Hamburg, Universiẗat, Diss., 2000.

The genus Populus consists of many ecologically and economically important forest tree species. Their rapid growth makes them one of the most productive hardwoods growing in temperate latitudes. Populus spp. frequently hybridize where their ranges overlap, and poplar hybrids are the most frequently planted genotypes for fiber production. To better understand the genomics of hybridization in Populus, we sampled and sequenced the genome of 574 poplar trees from six east-west transects across the hybrid zone between Populus trichocarpa and Populus balsamifera in western North America. I used these data to characterize population structure within and between transects, and hybridization between the species. There was a consistent transition from greater P. balsamifera ancestry in the north and east to greater P. trichocarpa ancestry in the south and west. Hybridization between the species was common across each of the six transects, though more common in colder climates. The results also showed that both latitude and longitude affect the genetic structure of this species complex, and that subtle introgression from P. balsamifera may facilitate adaptation of P. trichocarpa to colder climates. / Master of Science / The genus Populus has many ecologically and economically important forest tree species. Balsam poplar (Populus balsamifera) and black cottonwood (Populus trichocarpa) are two such species, both for fiber production and models for understanding tree biology and adaptation. Whereas black cottonwood is distributed close to the west coast of North America from California through Alaska, balsam poplar mostly occurs across the interior of Canada from Newfoundland through Alberta. Where their ranges overlap, the species often hybridize. In this study, we used genome sequencing of trees collected across six east-west transects from Washington state through British Columbia, Canada, and Alaska to understand genetic variation and the geography of hybridization. I found evidence of widespread hybridization across all transects. While the influence of P. balsamifera was extensive in northern populations, a large number of pure P. trichocarpa were found in southern populations. The transition from P. trichocarpa to P. balsamifera was also steeper in the south than the north, with a narrower hybrid zone in the south. Additionally, I found that gene flow among some populations was limited by temperature and geographical barriers. Taken together, my results suggest genetic structure and hybridization within and between these species is driven by climate variation, and that P. balsamifera ancestry may help northern P. trichocarpa populations adapt to their local environments.

No description available.

Submitted by Mendes Eduardo (dasilva@ufba.br) on 2013-07-17T23:43:33Z No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Approved for entry into archive by Vilma Conceição(vilmagc@ufba.br) on 2013-07-19T18:58:18Z (GMT) No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Made available in DSpace on 2013-07-19T18:58:19Z (GMT). No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Capes, Fapesb / A relação entre diversidade, complexidade e estabilidade com função do ecossistema tem sido uma importante questão na história da ecologia (Bengtsson, 1998). Tilman (1999) destaca que inicialmente o interesse desta relação residia nos efeitos da diversidade e complexidade trófica sobre a estabilidade dos ecossistemas e comunidades, contudo, este interesse enfraqueceu-se e apenas no início da década de 1990 começou a reaparecer, com interesses principalmente na relação da biodiversidade com os processos e serviços ecossistêmicos. Desde então, nesses últimos vinte anos, este programa de pesquisa tem crescido e recebendo destaque na literatura de ecologia (ver revisões de Giller et al., 2004; Reiss et al., 2009; Sandini e Solomini, 2009). Em uma abordagem de ciênciometria realizada por Caliman et al. (2010), os autores verificaram que os artigos publicados sobre o tema foi a uma baixa freqüência em relação a literatura ecológica no início da década de 90, aumentando bastante a partir de 1997, e conquistando uma significante freqüência ao longo dos quatro últimos anos analisados, de 2003 a 2007. Alguns estudos analisando esta questão têm utilizado a decomposição foliar como processo funcional de estudo (Briones e Ineson, 1996; Salamanca et al., 1998), principalmente na última década (Lecerf et al., 