Auswahl der wissenschaftlichen Literatur zum Thema „Gibberellins Metabolism“

Abstract Gibberellins are produced by all vascular plants and several fungal and bacterial species that associate with plants as pathogens or symbionts. In the 60 years since the first experiments on the biosynthesis of gibberellic acid in the fungus Fusarium fujikuroi, research on gibberellin biosynthesis has advanced to provide detailed information on the pathways, biosynthetic enzymes and their genes in all three kingdoms, in which the production of the hormones evolved independently. Gibberellins function as hormones in plants, affecting growth and differentiation in organs in which their concentration is very tightly regulated. Current research in plants is focused particularly on the regulation of gibberellin biosynthesis and inactivation by developmental and environmental cues, and there is now considerable information on the molecular mechanisms involved in these processes. There have also been recent advances in understanding gibberellin transport and distribution and their relevance to plant development. This review describes our current understanding of gibberellin metabolism and its regulation, highlighting the more recent advances in this field.

A major part of Clemson light quality research program focuses on understanding the mechanisms of plant growth alteration under spectral filters. We have extended this research to understand the molecular basis for plant height control by spectral filters. From the whole plant research we have found that gibberellins (GA) play a key role in height control under spectral filters. However, it is not clear whether an alteration of endogenous gibberellin levels or a change in sensitivity to gibberellins is causing the observed effects. Since gibberellins are a key hormone in cell expansion and flower development, an understanding of gibberellin regulation and metabolism under spectral filters is critical for the control of height and flowering of plants grown under these filters. For the molecular study, we have selected the gene that code for enzyme GA 20-oxidase, one of the key enzymes involved in producing functional GAs in the mevalonic acid pathway. GA 20-oxidase is thought to be a site of regulation of GA synthesis by the environment. We are currently studying the regulation of the expression of this gene by light quality using Northern analysis. Results from temporal and tissue specific regulation of chrysanthemum plants grown under CuSO4 filters will be presented.

The vegetative forms of male (XY), female (XX), and hermaphrodite (XYh) papaya (Carica papaya L.) plants are phenotypically identical. However, the flower and inflorescence morphology of each sex type is unique. Gynodioecious varieties SunUp, SunUp Diminutive mutant, and dioecious AU9 were used to test the response of papaya to gibberellic acid (GA3). Exogenous applications of GA3 on female and hermaphrodite flowers of papaya did not yield any sex reversal phenotype but caused a significant increase in peduncle elongation and inflorescence branch number in all treated plants. An increase in flower number was seen in females but not hermaphrodites or males. There was an increase in plant height for all treated plants except SunUp Diminutive mutant, suggesting that the mechanism causing the dwarf phenotype is independent of gibberellins. Gibberellin metabolism genes were identified in the papaya genome, none of which mapped to the sex-determining region of either the male- or hermaphrodite-specific region of papaya Y or Yh chromosome. We hypothesize that a transacting regulatory element that enhances gibberellin biosynthesis plays a role in the extreme length of the male papaya peduncle.

The plant-specific receptor-like cytoplasmic kinases (RLCKs) form a large, poorly characterized family. Members of the RLCK VI_A class of dicots have a unique characteristic: their activity is regulated by Rho-of-plants (ROP) GTPases. The biological function of one of these kinases was investigated using a T-DNA insertion mutant and RNA interference. Loss of RLCK VI_A2 function resulted in restricted cell expansion and seedling growth. Although these phenotypes could be rescued by exogenous gibberellin, the mutant did not exhibit lower levels of active gibberellins nor decreased gibberellin sensitivity. Transcriptome analysis confirmed that gibberellin is not the direct target of the kinase; its absence rather affected the metabolism and signalling of other hormones such as auxin. It is hypothesized that gibberellins and the RLCK VI_A2 kinase act in parallel to regulate cell expansion and plant growth. Gene expression studies also indicated that the kinase might have an overlapping role with the transcription factor circuit (PIF4-BZR1-ARF6) controlling skotomorphogenesis-related hypocotyl/cotyledon elongation. Furthermore, the transcriptomic changes revealed that the loss of RLCK VI_A2 function alters cellular processes that are associated with cell membranes, take place at the cell periphery or in the apoplast, and are related to cellular transport and/or cell wall reorganisation.

