Orientador: Alessandro de Mello Varani / Coorientador: Marcos Túlio Oliveira / Banca: Jesus Aparecido Ferro / Banca: Henrique Ferreira / Resumo: Xanthomonas citri subsp. citri (Xac) é um fitopatógeno responsável por causar o Cancro Cítrico, relacionado a grandes perdas econômicas para a citricultura. Esta bactéria utiliza diversos mecanismos moleculares para infectar o hospedeiro, dentre eles, o Sistema de Secreção Tipo III (T3SS), considerado o principal fator de virulência expresso in planta pela Xac. Sabe-se que a ativação do T3SS é controlada por dois reguladores: HrpG e HrpX. Porém, os mecanismos que controlam estes reguladores e posteriormente a expressão do T3SS in planta ainda são pouco compreendidos. Estudos realizados por nosso grupo de pesquisa sugerem que a concentração de fosfato inorgânico (Pi) presente em meio de cultura ou em espaço apoplástico, onde a Xac causa a infecção em plantas, pode estar relacionado com a ativação do T3SS, sugerindo uma possível relação entre o Pi com os reguladores HrpG e HrpX. Em Xac, a detecção e transportorte do Pi é realizada pelo sistema de dois componentes (TCS) PhoR/PhoB, codificado pelo operon pho. Afim de averiguar a possível relação entre PhoR/PhoB com os reguladores do T3SS HrpG e HrpX, ensaios de modelagem molecular foram realizados, indicando que a proteína PhoR poderia interagir fisicamente com HrpG, fosforilando-a, e sugerindo um possível mecanismo de interação entre o TCS PhoR/PhoB e os genes reguladores do T3SS. Para testar a hipótese de interação física entre HrpG e PhoR, as proteínas recombinantes PhoR, PhoB e HrpG de Xac foram expressas em células de Escher... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Xanthomonas citri subsp. citri (Xac) is a plant pathogen that causes citrus canker, responsible for significant economic losses in citriculture. This bacteria uses several molecular mechanisms to infect the host, such as the Type III Secretion System (T3SS), which is considered the main factor of virulence expressed in plant by Xac. Activation of T3SS is controlled by two regulators, HrpG and HrpX, however, the mechanisms that control these regulators and subsequently the expression of T3SS in planta are poorly understood. Previosuly, our research group identified that the concentration of inorganic phosphate (Pi) present in culture media or in the apoplastic space, where Xac causes infection in plants, may be related to the activation of T3SS, suggesting a possible relationship between Pi and the HrpG and HrpX regulators. In Xac, the detection and transport of Pi is performed by the two-component system (TCS) PhoR/PhoB, encoded by the operon pho. In order to investigate the possible relationship between PhoR/PhoB and the regulators of T3SS HrpG and HrpX, molecular modeling analyses were performed and indicated that the PhoR protein could physically interact with HrpG and phosphorylate it, suggesting a possible mechanism of interaction between TCS PhoR / PhoB and the T3SS regulatory genes with subsequent activation of T3SS. To test the hypothesis, recombinant forms of PhoR, PhoB and HrpG were expressed in Escherichia coli BL21 cells for the purpose of performing pull-down ass... (Complete abstract click electronic access below) / Mestre

Orientador: Henrique Ferreira / Resumo: O cancro cítrico é uma doença que afeta todas as variedades economicamente importantes de citros cultivadas ao redor do mundo. Atualmente representa uma ameaça aos maiores produtores mundiais de laranjas doce e de suco concentrado: o estado de São Paulo, Brasil, e estado da Flórida, EUA. O agente etiológico mais importante do cancro é a bactéria Gram-negativa Xanthomonas citri subsp. citri (X. citri) patotipo A, cujo genoma tem sido estudado e impulsionado descobertas e avanços na compreensão da doença e de seu agente causador. Contudo, mecanismos celulares essenciais são ainda pouco explorados neste micro-organismo. Desta forma, a compreensão de tais mecanismos e de seus efetores pode ser explorado no desenvolvimento de antimicrobianos e de novas estratégias para o combate ao cancro cítrico. Nosso grupo mostrou recentemente que ésteres de ácido gálico são potentes inibidores da divisão cromossômica e celular em X. citri. No presente trabalho, demos continuidade aos estudos com o objetivo de caracterizar processos essenciais à infecção ocasionada por X. citri, como a motilidade. As análises de bioinformática revelaram que a ORF XAC1934 estaria relacionada com motilidade em X. citri, uma vez que há uma grande identidade desta ORF com fleN, um gene regulador da formação flagelar em outros micro-organismos. Os resultados de motilidade e potencial infectivo in planta do mutante deletado desta ORF corroboraram a literatura, apresentando padrões semelhantes a estudos com mutantes d... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Citrus canker is a disease that affects all economically important varieties of citrus cultivars worldwide. Currently, it represents a threat to the world’s biggest sweet orange juice producers: São Paulo state, Brazil, and Florida, USA. The canker etiologic agent is the Gram-negative bacterium Xanthomonas citri subsp. citri (X. citri). Its genome knowledge has driven to discoveries and advances in the study of the causal agent of this disease. However, this microorganism’s essential microbiological processes are still underexplored. Therefore, the understanding of these mechanisms and its effectors can be useful in antibiotics development in order to prevent citrus canker infections. Our group have shown recently that esters of galic acid are potent inhibitors of cell division in X. citri. In this work, we continue to study essential processes for citrus canker infection such as motility. Bioinformatics analyses reveled that ORF XAC1934 is related to motility in X. citri, because there is an identity to fleN, a microorganism flagellar formation regulator gene. The motility and infective potential in planta results of the mutant deleted for this ORF corroborate the literature, showing a similar pattern presented in Pseudomonas aeruginosa and Vibrio cholerae deleted mutants for fleN. Despite this, there was no subcellular localization of the studied ORF protein. It suggests that this ORF does not interfere in flagellar localization nor in adequate divisional septa formation as... (Complete abstract click electronic access below) / Mestre

