MADS-box genes are important regulators of reproductive development in seed plants, including both flowering plants and conifers. In this thesis the evolution of the AGAMOUS subfamily of MADS-box genes, and what the ancestral function of this group of genes might have been in the early seed plants about 300 million years ago, was addressed by the discovery of two novel conifer genes, both basal to all previously known AGAMOUS subfamily genes. DAL20, the most basal of these genes, was exclusively expressed in roots, unlike all previously known AGAMOUS subfamily genes. I also studied the evolutionary mechanisms leading to functional diversification of duplicated genes in two different subfamilies of MADS-box genes; the AGAMOUS and AGL6 subfamilies. Focus was on studying changes in gene expression pattern, representing changes in the transcriptional regulation between the genes, and on comparing the functional properties of the gene products, representing changes in the protein-coding sequence between the genes. Duplicated genes in the AGL6 subfamily were found to have evolved by both mechanisms. In the AGAMOUS subfamily I found duplicated spruce genes; DAL2 and DAL20, that appear to have functionally diversified mainly by changes in the transcriptional regulation. Conifer AGAMOUS subfamily genes were also used in a comparative developmental-genetics approach to evaluate hypotheses, based on the morphology of fossil and extant conifer seed cones, on the identity of the female reproductive organ, the ovuliferous scale, and the evolution of seed cone morphology in the conifer families Pinaceae, Taxodiaceae and Cupressaceae. Seed cones in these families have been hypothesized to have homologous ovule-bearing organs, but I found substantial differences in the expression patterns of orthologous AGAMOUS subfamily genes in seed cones of these families that are not compatible with this hypothesis, indicating that the evolutionary history of conifer seed cones is more diverse than previously thought.

Des études chez les animaux ont montré que ZRF1 a une fonction lectrice au niveau de H2Aub1 dans la dérépression de gènes réprimés par polycomb. Deux gènes homologues au gène humain ZRF1 ont été identifiés dans le génome d'Arabidopsis, et ont par la suite été appelés AtZRF1 a etAtZRF1 b. La caractérisation fonctionnelle de ces gènes n'a pas encore été rapportée. Ma première objective était d'obtenir des connaissances générales sur AtZRF1 a et AtZRF1 b. Tous les deux sont exprimés dans des plantes d'Arabidopsis et la protéine AtZRF1 b est localisée dans le noyau et dans le cytoplasme. En plus, nous avons trouvé que la protéine AtZRF1 b lie H2Aub1 avec les mêmes caractéristiques que la protéine ZRF1 humaine. J'ai utilisé les outils génétiques puissants disponibles pour Arabidopsis pour étudier la fonction d'AtZRF1 a et AtZRF1 b. Plusieurs lignées d'insertion de T-DNA indépendantes ont été identifiées. A cause d'une rédondance fonctionelle,des mutants simples n'ont pas de défauts de développement évidents. C'est pourquoi j'ai étudié un mutant double qui montrent une perte de fonction pour les deux gènes AtZRF1 a et AtZRF1 b. Ce double mutant révèle des rôles importants pour ces gènes dans la croissance et le développement,qui vont de la prolifération cellulaire et la différenciation jusqu'au contrôle du temps de floraison. J'ai ensuite étudié les rôles d'AtZRF1 a et AtZRF1 b dans la régulation de la transcription et j'ai constaté que AtZRF1 a et AtZRF1 b ont une fonction similaire a PRC1. Finalement, j'ai étudié les niveaux de H3K4me3, H3K27me3 et H2Aub1 dans la chromatine de certains gènes dont l'expression est perturbée dans les doubles mutants. Les résultats montrent que la déubiquitination de H2Aubi1 n'est pas un événement majeur dans la régulation de la transcription chez Arabidopsis. / Studies in animais show that ZRF1 can read the histone H2AK119ub1 modification in the derepression of polycomb-repressed genes. Two homologs of human ZRF1 have been identified in the Arabidopsis genome, and here in after are named AtZRF1 a and AtZRF1 b. So far, their functional characterization had not been reported. My first objective was to acquire basic knowledge about AtZRF1 a and AtZRF1 b. Both are broadly expressed in Arabidopsis plants and the AtZRF1 b protein is localized in the nucleus and thecytoplasm. Moreover, we found that AtZRF1 b binds H2Aub1 with characteristics similar to those previously reported for the human ZRF1 protein. I subsequently used the powerful genetic tools available in Arabidopsis to investigate the AtZRF1 a and AtZRF1b function. Several independent T-DNA insertion Arabidopsis mutant lines were identified. Because of functional redundancy, single mutants have no obvious developmental defects. I therefore focused on double mutants displaying loss of function of both AtZRF1a and AtZRF1 b. The study of a double mutant revealed important roles for these genes in plant growth and development ranging from cell proliferation and differentiation to flowering time control.I then investigated the roles of AtZRF1 a and AtZRF1 b in gene transcription regulation and found that AtZRF1a and AtZRF1 b function in a way that is partially similar to PRC1 function. Lastly, I investigated H3K4me3, H3K27me3 and H2Aub1 levels in the chromatin regions of some expression-perturbed genes in double mutants. The results show that ZRF1-mediated deubiquitination of H2Aub1 is not a major event in transcription regulation in Arabidopsis.

