"Supermice" (TRrGH mice) contain multiple copies of rat growth hormone genes incorporated into a single chromosome. This results in double normal growth rates reaching adult body sizes twice that of normal mice. To determine how exposure to constant light (LL) affects various physiological processes, reproduction, feeding, and behaviour were examined in LL-reared TRrGH mice. Fertility, organ allometries, feeding rates, behavioural time budgets, and circadian feeding and sleep rhythms were compared for both LL and standard 12h dark: 12h light (LD). Both TRrGH and normal females exhibited a significant decrease in fertility in LL. On a mass-specific basis, TRrGH females showed increased combined ovary mass and a reduction in thymus and heart size in LL. TRrGH males demonstrated increased testes mass in LL. When adrenal size was compared between males and females, both TRrGH and normal females exhibited larger adrenals than their male counterparts in both light treatments. The fertility decrease observed in LL may have been associated with reduced food intake. LL-reared TRrGH females ate less than those in LD, although significantly more than TRrGH males in both LL and LD. When compared to normal mice, both sexes of TRrGH mice ate less in both photoperiods. The feeding rates of transgenic GLUT -4 mice were also examined. GLUT -4 mice contain double the amount of insulin responsive GLUT -4 glucose transporters which results in an increased blood glucose clearance rate. These mice, like TRrGH mice, ate less than normals, although a different age-related feeding pattern was observed. TRrGH mice in LL are behaviourally more lethargic than those reared in LD, and spend less time feeding and drinking. Circadian feeding and sleep patterns were shifted in LL by approximately 12 hours, and exhibited reduced peak amplitudes. Ultradian patterns appeared to survive the breakdown of circadian organization. TRrGH mice demonstrate a hormonal imbalance due to the excess allocation of energy into growth. It appears that, in LL, hormonal systems are further altered resulting in an increase in reproductive impairment associated with reduced feeding. One of these altered hormones may be estrogen. Hormones involved in hypothalamic-pituitary-adrenal axis (stress axis) are also implicated. It is concluded that photoperiod is important in regulating physiological processes, and TRrGH mice are more susceptible to environmental alterations due to their altered endocrinological state. / Thesis / Master of Science (MS)

Le réchauffement climatique constitue une problématique d'actualité très préoccupante en raison de ses effets potentiels sur la biodiversité et le secteur agricole. Mieux comprendre l'adaptation des plantes face à ce phénomène récent représente donc un intérêt majeur pour la science et la société. L'étude de populations naturelles provenant d'un gradient d'altitude permet de corréler l'impact d'un ensemble de conditions climatiques (température, humidité, radiation, etc.) à des traits phénotypiques. Ces différentes populations sont dites adaptées à leurs conditions climatiques in natura. En cultivant ces plantes dans des conditions standardisées de laboratoire (intensité lumineuse, substrat, température, arrosage, etc...), la variabilité phénotypique observée, est alors due essentiellement à la variabilité génétique intrinsèque à chaque plante, donc à son génotype. La mise en culture de ces mêmes plantes en changeant une seule variable, par exemple la température, permet de mettre en évidence un phénotype caractéristique. Ce phénotype observé peut être une réponse d'acclimatation d'un génome adapté. Le projet WallOmics vise à caractériser l'adaptation des plantes à l'altitude par l'étude de populations naturelles d'Arabidopsis thaliana provenant des Pyrénées. Les acteurs moléculaires de l'adaptation des plantes au climat sont encore mal connus mais il apparaît que la paroi des cellules végétales pourrait avoir un rôle important dans ce processus. En effet, celle-ci représente le squelette des plantes et leur confère une rigidité tout en représentant une barrière externe sensible et dynamique face aux changements environnementaux. Sa structure et sa composition peuvent être modifiées à tout moment. Il est d'ailleurs possible de dire que cette paroi végétale donne la forme générale de la plante (taille, forme, densité, etc...), son phénotype observable. Ce projet se consacrera principalement à l'étude des parois des cellules végétales. Les nouvelles technologies ont permis l'émergence des données dites "omiques", c'est-à-dire de vastes ensembles de données provenant de niveaux biologiques multiples, comme des données écologiques, de phénotypages, biochimiques, protéomiques, transcriptomiques et génomiques. L'étude et la mise en relation de ces données ont favorisé le développement d'approches globales qui visent à établir une réponse à plusieurs échelles. C'est justement par ce type d'approche non mécanistique que le projet WallOmics a contribué à établir les bases moléculaires des modifications des parois face aux changements climatiques. / Global warming is a current issue of great concern because of its potential effects on biodiversity and the agricultural sector. Better understanding the adaptation of plants to this recent phenomenon is therefore a major interest for science and society. The study of natural populations from an altitude gradient allows correlating a set of climatic conditions (temperature, humidity, radiation, etc...) with phenotypic traits. These different populations are considered as adapted to their climatic conditions in natura. By cultivating these plants under standardized laboratory conditions (light intensity, substrate, temperature, watering, etc.), the observed phenotypic variability, is essentially due to the genetic variability intrinsic to each genotype. The growth of these same plants by changing a single variable, for example temperature, makes possible to highlight a characteristic phenotype. This phenotype may be an acclimation response of a relevant genome. The WallOmics project aims at characterizing the adaptation of plants to altitude by studying natural populations of Arabidopsis thaliana from the Pyrenees. The molecular actors of the adaptation of plants are still poorly described, but it appears that the plant cell wall could play an important role in this process. Indeed, it represents the skeleton of plants and gives them rigidity while representing a dynamic and sensitive external barrier to environmental changes. Its structure and composition can be modified at any time. It is also possible to say that the plant cell wall gives the general shape of the plant (size, shape, density, etc.), that is its observable phenotype. This project will focus mainly on the study of the plant cell wall. New technologies have enabled the emergence of the so-called "omics" data, large sets of data at multiple biological levels, such as ecological, phenotypic, metabolomic, proteomic, transcriptomic and genomic data. The study and the links between these data have favoured the development of integrative approaches aimed at establishing a response at several scales. It is precisely by this type of non- mechanistic approach that the WallOmics project has contributed to establish the molecular players of plant cell wall modifications in the global warming context.