2007; ; Ball et al., 2008; Chapman e Newman, 2010; Barantal et al., 2011). Porém em menor quantidade nos ecossistemas aquáticos (Swan e Palmer, 2004; Kominoski et al., 2007; Moretti et al., 2007a; Abelho, 2009; Kominoski et al., 2009; Hoorens et al., 2010). Em ecossistemas lóticos, a vegetação circundante (ripária) constitui uma zona de transição entre o rio e os terrenos adjacentes mais acima (Mishall e Rugensk 2006). Esta vegetação ripária está intimamente relacionada à cadeia alimentar do rio, através do fornecimento de detritos foliares originária do folhiço como principal suprimento de energia (Benfield, 2006; Abelho, 2009). Os estudos iniciais de decomposição foliar se focavam em folhas de espécies individuais e a comparação entre elas, visando estabelecer os fatores principais que influenciam neste processo (Webster e Benfield, 1986; Abelho, 2001; Gartner e Cardon, 2004). A composição química do detrito foliar em decomposição é um importante fator para determinar a taxa de decomposição em muitos sistemas 2 (Hoorens et al., 2010; Bonanomi et al., 2010). E, juntamente com os fatores físicos e químicos, podem interferir nos mecanismos da biota que atua na decomposição (Webster e Benfield, 1986; Suberkropp e Chauvet, 1995; Jonsson e Wardle, 2008). Posteriormente, dado a existência de grande quantidade de espécies nas formações vegetais, e ao fato de o processo de decomposição de seus detritos ocorrerem em conjunto, misturadas uns com os outros, a indagação passou a ser se elas podem se influenciar, (Gartner e Cardon, 2004; Abelho, 2009). Nesta perspectiva, muitos estudos verificaram o efeito da riqueza de espécies em uma mistura na decomposição da mistura como um todo (Swan e Palmer, 2004; Sanpera-Calbet et al., 2009; Bonanomi et al., 2010), e outros verificaram a partir da comparação da decomposição observada da mistura, e o esperado em relação á decomposição individual de cada componente da mistura (Gartner e Cardon, 2004; Ball et al., 2008; Abelho, 2009). Nestes, é verificado ausência de efeito quando o esperado e o observado da variável de resposta não diferem significativamente, e um efeito quando diferem, significando que ocorreu algum tipo de interferência de um ou mais componentes da mistura sobre outros (Lecerf et al., 2007). Contudo, os resultados com experimentos de misturas têm sido diversos, mostrando efeitos positivos (aumento da decomposição), negativos (redução da decomposição) ou sem efeitos (Swan e Palmer, 2004; Moretti et al., 2007a; Abelho, 2009; Hoorens et al., 2010). Também são diversos quanto ao efeito da mistura na comunidade colonizadora e vice-versa, podendo ocorrer estimulo da colonização ou ausência de efeito (Leroy e Marks, 2006; Kominoski et al., 2007; Kominoski et al., 2009; Chapman e Newman, 2010). Além disso, poucos estudos têm verificado os mecanismos pelos quais os efeitos ocorrem, ou seja, quais componentes foliares da mistura estão sofrendo o efeito (Salamanca et al. 1998; Moretti et al. 2007a, Sanpera-Calbet et al., 2009; Hoorens et al., 2010). Portanto, os mecanismos pelo quais como a composição de espécies de uma mistura afeta as taxas de decomposição em misturas ainda é uma questão em aberto, (Hoorens et al., 2010) e necessitando de esforços e estudos para uma melhor compreensão do processo. / Salvador

Submitted by Mendes Eduardo (dasilva@ufba.br) on 2013-08-02T20:12:44Z No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Approved for entry into archive by Vilma Conceição (vilmagc@ufba.br) on 2014-02-06T13:34:10Z (GMT) No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Made available in DSpace on 2014-02-06T13:34:11Z (GMT). No. of bitstreams: 1 2011__Carneiro AC__Dissertação.pdf: 570609 bytes, checksum: 3e8ec3edf18e6e875d4899e0ce339ba6 (MD5) / Capes, Fapesb / A relação entre diversidade, complexidade e estabilidade com função do ecossistema tem sido uma importante questão na história da ecologia (Bengtsson, 1998). Tilman (1999) destaca que inicialmente o interesse desta relação residia nos efeitos da diversidade e complexidade trófica sobre a estabilidade dos ecossistemas e comunidades, contudo, este interesse enfraqueceu-se e apenas no início da década de 1990 começou a reaparecer, com interesses principalmente na relação da biodiversidade com os processos e serviços ecossistêmicos. Desde então, nesses últimos vinte anos, este programa de pesquisa tem crescido e recebendo destaque na literatura de ecologia (ver revisões de Giller et al., 2004; Reiss et al., 