Verticillium wilt, caused by the soil-borne Verticillium dahliae Klebahn is a serious problem in the production of sunflower worldwide. To date, information on sunflower resistance to Verticillium spp. is very scarce, although it is critical for an effective management of this pathogen. In this study, two highly aggressive (Vd1396-9 and Vd1398-21) and two weakly aggressive V. dahliae isolates (Vs06-07 and Vs06-14) were used to inoculate moderately resistant (IS6111) and susceptible (IS8048) sunflower hybrids. VdNEP (V. dahliae necrosis and ethylene-inducing protein), an elicitor from V. dahliae, was also used to infiltrate sunflower plants. Our results indicate that VdNEP has a dual role in the interaction between sunflower and V. dahliae. VdNEP acted not only as a pathogenicity factor on sunflower by inducing wilting symptoms such as chlorosis, necrosis and vascular discoloration, but also as an elicitor triggering defense responses of the host. VdNEP induced the hypersensitive cell death in Nicotiana benthamiana leaves and sunflower cotyledons. Moreover, VdNEP activated the production of reactive oxygen species and the accumulation of fluorescent compounds in sunflower leaves. Pathogenesis-related genes (Ha-PR-3, and Ha-PR-5), two defensin genes (Ha-PDF and Ha-CUA1) and genes encoding Ha-ACO, Ha-CHOX, Ha-GST and Ha-SCO were up-regulated by VdNEP, suggesting that multiple signaling pathways are involved in this interaction. Two SA-related genes (Ha-PAL and Ha-NML1) were slightly suppressed after infiltration with VdNEP, suggesting a possible involvement of VdNEP in affecting sunflower defenses.

<p>While the many completely sequenced genomes of bacterial pathogens contain all the determinants of the host-pathogen interaction, and also every possible drug target and recombinant vaccine candidate, computational tools for selecting suitable candidates for further experimental analyses are limited to date. The overall objective of my PhD project was to attempt to design reusable systems that employ the two most important features of bacterial evolution, horizontal gene transfer and adaptive mutation, for the identification of potentially novel virulence-associated factors and possible drug targets. In this dissertation, I report the development of two novel technologies that uncover novel virulence-associated factors and mechanisms employed by bacterial pathogens to effectively inhabit the host niche. More importantly, I illustrate that these technologies may present a reliable starting point for the development of screens for novel drug targets and vaccine candidates, significantly reducing the time for the development of novel therapeutic strategies. Our initial analyses of proteins predicted from the preliminary genomic sequences released by the Sanger Center indicated that a significant number appeared to be more similar to eukaryotic proteins than to their bacterial orthologs. In order determine whether acquisition of genetic material from eukaryotes has played a role in the evolution of pathogenic bacteria, we developed a system that detects genes in a bacterial genome that have been acquired by interkingdom horizontal gene transfer.. Initially, 19 eukaryotic genes were identified in the genome of Mycobacterium tuberculosis of which 2 were later found in the genome of Pseudomonas aeruginosa, along with two novel eukaryotic genes.</p> <p>Surprisingly, six of the M. tuberculosis genes and all four eukaryotic genes in P. aeruginosa may be involved in modulating the host immune response through altering the steroid balance and the production of pro-inflammatory lipids. We also compared the genome of the H37Rv M. tuberculosis strain to that of the CDC- 1551 strain that was sequenced by TIGR and found that the organisms were virtually identical with respect to their gene content, and hypothesized that the differences in virulence may be due to evolved differences in shared genes, rather than the absence/presence of unique genes. Using this observation as rationale, we developed a system that compares the orthologous gene complements of two strains of a bacterial species and mines for genes that have undergone adaptive evolution as a means to identify possibly novel virulence &ndash / associated genes. By applying this system to the genome sequences of two strains of Helicobacter pylori and Neisseria meningitidis, we identified 41 and 44 genes that are under positive selection in these organisms, respectively. As approximately 50% of the genes encode known or potential virulence factors, the remaining genes may also be implicated in virulence or pathoadaptation. Furthermore, 21 H. pylori genes, none of which are classic virulence factors or associated with a pathogenicity island, were tested for a role in colonization by gene knockout experiments. Of these, 61% were found to be either essential, or involved in effective stomach colonization in a mouse infection model. A significant amount of strong circumstantial and empirical evidence is thus presented that finding genes under positive selection is a reliable method of identifying novel virulence-associated genes and promising leads for drug targets.</p>

Lic.-avh. Uppsala : Sveriges lantbruksuniv. / Härtill 2 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2006. / Härtill 4 uppsatser.