ABSTRACT The fungus Fusarium fujikuroi (Gibberella fujikuroi MP-C) produces metabolites of biotechnological interest, such as gibberellins, bikaverins, and carotenoids. Gibberellin and bikaverin productions are induced upon nitrogen exhaustion, while carotenoid accumulation is stimulated by light. We evaluated the effect of nitrogen availability on carotenogenesis in comparison with bikaverin and gibberellin production in the wild type and in carotenoid-overproducing mutants (carS). Nitrogen starvation increased carotenoid accumulation in all strains tested. In carS strains, gibberellin and bikaverin biosynthesis patterns differed from those of the wild type and paralleled the expression of key genes for both pathways, coding for geranylgeranyl pyrophosphate (GGPP) and kaurene synthases for the former and a polyketide synthase for the latter. These results suggest regulatory connections between carotenoid biosynthesis and nitrogen-controlled biosynthetic pathways in this fungus. Expression of gene ggs1, which encodes a second GGPP synthase, was also derepressed in the carS mutants, suggesting the participation of Ggs1 in carotenoid biosynthesis. The carS mutations did not affect genes for earlier steps of the terpenoid pathway, such as fppS or hmgR. Light induced carotenoid biosynthesis in the wild type and carRA and carB levels in the wild-type and carS strains irrespective of nitrogen availability.

Bioactive gibberellic acids (GAs) are diterpenoid plant hormones that are biosynthesized through complex pathways and control various aspects of growth and development. Although GA biosynthesis has been intensively studied, the downstream metabolic pathways regulated by GAs have remained largely unexplored. We investigated Tnt1 retrotransposon insertion mutant lines of Medicago truncatula with a dwarf phenotype by forward and reverse genetics screening and phylogenetic, molecular, biochemical, proteomic and metabolomic analyses. Three Tnt1 retrotransposon insertion mutant lines of the gibberellin 3-beta-dioxygenase 1 gene (GA3ox1) with a dwarf phenotype were identified, in which the synthesis of GAs (GA3 and GA4) was inhibited. Phenotypic analysis revealed that plant height, root and petiole length of ga3ox1 mutants were shorter than those of the wild type (Medicago truncatula ecotype R108). Leaf size was also much smaller in ga3ox1 mutants than that in wild-type R108, which is probably due to cell-size diminution instead of a decrease in cell number. Proteomic and metabolomic analyses of ga3ox1/R108 leaves revealed that in the ga3ox1 mutant, flavonoid isoflavonoid biosynthesis was significantly up-regulated, while nitrogen metabolism was down-regulated. Additionally, we further demonstrated that flavonoid and isoflavonoid biosynthesis was induced by prohexadione calcium, an inhibitor of GA3ox enzyme, and inhibited by exogenous GA3. In contrast, nitrogen metabolism was promoted by exogenous GA3 but inhibited by prohexadione calcium. The results of this study further demonstrated that GAs play critical roles in positively regulating nitrogen metabolism and transport and negatively regulating flavonoid biosynthesis through GA-mediated signaling pathways in leaves.

Thesis (Ph. D.)--Ohio State University, 2002.
Title from first page of PDF file. Document formatted into pages; contains xi, 148 p.; also contains graphics (some col.). Includes abstract and vita. Advisor: James Metzger, Dept. of Horticulture and Crop Science. Includes bibliographical references (p. 132-148).