2009; Sandini e Solomini, 2009). Em uma abordagem de ciênciometria realizada por Caliman et al. (2010), os autores verificaram que os artigos publicados sobre o tema foi a uma baixa freqüência em relação a literatura ecológica no início da década de 90, aumentando bastante a partir de 1997, e conquistando uma significante freqüência ao longo dos quatro últimos anos analisados, de 2003 a 2007. Alguns estudos analisando esta questão têm utilizado a decomposição foliar como processo funcional de estudo (Briones e Ineson, 1996; Salamanca et al., 1998), principalmente na última década (Lecerf et al., 2007; ; Ball et al., 2008; Chapman e Newman, 2010; Barantal et al., 2011). Porém em menor quantidade nos ecossistemas aquáticos (Swan e Palmer, 2004; Kominoski et al., 2007; Moretti et al., 2007a; Abelho, 2009; Kominoski et al., 2009; Hoorens et al., 2010). Em ecossistemas lóticos, a vegetação circundante (ripária) constitui uma zona de transição entre o rio e os terrenos adjacentes mais acima (Mishall e Rugensk 2006). Esta vegetação ripária está intimamente relacionada à cadeia alimentar do rio, através do fornecimento de detritos foliares originária do folhiço como principal suprimento de energia (Benfield, 2006; Abelho, 2009). Os estudos iniciais de decomposição foliar se focavam em folhas de espécies individuais e a comparação entre elas, visando estabelecer os fatores principais que influenciam neste processo (Webster e Benfield, 1986; Abelho, 2001; Gartner e Cardon, 2004). A composição química do detrito foliar em decomposição é um importante fator para determinar a taxa de decomposição em muitos sistemas(Hoorens et al., 2010; Bonanomi et al., 2010). E, juntamente com os fatores físicos e químicos, podem interferir nos mecanismos da biota que atua na decomposição (Webster e Benfield, 1986; Suberkropp e Chauvet, 1995; Jonsson e Wardle, 2008). Posteriormente, dado a existência de grande quantidade de espécies nas formações vegetais, e ao fato de o processo de decomposição de seus detritos ocorrerem em conjunto, misturadas uns com os outros, a indagação passou a ser se elas podem se influenciar, (Gartner e Cardon, 2004; Abelho, 2009). Nesta perspectiva, muitos estudos verificaram o efeito da riqueza de espécies em uma mistura na decomposição da mistura como um todo (Swan e Palmer, 2004; Sanpera-Calbet et al., 2009; Bonanomi et al., 2010), e outros verificaram a partir da comparação da decomposição observada da mistura, e o esperado em relação á decomposição individual de cada componente da mistura (Gartner e Cardon, 2004; Ball et al., 2008; Abelho, 2009). Nestes, é verificado ausência de efeito quando o esperado e o observado da variável de resposta não diferem significativamente, e um efeito quando diferem, significando que ocorreu algum tipo de interferência de um ou mais componentes da mistura sobre outros (Lecerf et al., 2007). Contudo, os resultados com experimentos de misturas têm sido diversos, mostrando efeitos positivos (aumento da decomposição), negativos (redução da decomposição) ou sem efeitos (Swan e Palmer, 2004; Moretti et al., 2007a; Abelho, 2009; Hoorens et al., 2010). Também são diversos quanto ao efeito da mistura na comunidade colonizadora e vice-versa, podendo ocorrer estimulo da colonização ou ausência de efeito (Leroy e Marks, 2006; Kominoski et al., 2007; Kominoski et al., 2009; Chapman e Newman, 2010). Além disso, poucos estudos têm verificado os mecanismos pelos quais os efeitos ocorrem, ou seja, quais componentes foliares da mistura estão sofrendo o efeito (Salamanca et al. 1998; Moretti et al. 2007a, Sanpera-Calbet et al., 2009; Hoorens et al., 2010). Portanto, os mecanismos pelo quais como a composição de espécies de uma mistura afeta as taxas de decomposição em misturas ainda é uma questão em aberto, (Hoorens et al., 2010) e necessitando de esforços e estudos para uma melhor compreensão do processo. / Salvador, Bahia

