No description available.

The effect of controlled atmosphere (CA) storage, and antioxidant treatment on polyphenoloxidase (EC 1. 1418.1:PPO), peroxidase (EC11.11.1.7:POD), and superoxide dismutase (EC 1.15.1.1:S0D) activities and superficial scald and soft scald development in 'Virginiagold','Stayman', and 'Rome' apples (Malus domestica Borkh.) was investigated. 'Virginiagold' apples treated postharvest with an aqueous solution of diphenylamine (DPA) + 1,2, dihydro -6- ethoxy -2,2,4-trimethylquinoline (ethoxyquin) and stored in CA exhibited lower soft scald incidence and higher firmness than comparable fruits stored at O°C in air storage. Fruit firmness and titratable acids (TA) decreased continuously, while ethylene increased in storage. Titratable acids and firmness were positively correlated, while TA and ethylene and firmness and ethylene were negatively correlated. 'Stayman' and 'Rome' apples analyzed during storage showed increase in levels of λ±-famesene and its oxidation products conjugated trienes. During storage fruits showed an increase in the activities of polyphenoloxidase (PPO), peroxidase (POD), and superoxide dismutase (SOD), which reached a maximum when scald symptoms in 'Stayman' were observed. Our results indicate that 'Stayman' apples exhibited scald and 'Rome' did not, because 'Stayman' apples had a ten fold higher PPO activity than 'Rome.' / Master of Science

Consumers are often confused and reluctant to purchase products from fresh retail meat counters that exhibit significant color variations. This hesitation to purchase results in annual profit loss to the pork industry. Processes to minimize color variation remain a major focus of the industry and many meat science programs across the globe. Previously, we found inherent muscle characteristics contribute to variations in pork quality but these characteristics fail to explain the high frequency of two-toning and other pork quality defects routinely occurring in many hog processing facilities. Therefore, we hypothesized harvesting practices, such as scald alter color across muscles of the ham. Scald time was initially investigated using 32 carcasses subjected to either a 4 (n=16) or 8 (n=16) min scald time. Samples were collected before or after scalding and at 24 hrs. A 50% reduction in scald time resulted in (p < 0.0001) lighter muscle color (L*) early postmortem, although the 8 min scald treatment was lighter (p < 0.005) at 24 hrs. Although differences in pH (p < 0.0001) and color were noted, ultimate carcass temperature was not affected. To that end, we moved to validate our hypothesis in an industrial plant setting. Carcasses (n=200) were assigned treatments of 6.5 or 7.5 min scald times, and SM muscle samples were collected at 24 hrs. Surprisingly, the shorter scald time resulted in (p < 0.05) a lighter color, contradicting our first study. To explore this color issue further, we uncoupled scald from the dehairing process. To achieve this goal, carcasses (n=24) were assigned to either an 8 or 16 min time to dehair, with or without scalding. Protracted time to dehair resulted in higher ultimate pH (p < 0.005) and less color variation across the muscle (p < 0.05). Though a color gradient remained, the variation across the muscle was reduced by increasing time to dehair. These data show time to dehair affects pork quality development and suggest that delaying time to physical manipulation of the carcass may improve pork color, thus increasing consumer acceptance. / Master of Science