O presente trabalho teve o objetivo de avaliar os efeitos da vegetação intercalar composta por gramíneas e leguminosas perenes e da cobertura morta, obtida pelo manejo mecânico da vegetação intercalar, e herbicidas aplicados em pós-emergência, na linha da cultura, sobre a população de plantas daninhas, características químicas do solo, estado nutricional, desenvolvimento vegetativo e produção de citros. O experimento foi conduzido, durante as safras 2004/2005 e 2005/2006, na Fazenda São Judas, Lucianópolis - SP, em um pomar de laranja Pêra (Citrus sinensis (L.) Osbeck.), plantado em outubro de 2002. O delineamento utilizado foi o de blocos ao acaso, com parcelas subdivididas sendo 7 tratamentos e 2 subtratamentos, com 4 repetições. Os tratamentos foram: 1) vegetação intercalar de Brachiaria ruziziensis R. Germ. & Evrard, sem cobertura morta na linha da cultura; 2) vegetação intercalar de B. ruziziensis, com cobertura morta1 na linha da cultura; 3) vegetação intercalar de B. ruziziensis e Arachis pintoi Krap. & Greg com cobertura morta1 na linha da cultura; 4) vegetação intercalar de B. ruziziensis e Stylosantes spp. com cobertura morta1 na linha da cultura; 5) vegetação intercalar composta por Brachiaria plantagineacom cobertura morta1 na linha da cultura 6) vegetação intercalar de Arachis pintoi com cobertura morta1 na linha da cultura; 7) vegetação intercalar de estilosantes \'mineirão\' (Stylosathes macrocephala (25%), S. capitata (60%) e S. guianensis (15%)) com cobertura morta1 na linha da cultura. Os herbicidas aplicados às subparcelas foram: 1) glyphosate a 1260 g e. a. ha-1 e 2) paraquat a 400 g i. a. ha-1. Pelos dados obtidos pode-se observar que: a vegetação intercalar dos tratamentos 2, 3 e 4 obtiveram as maiores produções de fitomassa e cobertura morta, seguido pelos tratamentos 5 e 7 e a menor produção de fitomassa foi obtida pelo tratamento 6. A cobertura morta de B. ruziziensis proporcionou menor densidade de plantas daninhas por até 90 dias. O teor de matéria orgânica, nas entrelinhas, na camada de 0-0,10 m, nos tratamentos 2 e 4 foi superior em 3,79 e 3,48 g cm-3 em relação ao tratamento 6, enquanto que na camada de 0,20-0,40 m, o teor de matéria orgânica, do tratamento 6, foi superior em 4,6, 5,1 e 3,9 g cm-3 em relação aos tratamentos 1, 3 e 4, respectivamente. Nas linhas da cultura, o tratamento 4 e 3 apresentaram teor de K superior em 1,28 e 0,95 mmolc dm-3, respectivamente, em relação ao tratamento 6, nas camadas de 0-0,10 e 0,10-0,20 m de solo. O estilosantes proporcionou incrementos no teor foliar de N de 2,58 e 2,55 g kg-1, em relação aos tratamentos 1 e 2. O teor foliar de P do tratamento 4 foi superior ao tratamento 1 em 0,31 g kg-1, sendo observada uma correlação entre a densidade do sistema radicular na camada de 0-0,10 m de solo e o teor foliar de P. Não foi verificado