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Salinity is a challenge for crop productivity. Hence, plants exposed to saline environments reduce their vegetative and reproductive growth due to adverse effects of specific ions on metabolism and water relations. In order to cope with salinity, plants display physiological mechanisms based on three main aspects: i) source-sink relationships, ii) resource allocation and iii) alterations in endogenous hormone levels. The roles of developmental and hormonal mechanisms in salt response were investigated here. We employed mutants and transgenic tomato plants affecting different aspects of plant development and hormone response in the same genetic background (cultivar Micro-Tom). The following genotypes were used: Galapagos dwarf (Gdw), Lanata (Ln), lutescent (l), single flower truss (sft), sft heterozygous (sft/+), diageotropica (dgt), entire (e), Never ripe (Nr), epinastic (epi), procera (pro), notabilis (not), anti sense Chloroplastic carotenoid cleavage dioxygenase 7 (35S::asCCD7) and Salicylate hydroxylase (35S::nahG). Among the developmental genotypes studied, sft and l, involved in flower induction and senescence, respectively, were less affected when exposed to salt stress. Although l is considered deleterious due to its precocious senescence, it presented greater shoot biomass and leaf area during salinity. The heterozygous sft/+, whose high productivity was recently linked to an improved vegetative-to-reproductive balance, changed this balance and lowered its yield more than the control MT upon salt treatment. In the analysis of genotypes affecting hormonal status/signaling four kinds of salt responses among the genotypes were observed: i) High shoot growth in spite of high Na:K ratio presented by the strigolactone deficient and high branching CCD7 transgene; ii) High shoot growth and reduced accumulation of Na in tissues (probably due to dilution) presented by the auxin constitutive response e mutant; iii) The opposite response observed in \"ii\" presented by the low auxin sensitivity dgt mutant and iv) growth inhibition combined with reduced levels of Na and higher accumulation of K presented by the not mutant, which produces less ABA. Taken together, the results presented here points to novel developmental mechanisms, such as the promotion of moderate senescence and vegetative growth, and hormonal imbalances to be explored in the pursuing of crops resistant to salt stress. / A salinidade é um desafio para a produtividade agrícola, uma vez que plantas expostas à salinidade tem o crescimento vegetativo e reprodutivo reduzido devido aos efeitos adversos de íons específicos no metabolismo e nas relações hídricas. A fim de lidar com a salinidade, as plantas desempenham mecanismos fisiológicos baseados em três principais características: i) relações fonte-dreno; ii) alocação de reservas e iii) alterações nos níveis endógenos de hormônios. Nesse trabalho, investigamos a relação entre os processos de desenvolvimento e de regulação hormonal com a resposta à salinidade. Para tanto foram usados genótipos de tomateiro com alteração em diferentes vias de desenvolvimento e de produção ou sinalização de hormônios vegetais. Os seguintes genótipos foram usados: Galapagos dwarf (Gdw), Lanata (Ln), lutescent (l), single flower truss (sft), sft heterozygous (sft/+), diageotropica (dgt), entire (e), Never ripe (Nr), epinastic (epi), procera (pro), notabilis (not), anti sense Dioxigenase cloroplastídica de carotenoide 7 (35S::asCCD7) e Salicilato hidroxilase (35S::nahG). Entre os genótipos de desenvolvimento estudados, sft e l, relacionados à menor indução floral e senescência respectivamente, foram os menos afetados quando expostos à salinidade. O genótipo l acumulou maior biomassa e área foliar, apesar de ser considerado deletério devido à senescência precoce. As plantas heterozigotas, sft/+, cuja maior produtividade foi recentemente relacionada a um melhor balanço vegetativo/reprodutivo, alteraram esse balanço sob salinidade e reduziram sua produtividade mais que o controle MT sob estresse salino. Na análise dos genótipos com alteração hormonais foram observados quatro tipos de respostas à salinidade: i) elevado crescimento da parte aérea, apesar da razão Na:K ser alta no genótipo CCD7 cujo transgene induz deficiência de estrigolactona e excessiva ramificação; ii) elevado crescimento e acúmulo reduzido de Na nos tecidos (devido provavelmente a diluição) apresentada pelo mutante de resposta constitutiva a auxina e; iii) o oposto da resposta anterior foi apresentado pelo mutante pouco sensível à auxina , dgt; iv) inibição do crescimento combinado com nível reduzido de Na e alto acúmulo de K apresentada pelo mutante not que produz menos ácido abscísico. Considerados em conjunto, os resultados apresentaram temas para novos mecanismos de desenvolvimento, como a promoção moderada de senescência e do crescimento vegetativo além dos desbalanços hormonais, para serem explorados na busca de culturas resistentes ao estresse salino.