Large doses of recombinant growth factors formulated in solution form directly injected into the body is usual clinical practice in treating second-degree scald injuries, with promising results, but this approach creates side effects; furthermore, it may not allow appropriate levels of the factor to be sensed by the target injured tissue/organ in the specific time frame, owing to complications arising from regeneration. In this research, two delivery methods (infusion pumping and local topical application) were applied to deliver recombinant human erythropoietin (rHuEPO) for skin regeneration. First, rHuEPO was given in deep second-degree scald injury sites in mice by infusion pump. Vascularization was remarkably higher in the rHuEPO pumping group than in controls. Second, local topical application of rHuEPO gel was given in deep second-degree scald injury sites in rats. Histological analysis showed that epithelialization rate was significantly higher in the rHuEPO gel-treated group than in controls. Immunohistochemical studies showed that the rHuEPO gel-treated group showed remarkably higher expression of skin regeneration makers than the control group. An accurate method for visualization and quantification of blood vessel networks in target areas has still not been developed up to this point, because of technical difficulties in detecting such thin blood vessels. A method which utilizes a series of steps to enhance the image, removes noise from image background, and tracks the vessels edges for vessel segmentation and quantification has been used in this study. Using image analysis methods, we were able to detect the microvascular networks of newly formed blood vessels (less than 500 μm thickness), which participate in the healing process, providing not only nutrition and oxygen to grow tissues but also necessary growth factors to grow tissue cells for complete skin regeneration. The rHuEPO-treated group showed higher expression of stem cell markers (CD 31, CD 90, CD 71, and nestin), which actively contribute to in-wound-healing processes for new hair follicle generation as well as skin regeneration. Collectively, both rHuEPO group pumping into the systemic circulation system, and injection into the local injury area, prompted mice and rats to form new blood vessel networks in scald injury sites, which significantly participate in the scald healing process. These results may lead to the development of novel treatments for scald wounds.

O destaque da cana-de-açúcar como fonte de energia renovável tem motivado a busca por melhorias no processo de cultivo e processamento da planta, buscando o aumento da produtividade dos canaviais. Dentre os fatores limitantes para o aumento da produção de cana-de-açúcar, destaca-se a ocorrência de fitodoenças, como por exemplo a escaldadura das folhas, causada pela bactéria Xanthomonas albilineans. Essa doença causa a diminuição do valor energético do caldo extraído da planta, e a ausência de tratamento químico ou biológico acarreta na necessidade de reforma precoce dos canaviais, causando perdas significativas para o agronegócio brasileiro. Portanto, existe uma grande necessidade no desenvolvimento de novas moléculas capazes de atuar como defensivos agrícolas com eficiência e especificidade. Neste trabalho, duas estratégias foram empregadas para a identificação de moléculas como potenciais candidatos a agroquímicos. Na primeira, avaliou-se o potencial inibidor de moléculas de origem natural ou sintética em ensaios fenotípicos contra a cultura de X. albilineans, identificando dois derivados, um de nitrotiofeno e um de nitrofurano, capazes de inibir o crescimento bacteriano. Na segunda estratégia, duas enzimas da via de biossíntese de folatos, 2-amino-4-hidroxi-6-hidroximetil di-hidropterina pirofosfoquinase (XaHPPK) e 7,8-di-hidroneopterina aldolase (XaDHNA), foram selecionadas como alvos moleculares. Métodos em biologia molecular e biologia estrutural foram empregados para a obtenção de proteínas puras e solúveis, visando-se a elucidação das estruturas tridimensionais e caracterização bioquímica dos alvos. Estudos de desnaturação térmica foram conduzidos para determinação da afinidade da XaHPPK pelo substrato natural 7,8-di-hidropterina (Kd = 97 &plusmn; 3 &micro;M). Os experimentos de biologia estrutural resultaram na determinação da estrutura da XaHPPK a 2,3 &Aring; de resolução (PDB ID, 5VSP) com o grupo espacial P212121. A obtenção da estrutura a alta resolução permitiu a aplicação de estratégias computacionais