The Green Revolution introduced wheat varieties containing semi-dwarfing genes (Rht) that encode gibberellin (GA)-insensitive forms of the growth-repressing DELLA proteins, conferring improved resistance to lodging and improved harvest index. Reduction in the use of nitrogen (N) fertilizers is required to minimise environmental damage. Since most Rht varieties have been selected under high N inputs, new semi-dwarfing alleles may need to be developed. The response of tall, semi-dwarf and dwarf lines of wheat to N rate was examined in the field, but failed to provide evidence of higher N -responsiveness of rht tall varieties compared to Rht-1 semi-dwarfs and dwarfs. Expression of GA biosynthetic and signalling genes was monitored in elongating stems in field and controlled environment conditions under different N and water regimes. Although peduncle GA levels were reduced under N stress, there was no evidence that the effect of N supply on stature was directly mediated by changes in the transcription level ofGA metabolic genes. GA-biosynthetic genes were assessed as novel sources of dwarfism that may respond differently to environmental stresses such as N supply. A number of TILLING lines carrying mutations in the three homoeologues of GA20ox1 were crossed in order to generate combinations of mutant alleles. Triple knock-out plants from four combinations of alleles were identified by KASP genotyping assay in the F2 generation and all plants from the segregating populations were assessed for final height. There was a correlation between the genotypes and height, with triple knockouts being the shortest and wild types the tallest. Data from an F 3 population of the a1b.b1b.d1c genotype confirmed this observation and showed that reduced-height mutants maintained the same grain size and number as the wild-type plants. Therefore GA200xi may be classified as a novel wheat semi-dwarfing gene with potentially beneficial effects on height reduction without negatively affecting yield.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
This study was carried out to analyze the physiological, metabolic and anatomic impacts promoted by both the endogenous and/or artificial variation of gibberellins (GAs) on tomato plants (Solanum lycopersicum L.). To this end, different experiments were performed using wild-type (WT) and mutant plants in the biosynthesis of gibberellins (gib3, moderately deficient; gib2, mildly deficient and gib1, extremely deficient). In the first experiment I used WT and the mutant plants gib3, gib2 and gib1 and evaluated the effects of endogenous reduction of GA levels. It was observed that the reduced levels of GAs negatively affected the growth and that this slower growth is not associated with lower photosynthetic rates. The higher net photosynthesis (A N ) found in the mutants were associated with both increased stomatal density and higher stomatal (g s ) and mesophyll (g m ) conductances. One clear imbalance between carbon metabolism and growth seems to occur in plants with reduced GAs levels, given that reductions in the levels of the majority of the metabolites occurred concomitantly to higher A N . Moreover, higher A N was accompanied by elevated respiratory rate and increments in protein concentration, suggesting a shift of energy in the form of ATPs to other routes, since more energy production was not associated with higher biomass accumulation. In the second experiment I used plants WT and gib3, the genotype most similar to WT in the first experiment, and subjected those plants to artificial variations in the content of GAs by applying GAs and/or paclobutrazol (PBZ), a GA biosynthesis inhibitor. The results obtained allowed the identification of both metabolic and physiological changes associated with both endogenous GAs variation, as well as the artificial variation caused by varying the GAs regime. In both genotypes growth was strongly reduced in presence of PBZ whereas it was incremented when applying GAs. Lower growth rates were accompanied by higher dark respiration (R d ) and higher A N , the former being influenced by larger stomatal density and stomatal opening, leaf thickness, as well as g s and absorptance. The levels of the majority of metabolites evaluated were positively associated with GAs content. Little or no variation in chlorophyll fluorescence a and antioxidative system parameters indicated no apparent stress. Taken as a whole, the information obtained within this study provide a better understanding of the physiological, molecular and metabolic disorders associated with GA deficiency in plants; however, future metabolic and molecular studies are still required to allow us a better understanding of the effects of reduced GA levels on the metabolism of these plants.