The goals of this research project were to identify the various insects observed to visit inflorescences of Echinacea angustifolia DC, and to rank these visitors according to their importance as pollinators of E. angustifolia in Saskatchewan. Studying nectar and the nectary is essential to understanding the interaction of disc florets with pollinators. Nectar-sugar production by disc florets of E. angustifolia and E. purpurea (L. Moench) was quantified from anthesis to cessation with production per disc floret peaking in the afternoon of the staminate phase (191.7 µg) and at midday of the first day of the pistillate phase (156.6 µg), respectively. Morphology of the disc-like floral nectaries of both Echinacea species was studied, as well as the ultrastructure of the nectary of E. purpurea. Modified stomata on the nectary rim are the most likely exits for nectar, but creases in the epidermis may also participate. The nectary of E. purpurea is vascularized by phloem alone, which occurred adjacent to the epidermis. Companion cells possessed wall ingrowths, and these cells may unload arriving sugar destined for either an apoplastic or symplastic pathway. Lobed nuclei were a key feature of secretory parenchyma cells, as was a predominance of mitochondria, suggesting that energy-requiring eccrine secretion predominates in E. purpurea. E. angustifolia exhibited a generalist pollination system, with pollinating insects belonging to the orders Coleoptera, Diptera, Hymenoptera, and Lepidoptera. The pollination efficiency of visitors was determined by single insect visits to bagged, virgin inflorescences followed by quantifying pollen tubes at the bases of receptive styles and/or calculating the percentage of shrivelled styles. It was determined that bumble bees (Bombus spp.) were efficient pollinators, indicating that they would likely contribute much to the pollination of E. angustifolia. Grasshopper bee flies (Systoechus vulgaris Loew) were plentiful but individually were not efficient pollinators, but taken together, they provided much pollination. Golden blister beetles (Epicauta ferruginea Say) were efficient pollinators but where yellow-petalled flowers occurred, their numbers on E. angustifolia decreased. Honey bees (Apis mellifera L.) were efficient pollinators and were present in low numbers without managed introduction. Pierid (2003) butterflies were regular visitors and efficient pollinators, and likely contributed significantly to E. angustifolia pollination. When introduced, the alfalfa leafcutter bee (Megachile rotundata Fabr.) preferred not to forage on E. angustifolia and as such, these solitary bees were not suitable as managed pollinators. In large agricultural plantings of E. angustifolia, however, native insects may not be capable of providing sufficient pollination for seed production when floral competition occurs.