Made available in DSpace on 2014-06-11T19:32:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-07-08Bitstream added on 2014-06-13T21:03:52Z : No. of bitstreams: 1 souza_ec_dr_jabo.pdf: 821266 bytes, checksum: 46390da0d02b9c37aa41e4af297432aa (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O cancro cítrico é uma das principais doenças da cultura do citros, provocando lesões nas folhas, ramos e frutos, tendo como consequência a queda dos frutos e folhas, o que leva à perdas significativas na produção. A partir do sequenciamento completo do genoma da bactéria gram-negativa Xanthomonas citri subsp. citri (Xac), agente causal do cancro cítrico, abriu-se a possibilidade da utilização de estratégias de análise genômica funcional no estudo da função de genes da bactéria relacionados com a infecção na planta e com o desenvolvimento da doença. Uma das estratégias utilizadas foi a obtenção de mutantes de Xac contendo genes relacionados à patogenicidade e virulência interrompidos pelo método de mutagênese insercional aleatória utilizando o transposon Tn5 (LAIA et al., 2009). No presente trabalho a técnica de microarranjos de DNA foi utilizada para avaliar a expressão global de genes de dois mutantes de Xac 72 h após a infecção in planta. Em um dos mutantes (8B7) o gene interrompido foi o xrvA, um regulador de virulência, e no outro mutante (18D6) o gene interrompido codifica uma histidina quinase híbrida sensora que faz parte de um sistema de transdução de sinal de dois componentes. Os resultados das hibridizações revelaram um total de 553 genes diferencialmente expressos para os dois mutantes estudados quando comparado com o genótipo selvagem (Xac 306), sendo 323 no mutante 8B7 e 230 no mutante 18D6. Esses genes foram divididos em diferentes categorias funcionais e uma análise funcional comparativa revelou que eles podem desempenhar um papel importante no processo de patogenicidade / Citrus canker is a major disease affecting citrus crops worldwide, causing lesions on leaves, branches and fruits that results in the falling of fruit and leaves, leading to significant losses in orange production. The complete genome sequencing of Xanthomonas citri subsp. citri (Xac), a Gram-negative bacteria and the causal agent of citrus canker, allowed the possibility of using functional genomic strategies to study the function of genes related to plant infection and disease development in this bacteria. One strategy was to produce mutants for phatogenicity and virulence genes by random insertional mutagenesis using Tn5 Transposon (LAIA et al., 2009). In the present work DNA microarray analysis was used to evaluate the global gene expression profile of two Xac mutants after 72 hours of plant infection. One mutant (8B7) carry a mutation in the xrvA gene (XAC1495), a virulence regulator, and the other (18D6) carry a mutation in a hybrid histidine quinase sensor of a two-component signal transduction system. The results revealed a total of 553 differentially expressed genes for the two mutant strains compared with Xac wild type, with 323 in the mutant 8B7, and 230 in the mutant 18D6. These genes were allocated into several functional categories and a comparative functional analysis showed that they can play an important role in the pathogenicity and virulence of Xac