para a descoberta de potenciais inibidores. Os estudos da XaDHNA possibilitaram a coleta de um conjunto de dados à 3,5 &Aring; de resolução, no grupo espacial I422. Os experimentos e resultados obtidos neste doutorado ampliam o conhecimento sobre a via de biossíntese de folatos em X. albilineans e abrem o caminho para a descoberta de novos inibidores antibacterianos utilizando técnicas baseadas na estrutura do alvo. / The importance of sugarcane as a source of renewable energy has pushed researchers to search for improvements in the process of cultivation and processing of the plant, looking after increase the productivity of sugarcane crops. Among known facts that limits sugarcane production, we highlight the occurrence of plant diseases, such as leaf scald, a bacterial disease caused by Xanthomonas albilineans. This disease decreases the energetic value of the broth extracted from the cane, and the absence of chemical or biological treatment entails the need for early refresh sugarcane plantations, causing significant losses for Brazilian agribusiness. Therefore, the economic interest in the development of new molecules capable of acting as agricultural defenses with efficiency and specificity is motivating. Acting on the essential biochemical pathways of the pathogen is a recurring strategy in the development of bioactive molecules. Thus, several inhibitor identification strategies were used. Firstly, the inhibitory potential of molecules from natural or synthetic origins were evaluated in phenotypic assays against the culture of X. albilineans, identifying two nitrothiophene and nitrofuran derivatives capable of inhibiting bacterial growth at 2 mM. In another strategy, the essential pathway of X. albilineans for folate biosynthesis was selected and two proteins of this pathway investigated: 2-amino-4-hydroxy-6-hydroxymethyl dihydropteridine pyrophosphokinase (XaHPPK) and 7,8-dihydroneopterin aldolase (XaDHNA). Both molecular biology and structural biology methods were used to obtain pure and soluble proteins, aiming the obtaining of three-dimensional structures and biochemical characterization of targets. Studies with the XaHPPK protein for kinetic characterization made possible to calculate the Kd apparent (Kd = 97 &plusmn; 3 &mu;M) for the substrate 7,8-dihydropterin. Structural biology experiments resulted in a 2.3 &Aring; resolution structure in the space group P212121, available in the PDB under the 5VSP identifier. Structure based drug design for XaHPPK structure, SBDD, were performed using ZINC15 database with hierarchical filters and the Glide docking software. The XaDHNA studies enabled the collection of a set of data at 3.5 &Aring; resolution in the space group I422. The experiments and results obtained in this doctorate increase the knowledge about the folate biosynthesis pathway in X. albilineans and open the way for the discovery of new antibacterial inhibitors using structure based drug design.

A escaldadura das folhas, causada pela bactéria Gram-negativa Xanthomonas albilineans, é uma das doenças mais importantes que afetam o cultivo da cana-de-açúcar, causando significativa diminuição da produtividade, necessidade de reforma precoce dos canaviais e queda da qualidade do caldo extraído. O impacto dessa doença somado à ausência de agentes químicos ou biológicos para o controle estimula a pesquisa para a descoberta e desenvolvimento de moléculas bioativas como candidatos a novos defensivos agrícolas. Nesse contexto, a enzima N5, N10-metilenotetrahidrofolato desidrogenase ciclohidrolase (FolD) destaca-se como potencial alvo molecular. O projeto de doutoramento visou a caracterização estrutural e funcional da FolD de X. albilineans (XaFolD), além da triagem de moléculas candidatas a inibidores. Para tanto, foram conduzidos estudos integrados em biologia molecular estrutural e química biológica. A expressão heteróloga e purificação da XaFolD resultaram na produção de proteína funcional e adequada aos ensaios de cristalização. A caracterização