The goals of this research project were to identify the various insects observed to visit inflorescences of Echinacea angustifolia DC, and to rank these visitors according to their importance as pollinators of E. angustifolia in Saskatchewan. Studying nectar and the nectary is essential to understanding the interaction of disc florets with pollinators. Nectar-sugar production by disc florets of E. angustifolia and E. purpurea (L. Moench) was quantified from anthesis to cessation with production per disc floret peaking in the afternoon of the staminate phase (191.7 µg) and at midday of the first day of the pistillate phase (156.6 µg), respectively. Morphology of the disc-like floral nectaries of both Echinacea species was studied, as well as the ultrastructure of the nectary of E. purpurea. Modified stomata on the nectary rim are the most likely exits for nectar, but creases in the epidermis may also participate. The nectary of E. purpurea is vascularized by phloem alone, which occurred adjacent to the epidermis. Companion cells possessed wall ingrowths, and these cells may unload arriving sugar destined for either an apoplastic or symplastic pathway. Lobed nuclei were a key feature of secretory parenchyma cells, as was a predominance of mitochondria, suggesting that energy-requiring eccrine secretion predominates in E. purpurea. E. angustifolia exhibited a generalist pollination system, with pollinating insects belonging to the orders Coleoptera, Diptera, Hymenoptera, and Lepidoptera. The pollination efficiency of visitors was determined by single insect visits to bagged, virgin inflorescences followed by quantifying pollen tubes at the bases of receptive styles and/or calculating the percentage of shrivelled styles. It was determined that bumble bees (Bombus spp.) were efficient pollinators, indicating that they would likely contribute much to the pollination of E. angustifolia. Grasshopper bee flies (Systoechus vulgaris Loew) were plentiful but individually were not efficient pollinators, but taken together, they provided much pollination. Golden blister beetles (Epicauta ferruginea Say) were efficient pollinators but where yellow-petalled flowers occurred, their numbers on E. angustifolia decreased. Honey bees (Apis mellifera L.) were efficient pollinators and were present in low numbers without managed introduction. Pierid (2003) butterflies were regular visitors and efficient pollinators, and likely contributed significantly to E. angustifolia pollination. When introduced, the alfalfa leafcutter bee (Megachile rotundata Fabr.) preferred not to forage on E. angustifolia and as such, these solitary bees were not suitable as managed pollinators. In large agricultural plantings of E. angustifolia, however, native insects may not be capable of providing sufficient pollination for seed production when floral competition occurs.

Cyclic nucleotide-gated channels (CNGCs) are non-selective cation channels that were first identified in vertebrate photosensory and olfactory neurons. Although the physiological roles and biophysical properties of animal CNGCs have been well studied, much less is known about these channels in plants. The Arabidopsis genome encodes twenty putative CNGC subunits that are postulated to form channel complexes that mediate various physiological processes involving abiotic and biotic stress responses, ion homeostasis and development. The identification of Arabidopsis autoimmune CNGC mutants, such as defense no death class (dnd1 and dnd2), and the constitutive expressor of pathogenesis related genes 22 (cpr22) implicate AtCNGC2, 4, 11 and 12 in plant immunity. Here, I present a comprehensive study of the molecular mechanisms involved in CNGC-mediated signaling pathways with emphasis on pathogen defense. Previously, a forward genetics approach aimed to identify suppressor mutants of the rare gain-of-function autoimmune mutant, cpr22, identified key residues that are important for CNGC subunit interactions and channel function. First, I present a structure-function analysis of one of these suppressor mutants (S58) that revealed a key residue in the cyclic nucleotide binding domain involved in the stable regulation of CNGCs. Second, I present a new suppressor screen using AtCNGC2 T-DNA knockout mutants that specifically aimed to identify novel downstream components of CNGC-mediated pathogen defense signaling. In this screen, I successfully isolated and characterized the novel Arabidopsis mutant, repressor of defense no death 1 (rdd1), and expanded this study to demonstrate its involvement in AtCNGC2 and AtCNGC4-mediated signal transduction. Additionally, I demonstrated for the first time, the physical interaction of AtCNGC2 and AtCNGC4 subunits in planta. The findings presented in this thesis broaden our current knowledge of CNGCs in plants, and provide a new foundation for future elucidation of the structure-function relationships and signal transduction mediated by these channels.

