Developmental plasticity and evolution of the Caenorhabditis germline and reproductive system

L’environnement est une variable essentielle de la traduction des génotypes en phénotypes: ainsi, un génotype donné peut donner naissance à des phénotypes distincts en réponse aux variations environnementales. Ce phénomène, appelé plasticité phénotypique, est universel. Mon projet avait pour objectif d’analyser de façon quantitative et intégrée la plasticité de la reproduction et son évolution chez les nématodes Caenorhabditis, en étudiant les caractéristiques de la lignée germinale. Ce travail a également mis en lumière la sensibilité à l’environnement des traits d’histoire de vie en rapport avec la fitness, et leur évolution. J’ai d’abord analysé la plasticité et les interactions génotype/environnement des traits phénotypiques d’histoire de vie et de la lignée germinale de C. elegans en réponse à des variations environnementales pertinentes sur le plan écologique. J’ai mis en évidence des effets hautement variables de l’environnement et du génotype, et des interactions génotype/environnement pour chacun de ces traits. J’ai ensuite examiné l’évolution intra- et inter-espèces de la lignée germinale et de la reproduction dans le genre Caenorhabditis, et plus particulièrement les variations évolutives dans la sensibilité thermique de la reproduction. J’ai montré que la réduction de la fertilité lors de l’exposition à des températures élevées ne s’expliquait pas seulement par des défauts de spermatogenèse mais également par un large spectre d’erreurs de l’oogenèse. Enfin, j’ai participé à des expériences d’évolution expérimentale visant à quantifier les changements de la lignée germinale qui accompagnent l’adaptation de populations C. elegans à un nouvel environnement.The environment is an integral part of the translation of genotypes into phenotypes, and a given genotype may generate different phenotypes in response to environmental variation. This phenomenon, called developmental or phenotypic plasticity is universal. My project aimed to conduct an integrative and evolutionary analysis of developmental plasticity in reproductive and underlying germline traits of Caenorhabditis nematodes. This research thus also sheds light on the environmental sensitivity of life history traits.First, I analysed the extent of plasticity and genotype-by-environment interactions for C. elegans life history and germline traits in response to ecologically relevant environmental variation. I found highly variable effects of environment and genotype, as well as genotype-by-environment interactions for life history and germline traits. Second, I examined intra- and interspecific evolution of Caenorhabditis germline processes and reproduction, primarily in the context of evolutionary variation in thermal sensitivity of reproduction. I found that heat-induced fertility reduction is not only due to defects in spermatogenesis but also to a wide spectrum of oogenesis errors, which are strongly dependent on species and genotype. Specifically, in C. elegans, high temperature induces consistent defects in mitosis-meiosis progression due to a deregulation of Delta/Notch signalling in the germ stem cell niche. Third, I carried out a population-level study aimed at quantifying germline developmental changes underlying adaptation to a novel environment, making use of C. elegans experimental evolution populations

Developmental plasticity and evolution of the Caenorhabditis germline and reproductive system