O presente trabalho foi conduzido com intuito de analisar os impactos causados pela variação endógena e/ou artificial (aplicação de GAs e paclobutrazol-PBZ) dos níveis de giberelinas sobre a fisiologia, metabolismo e anatomia de plantas de tomate (Solanum lycopersicum L.). Para tal, diferentes experimentos foram realizados utilizando-se plantas tipo selvagem (WT) e mutantes na biossíntese de giberelinas (gib3: moderadamente deficiente, gib2: medianamente deficiente e gib1: extremamente deficiente). No primeiro experimento foram utilizadas plantas WT e os mutantes gib3, gib2 e gib1 avaliando-se os efeitos da redução endógena dos níveis de GAs. Os resultados mostraram que a redução dos níveis de GAs afetou negativamente o crescimento dessas plantas e que este menor crescimento não estaria associado a menores taxas fotossintéticas. A elevada fotossíntese (A N ) nos mutantes apresentou-se associada com uma maior densidade e abertura estomática, assim como maiores condutâncias estomática (g s ) e mesofílica (g m ). Um desbalanço entre o metabolismo do carbono e crescimento parece ocorrer plantas com redução na concentração de GAs, visto que reduções nos teores da maioria dos metabólitos ocorreram concomitantemente com elevada A N . Ademais, maior A N foi acompanhada de uma elevada taxa respiratória e incrementos na concentração de proteínas, sugerindo um desvio de energia em forma de ATPs para outras rotas, já que uma maior produção de energia não se traduziu em acúmulo de biomassa. No segundo experimento foram utilizadas plantas WT e gib3, genótipo mais semelhante ao WT no primeiro experimento, submetidas à variações artificiais no conteúdo de GAs mediante a aplicação de GAs e/ou PBZ. Os resultados obtidos permitiram a identificação de mudanças metabólicas e fisiológicas associadas tanto à variação endógena de GAs, assim como as ocasionadas pela variação artificial de GAs. Para ambos os genótipos, o crescimento foi bastante reduzido em presença de PBZ e apresentou incrementos quando da aplicação de GAs. Menores taxas de crescimento foram acompanhadas de maiores respiração no escuro (R d ) e A N , a última influenciada por maiores densidade e abertura estomática, espessura foliar, assim como g s e absortância. A maioria dos metabólitos foi positivamente correlacionada com o conteúdo de GAs. Pouca ou nenhuma variação em parâmetros da fluorescência da clorofila a e sistema antioxidativo indicam ausência de estresses aparentes. Consideradas em conjunto, as informações obtidas com o presente estudo oferecem uma melhor compreensão dos mecanismos fisiológicos, moleculares e metabólicos associados à deficiência de GAs em plantas; contudo, estudos metabólicos e moleculares mais detalhados ainda serão necessários para uma melhor compreensão dos efeitos da redução dos níveis de GAs sobre o metabolismo dessas plantas.

O amadurecimento é uma etapa exclusiva do estágio de desenvolvimento dos frutos, que envolve uma série de transformações metabólicas a partir de diferentes fontes de energia. Ele é mediado por um dinâmico complexo enzimático, resultando em síntese/degradação e conversão de compostos que tornarão o fruto aceitável para o consumo. Dependendo do tipo de fruto, essa fonte de energia pode ser na forma de ácidos orgânicos, sacarose vinda da própria planta e na forma de amido. A banana (Musa acuminata) é uma fruta de comportamento climatérico que utiliza como principal fonte de carbono o amido, que é reduzido durante o climatério de teores que variam de 12 a 20% a menos de 1 %. Concomitante à esta degradação, o teor de sacarose pode atingir até 15%, dependendo da cultivar. O ácido giberélico (GA3) é um fitohormônio da família das giberelinas que tem sido muito estudado em cereais por aumentar a transcrição gênica das α-amilase. Em frutos, ele é responsável por manter a textura firme e o teor de sólidos solúveis, e atrasar o amadurecimento. Ao estudar a influência do GA3 no metabolismo amido-sacarose em fatias de banana, observou-se neste trabalho que o fitohormônio não alterou o pico respiratório nem a síntese de etileno. Entretanto, atrasou a degradação do amido e o acúmulo de açúcares solúveis por três dias. Este atraso foi acompanhado pela diminuição/atraso na atividade das enzimas que degradam o amido e sintetizam sacarose, α e β-amilase e sacarose fosfato sintase, respectivamente, sendo que não foi observada uma diferença no aumento de expressão gênica da sacarose fosfato sintase e das fosforilases.