efeitos dos tratamentos e herbicidas no desenvolvimento vegetativo, bem como na produção total no período avaliado. / The objective of this research was to evaluate the effects of cover crops from grass and perennial leguminous in the orchard inter-rows, mulch, produced through mechanical management with a lateral rotary mower from inter-row cover crops associated with herbicides applied in pos-emergence, on the rows, on population dynamics of weeds, soil chemical characteristics and development, nutrition and citros production. The experiment was carried out at the São Judas farm, Lucianópolis - SP - Brazil during the harvest of 2004/2005 and 2005/2006 in a citrus orchard of Citrus sinensis L. Osbeck cv. Pera, planted in October, 2002. The experimental design used was of randomized blocks with subdivided plots and 4 replications. The treatments were; 1) Cover crop of Brachiaria ruziziensis R. Germ. & Evrard, without mulch on the row; 2) Cover crop of B. ruziziensis and mulch on the row, produced through mechanical management with a lateral rotary mower (REL) from this cover crop; 3) Cover crop of B. ruziziensis and Arachis pintoi Krap. & Greg and mulch on the row, produced through REL from this cover crop; 4) Cover crop of B. ruziziensis and estilosantes \"mineirão\" (Stylosathes macrocephala (25%), S. capitata (60%) e S. guianensis (15%)) and mulch on the row, produced through REL from this cover crop; 5) Cover crop of Brachiaria plantaginea and mulch on the row, produced through REL from this cover crop; 6) Cover crop of Arachis pintoi and mulch on the row, produced through REL from this cover crop; 7) Cover crop of estilosantes \"mineirão\" and mulch on the row, produced through REL from this cover crop.The herbicides applied into the subplots were: 1) glyphosate at the rate 1260 g a.e. ha-1 and 2) paraquat at the rate 400 a.i. ha-1. In these experiments, it could be observed that: the cover crops from the treatments 2, 3 and 4 got higher wet biomass and mulch than others treatments; B. ruziziensis mulch decrease the weeds density until 90 days after the distribution; in the inter-row, into 0-0,10 m soil layer, the treatments 2 and 4 organic matter, was higher than treatment 6, however, into 0,20-0,40 m soil layer, treatment 6 organic matter was higher than treatments 1, 3 and 4. Into the rows, treatments 4 and 3 achieved K tenor higher than treatment 6 in 1,28 and 0,95 mmolc dm-3, respectively, into 0-0,10 and 0,10-0,20 m soil layers. Estilosantes promoted N foliar increases of 2,58 and 2,55 g kg-1 regarding treatments 1 and 2. Treatment 4 P foliar tenor was higher than treatment 1 in 0,31 g kg-1. It was observed a correlation between root density into superficial layer soil and P foliar tenor. It was not verified any effect of treatment or herbicides on development and total citros production.