Thesis (M.S.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references (leaves 79-88). Also available via World Wide Web.

Thesis (Ph.D.)--Murdoch University, 2003. / Thesis submitted to the Division of Science and Engineering. Bibliography: leaves 185-202.

Thesis (Ph.D.)(Microbiology))--University of Pretoria, 2006. / Summary in English. Includes bibliographical references.

Thesis (M.S.)--California Polytechnic State University, 2009. / Title from PDF title page; viewed on June 5, 2009. "May 2009." "In partial fulfillment of the requirements for the degree [of] Master of Science in Forestry Sciences." "Presented to the faculty of California Polytechnic State University, San Luis Obispo." Major professor: Walter R. Mark, Ph.D. Includes bibliographical references (p. 39-43). Also available on microfiche.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:28:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-31Bitstream added on 2014-06-13T19:37:01Z : No. of bitstreams: 1 reis_em_me_prud.pdf: 457113 bytes, checksum: 1e14d0c874fd9ea5c0cf226d8aa7f99c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Esta pesquisa tem como objetivo analisar a citricultura paulista a partir do aparecimento da doença de citros denomin ada cancro cítrico no município de Presidente Prudente – SP, no ano de 1957. O combate ao cancro cítrico mobilizou os poderes públicos e privados no Estado de São Paulo, desencadeando o maior embargo fitossanitário da história da agricultura brasileira. As conseqüências desse embargo refletem até os dias atuais um quadro de exclusão frente aos poucos produtores da Região de Presidente Prudente – SP. Além disso, provocou um intenso debate na região a respeito do papel desempenhado pelo FUNDECITRUS, em suas a ções de erradicação do cancro cítrico na região, promovendo assim de acordo com os produtores um tratamento desigual para os produtores da região em questão e os produtores da região nobre da citricultura ao Norte do Estado. / The objective of this research is to analyze the citriculture State São Paulo starting from the emergence of the disease of citric denominated citrus canker in the municipal district of Presidente Prudente - SP, in the year of 1957. The combat to the citrus canker mobilized the public and private powers in the State of São Paulo, unchaining the largest seizure phytosanitary of the history of the Brazilian agriculture. The consequences of that seizure contemplate little by little until the current days a picture and exclusion front producing Region of Presidente Prudente - SP. Besides, it provoked an intense debate in the area regarding the paper carried out by FUNDECITRUS, in their action s of erradication of the citrus canker in the area, promoting like this in agreement with the producers an unequal treatment for the producing of the area in subject and the producing of the noble area of the citriculture to the North of the State.

Dissertation (MSc)--University of Pretoria, 2009. / Microbiology and Plant Pathology / Unrestricted

A survey of dipterocarp forest in four sites revealed that the incidence of stem canker was relatively low but high localized incidences were recorded. No consistent association was obtained between the presence of mechanical damage and cankers. Cankers occurred more frequently on dipterocarps and less frequently on euphorbs. Field studies and experimental manipulations were used to compare sapling resistance and responsiveness to wounding and stem breakage in relatively nutrient-rich, alluvial forest and relatively nutrient-poor, sandstone ridge forest. Species found on sandstone ridges showed greater resistance to damage (e.g., greater stem flexibility, narrower crowns) than those on alluvial soils. Species common on alluvial soils tended to be more responsive to damage (e.g., faster wound closure rates, more likely to re-sprout). Results from manipulation experiments conducted on pot-grown seedlings were consistent with results from the field studies, where conditions of greater nutrient availability, saplings closed wounds at faster rates, had less flexible stems, more narrow crowns, and lower levels of foliar total phenolics. Species showed differential rezones to resource availability which, in part, may relate to contrasting strategies for investment in passive defence (i.e., resins and phenolics) over investment in growth. Through their narrower crowns, greater whole stem flexibility, and lesser stem taper, tree species characteristic of sandstone ridges had greater resistance to mechanical damage from debris falling from above than congeneric species characteristic of alluvial soils. Tree species characteristic of alluvial soils were more responsive to damage than congeners on sandstone ridges, by producing earlier and longer sprouts following stem snapping and more rapid rates of wound closure following wounding.