Cyclic nucleotide-gated channels (CNGCs) are non-selective cation channels that were first identified in vertebrate photosensory and olfactory neurons. Although the physiological roles and biophysical properties of animal CNGCs have been well studied, much less is known about these channels in plants. The Arabidopsis genome encodes twenty putative CNGC subunits that are postulated to form channel complexes that mediate various physiological processes involving abiotic and biotic stress responses, ion homeostasis and development. The identification of Arabidopsis autoimmune CNGC mutants, such as defense no death class (dnd1 and dnd2), and the constitutive expressor of pathogenesis related genes 22 (cpr22) implicate AtCNGC2, 4, 11 and 12 in plant immunity. Here, I present a comprehensive study of the molecular mechanisms involved in CNGC-mediated signaling pathways with emphasis on pathogen defense. Previously, a forward genetics approach aimed to identify suppressor mutants of the rare gain-of-function autoimmune mutant, cpr22, identified key residues that are important for CNGC subunit interactions and channel function. First, I present a structure-function analysis of one of these suppressor mutants (S58) that revealed a key residue in the cyclic nucleotide binding domain involved in the stable regulation of CNGCs. Second, I present a new suppressor screen using AtCNGC2 T-DNA knockout mutants that specifically aimed to identify novel downstream components of CNGC-mediated pathogen defense signaling. In this screen, I successfully isolated and characterized the novel Arabidopsis mutant, repressor of defense no death 1 (rdd1), and expanded this study to demonstrate its involvement in AtCNGC2 and AtCNGC4-mediated signal transduction. Additionally, I demonstrated for the first time, the physical interaction of AtCNGC2 and AtCNGC4 subunits in planta. The findings presented in this thesis broaden our current knowledge of CNGCs in plants, and provide a new foundation for future elucidation of the structure-function relationships and signal transduction mediated by these channels.

Cotton has been a world-wide economic staple in textiles and oil production. There has been a concerted effort for cotton improvement to increase yield and quality to compete with non-natural man-made fibers. Unfortunately, cultivated cotton has limited genetic diversity; therefore finding new marketable traits within cultivated cotton has reached a plateau. To alleviate this problem, traditional breeding programs have been attempting to incorporate practical traits from wild relatives into cultivated lines. This incorporation has presented a new problem: uncultivated cotton hampered by photoperiodism. Traditionally, due to differing floral times, wild and cultivated cotton species were unable to be bred together in many commercial production areas world-wide. This worldwide breeding problem has inhibited new trait incorporation. Before favorable traits from undomesticated cotton could be integrated into cultivated elite lines using marker-assisted selection breeding, the markers associated with photoperiod independence needed to be discovered. In order to increase information about this debilitating trait, we set out to identify informative markers associated with photoperiodism. This study was segmented into four areas. First, we reviewed the history of cotton to highlight current problems in production. Next, we explored cotton’s floral development through a study of floral transition candidate genes. The third area was an in-depth analysis of Phytochrome C (previously linked to photoperiod independence in other crops). In the final area of study, we used Genotype-By-Sequencing (GBS), in a segregating population, was used to determine photoperiod independence associated with single nucleotide polymorphisms (SNPs). In short, this research reported SNP differences in thirty-eight candidate gene homologs within the flowering time network, including photoreceptors, light dependent transcripts, circadian clock regulators, and floral integrators. Also, our research linked other discrete SNP differences, in addition to those contained within candidate genes, to photoperiodicity within cotton. In conclusion, the SNP markers that our study found may be used in future marker assisted selection (MAS) breeding schemas to incorporate desirable traits into elite lines without the introgression of photoperiod sensitivity.

Made available in DSpace on 2016-08-15T20:30:57Z (GMT). No. of bitstreams: 1 DanielSP_DISSERT.pdf: 1561196 bytes, checksum: b284038c0016d3ae3285d101b795f237 (MD5) Previous issue date: 2008-07-25 / Néctar; entomofauna; Merremia aegyptia / O objetivo deste trabalho foi o de investigar se os diferentes horários de coleta de néctar em áreas apícolas influenciam no volume, concentração de açúcar e açúcar total produzido por suas flores, no momento da antese, bem como verificar possíveis alterações nas características do néctar ao longo do tempo e discutir as conseqüências no potencial apícola das áreas de jitirana-branca (Merremia aegyptia). E ainda, a relação entre esta produção de atrativos florais e o comportamento dos polinizadores potenciais, dentre estes a Apis mellifera L. (abelha africanizada), e os requerimentos de polinização da jitirana branca. A pesquisa foi realizada em uma área de preservação de Caatinga, no Campus da FATEC Sertão Central, Quixeramobim-Ceará. Foi constatado que: A jitirana branca é uma cornucópia; sua densidade floral por m² foi em média 33,7 flores; apresentou ampla gama de visitantes florais (hymenopteros, coleópteros, hemípteros, dípteros, e pássaros); seu volume de néctar variou de acordo com o horário de coleta e não há reposição de néctar na flor após as 11:00 horas (A.M.); e a polinização mais eficiente corresponde a autopolinização.