A cana-de-açúcar (Saccharum spp.) é uma cultura de grande importância social, econômica e ambiental para o Brasil, ocupa 7,1 milhões de hectares, com produção de aproximadamente 570 milhões de toneladas. A disponibilidade hídrica é a principal causa da redução da produtividade, sendo o início do desenvolvimento o período mais sensível a déficit hídrico. São necessárias mais pesquisas para entender claramente os mecanismos de resposta da cultura ao déficit hídrico. Assim, o presente trabalho teve como objetivo avaliar o desenvolvimento vegetativo e resistência à seca de duas variedades da cultura de cana-de-açúcar (RB867515 e SP81-3250) durante a fase inicial de desenvolvimento quando submetidas a diferentes níveis de estresse hídrico para quatro profundidades de solo. O experimento foi realizado na área de pesquisa do Departamento de Engenharia de Biossistemas na Escola Superior de Agricultura Luiz de Queiroz (ESALQ/USP) em ambiente protegido (casa de vegetação), o solo utilizado foi classificado como Latossolo Vermelho Amarelo, textura franco arenosa, denominado Série Sertãozinho. Utilizaram-se caixas dágua de 100 litros preenchidas com diferentes camadas de pedra brita nº 02, e solo, compondo camadas de 40, 30, 20 e 10 cm. Os níveis de déficit hídrico (N) foram aplicados interrompendo-se as irrigações por diferentes períodos, sendo que a evapotranspiração de referência acumulada (EToAc) foi de 0, 21, 38 e 58 mm até o tratamento ser novamente irrigado para N1, N2, N3 e N4 respectivamente. O sistema de irrigação utilizado foi por gotejamento e o manejo realizado com base em dados de umidade do solo obtidos a partir de leituras de tensiômetros. O delineamento foi em blocos ao acaso (DBC) em esquema fatorial 2 x 4 x 4 com os tratamentos dispostos em faixas, totalizando 32 tratamentos, sendo a parcela experimental representada por uma caixa contendo quatro touceiras de cana-de-açúcar. Observou-se que as plantas cultivadas em solo com profundidade de 10 cm apresentaram redução significativa na extensão máxima do colmo primário, massa de folhas do colmo primário, massa de folhas e bainha+colmo dos perfilhos, mesmo não tendo restrição hídrica. Para solos rasos, a variedade SP81-3250 foi mais sensível ao déficit hídrico, com grande redução na massa seca de folhas e bainha+colmo dos perfilhos. O desenvolvimento das plantas em solos de 30 e 40 cm de profundidade não apresentou diferença de sensibilidade ao déficit hídrico entre as variedades. Uma vez que o nível de água disponível do solo seja esgotado, a tolerância à seca das variedades estudadas é relativamente baixa. Balanços hídricos com valores menores que -13 mm causam queda significativa na população final de plantas, independentemente da variedade, sendo que, a partir de um valor acumulado de -35 mm, nenhuma planta sobreviveu. / Sugar cane (Saccharum spp.) is an important crop from social, economic and environmental points of view for Brazil. It occupies 7,1 million hectares, producing approximately 570 million tons per year. Total available water in the soil (TWA) is the main cause of low productivity of certain areas, and the early development period it is one of most sensitive to water deficit. More research is needed to clearly understand mechanisms of crop response to drought, so this study aimed to evaluate plant growth and drought resistance of two varieties of the crop of sugar cane (RB867515 and SP81- 3250) during the initial phase of development, under different water stress levels for different soil depths. The experiment was conducted at the Biosystems Engineering Department at the School of Agriculture \"Luiz de Queiroz (ESALQ/USP) under greenhouse conditions; the soil used was classified as Typic Yellow, sandy loam, called Series Sertãozinho. Fiber cement containers were used, filled with 100 liters of different gravel layers and soil, forming layers 40, 30, 20 and 10 cm of soil. The levels of water deficit (N) were applied interrupting the irrigation for different periods of cumulative reference evapotranspiration (EToAc): 0, 21, 38 and 58 mm, before reirrigated treatment for N1, N2, N3 and N4 respectively. Irrigation management was carried out based on a drip irrigation system and tensiometer readings. The design was a randomized block design (RBD) in factorial 2 x 4 x 4 with treatments arranged in bands, totalizing 32 treatments (containers), presenting four clumps of sugar cane per recipient. It was observed that plants growing in 10 cm soil depths showed a significant reduction to the fullest extent of the primary stem, leaf mass of primary stem, leaf mass and stem sheath of tillers, although not differing under water restriction. For shallow soils the variety SP81-3250 was more sensitive to drought, with a large reduction in dry weight of leaves and stalks + sheath of the tillers. The development of plants in soils 30 and 40 cm soil depths showed no difference in sensitivity to water deficit among varieties. The percentage of plants alive correlated very well with the value of climatic water balance, and the treatments with climatic water balance more negative than -13 mm had a significant reduction in final plant population, without difference among varieties; after - 35 mm of water deficit, 100% of the plants died.