L environnement est une variable essentielle de la traduction des génotypes en phénotypes: ainsi, un génotype donné peut donner naissance à des phénotypes distincts en réponse aux variations environnementales. Ce phénomène, appelé plasticité phénotypique, est universel. Mon projet avait pour objectif d analyser de façon quantitative et intégrée la plasticité de la reproduction et son évolution chez les nématodes Caenorhabditis, en étudiant les caractéristiques de la lignée germinale. Ce travail a également mis en lumière la sensibilité à l environnement des traits d histoire de vie en rapport avec la fitness, et leur évolution. J ai d abord analysé la plasticité et les interactions génotype/environnement des traits phénotypiques d histoire de vie et de la lignée germinale de C. elegans en réponse à des variations environnementales pertinentes sur le plan écologique. J ai mis en évidence des effets hautement variables de l environnement et du génotype, et des interactions génotype/environnement pour chacun de ces traits. J ai ensuite examiné l évolution intra- et inter-espèces de la lignée germinale et de la reproduction dans le genre Caenorhabditis, et plus particulièrement les variations évolutives dans la sensibilité thermique de la reproduction. J ai montré que la réduction de la fertilité lors de l exposition à des températures élevées ne s expliquait pas seulement par des défauts de spermatogenèse mais également par un large spectre d erreurs de l oogenèse. Enfin, j ai participé à des expériences d évolution expérimentale visant à quantifier les changements de la lignée germinale qui accompagnent l adaptation de populations C. elegans à un nouvel environnement.The environment is an integral part of the translation of genotypes into phenotypes, and a given genotype may generate different phenotypes in response to environmental variation. This phenomenon, called developmental or phenotypic plasticity is universal. My project aimed to conduct an integrative and evolutionary analysis of developmental plasticity in reproductive and underlying germline traits of Caenorhabditis nematodes. This research thus also sheds light on the environmental sensitivity of life history traits.First, I analysed the extent of plasticity and genotype-by-environment interactions for C. elegans life history and germline traits in response to ecologically relevant environmental variation. I found highly variable effects of environment and genotype, as well as genotype-by-environment interactions for life history and germline traits. Second, I examined intra- and interspecific evolution of Caenorhabditis germline processes and reproduction, primarily in the context of evolutionary variation in thermal sensitivity of reproduction. I found that heat-induced fertility reduction is not only due to defects in spermatogenesis but also to a wide spectrum of oogenesis errors, which are strongly dependent on species and genotype. Specifically, in C. elegans, high temperature induces consistent defects in mitosis-meiosis progression due to a deregulation of Delta/Notch signalling in the germ stem cell niche. Third, I carried out a population-level study aimed at quantifying germline developmental changes underlying adaptation to a novel environment, making use of C. elegans experimental evolution populations.NICE-Bibliotheque electronique (060889901) / SudocSudocFranceF

Systematic Review of the Interaction between Nutrition and Immunity in Livestock: Effect of Dietary Supplementation with Synthetic Amino Acids

Infectious diseases represent one of the most critical threats to animal production worldwide. Due to the rise of pathogen resistance and consumer concern about chemical-free and environmentally friendly productions, the use of antimicrobials drugs is no longer desirable. The close relationship between nutrition and infection has led to numerous studies about livestock. The impact of feeding strategies, including synthetic amino acid supplementation, on host response to various infections has been investigated in different livestock animals. This systematic review provides a synthesis of the experimental studies on the interactions between synthetic amino acid supplementation and immune response to infectious diseases in livestock. Following PRISMA guidelines, quantitative research was conducted using two literature databases, PubMed and Web of Science. The eligibility criteria for the research articles were: (1) the host is a livestock animal; (2) the supplementation with at least one synthetic amino acid; (3) at least one mediator of immunity is measured; (4) at least one production trait is measured. Data were extracted from 58 selected studies. Articles on poultry were the most numerous; few contained experiments using ruminants and pigs. Most of the authors hypothesized that synthetic amino acid supplementation would particularly improve the animals’ immune response against intracellular pathogens. An increase in T and natural killer lymphocytes and macrophages activation, intracellular redox state, lymphocytes proliferation and antibodies production were the most described immune mechanisms associated with synthetic amino acid supplementation. Most of the selected studies focused on three amino acids (methionine, threonine and arginine), all of which are associated with a significant improvement of the host immune response. The use of synthetic amino acid supplementation appears as an encouraging perspective for livestock infectious disease management, and research must concentrate on more analytical studies using these three amino acids

The Role of eIF1 in Translation Initiation Codon Selection in Caenorhabditis elegans