Salinity is a challenge for crop productivity. Hence, plants exposed to saline environments reduce their vegetative and reproductive growth due to adverse effects of specific ions on metabolism and water relations. In order to cope with salinity, plants display physiological mechanisms based on three main aspects: i) source-sink relationships, ii) resource allocation and iii) alterations in endogenous hormone levels. The roles of developmental and hormonal mechanisms in salt response were investigated here. We employed mutants and transgenic tomato plants affecting different aspects of plant development and hormone response in the same genetic background (cultivar Micro-Tom). The following genotypes were used: Galapagos dwarf (Gdw), Lanata (Ln), lutescent (l), single flower truss (sft), sft heterozygous (sft/+), diageotropica (dgt), entire (e), Never ripe (Nr), epinastic (epi), procera (pro), notabilis (not), anti sense Chloroplastic carotenoid cleavage dioxygenase 7 (35S::asCCD7) and Salicylate hydroxylase (35S::nahG). Among the developmental genotypes studied, sft and l, involved in flower induction and senescence, respectively, were less affected when exposed to salt stress. Although l is considered deleterious due to its precocious senescence, it presented greater shoot biomass and leaf area during salinity. The heterozygous sft/+, whose high productivity was recently linked to an improved vegetative-to-reproductive balance, changed this balance and lowered its yield more than the control MT upon salt treatment. In the analysis of genotypes affecting hormonal status/signaling four kinds of salt responses among the genotypes were observed: i) High shoot growth in spite of high Na:K ratio presented by the strigolactone deficient and high branching CCD7 transgene; ii) High shoot growth and reduced accumulation of Na in tissues (probably due to dilution) presented by the auxin constitutive response e mutant; iii) The opposite response observed in \"ii\" presented by the low auxin sensitivity dgt mutant and iv) growth inhibition combined with reduced levels of Na and higher accumulation of K presented by the not mutant, which produces less ABA. Taken together, the results presented here points to novel developmental mechanisms, such as the promotion of moderate senescence and vegetative growth, and hormonal imbalances to be explored in the pursuing of crops resistant to salt stress. / A salinidade é um desafio para a produtividade agrícola, uma vez que plantas expostas à salinidade tem o crescimento vegetativo e reprodutivo reduzido devido aos efeitos adversos de íons específicos no metabolismo e nas relações hídricas. A fim de lidar com a salinidade, as plantas desempenham mecanismos fisiológicos baseados em três principais características: i) relações fonte-dreno; ii) alocação de reservas e iii) alterações nos níveis endógenos de hormônios. Nesse trabalho, investigamos a relação entre os processos de desenvolvimento e de regulação hormonal com a resposta à salinidade. Para tanto foram usados genótipos de tomateiro com alteração em diferentes vias de desenvolvimento e de produção ou sinalização de hormônios vegetais. Os seguintes genótipos foram usados: Galapagos dwarf (Gdw), Lanata (Ln), lutescent (l), single flower truss (sft), sft heterozygous (sft/+), diageotropica (dgt), entire (e), Never ripe (Nr), epinastic (epi), procera (pro), notabilis (not), anti sense Dioxigenase cloroplastídica de carotenoide 7 (35S::asCCD7) e Salicilato hidroxilase (35S::nahG). Entre os genótipos de desenvolvimento estudados, sft e l, relacionados à menor indução floral e senescência respectivamente, foram os menos afetados quando expostos à salinidade. O genótipo l acumulou maior biomassa e área foliar, apesar de ser considerado deletério devido à senescência precoce. As plantas heterozigotas, sft/+, cuja maior produtividade foi recentemente relacionada a um melhor balanço vegetativo/reprodutivo, alteraram esse balanço sob salinidade e reduziram sua produtividade mais que o controle MT sob estresse salino. Na análise dos genótipos com alteração hormonais foram observados quatro tipos de respostas à salinidade: i) elevado crescimento da parte aérea, apesar da razão Na:K ser alta no genótipo CCD7 cujo transgene induz deficiência de estrigolactona e excessiva ramificação; ii) elevado crescimento e acúmulo reduzido de Na nos tecidos (devido provavelmente a diluição) apresentada pelo mutante de resposta constitutiva a auxina e; iii) o oposto da resposta anterior foi apresentado pelo mutante pouco sensível à auxina , dgt; iv) inibição do crescimento combinado com nível reduzido de Na e alto acúmulo de K apresentada pelo mutante not que produz menos ácido abscísico. Considerados em conjunto, os resultados apresentaram temas para novos mecanismos de desenvolvimento, como a promoção moderada de senescência e do crescimento vegetativo além dos desbalanços hormonais, para serem explorados na busca de culturas resistentes ao estresse salino.