Rapid Alkalinization Factor (RALF) pertence a uma crescente família de peptídeos com características hormonais em plantas. Inicialmente isolado de folhas de plantas de tabaco, peptídeos RALF podem ser encontrados em todo reino vegetal e são expressos em plantas ubiquamente. Plantas de cana-de-açúcar apresentam quatro isoformas dos genes SacRALF e foi identificado que o gene SacRALF1 é expresso predominantemente. Transcritos de SacRALF1 são abundantes nas zonas de elongação de pontas de raízes, e todos os quatro genes SacRALF são mais expressos em folhas jovens e em expansão do que em folhas expandidas. Nos limbos foliares, transcritos dos genes SacRALF foram encontrados em alta concentração na parte basal da folha e baixa concentração na porção apical. O conjunto das análises de expressão gênica neste estudo sugerem que a expressam dos genes SacRALF está localizada nas zonas de elongação de raízes e folhas. Folhas maduras, que são desprovidas de células em elongação, não mostraram expressão considerável dos genes SacRALF. Culturas de suspensão celular embriogênica de cana-de-açúcar mostraram um nível constitutivo de transcritos de genes SacRALF. O peptídeo SacRALF1 foi adicionado ao meio de cultura e inibiu o crescimento de microcalli derivado de culturas de suspensão celular em concentrações tão baixas quanto 0,1 µM. Microcalli expostos ao SacRALF1 exógeno mostraram um número reduzido de células elongadas. Os resultados obtidos sugerem que os peptídeos RALF possuem uma função no desenvolvimento de plantas, particularmente na elongação celular. / Rapid Alkalinization Factor (RALF) is part of a growing family of peptides with hormone characteristics in plants. Initially isolated from leaves of tobacco plants, RALF peptides can be found throughout the plant kingdom and they are expressed in plants ubiquitously. Sugarcane plants have four isoforms of SacRALF genes and SacRALF1 isoform is expressed predominantly. SacRALF1 transcripts are abundant in the elongation zone of root tips and all four SacRALF genes are more expressed in young and expanding leaves than in expanded leaves. In leaf blades, SacRALF gene transcripts were found at high levels at the basal portion of the leaf and at low levels at the apical portion. The whole set of gene expression analyses showed in this study, suggest that SacRALF genes expression is localized in elongation zones of roots and leaves. Mature leaves that are devoid of elongating cells do not show considerable expression of SacRALF genes. Sugarcane embryogenic cell suspension cultures showed a nearly constitutive level of SacRALF gene transcripts. SacRALF1 peptide was added to culture media and inhibited the growth of microcalli derived from cell suspension cultures at concentrations as low as 0.1 µM. Microcalli exposed to exogenous SacRALF1 showed a reduced number of elongated cells. The findings suggest that RALF peptides have a role in plant development, particularly in cell elongation.

Le contrôle moléculaire du patterning au cours des processus développementaux est aujourd’hui bien décrit chez les organismes multicellulaires. A l’inverse, la contribution de la croissance dans l’émergence des patterns reste peu explorée, et est souvent réduite à un rôle passif. Au cours de cette thèse, j’ai étudié cette question en utilisant le méristème apical caulinaire (MAC) d’Arabidopsis comme modèle. Le méristème est un groupe de cellules en divisions situé à l’extrémité de toutes les tiges et les branches et qui génère tous les organes aériens de la plante selon un patron stéréotypé, aussi appelé phyllotaxie. Dans une première partie, j’ai étudié comment la croissance de la tige pouvait influencer le patron phyllotactique. Plus précisément, en découplant dépôt de la cellulose dans la paroi et l’orientation des microtubules, j’ai montré que le patron de phyllotaxie devenait bimodal en raison de l’induction d’une torsion lors de la croissance de la tige. Dans une seconde partie, j’ai analysé le lien entre forme du MAC et expression génétique. En particulier, j’ai pu corréler l’expression d’un gène maître : SHOOTMERISTEM LESS (STM) au degré de courbure dans le MAC. De plus, en utilisant des approches de micromécaniques, j’ai aussi pu montrer que l’expression de STM pouvait être induite par le patron de contraintes localement généré par la courbure. Pour finir, j’ai aussi étudié comment la taille du méristème influence la robustesse du pattern de phyllotaxie sur la tige en modulant la fréquence d’initiation des organes. L’ensemble de ce travail met ainsi en avant le rôle de la croissance dans le patterning, notamment via des mécanismes de rétrocontrôles géométriques et mécaniques. / The molecular mechanisms behind the emergence of patterns during developmental processes have been well described in multicellular organisms. However, the contribution of growth in patterning is still poorly understood; growth is often seen as a passive output of the activity of the patterning signals. In this PhD, I have studied the relation between growth and patterning using the shoot apical meristem of Arabidopsis as a model system. The meristem is a group of dividing cells located at the tip of every stems and branches that generates all the aerial organs of the plant following a typical spatio-temporal pattern also called phyllotaxis. In a