As drought can impinge significantly on forest health and productivity, the mechanisms by which forest trees respond to drought is of interest. The research presented herein examined the intra-specific variation in the Populus balsamifera drought response, examining the potential role of the transcriptome to configure growth, metabolism and development in response to water deficit. Amassing evidence indicates that different species of Populus have divergent mechanisms and Three lines of inquiry were pursued to investigate the intraspecific variation the drought response in P. balsamifera. First, the transcriptome responses of six genotypes of P. balsamifera were examined using Affymetrix Poplar GeneChips under well-watered and water-deficit conditions. A core species-level transcriptome response was identified. Significantly, intraspecific variation in the drought transcriptome was also identified. The data support a role for genotype-derived variation in the magnitude of P. balsamifera transcriptome remodelling playing a role in conditioning drought responsiveness. Second, the impact of drought-stress induced declines in stomatal conductance, as well as an alteration in stomatal development in two genotypes was examined. Patterns of transcript abundance of genes hypothesised to underpin stomatal development had patterns congruent with their role in modulation of stomatal development. These results suggest that stomatal development may play a role as a long-term mechanism to limit water loss from P. balsamifera leaves under conditions of drought-stress. Finally, the drought-induced metabolome of six P. balsmaifera genotypes was interrogated. Metabolite profiling reveled amino acids such as isoleucine and proline and sugars such as galactinol and raffinose were found with increased abundance, whereas TCA intermediates succinic and malic acid were found with decreased abundance in response to drought. Comparative analysis of the metabolome and the transcriptome revealed genotypic-specific variation in energy and carbohydrate metabolism. Taken together, the findings reported in this thesis form a foundation to understand the basis of intraspecific variation in the drought response in P. balsamifera. Transcripts and metabolites that contribute to within-species differences in drought tolerance were defined. These molecular components are useful targets for both future study, as well as efforts aimed at protecting and growing trees of this important species under challenging environmental conditions.

As drought can impinge significantly on forest health and productivity, the mechanisms by which forest trees respond to drought is of interest. The research presented herein examined the intra-specific variation in the Populus balsamifera drought response, examining the potential role of the transcriptome to configure growth, metabolism and development in response to water deficit. Amassing evidence indicates that different species of Populus have divergent mechanisms and Three lines of inquiry were pursued to investigate the intraspecific variation the drought response in P. balsamifera. First, the transcriptome responses of six genotypes of P. balsamifera were examined using Affymetrix Poplar GeneChips under well-watered and water-deficit conditions. A core species-level transcriptome response was identified. Significantly, intraspecific variation in the drought transcriptome was also identified. The data support a role for genotype-derived variation in the magnitude of P. balsamifera transcriptome remodelling playing a role in conditioning drought responsiveness. Second, the impact of drought-stress induced declines in stomatal conductance, as well as an alteration in stomatal development in two genotypes was examined. Patterns of transcript abundance of genes hypothesised to underpin stomatal development had patterns congruent with their role in modulation of stomatal development. These results suggest that stomatal development may play a role as a long-term mechanism to limit water loss from P. balsamifera leaves under conditions of drought-stress. Finally, the drought-induced metabolome of six P. balsmaifera genotypes was interrogated. Metabolite profiling reveled amino acids such as isoleucine and proline and sugars such as galactinol and raffinose were found with increased abundance, whereas TCA intermediates succinic and malic acid were found with decreased abundance in response to drought. Comparative analysis of the metabolome and the transcriptome revealed genotypic-specific variation in energy and carbohydrate metabolism. Taken together, the findings reported in this thesis form a foundation to understand the basis of intraspecific variation in the drought response in P. balsamifera. Transcripts and metabolites that contribute to within-species differences in drought tolerance were defined. These molecular components are useful targets for both future study, as well as efforts aimed at protecting and growing trees of this important species under challenging environmental conditions.