The selection of a proper AUG start codon requires the base-pairing interactions between the codon on the mRNA and the anticodon of the initiator tRNA. This selection process occurs in a pre-initiation complex that includes multiple translation initiation factors and the small ribosomal subunit. To study how these initiation factors are involved in start codon recognition in multicellular organisms, we isolated mutants that allow the expression of a GFP reporter containing a non-AUG start codon. Here we describe the characterization of mutations in eif-1, which encodes the Caenorhabditis elegans translation initiation factor 1 (eIF1). Two mutations were identified, both of which are substitutions of amino acid residues that are identical in all eukaryotic eIF1 proteins. These residues are located in a structural region where the amino acid residues affected by the Saccharomyces cerevisiae eIF1 mutations are also localized. Both C. elegans mutations are dominant in conferring a non-AUG translation initiation phenotype and lead to growth arrest defects in homozygous animals. By assaying reporter constructs that have base changes at the AUG start codon, these mutants are found to allow expression from most reporters that carry single base changes within the AUG codon. This trend of non-AUG mediated initiation was also observed previously for C. elegans eIF2β mutants, indicating that these two factors play a similar role. These results support that eIF1 functions in ensuring the fidelity of AUG start codon recognition in a multicellular organism

The Genetics of Thermoregulation in Pigs: A Review

14 Pág. Departamento de ​Mejora Genética AnimalHeat stress (HS) affects pig performance, health and welfare, resulting in a financial burden to the pig industry. Pigs have a limited number of functional sweat glands and their thermoregulatory mechanisms used to maintain body temperature, are challenged by HS to maintain body temperature. The genetic selection of genotypes tolerant to HS is a promising long-term (adaptation) option that could be combined with other measures at the production system level. This review summarizes the current knowledge on the genetics of thermoregulation in pigs. It also discusses the different phenotypes that can be used in genetic studies, as well as the variability in thermoregulation between pig breeds and the inheritance of traits related to thermoregulation. This review also considers on-going challenges to face for improving heat tolerance in pigs.Peer reviewe

Germ cell apoptosis is critical to maintain Caenorhabditis elegans offspring viability in stressful environments

International audienceMaintaining reproduction in highly variable, often stressful, environments is an essential challenge for all organisms. Even transient exposure to mild environmental stress may directly damage germ cells or simply tax the physiology of an individual, making it difficult to produce quality gametes. In Caenorhabditis elegans , a large fraction of germ cells acts as nurse cells, supporting developing oocytes before eventually undergoing so-called physiological germ cell apoptosis. Although C . elegans apoptosis has been extensively studied, little is known about how germline apoptosis is influenced by ecologically relevant environmental stress. Moreover, it remains unclear to what extent germline apoptosis contributes to maintaining oocyte quality, and thus offspring viability, in such conditions. Here we show that exposure to diverse environmental stressors, likely occurring in the natural C . elegans habitat (starvation, ethanol, acid, and mild oxidative stress), increases germline apoptosis, consistent with previous reports on stress-induced apoptosis. Using loss-of-function mutant alleles of ced-3 and ced-4 , we demonstrate that eliminating the core apoptotic machinery strongly reduces embryonic survival when mothers are exposed to such environmental stressors during early adult life. In contrast, mutations in ced-9 and egl-1 that primarily block apoptosis in the soma but not in the germline, did not exhibit such reduced embryonic survival under environmental stress. Therefore, C . elegans germ cell apoptosis plays an essential role in maintaining offspring fitness in adverse environments. Finally, we show that ced-3 and ced-4 mutants exhibit concomitant decreases in embryo size and changes in embryo shape when mothers are exposed to environmental stress. These observations may indicate inadequate oocyte provisioning due to the absence of germ cell apoptosis. Taken together, our results show that the central genes of the apoptosis pathway play a key role in maintaining gamete quality, and thus offspring fitness, under ecologically relevant environmental conditions

Complex heterochrony underlies the evolution of <em>Caenorhabditis elegans</em> hermaphrodite sex allocation