first part, the influence of post-meristematic growth on phyllotaxis was assessed. More precisely, by uncoupling cellulose deposition from the orientation of the microtubule array, I showed that the resulting stem torsion induces the emergence of a new and robust bimodal phyllotactic pattern. In a second part, the relation between meristem shape and gene expression was analyzed. More precisely, I correlated the expression of a master regulatory gene: SHOOT MERISTEMLESS (STM) to tissue curvature in the boundary domain that separates the emerging organ from the meristem. Furthermore, I showed that STM expression can be induced by micromechanical perturbations thus suggesting that shape-derived mechanical stresses in the meristem boundary contribute to STM expression. Finally, I also studied how meristem size can influence the robustness of the pattern of phyllotaxis along the stem through a modulation of the frequency of organ initiation. Altogether, this work highlights the important contribution of growth in patterning, notably thanks to the existence of geometrical and mechanical feedbacks.

Les derniers acteurs de la voie de signalisation à l’éthylène sont des facteurs de transcription appelés ERF (Ethylene Response Factors). La connaissance de leur rôle spécifique dans la régulation des processus développementaux dépendant de l’éthylène reste limitée. Les travaux présentés dans la thèse concernent la caractérisation fonctionnelle du gène Sl-ERF.B3, un membre de cette grande famille de régulateurs transcriptonnels dans la tomate (Solanum lycopersicum). Utilisant une stratégie répresseur dominant ; il est montré en particulier que ce gène intervient dans la mise en place de la réponse à l’éthylène et dans le contrôle de la maturation du fruit. L’expression d’une construction ERF.B3-SRDX, une version chimérique de Sl-ERF.B3 fusionné à un domaine répresseur de type EAR, entraine des phénotypes pléotropiques aussi bien dans la signalisation de l’éthylène que dans le développement des parties végétatives et des organes reproducteurs. Ainsi, une altération de la triple réponse à l’éthylène est constatée chez les lignées transgéniques et au stade adulte, les plantes présentent des phénotypes d’épinastie des feuilles, de sénescence prématurée des fleurs et d’abscission accélérée des fruits. L’ensemble de ces observations est corrélée avec une modification de l’expression de gènes impliqués dans la biosynthèse et la réponse à l’éthylène. Ces données suggèrent que ERF.B3 intervient dans un mécanisme de rétro-control de la réponse à l’éthylène en agissant à la fois sur les gènes de biosynthèse et de signalisation de l’hormone. Au niveau du fruit, la sur-expression d’ERF.B3-SRDX entraine une modification du processus de maturation avec un retard notable de l’avènement de l’acquisition de la compétence à murir. Cependant, une fois la maturation initiée, elle s’accompagne d’une forte production d’éthylène et d’une accélération du ramollissement du fruit. A l’inverse, l’accumulation de pigment est inhibée par altération de la voie de biosynthèse des caroténoïdes. Ces données phénotypiques sont corrélées avec le niveau d’expression des gènes clés impliqués dans ces processus. Les résultats indiquent que dans les lignées transgéniques, il y a découplage de certaines caractéristiques de la maturation du fruit et permettent de mettre en lumière le rôle d’ERF.B3 dans la régulation des processus de développement dépendant de l’éthylène chez la tomate. / Ethylene Response Factors (ERFs) are known to be the last transcription factors of the ethylene transduction pathway. Their specific role in ethylene-dependent developmental processes remains poorly understood. This work demonstrated a specific role of Sl- ERF.B3, a member of the ERF gene family in tomato (Solanum lycopersicum), in mediating ethylene response and fruit ripening through a dominant repressor strategy. ERF.B3-SRDX dominant repressor etiolated seedlings displayed partial constitutive ethylene-response in the absence of ethylene and adult plants exhibited typical ethylenerelated alterations such as leaf epinasty, premature flower senescence and accelerated fruit abscission. The multiple symptoms related to enhanced ethylene sensitivity correlate with the altered expression of ethylene biosynthesis and signaling genes, suggesting the involvement of Sl-ERF.B3 in a feedback mechanism regulating components of ethylene production and response. In addition, over-expression of ERF.B3-SRDX in tomato results in alterations in both fruit morphology and ripening process. The attainment of competence to ripen is dramatically delayed in ERF.B3-SRDX fruits but once ripening proceeds it is associated with high climacteric ethylene production and enhanced fruit softening while pigment accumulation is strongly reduced. Moreover, a number of genes involved in the fruit ripening process showed expression pattern deviating from that of wild type. These data suggest a putative role of Sl-ERF.B3 in the transcriptional network underlying the ripening process and uncover a mean for uncoupling some of the main features of fruit ripening such as fruit softening and pigment accumulation. Overall, the study highlighted the importance of an ERF gene in ethylene-mediated developmental processes such as plant growth and fruit ripening.