In the Amazon region, formations of coastal vegetation on sandy soils {restinga) cover an area of approximately 1000 km2. In contrast to the restinga vegetation of southern and southeastern Brazil, restinga vegetation in the north of the country is not well known. This study presents a description of the woody vegetation of restinga dunes and the relationship between floristics, vegetation structure and topography near Vila Bonifácio, Ajuruteua península, Pará. A key to the woody species of the Vila Bonifácio restinga is presented as well as a short summary of the characters important for the identification of each species. The study site features a complex of dune ridges within an area of marshes, surrounded by mangroves. Vegetation structure was investigated along 4 transects of 10 m width and lengths of 100-170 m, each crossing obliquely the same dune ridge. Begin and end of ali transects were localized within the marsh-dune ecotone on either side of the transect. Elevation and influence of tidal inundation were documented along topographic profiles across each transect. Within transects, basal diameter, height as well as length of prostrate stem portions of ali trees and shrubs with a basal stem diameter >2.5 cm were recorded. If possible, fertile shoots of each occurring species were collected and deposited in local and regional herbaria. 15 woody plant species were identified within the sampling area, 3 additional species were found outside the transects. The species with the highest importance value was Pouteria ramiflora (Sapotaceae); other important constituents of the dune vegetation were members of Myrtaceae {Myrcia cuprea. Eugenia flavescens) and Arecaceae (Aslrocaryum sp.). Most plants were small trees or shrubs, with the notable exception of Humiria balsamifera (Humiriaceae) and P. ramiflora, reaching stem diameters of about 30 cm and heights >10 m in some parts of the area. The total basal area of ali transects accounted to 9.9 nr-ha'1, the overall tree density was 2.293,48 individuals-ha'1. Large stem diameters of P. ramiflora were only encountered at low elevation; similarly, height of P. ramiflora, Protium heptaphyllum and Ouratea ssp. was reduced at higher elevations. No convincing relationship between density and elevation was detected. The species inventory of Vila Bonifácio overlaps with that of the small number of other well-known restingas along the coast of Pará but future, more detailed surveys are necessary to arrive at a conclusive characterisation of the restinga flora of this state. / Na região amazônica, as formações de vegetação costeira de solos arenosos {restinga) cobrem uma área de aproximadamente 1000 km2. Ao contrário da vegetação de restingas do sul e sudeste do Brasil, na região norte esta vegetação ainda não é bem conhecida. Este estudo apresenta a descrição da vegetação arbustivo-arbórea de dunas e a relação entre composição florística, estrutural e topográfica próximo à Vila Bonifácio, península de Ajuruteua, Pará. Uma chave de identificação das espécies arbustivo-arbóreas ocorrentes na área também foi elaborada, bem como uma suscinta descrição das características vegetativas importantes para a identificação de cada espécie. A área de estudo apresenta um complexo de dunas com vegetação de campos, rodeadas por manguezais. A estrutura da vegetação foi analisada ao longo de quatro trasecções de 10 m de largura e comprimentos que variaram de 100-170 m, cada uma atravessando obliquamente o cordão de dunas. O início e o fim de todos os transectos estavam localizados dentro do ecótono campo-dunas. A elevação e a influência da inundação pela maré foram verificadas ao longo de perfis topográficos que atravessaram cada transecto. Dentro das transecções foram medidos o diâmetro à altura do solo (DAS), altura e comprimento (dos troncos sinuosos) de todos os indivíduos arbustivo-arbóreos com DAS >2,5 cm. Ramos férteis de cada espécie ocorrente foram coletados e depositados no herbário do campus de Bragança. Foram identificadas 15 espécies arbustivo-arbóreas no levantamento florístico, 3 espécies adicionais foram encontradas fora dos transectos e incluídas na chave taxonômica. A espécie com maior valor de impotância foi Pouteria ramiflora (Sapotaceae); outras famílias importantes da vegetação de dunas foram Myrtaceae {Myrcia cuprea. Eugenia f/avescens) e Arecaceae (Asírocaryum sp.). A maioria dos indivíduos foi de árvores pequenas ou arbustos, exceto, Humiria halsamifera (Humiriaceae) e P. ramiflora, que alcançaram diâmetros de cerca de 30 cm e alturas >10 m em alguns pontos da área. A área basal total de todas as transecções foi 9,9 nr-ha'1, a densidade total foi 2.293,48 ind-ha'1. Os maiores diâmetros de P. ramiflora foram encontrados somente em baixas elevações; a altura de P. ramiflora, Protium heptaphyllum e Ouratea sp. foram reduzidas em elevações mais baixas. Não houve uma relação significativa entre densidade e elevação. A análise do inventário das espécies arbustivo-arbóreas da restinga da Vila Bonifácio coincide com o pequeno número de espécies já bem conhecidas das restingas da costa do Pará mas, estudos futuros são necessários para se chegar a uma caracterização conclusiva da vegetação arbustivo- aebórea da restinga deste estado.