das atividades desidrogenase e ciclohidrolase da XaFolD indicou os valores de KM para os substratos de ambas as reações, N5, N10-metileno-tetrahidrofolato (50 &plusmn; 10 &micro;M) e N5, N10-metenil-tetrahidrofolato (32 &plusmn; 3 &micro;M) e do cofator NADP+ (688 &plusmn; 81 &micro;M). A estrutura da XaFolD na forma apo, elucidada a 2,1 &Aring; de resolução, revelou uma proteína constituída por 11 hélices alfa e 9 fitas beta distribuídas em um domínio N-terminal catalítico e um domínio C-terminal de ligação ao dinucleotídeo. A enzima pura foi utilizada para a triagem de 1.124 fragmentos por interferometria de biocamada (BLI) e foram identificados três ligantes, DDD00808259 (KD = 260 &mu;M), DDD01305586 (KD = 3 mM) e DDD00100784 (KD = 210 &mu;M), com valores de afinidade na faixa do submilimolar até baixo milimolar. Paralelamente, uma abordagem computacional foi empregada para a triagem virtual de base de dados de compostos como candidatos a ligantes da XaFolD. Os critérios utilizados resultaram na seleção e aquisição de 31 compostos de diferentes classes químicas para avaliação da atividade inibitória frente a enzima alvo. Por fim, ensaios fenotípicos de triagem de inibidores resultaram na descoberta de compostos capazes de inibir o crescimento in vitro de X. albilineans. Dentre os inibidores identificados o composto THP2 apresentou a maior potência, com valor determinado de EC50 igual a 23 &plusmn; 2 &mu;M. Os dados estruturais, cinéticos e biofísicos obtidos nesta tese de doutoramento formam a base experimental e computacional para a descoberta e planejamento de inibidores candidatos a novos agroquímicos para o tratamento da escaldadura das folhas. / The leaf scald disease is a severe condition which affects sugarcane crops. Leaf scald is caused by the Gram-negative bacteria Xanthomonas albilineans and it has a dramatic impact on crop productivity, including the yield reduction and dropping the quality of the juice. The impact of this disease besides the absence of chemical or biological agents to treat it stimulates the research towards the discovery and development of bioactive molecules as lead candidates to new agrochemicals. In this context, the enzyme N5, N10-methylenetetrahydrofolate dehydrogenase-cyclohydrolase (XaFolD) stands out as a potential molecular target. Facing this scenario, the PhD project comprised the structural and functional characterization of X. albilineans FolD (XaFolD) and the screening of molecules to identify inhibitors. For this purpose, integrated studies in structural molecular biology and biological chemistry have been carried out. Suitable protein for crystallization and kinetic assays was produced by heterologous expression. The XaFolD dehydrogenase and cyclohydrolase activities were characterized, revealing KM values of 50 &plusmn; 10 &micro;M for N5, N10- methylenetetrahydrofolate, 32 &plusmn; 3 &micro;M for N5, N10-methenyltetrahydrofolate, and 688 &plusmn; 81 &micro;M for NADP+. The structure of XaFolD in the apo form was elucidated at 2.1 &Aring; resolution and it revealed a protein consisting of 11 alpha helices and 9 beta sheets distributed in the catalytic N-terminal domain and the C-terminal dinucleotide binding domain. Screening of 1,124 fragments by biolayer interferometry (BLI) revealed three ligands, DDD00808259, DDD01305586 and DDD00100784, with determined KD values of 260 &micro;M, 3 mM and 210 M, respectively. Furthermore, a virtual screening was performed to identify XaFolD ligands. As a result, 31 chemically diverse compounds were selected to be evaluated by potency assays. Additionally, phenotypical assays against X. albilineans have been performed and inhibitors were identified. Among them, the compound THP2 presented the highest potency, with a determined value of EC50 equal to 23 &plusmn; 2 &micro;M. The structural, kinetic, and biophysical data obtained in this PhD thesis provide the molecular basis for discovering and planning bioactive molecules as agrochemicals to control leaf scald disease.