The ripening is an exclusive stage of fruit development, that involves a serie of metabolic transformation from different energy source. It is mediated by a dynamic enzymatic complex, resulting in formation/degradation of different coumpouds that will render fruit acceptable for the consumption. Depending on the type of fruit, this energy source can be in the form of organic acid, sucrose of the plant or starch. Banana (Musa acuminata) is a climateric fruit that uses starch as main carbon source, which is reduced during banana ripening of levels that vary from 12 to 20% to less than 1 %. Concomitant to the this degradation, the levels of sucrose can reach up to 15%, depending of the cultivar. The gibberellic acid, GA3-mediated is a plant growth regulation of the giberellins family, that has been studied in cereals because of their enhancing effect of gene expression of αamylase. In fruits, it is responsible for keeping the texture firm and the soluble solid levels, and delaying the ripening. The influence of the GA3 in the starch-sucrose metabolism in banana slices, were observed. That the phytohormone did not modify the respiratory peak nor the synthesis of ethylene. However, it delayed the starch degradation and the soluble sugars accumulation for about three days. This delay was followed by decrease and/or delay in the activity of the enzymes related to starch degradation: the α and β-amylases; and sucrose synthesis the sucrose phosphate synthase (SPS). However, was not observed a difference in the increase of gene expression of SPS and phosphorilase

Using gentian and petunia as the experimental systems, potential alternative post-harvest treatments for cut flowers were explored in this project. Pulsing with GA₃ (1 to 100 µM) or sucrose (3%, w/v) solutions delayed the rate of senescence of flowers on cut gentian stems. The retardation of flower senescence by GA₃ in both single flower and half petal systems was accompanied by a delay in petal discoloration. The delay in ion leakage increase or fresh weight loss was observed following treatment with 5 or 10 µM GA₃ of the flowers at the unopen bud stage. Ultrastructural analysis showed that in the cells of the lower part of a petal around the vein region, appearance of senescence-associated features such as degradation of cell membranes, cytoplasm and organelles was faster in water control than in GA₃ treatment. In particular, degeneration of chloroplasts including thylakoids and chloroplast envelope was retarded in response to GA₃ treatment. In the cells of the top part of a petal, more carotenoids-containing chromoplasts were found after GA₃ application than in water control. In petunia, treatment with 6% of ethanol or 0.3 mM of STS during the flower opening stage was effective to delay senescence of detached flowers. The longevity of isolated petunia petals treated with 6% ethanol was nearly twice as long as when they were held in water. Senescence-associated petal membrane damage, weight decline, ovary growth and decrease in protein and total RNA levels were counteracted in ethanol-treated petals. The accumulation of ROS, particularly superoxide and hydrogen peroxide, was also inhibited or delayed by ethanol application. Anti-senescence mechanisms, particularly the changes of oxidative / antioxidant metabolism involved in petal senescence, were investigated. In gentian, activities of AP and SOD but not POD in the GA₃-treated petals were significantly higher than those of the control. In isolated petunia petals, the decreased trends of antioxidative SOD and AP activities during senescence were apparently prevented in response to ethanol treatment although the levels of ascorbate and photo-protective carotenoids were not affected. Furthermore, by optimizing a range of critical PCR parameters such as primer combinations, cDNA concentrations and annealing temperatures, a reliable protocol has been established for quantifying the expression level of Cu-Zn SOD gene in petunia petals using SYBR Green I based real-time RT-PCR. A 228 bp gene fragment of Cu-Zn SOD was isolated from petunia (var. 'hurrah') using RT-PCR. It was found that the mRNA level (relative to 18S rRNA level) of Cu-Zn SOD decreased significantly after 6 days in water. However, there was about a 55-fold increase in Cu-Zn mRNA level after 6 days of ethanol treatment when compared to water-treated petals. Similarly, down-regulation of the mRNA level of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was also observed during senescence of petunia petals. Increased vase life of petunia petals by ethanol treatment was correlated with promotion of GAPDH expression by a factor of about 16 on day 6. Taking together, the anti-senescence effects of GA₃ and ethanol are at least partially associated with an increased efficiency of petal system utilizing ROS since the selected antioxidants were significantly maintained when compared to the corresponding values for the control.