The composition of lignin in the outer cell-wall layers of spruce and poplar has been studied and the data obtained have been compared with those of the mature reference wood in which the secondary cell wall predominates. Materials with exclusively or predominantly outer cell-wall layers were examined. Accurate data relating to the lignin monomer composition and the number of β-O-4´ bonds were obtained from pure middle lamella/primary cell wall lignin. Firstly, a 10 000 year old white spruce material, with most of the secondary cell wall missing, was studied. The aged lignin was composed of guaiacyl units only, and was slightly more condensed but otherwise similar to the reference lignin. Secondly, the developing xylem of a Norway spruce clone was analyzed during a growth season. In spring and early summer, growth is very rapid and the intention was to sample tissues in which the secondary cell-wall layers had not yet lignified, but where the outer layers at least had started to lignify. Microscopy, Klason lignin and carbohydrate analyses showed that the lignin in the developing xylem of samples from mid-June was located exclusively in the middle lamella. The lignin was more condensed, was composed of guaiacyl units only and contained more end-groups than the reference Norway spruce wood. Thirdly, the cambial tissues of a Balsam poplar clone were surveyed during a growth season. Both the phloem side and the xylem side of the cambial region were examined. The Klason lignin content and carbohydrate monomer distribution showed that in June and August the tissues on the phloem side contained material with mainly middle lamella/primary walls. In June, the xylem side in the cambial region contained mainly middle lamella/primary walls, and in August the secondary cell wall carbohydrates were being deposited. Both tissues contained lignin that was more condensed and had more end-groups than the reference lignin. In mid-June, the developing xylem had a ratio of syringyl to guaiacyl units of 0.6, whereas the ratio for the reference wood was 1.3. In the final study, lignin from the primary cell walls from a hybrid aspen cell suspension culture was investigated. The lignin contained only guaiacyl units which were more condensed than those observed in the reference poplar wood. / <p>QC 20100920</p>

La prévalence de l’obésité, du diabète de type 2, et du syndrome métabolique, sont à la hausse chez les Cris d’Eeyou Istchee (CEI-Nord du Québec). Ces problèmes sont aggravés par leur diète non traditionnelle, leur sédentarité, ainsi que par une résistance culturelle aux produits pharmaceutiques. Afin de développer des traitements antidiabétiques culturellement adaptés, notre équipe a effectué une enquête ethnobotanique qui a identifié 17 plantes provenant de la pharmacopée traditionnelle des CEI. À partir des études de criblage effectuées in vitro, deux plantes parmi les 17 ont attiré notre attention. Populus balsamifera L. (Salicaceae) pour ses propriétés anti-obésité et Larix laricina K. Koch (Pinaceae) pour ses propriétés antidiabétiques. P. balsamifera et son composé actif salicortin ont inhibé l’accumulation de triglycérides durant l’adipogénèse dans les adipocytes 3T3-L1. L. laricina a augmenté le transport de glucose et l’activation de l’AMPK dans les cellules musculaires C2C12, l’adipogénèse dans les 3T3-L1 et a démontré un fort potentiel découpleur (propriété anti-obésité). Les objectifs de cette thèse sont d'évaluer les potentiels anti-obésité et antidiabétique et d’élucider les mécanismes d'action de P. balsamifera, salicortin, et L. laricina chez la souris C57BL/6 rendue obèse par une diète riche en gras (HFD). Les souris ont été soumises pendant huit (étude préventive) ou seize semaines (étude traitement) à une HFD, ou à une HFD dans laquelle P. balsamifera, salicortin, ou L. laricina a été incorporé soit dès le départ (prévention), ou dans les 8 dernières des 16 semaines d'administration de HFD (traitement). iv Les résultats démontrent que P. balsamifera (dans les deux études) et salicortin (évalué dans l’étude traitement) diminuent: le poids corporel, le gras rétropéritonéal, la sévérité de la stéatose et l’accumulation de triglycérides hépatique (ERK impliqué), les niveaux de glycémie et d'insuline, et le ratio leptine/adiponectine. Dans les deux études, P. balsamifera a significativement réduit la consommation de nourriture mais cet effet coupe-faim nécessite d’être approfondi. Dans l'étude préventive, P. balsamifera a augmenté la dépense énergétique (hausse de la température à la surface de la peau et de l’activation de la protéine découplante-1; UCP-1). Les voies de signalisation