Includes bibliographical references

Scald disease (Rhynchosporium secalis) is one of the major plant diseases causing considerable yield loss in barley (Hordeum vulgare) plantations in Turkey. To develop, scald resistant barley varieties, C.R.I.F.C. of Turkey has a large accumulated collection of barley seed sources in hand, but these samples are difficult to be followed and used in the breeding programs due to lack of genetic studies on them. Thus, the objective of this study was to characterize and fingerprint of eighty barley seed sources, and assess the magnitude and pattern of genetic diversity that could be used to have more efficient scald disease resistant breeding programs in the future. Forty scald disease resistant and 40 scald sensitive Turkish barley seed sources were screened using 6 simple sequence repeats (SSR) primers. Each of barley seed source were represented with four seeds, assuming they are genetically uniform since barley is a self-pollinated crop. Estimated genetic parameters indicated that scald disease resistant and sensitive barley seed sources still maintain large amount of genetic diversity. For example, expected heterozygosity was 0.62&plusmn / 0.01 and 0.64&plusmn / 0.01 for resistant and sensitive Turkish barley seed sources, respectively. Thirty-nine percent of total genetic variation was between populations for resistant and 46% for sensitive group, while 61% of total variation was within populations for resistant group and 54% for sensitive group. When overall Turkish barley seed sources were considered, genetic distances between scald sensitive seed source S18 and resistant R1 as well as between sensitive S28 and resistant R1 were large. Scald resistant and sensitive barley seed sources were generally located in different clusters in dendrogram. The presence of R25, R39 and S16 barley seed sources with high genetic diversity parameters among studied seed sources, suggests that this diversity could be important drive in future barley breeding program in Turkey. However, further study is needed to illustrate genetic divergence of Turkish barley seed sources with use of more molecular markers.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The most widely way used to store apples is the controlled atmosphere (CA), were the oxygen is reduced, but this is far above the lower oxygen limit (LOL) tolerated by the fruit. The use of technologies that allow the monitoring of oxygen levels at least tolerated by the fruit can help maintain quality and reduce the incidence and of physiological disorders and postharvest diseases. The dynamic controlled atmosphere (DCA) is one of these technologies, which change the O2 throughout the storage period according to the fruit metabolism. The objective of this study was to evaluate effect of DCA storage monitored by the respiratory quotient (RQ) and chlorophyll fluorescence (CF), as well as their interaction with the application of 1-methylcyclopropene (1-MCP) on the physicochemical quality and physiological disorders, especially superficial scald of 'Granny Smith' apple. The following storage conditions were evaluated: a) Conventional CA with 1.5 kPa O2 plus 1.0 kPa CO2; b) DCA-RQ 1.3; c) DCA - RQ 1.5; d) DCA - RQ 1.7; e) DCA-CF (HarvestWatchTM DCA). The CO2 partial pressure was maintained at 1.2 kPa and the temperature at 1.5 °C in all treatments. After 9 months of storage, at the fruits removal from the storage chamber, evaluations were performed for superficial scald incidence and severity, decay and healthy fruits incidence. The other evaluations were performed after a 7 days period of shelf life at 20 ° C in. Fruits stored under DCA had lower ethylene production and respiration as compared to fruits stored in conventional CA, because of the lower 1-acid-aminocyclopropane-1-carboxylic enzyme activity by apples stored in DCA-RQ 1.5 and 1.7. The storage of apples in DCA-RQ 1.5 