Orientador: Marcos Silveira Buckeridge
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: A cana-de-açúcar pertence a família Poaceae e ao gênero Saccharum. Espécies pertencentes a essa família apresentam a via de fotossíntese C4, mais eficiente para a produção de biomassa quando comparadas com as plantas com metabolismo fotossintético C3 em condições de temperaturas elevadas. A cana-de-açúcar transformou-se em um importante potencial econômico e fonte de energia no mundo, devido a sua capacidade de estocar sacarose (cerca de 50% de seu peso seco) e produzir bioetanol. Nos últimos anos tornou-se alvo prioritário para diversos estudos através do melhoramento genético, biologia molecular, bioquímica e estudos fisiológicos. Os produtos provenientes da cana são amplamente utilizados pela população mundial e representam uma fonte alternativa para a geração de energia. O Brasil ocupa uma posição de destaque entre os países produtores de cana-de-açúcar (34% da produção mundial). Devido a sua origem interespecífica a cana possui um dos genomas mais complexos entre as espécies vegetais tornando-se um importante objeto de estudo para a obtenção de variedades produtivas e ou eficientes, melhor adaptadas às condições climáticas. A propagação clonal através do cultivo in vitro possibilita a obtenção mais rápida de indivíduos da espécie. A utilização de métodos de assepsia para a desinfestação e desinfecção sem causar danos aos tecidos que levam a morte da planta tornou-se um grande desafio para a obtenção de novas plântulas que permitam os estudos de biotecnologia. E o grande interesse em se estudar plantas de cana-de-açúcar se dá pelo acúmulo da sacarose, que ocorre na região do entrenó durante o desenvolvimento da planta. A genética clássica busca a melhora dessa característica, principalmente através do aumento da biomassa realizada pela fixação de carbono, no entanto, há um limitado aumento do conteúdo de sacarose. A giberelina é um fitormônio vegetal, largamente utilizada na agricultura e desempenha uma variedade de funções fisiológicas em plantas. O GA3 produzido industrialmente tem sido aplicado para estimular o crescimento da cana-de-açúcar, para auxiliar a germinação de cevada, na produção de frutas e verduras, entre outras. As giberelinas são extremamente ativas na indução do alongamento do caule. Estudos mostram que a aplicação de GAs provoca aumento no tamanho da célula e no número de células, indicando que as GAs atuam tanto no alongamento da célula como na divisão celular, o que potencializa um aumento na produtividade de sacarose. Já o paclobutrazol (PBZ) atua inibindo a biossíntese de giberelinas. Ele bloqueia a biossíntese de GA, pois interfere nos primeiros passos da rota de oxidação do caureno, impedindo a formação das GAs, e por isso funciona como um controle negativo dos mecanismos de ação das giberelinas. Tanto a presença do paclobutrazol quanto da GA3 induzem alterações da expressão de genes específicos e a ativação de vias de sinalização que agem cooperativamente na tentativa de aliviar o efeito do estresse na tentativa de estabelecer o retorno à homeostasia celular. Nosso maior objetivo nesse estudo é tentar identificar o mecanismo de ação das GAs, para permitir uma melhor compreensão das alterações tanto morfológicas e fisiológicas sofrida pelas plântulas. Para isso em nossos estudos foram selecionados genes que pudessem apresentar relação com metabolismo de carboidratos, com respostas hormonais, com metabolismo de ácidos nucleícos, com a fotossíntese, com o desenvolvimento, com divisão celular, com metabolismo de proteínas, além de diversos fatores de transcrição que possam estar envolvidos nesses processos, baseados em resultados do metabolismo de carboidratos encontrados nas analises bioquímicas das plântulas, assim como nos cortes anatômicos. O resultados mostraram interferência do GA3 no acúmulo de carboidratos, no alongamento celular, em genes relacionados com a via de transdução de sinal das AUX, biossíntese de AUX, GA, além de genes e fatores de transcrição relacionados com o ciclo celular, fotossíntese, fixação de carbono e diversos estresses, entre eles o osmótico.