activées par P. balsamifera et par salicortin (de façon plus modeste) sont impliquées dans: la production de glucose hépatique (Akt), l’expression de Glut4 dans le muscle squelettique, la captation du glucose et du métabolisme des lipides (Akt dans le tissu adipeux), la différenciation des adipocytes (ERK et PPARg), l’inflammation dans le foie (IKKαβ), et l'oxydation des acides gras dans le muscle, le foie, ou le tissu adipeux (PPARa et CPT-1). D’autre part, L. laricina a également diminué les niveaux de glycémie et d’insuline, le ratio leptine/adiponectine, le gras rétropéritonéal et le poids corporel. Ces effets ont été observés en conjonction avec une augmentation de la dépense énergétique: hausse de température à la surface de la peau (prévention) et amélioration de la fonction mitochondriale et de la synthèse d'ATP (traitement). En conclusion, l’utilisation de P. balsamifera, salicortin et L. laricina comme des traitements alternatifs et culturellement adaptés aux CEI représente une contribution importante dans la prévention et le traitement de l’obésité et du diabète. / The prevalence of obesity, insulin resistance, and the metabolic syndrome is increasing among the Cree of Eeyou Istchee (CEI - Northern Quebec). Non-traditional diet and sedentary lifestyle along with cultural disconnect of modern type 2 diabetes (T2D) therapies are involved. In order to establish culturally adapted antidiabetic treatments, our research team conducted an ethnobotanical survey, where 17 plants were identified from the CEI traditional pharmacopoeia. Based on data obtained from in vitro screening studies, two plant species out of 17 were of particular interest for their properties as antiobesity, namely Populus balsamifera L. (Salicaceae), and antidiabetic agents, namely Larix laricina K. Koch (Pinaceae). P. balsamifera and its active salicortin inhibited triglyceride accumulation during adipogenesis in 3T3-L1 adipocytes. L. laricina increased glucose uptake and AMPK activation in C2C12 myotubes, adipogenesis in the 3T3-L1 adipocyte cell line, and was observed as one of the strongest uncouplers, severely disrupting mitochondrial function (increasing fuel consumption/metabolic rate; antiobesity property). The purpose of this PhD thesis is to evaluate the antiobesity and antidiabetic potential of P. balsamifera, salicortin, and L. laricina, in an in vivo model of diet-induced obese (DIO) C57BL/6 mice, as well as to investigate their possible mechanisms of action. Mice were subjected for eight (prevention study) or sixteen weeks (treatment study) to a high fat diet (HFD), or HFD to which P. balsamifera, salicortin, or L. laricina were incorporated either at onset (prevention), or in the last 8 of the 16 weeks of administration of the HFD (treatment). The results showed that P. balsamifera (in either study) and salicortin (incorporated in HFD only in treatment study) decreased the weight of whole vii body, retroperitoneal fat pad, reduced the severity of hepatic macrovesicular steatosis and triglyceride accumulation (ERK pathway implicated). They also decreased glycemia and improved insulin sensitivity by diminishing insulin levels, and altering adipokine secretion whereby reducing the leptin/adiponectin ratio. In both studies, P. balsamifera significantly reduced food intake. This appetite-reducing effect needs to be investigated further. In the prevention study this was accompanied by an increase in energy expenditure (increase in skin temperature and tends to increase expression of uncoupling protein-1; UCP-1). The signaling pathways activated by P. balsamifera and slightly by salicortin are implicated in either controlling hepatic glucose output (Akt), skeletal muscle Glut4 expression, glucose uptake and lipid metabolism in adipose tissue (Akt), adipocyte differentiation (ERK pathway and PPARg), decreasing the hepatic inflammatory state (IKKab), and increasing muscular, hepatic, or adipose tissue fatty acid oxidation (PPARa, CPT-1). As for L. laricina, it effectively decreased glycemia levels, insulin levels and the leptin/adiponectin ratio, improved insulin sensitivity and slightly decreased abdominal fat pad and body weights. This occurred in conjunction with increased energy expenditure as demonstrated by elevated skin temperature in the prevention study, and tendency to improve mitochondrial function and ATP synthesis in the treatment protocol. In conclusion, these results represent a major contribution, identifying P. balsamifera, salicortin, and L. laricina, as promising alternative, and culturally adapted therapies for the prevention and treatment care of obesity and diabetes among the CEI.