or 1.7 resulted in low superficial scald incidence. Under these conditions the application of 1-MCP had no benefit in reducing this disorder, suggesting that their application may be needless, but it is efficient when the fruits are stored in conventional CA and DCA-CF. In fruits DCA-RQ 1.7 storage occurred most volatile production associated with fermentative metabolism, but without decline of the fruit quality. Apples stored in DCA-RQ 1.7 kept greener color as compared to fruit stored in conventional CA due to the higher concentration of total chlorophyll. The firmness of the fruit stored in DCA-RQ fruit was higher as compared to the ones stored in CA, regardless of the application of 1-MCP. Under DCA-CF, application of 1-MCP has been shown not to be beneficial for maintaining the quality of the 'Granny Smith', as it provided the highest occurrence of decay. The storage in DCA provided higher number of healthy fruits as compared to the ones stored in CA. / A forma mais utilizada para o armazenamento de maçãs é a atmosfera controlada (AC), em que é reduzido o nível de O2, mas este fica muito acima do limite mínimo tolerado pelo fruto. O uso de tecnologias que permitem o monitoramento dos níveis de oxigênio no mínimo tolerado pelos frutos pode auxiliar a manutenção da qualidade e reduzir a incidência de distúrbios fisiológicos e podridões. A atmosfera controlada dinâmica (ACD) é uma destas tecnologias de controle e variação do O2 ao longo de todo o período de armazenamento de acordo com o metabolismo dos frutos. O objetivo deste trabalho foi avaliar o efeito do armazenamento em atmosfera controlada dinâmica monitorada pelos métodos do quociente respiratório (QR) e da fluorescência de clorofila (FC), bem como a sua interação com a aplicação de 1-metilciclopropeno (1-MCP) sobre a manutenção da qualidade e redução de distúrbios fisiológicos, especialmente a escaldadura superficial na maçã Granny Smith . As condições de armazenamento avaliadas foram: a) AC convencional com 1,0 kPa O2 mais 1,5 kPa CO2; b) ACD com quociente respiratório (QR) 1,3; c) ACD-QR 1,5; d) ACD-QR 1,7; e) ACD monitorada pela fluorescência de clorofila (ACD-FC) (HarvestWatchTM DCA). A pressão parcial de CO2 foi mantida em 1,2 kPa em todos os tratamentos e a temperatura em 1,5 °C. Após nove meses de armazenamento, no momento da saída dos frutos da câmara, foram realizadas avaliações quanto à incidência e severidade de escaldadura superficial, incidência de podridões e frutos sadios. As demais avaliações foram realizadas após um período de sete dias em que os frutos permaneceram expostos à temperatura de 20 °C com o objetivo de simular o período de prateleira. Frutos armazenados sob ACD apresentaram menor produção de etileno e respiração que frutos armazenados em AC convencional, como resultado da menor atividade da enzima ACC oxidase nas maçãs armazenadas em ACD-QR 1,5 e 1,7. O armazenamento de maçãs em ACD-QR 1,5 ou 1,7 favoreceu uma menor incidência de escaldadura superficial. Nestas condições a aplicação de 1-MCP não teve nenhum benefício na redução desse distúrbio, sugerindo que sua aplicação pode ser dispensada, porém é necessária quando os frutos são armazenados em AC convencional e ACD-FC. Nos frutos armazenados em ACD com QR 1,7 ocorreu maior produção de voláteis associados ao metabolismo fermentativo, contudo, não houve prejuízo à qualidade dos frutos. Maçãs armazenadas em ACD-QR 1,7 mantiveram coloração mais verde que frutos armazenados em AC convencional devido à maior concentração de clorofilas totais. A firmeza dos frutos armazenados em ACD-QR foi maior que frutos em AC, independentemente da aplicação de 1-MCP. Sob ACD-FC a aplicação de 1-MCP demonstrou não ser benéfica para a manutenção da qualidade das maçãs Granny Smith , uma vez que forneceu a maior ocorrência de podridões. O uso de ACD proporcionou um maior número de frutos sadios quando comparado a AC convencional.