International audienceHermaphroditic organisms are key models in sex allocation research, yet the developmental processes by which hermaphrodite sex allocation can evolve remain largely unknown. Here we use experimental evolution of hermaphrodite-male (androdioecious) Caenorhabditis elegans populations to quantify the developmental changes underlying adaptive shifts in hermaphrodite sex allocation. We show that the experimental evolution of increased early-life self-fertility occurred through modification of a suite of developmental traits: increased self-sperm production, accelerated oogenesis and ovulation, and increased embryo retention. The experimental evolution of increased self-sperm production delayed entry into oogenesis-as expected, given the sequentially coupled production of self-spermatogenesis and oogenesis. Surprisingly, however, delayed oogenesis onset did not delay reproductive maturity, nor did it trade-off with gamete or embryo size. Comparing developmental time dynamics of germline and soma indicates that the evolution of increased sperm production did not delay reproductive maturity due to a globally accelerated larval development during the period of self-spermatogenesis. Overall, heterochrony in gametogenesis and soma can explain adaptive shifts in hermaphrodite sex allocation

Allocation des ressources et tolérance à la chaleur chez le porc en croissance

National audienc

Effets d'une restriction alimentaire et d'une réalimentation sur les performances et le métabolisme de porcs européens (<em>Large White</em>) et caribéens (Créole) en croissance en climat tropical

National audienceReduction of feed intake is a common physiological response of growing pigs facing stressful environmental conditions. The aim of the present experiment was 1) to study the effects of a short-term drastic feed restriction and subsequent refeeding on pig metabolism, and 2) to study the differential response between 2 breeds, the Large White (LW) breed that has been selected for high growth performance and the Creole (CR) breed, which is characterized by its good adaptation to harsh tropical environmental conditions. An assay with a total of 36 castrated male pigs (18 LW and 18 CR) was carried out. For each breed, half of the animals were restrictively-fed at 50% of the standard allowance for 7 days and were then fed normally for the next 15 days. Growth performance, thermoregulatory responses and plasma metabolites were measured before, during and after feed restriction in the 2 groups. Results show that for all the measured traits, the difference in the response between the 2 breeds is small and rarely significant. Irrespective of breed, during feed restriction, ADG and feed efficiency were reduced (-75%, P< 0.001; -58%, P< 0.05, respectively), but that was counterbalanced by an increase in those same parameters during refeeding (+25%, P< 0.001 ; +49%, P< 0.001, respectively). Feed restriction also reduces skin temperature (-0.6°C, P< 0.01), rectal temperature (-0.4°C, P< 0.01) and respiratory rate (-12 breaths per minute, P< 0.01). Moreover, the results suggest that certain metabolites, such as alkaline phosphatase and blood urea, could be potential biomarker candidates for feed restriction

Plasticity of feeding behaviour traits in response to production environment (temperate vs. tropical) in group-housed growing pigs

International audienceHeat stress affects pig metabolism, health and welfare, resulting in reduced growth and important economic losses. The present experiment aimed to evaluate the effects of two climatic environments [temperate (TEMP) vs. tropical humid (TROP)] on feeding behaviour in growing pigs. The feeding behaviour traits were measured with automated feeders and included: daily feed intake, daily eating time, feeding rate, daily number of meals, feed intake per meal, and feeding time per meal. Pigs came from a backcross population between Large White (LW, heat sensitive) and Creole (CR, heat tolerant) pigs. The same 10 F1 LW × CR boars (sire families [SF]) were mated with related LW sows in each environment. Feeding behaviour was recorded for a total of 1,296 pigs (n = 634 pigs for TEMP and n = 662 pigs for TROP) between 11 and 23 weeks of age. Growth performance and thermoregulatory responses (rectal and skin temperatures) were also measured. Results show that TROP conditions affect feeding behaviour traits: animals had more meals per day but these meals were smaller both in duration and in size, resulting in lower daily feed intake and less time eating per day. Significant SF by environment (GxE) interactions were found for all feeding behaviour traits. When SF were distributed into robust and sensitive groups (previously defined according to performance and thermoregulatory traits), results showed group by environment interactions for all feeding traits, except meal frequency. Moreover, a significant difference in feeding rate between robust and sensitive group was detected in TEMP, suggesting that feeding rate may be a good candidate to evaluate heat tolerance