Master thesis deals with L grammar systems. The basic types of grammar systems are studied. There are analyzed different types of L grammars and their use in field of plant development simulation. The work focuses on open L grammars. A parallel system consisting of open L grammars is designed. Communication takes place through the exchange of information between plants and their environment. Implemented is real kind of tree. Simulated is typical environment in which this kind of tree occurs normally. The system properties are examined from the point of view of simulation and the time-consuming interpretation of strings. At the end of this thesis there are described some other options of future development of the project together with the possibilities of using the proposed system.

Brassinosteroids (BRs) have been recognized to alleviate damages caused by drought stress and to enhance tolerance to water deficit. Soaking of maize kernels before the sowing in solution with different 24-epibrassinolide concentrations (especially the 10-8 M) had a positive effect on growth of plants before and after the stress period, although it did not affected relative water content and photosynthetic parameters. After the recovery under optimal conditions there were no differences among the treatments. When compared to spraying, soaking of maize kernels was not proved to have any advantages, though its positive effect on plants germination under water deficit conditions could be possible. Based on the results of the second season experiment it is not possible to deduce the role of exogenous BRs application (spraying with 24-epibrassinolide) or endogenous BRs biosynthesis (spraying with biosynthesis inhibitor - brassinazole) in maize plants subjected to water deficit. However, decrease in relative water content in contrast to chlorophylls content increase during the days following after drought stress onset in both cultivars (contrastive in drought sensitivity) challenges for further investigation of this problem. Understanding the role of BRs in plant drought tolerance and resistance is...

Inseticidas e fungicidas geralmente são estudados quanto a sua eficiência no controle de pragas e doenças, entretanto podem provocar efeitos fisiológicos pouco conhecidos capazes de influenciar o desenvolvimento das culturas. O tiametoxam é um inseticida sistêmico do grupo dos neonicotinóides, da família nitroguanidina, que atua no receptor nicotínico acetilcolina de insetos, danificando o sistema nervoso dos mesmos, levando-os à morte. Este inseticida, largamente utilizado no controle de pragas iniciais e insetos sugadores, apresenta efeito bioativador, uma vez que mesmo na ausência da pragas, promove aumento em vigor e desenvolvimento nas plantas tratadas. Acredita-se que os efeitos do tiametoxam em plantas são indiretos, pois atuam na expressão dos genes responsáveis pela síntese e ativação de enzimas metabólicas, relacionadas ao crescimento da planta, alterando a produção de aminoácidos e precursores de hormônios vegetais. Existem alguns trabalhos com tiametoxam com o objetivo de verificar seus efeitos no metabolismo e desenvolvimento das plantas, mas os resultados ainda não são claros, evidenciando forte interação entre cultivares, épocas, condições de estresse e disponibilidade de nutrientes. Em função da grande utilização do inseticida tiametoxam na agricultura brasileira, o estudo deste agroquímico, no sentido de alterar o metabolismo e desenvolvimento de plantas, constitui-se de grande importância na agregação de informações à literatura biológica e agronômica. Os objetivos deste trabalho foram verificar o efeito da aplicação de tiametoxam em plantas de cana-de-açúcar, feijoeiro, soja, laranjeira e cafeeiro, em diferentes doses e formas de aplicação (tratamento de sementes, pulverização foliar e aplicação no solo), sobre parâmetros de desenvolvimento (área foliar, massa seca de folhas e raízes, comprimento radicular) e aspectos bioquímicos (teores foliares de nutrientes e atividade enzimática). Os experimentos