A escaldadura das folhas, causada pela bactéria Gram-negativa Xanthomonas albilineans, é uma das doenças mais importantes que afetam o cultivo da cana-de-açúcar, causando significativa diminuição da produtividade, necessidade de reforma precoce dos canaviais e queda da qualidade do caldo extraído. O impacto dessa doença somado à ausência de agentes químicos ou biológicos para o controle estimula a pesquisa para a descoberta e desenvolvimento de moléculas bioativas como candidatos a novos defensivos agrícolas. Nesse contexto, a enzima N5, N10-metilenotetrahidrofolato desidrogenase ciclohidrolase (FolD) destaca-se como potencial alvo molecular. O projeto de doutoramento visou a caracterização estrutural e funcional da FolD de X. albilineans (XaFolD), além da triagem de moléculas candidatas a inibidores. Para tanto, foram conduzidos estudos integrados em biologia molecular estrutural e química biológica. A expressão heteróloga e purificação da XaFolD resultaram na produção de proteína funcional e adequada aos ensaios de cristalização. A caracterização das atividades desidrogenase e ciclohidrolase da XaFolD indicou os valores de KM para os substratos de ambas as reações, N5, N10-metileno-tetrahidrofolato (50 &plusmn; 10 &micro;M) e N5, N10-metenil-tetrahidrofolato (32 &plusmn; 3 &micro;M) e do cofator NADP+ (688 &plusmn; 81 &micro;M). A estrutura da XaFolD na forma apo, elucidada a 2,1 &Aring; de resolução, revelou uma proteína constituída por 11 hélices alfa e 9 fitas beta distribuídas em um domínio N-terminal catalítico e um domínio C-terminal de ligação ao dinucleotídeo. A enzima pura foi utilizada para a triagem de 1.124 fragmentos por interferometria de biocamada (BLI) e foram identificados três ligantes, DDD00808259 (KD = 260 &mu;M), DDD01305586 (KD = 3 mM) e DDD00100784 (KD = 210 &mu;M), com valores de afinidade na faixa do submilimolar até baixo milimolar. Paralelamente, uma abordagem computacional foi empregada para a triagem virtual de base de dados de compostos como candidatos a ligantes da XaFolD. Os critérios utilizados resultaram na seleção e aquisição de 31 compostos de diferentes classes químicas para avaliação da atividade inibitória frente a enzima alvo. Por fim, ensaios fenotípicos de triagem de inibidores resultaram na descoberta de compostos capazes de inibir o crescimento in vitro de X. albilineans. Dentre os inibidores identificados o composto THP2 apresentou a maior potência, com valor determinado de EC50 igual a 23 &plusmn; 2 &mu;M. Os dados estruturais, cinéticos e biofísicos obtidos nesta tese de doutoramento formam a base experimental e computacional para a descoberta e planejamento de inibidores candidatos a novos agroquímicos para o tratamento da escaldadura das folhas. / The leaf scald disease is a severe condition which affects sugarcane crops. Leaf scald is caused by the Gram-negative bacteria Xanthomonas albilineans and it has a dramatic impact on crop productivity, including the yield reduction and dropping the quality of the juice. The impact of this disease besides the absence of chemical or biological agents to treat it stimulates the research towards the discovery and development of bioactive molecules as lead candidates to new agrochemicals. In this context, the enzyme N5, N10-methylenetetrahydrofolate dehydrogenase-cyclohydrolase (XaFolD) stands out as a potential molecular target. Facing this scenario, the PhD project comprised the structural and functional characterization of X. albilineans FolD (XaFolD) and the screening of molecules to identify inhibitors. For this purpose, integrated studies in structural molecular biology and biological chemistry have been carried out. Suitable protein for crystallization and kinetic assays was produced by heterologous expression. The XaFolD dehydrogenase and cyclohydrolase activities were characterized, revealing KM values of 50 &plusmn; 10 &micro;M for N5, N10- methylenetetrahydrofolate, 32 &plusmn; 3 &micro;M for N5, N10-methenyltetrahydrofolate, and 688 &plusmn; 81 &micro;M for NADP+. The structure of XaFolD in the apo form was elucidated at 2.1 &Aring; resolution and it revealed a protein consisting of 11 alpha helices and 9 beta sheets distributed in the catalytic N-terminal domain and the C-terminal dinucleotide binding domain. Screening of 1,124 fragments by biolayer interferometry (BLI) revealed three ligands, DDD00808259, DDD01305586 and DDD00100784, with determined KD values of 260 &micro;M, 3 mM and 210 M, respectively. Furthermore, a virtual screening was performed to identify XaFolD ligands. As a result, 31 chemically diverse compounds were selected to be evaluated by potency assays. Additionally, phenotypical assays against X. albilineans have been performed and inhibitors were identified. Among them, the compound THP2 presented the highest potency, with a determined value of EC50 equal to 23 &plusmn; 2 &micro;M. The structural, kinetic, and biophysical data obtained in this PhD thesis provide the molecular basis for discovering and planning bioactive molecules as agrochemicals to control leaf scald disease.