Dans le domaine de la biologie développementale, un des principaux défis est de comprendre comment des tissus multicellulaires, à l'origine indifférenciés, peuvent engendrer des formes aussi complexes que celles d'une fleur. De part son implication dans l'organogenèse florale, l'auxine est une phytohormone majeure. Nous avons donc déterminé son réseau binaire potentiel, puis y avons appliqué des modèles de clustering de graphes s'appuyant sur les profils de connexion présentés par ces 52 facteurs de transcription (FT). Nous avons ainsi pu identifier trois groupes, proches des groupes biologiques putatifs: les facteurs de réponse à l'auxine activateurs (ARF+), répresseurs (ARF-) et les Aux/IAAs. Nous avons détecté l'auto-interaction des ARF+ et des Aux/IAA, ainsi que leur interaction, alors que les ARF- en présentent un nombre restreint. Ainsi, nous proposons un mode de compétition auxine indépendent entre ARF+ et ARF- pour la régulation transcriptionelle. Deuxièmement, nous avons modélisé l'influence des séquences de dimérisation des FT sur la structure de l'interactome en utilisant des modèles de mélange Gaussien pour graphes aléatoires. Les groupes obtenus sont proches des précédents, et les paramètres estimés nous on conduit à conclure que chaque sous-domaine peut jouer un rôle différent en fonction de leur proximité phylogénétique.Enfin, nous sommes passés à l'échelle multi-cellulaire ou, par un graphe spatio-temporel, nous avons modélisé les premiers stades du développement floral d'A. thaliana. Nous avons pu extraire des caractéristiques cellulaires (3D+t) de reconstruction d'imagerie confocale, et avons démontré la possibilité de caractériser l'identité cellulaire en utilisant des méthodes de classification hiérarchique et des arbres de Markov cachés. / A striking aspect of flowering plants is that, although they seem to display a great diversity of size and shape, they are made of the same basics constituents, that is the cells. The major challenge is then to understand how multicellular tissues, originally undifferentiated, can give rise to such complex shapes. We first investigated the uncharacterised signalling network of auxin since it is a major phytohormone involved in flower organogenesis.We started by determining the potential binary network, then applied model-based graph clustering methods relying on connectivity profiles. We demonstrated that it could be summarise in three groups, closely related to putative biological groups. The characterisation of the network function was made using ordinary differential equation modelling, which was later confirmed by experimental observations.In a second time, we modelled the influence of the protein dimerisation sequences on the auxin interactome structure using mixture of linear models for random graphs. This model lead us to conclude that these groups behave differently, depending on their dimerisation sequence similarities, and that each dimerisation domains might play different roles.Finally, we changed scale to represent the observed early stages of A. thaliana flower development as a spatio-temporal property graph. Using recent improvements in imaging techniques, we could extract 3D+t cellular features, and demonstrated the possibility of identifying and characterising cellular identity on this basis. In that respect, hierarchical clustering methods and hidden Markov tree have proven successful in grouping cell depending on their feature similarities.