population. We determined heritability and transgression (when gene expression levels in the RILs are more extreme than the parents) and investigated their relation with eQTL changes with age. Transgressive segregation was widespread but depended on physiological age. The percentage of genes with an eQTL increased with a higher heritability in young worms. However, for old worms this percentage hardly increased. Using a single marker approach, we found that almost 20% of genes with heritability >0.9 had an eQTL in developing worms. Surprisingly, only 10% was found in old worms. Using a multimarker approach, this percentage increased to almost 30% for both age groups. Comparison of the single marker to a multiple marker eQTL mapping indicated that heritable regulation of gene expression becomes more polygenic in aging worms due to multiple loci and possible epistatic interactions. We conclude that linkage studies should account for the relation between increased polygenic regulation and diminished effects at older ages

Litter Quality Is a Stronger Driver than Temperature of Early Microbial Decomposition in Oligotrophic Streams: a Microcosm Study

[EN]Litter decomposition is an ecological process of key importance for forest headwater stream functioning, with repercussions for the global carbon cycle. The process is directly and indirectly mediated by microbial decomposers, mostly aquatic hyphomycetes, and influenced by environmental and biological factors such as water temperature and litter quality. These two factors are forecasted to change globally within the next few decades, in ways that may have contrasting effects on microbial-induced litter decomposition: while warming is expected to enhance microbial performance, the reduction in litter quality due to increased atmospheric carbon dioxide and community composition alteration may have the opposite outcome. We explored this issue through a microcosm experiment focused on early microbial-mediated litter decomposition under stream oligotrophic conditions, by simultaneously manipulating water temperature (10 degrees C and 15 degrees C) and litter quality (12 broadleaf plant species classified into 4 categories based on initial concentrations of nitrogen and tannins). We assessed potential changes in microbial-mediated litter decomposition and the performance of fungal decomposers (i.e., microbial respiration, biomass accrual, and sporulation rate) and species richness. We found stronger effects of litter quality, which enhanced the performance of microbial decomposers and decomposition rates, than temperature, which barely influenced any of the studied variables. Our results suggest that poorer litter quality associated with global change will have a major repercussion on stream ecosystem functioning.This study was financed by the Portuguese Foundation for Science and Technology (FCT), through the strategic projects UIDP/04292/2020 granted to MARE and start-up funds from the Donana Biological Station (EBD-CSIC) and Ikerbasque to LB. Financial support granted by the FCT to VF (IF/00129/2014, CEECIND/02484/2018) is also acknowledged. Special thanks to A. LandeiraDabarca and C. Grela-Docal for their assistance in field and laboratory work and to L. Barmuta, J. Chara, C. Colon-Gaud, M.O. Gessner, J.F. Goncalves Jr., B. McKie, R. Pearson, C. Swan, and C. Yule, among others, collaborators from GLoBE network, for collecting the plant litter

Tumor en hueco poplíteo en 1 niño: diagnóstico diferencial a propósito de 1 caso

Se presenta 1 caso de tumoración en hueco poplíteo en 1 paciente de 15 años de edad. En la exploración clínica inicial encontramos una tumoración de consistencia dura sin signos inflamatorios. Los estudios con RNM y gammagrafía ósea nos orientaban hacia una patología benigna. El estudio anatomopatológico realizado tras la exéresis de la tumoración lo caracterizó como zona de necrosis isquémica con calcificación distrófica de la inserción muscular del tendón del músculo semitendinoso.A 15-year-old boy with a poplited tumor in the knee is presented. The initial exploration showed a firm mass without inflammatory signs. RNM and bone scintigraphy disclosed benign pathology. The pathological diagnosis showed a central area of isquemic necrosis, with distrofic calcification of the semitendinous muscle

The Cryogenic System for the LHC Test String 2: Design, Commissioning and Operation

A 107-m long superconducting magnet string representing a full-cell of the LHC machine was designed for assembly and commissioning at CERN in order to validate the final design choices. This new facility, thereafter called Test String 2, and its cryogenic infrastructure cons ist of feed and return boxes coupled via transfer lines to a 6 kW @ 4.5 K refrigerator and to a low pressure pumping group, a separate cryogenic distribution line, an electrical feed box with HTS current leads, 2 quadrupole and 6 dipole prototype and pre-series superconducting magnets

Avian predators as a biological control system of common vole (Microtus arvalis) populations in NW Spain: experimental set-up and preliminary results

Jareño, D., Paz, A., Arroyo, L., Viñuela, J., Arroyo, B.E., Mougeot, F., Luque-Larena, J.J., Fargallo, J.A

Instrumentation, Field Network and Process Automation for the Cryogenic System of the LHC Test String

CERN is now setting up String 2, a full-size prototype of a regular cell of the LHC arc. It is composed of two quadrupole, six dipole magnets, and a separate cryogenic distribution line (QRL) for the supply and recovery of the cryogen. An electrical feed box (DFB), with up to 38 High Temperature Superconducting (HTS) leads, powers the magnets. About 700 sensors and actuators are distributed along four Profibus DP and two Profibus PA field buses. The process automation is handled by two controllers, running 126 Closed Control Loops (CCL). This paper describes the cryogenic control system, associated instrumentation, and their commissioning

Calidad de agua para riego en invernáculos de la región central de la Provincia de La Pampa

En zona aledaña a la ciudad de Santa Rosa, provincia de La Pampa, ha cobrado importancia el cultivo de hortalizas. El agua utilizada para el riego es extra Ida de perforaciones y eventualmente de alguna laguna. Es por ello que en este trabajo se determina la calidad del agua que se utiliza para el riego y se aportan datos concretos y posibles prácticas de manejo. En este trabajo, desarrollado durante los años 1997 y 1998, se determinaron las características químicas Relación de absorción de Sodio, Carbonato de Sodio Residual y concentración de cationes y aniones, y las características físicas pH, sales totales disueltas y conductividad eléctrica del agua de diferentes pozos, para luego clasificarla siguiendo el criterio del Laboratorio de Salinidad de Riverside (USDA) y de la FAO. El pH del agua de los pozos analizados no presentó ninguna restricción en ningún momento, mientras que de las otras características analizadas siempre se presentó alguna restricción en algún pozo. En los pozos muestreados, en general no se detectaron restos de nitritos ni de amonio, a excepción del pozo N° 8 que presentó un contenido de amonio comprendido en el rango de 0 a 10 partes por millón. En el agua de los pozos N° 1, N° 4, N° 5 Y N° 7 se halló que la concentración de arsénico es superior a la tolerancia admitida por la Organización Mundial de la Salud. Los pozos N° 8 Y N° 10 no presentaron ninguna restricción respecto al total de sales disueltas.Director: Ing. Agr. Nilda B. Reinaudi Cátedra de Química. Facultad de Agronomía. Universidad Nacional de La Pampa.Co-Director: Ing. Agr. Horacio C. Gregoire Cátedra de Horticultura, Facultad de Agronomía. Universidad Nacional de La Pampa