Abstract: The sugarcane belongs to the grasses's family and the Saccharum genus. Species belonging to this family have the C4 photosynthesis patway, more efficient for biomass production when compared the C3 photosynthetic metabolism plants, in high temperature condicions. The sugarcane became an important economic potential and energy in the world due to its ability to store sucrose (about 50% of its dry weight) and production of bioethanol. In recent years it has become priority for several studies through breeding, molecular biology, biochemistry and physiological studies. Products from sugarcane is widely used by the world's population and represent an alternative source for energy generation. Brazil occupies an outstanding position among the countries producing sugarcane (34% of world production). Because of its interspecific origin, the sugarcane has one of the more complex genomes of plant species became an important object of study for plant breeding and productive or efficient, better adapted to climatic conditions. The clonal propagation through in vitro possible to obtain faster plants copies. The use of aseptic methods for disinfestation and disinfection without causing tissue damage leading to death of the plant has become a major challenge for the procurement of new seedlings to allow the biotechnology study. And the great interest in studying sugarcane plant is caused by the accumulation of sucrose, which occurs in the internode region during the plant development. Classical genetics search to improve this feature, mainly by increasing the biomass held by sequestration, however, there is a limited increase in sucrose content. The gibberellin is a plant phytohormone widely used in the agriculture and plays a variety of physiological functions in the plants. The sintetic GA3 has been applied to stimulate the sugarcane growth, to assist the germination of barley, the production of fruits and vegetables, among others. The gibberellins are extremely active in inducing the elongation of the stem. Studies show that the application of GAs causes an increase in cell size and cell number, indicating that GAs act both in cell elongation and cell division, which leverage an increase in sucrose yield. Since the PBZ acts by inhibiting the biosynthesis of gibberellins. It blocks the biosynthesis of GA, because it interferes in the first steps of the kaurene oxidation patway, preventing the GAs formation, and therefore acts as a negative control mechanisms of action of gibberellins. Both the presence of paclobutrazol and the GA3 induced changes in gene expression and activation of specific signaling pathways that act cooperatively in trying to alleviate the effect of stress in trying to establish a return to cellular homeostasis. Our objectivity in this study is to try to identify the mechanism of action of GAs to allow a understanding of both morphological and physiological changes experienced by seedlings. To do this in our studies we selected genes that could present relationship with carbohydrate metabolism, hormonal responses, with the metabolism of nucleic acids, through photosynthesis, with the development, with cell division, with protein metabolism, and several transcription factors that may be involved in these processes, based on results of the metabolism of carbohydrates found in the biochemical analysis of the seedlings, as well as in anatomical cuts. The results showed interference of GA3 in the accumulation of carbohydrates in cell elongation in genes related to the route of signal transduction of AUX, AUX biosynthesis, GA, in addition to genes and transcription factors related to cell cycle, photosynthesis, fixing carbon and many stresses, including the osmotic.
Doutorado
Biologia Vegetal
Doutor em Biologia Vegetal