foram realizados em vasos, no Horto Experimental do Departamento de Ciências Biológicas da ESALQ/USP. Concluiu-se que a aplicação de tiametoxam em pulverização foliar, em cana-deaçúcar, aumenta a área foliar e o comprimento das raízes, amplia a espessura do córtex da raiz, incrementa o diâmetro do cilindro vascular e aumenta o número de metaxilemas; em feijoeiro, em tratamento de sementes, aumenta a área foliar, a massa seca da parte aérea e a atividade da nitrato redutase em folhas e em pulverização foliar aumenta a atividade da nitrato redutase e a atividade da fenilalanina amônia-liase em folhas; em soja, em tratamento de sementes, aumenta a área foliar, massa seca e comprimento das raízes e os teores foliares de cálcio e magnésio, e em pulverização foliar, reduz os teores de fósforo e cálcio, mas aumenta os teores de potássio; em mudas de laranjeira, aplicado no solo, aumenta a área foliar, a massa seca das folhas, a massa seca do caule e ramos e a área foliar média, mas reduz os teores foliares de nitrogênio, fósforo e enxofre; em mudas de café arábica, aplicado na raiz, aumenta o número de folhas, a massa seca de raízes finas e o comprimento das raízes. / Insecticides and fungicides are often studied to their efficiency in controlling pests and diseases, however can cause physiological effects little known that can affect crop growth. Thiamethoxan is a systemic insecticide from the neonicotinoid group, nitroguanidine family, which acts on nicotinic acetylcholine receptor of insects, damaging their nervous system, leading them to death. This insecticide, that is widely used for controlling pests and sucking insects, has bioactivator effect, since even in the absence of pests, promotes an increase in vigor and development in treated plants. It is believed that the effects of thiamethoxan in plants are indirect, because it acts in the genes expression responsible for metabolic enzymes activation and synthesis, related to plant growth, by modifying amino acids and plant hormones precursors production. There is a number of studies with thiamethoxan in the way to determine the effects on metabolism and development of plants, but the results are not clear, showing strong interaction between cultivars, stress conditions and nutrient availability. Due to the wide use of the insecticide thiamethoxan in Brazilian agriculture, the study of this insecticide in order to know the metabolism changes in the plants, brings a great importance in the collection of knowledge to the agronomic and biological literature. The objectives of this study was to evaluate the effect of thiamethoxan on sugar cane, common beans, soy, orange and coffee plants with different doses and forms of application (seed treatment, foliar spray and soil application) on developmental parameters (leaf area, dry mass of leaves and roots, root length) and biochemical aspects (nutrient content and enzymatic activity). The experiments were conducted in pots in the ESALQ / USP, Experimental Field of Biological Sciences Department. It was concluded that the application of thiamethoxan as foliar spray on sugar cane, increases leaf area and root length, increases the thickness of the cortex of the root, increases the diameter of the vascular cylinder and increases the number of vessels; in bean for seed treatment, increases the leaf area, dry mass of shoots and the activity of nitrate reductase in leaves, and foliar spray increases the activity of nitrate reductase and phenylalanine ammonia-lyase in leaves; in soybean, in seeds treatment, increases leaf area, dry weight of roots, root length and foliar calcium and magnesium, and foliar spray, reduces the amount of phosphorus and calcium, but increased levels of potassium; in orange trees, applicated on the soil, increases the leaf area, leaf area average, leaves dry mass, stems and branches dry mass, but reduces the amount of nitrogen, phosphorus and sulfur in the leaf; in arabica coffee seedlings, applied at the root, increases the number of leaves, fine roots dry mass and length of roots.