Made available in DSpace on 2014-06-11T19:33:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-09-24Bitstream added on 2014-06-13T21:06:46Z : No. of bitstreams: 1 carvalho_ems_dr_jabo.pdf: 998912 bytes, checksum: fca2c550ea3f00d2dbfbc2f1213a506f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A antracnose é freqüentemente encontrada em feijão-fava na região nordeste do Brasil, porém é pouco estudada. Nesse sentido, objetivou-se caracterizar o agente causal da antracnose, determinar a reação de genótipos a Colletotrichum truncatum e investigar a viabilidade da utilização da técnica de folhas destacadas em estudos relacionados a essa doença. Isolados foram caracterizados em relação a aspectos morfoculturais quando cultivados em meios de cultura batata-dextrose-ágar (BDA) e feijão-dextrose-ágar (FDA), em temperaturas de 26, 28 e 30ºC e fotoperíodo de 12 horas. A patogenicidade dos isolados e a reação dos genótipos foram avaliadas em folhas destacadas e na planta. O comportamento dos genótipos foi avaliado em duas épocas, no período chuvoso (17 de abril a 02 de junho/2008) e período seco (13 de junho a 29 de julho/2008). O delineamento utilizado foi o inteiramente casualizado com cinco e quatro repetições para avaliação da patogenicidade e dos genótipos, respectivamente. As características morfológicas e culturais variaram de acordo com o isolado e condições de cultivo, porém, foram compatíveis com as descritas para a espécie C. truncatum. A patogenicidade foi comprovada, porém não foram detectadas diferenças significativas entre os isolados. Os primeiros sintomas da doença apareceram aos três dias após a inoculação em folhas destacadas e plantas. Os genótipos UFPI - 578, UFPI - 468 e UFPI - 26 foram suscetíveis a C. truncatum. Quando avaliados em folha destacada não diferiram estatisticamente entre si no nível de infecção, independente da época. Em planta e na ausência de chuva, UFPI - 26 apresentou o maior nível de infecção, enquanto UFPI - 578, o menor. A correlação positiva e significativa (P<0,0001) entre folha destacada e planta comprova a viabilidade do emprego da técnica de folhas destacadas em estudos relacionados a essa doença / Anthracnose is often found in lima bean plantations in the northeast region of Brazil, however, has been little studied. In this sense, the goals were to characterize the causal agent of anthracnose, determine the reaction of genotypes to Colletotrichum truncatum and investigate the viability of using the technique of detached leaves in studies related to this disease. Isolates were characterized in relation to aspects morphocultural when grown in culture BDA and FDA, in temperatures of 26, 28 and 30ºC and photoperiod of 12 hours. The pathogenicity of the isolates and the reaction of the genotypes were evaluated in detached leaf and plant. The behavior of the genotypes were evaluated in two seasons, in the presence and absence of rain. The design was completely randomized to five and four replicates to evaluate the pathogenicity and genotypes, respectively. The cultural and morphological characteristics varied according with the isolates and conditions of the grown, but were compatible with those described for the species C. truncatum. The pathogenicity was proved no significant differences between the isolates. The first symptoms of the disease appeared to three days after inoculation in detached leaves and plants. The genotypes UFPI - 578, UFPI - 468 and UFPI - 26 were susceptible to C. truncatum. When evaluated in detached leaves did not differ significantly among themselves in the level of infection, independent of the season. In plants, UFPI - 26 was the most susceptible in season 2 with the highest level of infection, while the UFPI - 578 was the least susceptible. The positive and significant correlation (P <0.0001) between detached leaves and plant prove the viability of employment of detached leaves in studies related to this disease

Made available in DSpace on 2014-06-11T19:34:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-21Bitstream added on 2014-06-13T20:25:38Z : No. of bitstreams: 1 jesus_am_dr_botfca.pdf: 550406 bytes, checksum: d6dc4c631a5acce5f3a6af817fd94108 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / A bananeira (Musa spp.) é uma planta herbácia e sua fruta é uma das mais consumidas no mundo, principalmente nos países tropicais. Apesar da alta produtividade, o Brasil tem pequena participação no mercado internacional, devido ao elevado consumo interno e pela baixa qualidade dos frutos, que se deve a vários fatores como: genética da cultivar, tipo de solo, manejos agronômicos e sanitários. Dentre os problemas fitossanitários destacam-se os nematóides. Várias espécies de nematóides representam problemas para esta cultura. Radopholus similis, Meloidogyne spp., Pratylenchus coffeae, Helicotylenchus multicinctus e Rotylenchulus reniformis estão amplamente distribuídos nas principais regiões produtoras, causando perdas expressivas à bananicultura. Na presente pesquisa visou-se estudar a patogenicidade de M. incognita raça 2 e M. javanica em bananeira Prata Anã em substratos com diferentes fertilidades, utilizando vários níveis de população inicial de M. incognita raça 2 ou M. javanica (0, 2.000, 10.000 e 50.000 nematóides) por planta. Para isso, foram conduzidos dois experimentos em delineamento inteiramente casualizado. Cada parcela foi constituída de uma planta por vaso de 10L de capacidade, no experimento com M. incognita raça 2 e, vasos de 5L, para M. javanica. Os substratos utilizados em ambos experimentos foram: Substrato 1: contendo uma mistura de areia-solo-esterco na proporção 1:1:1 com textura arenosa e pH 7,0; substrato 2: (padrão) com textura média, com pH 5,6, sem adição de NPK; substrato 3: substrato 2 com pH ajustado para 6,4; substrato 4: substrato 3 com adição de NPK e substrato 5: substrato 2 com adição de NPK. A inoculação foi realizada uma semana após o transplantio das mudas. A avaliação final foi efetuada aos 135 dias da inoculação, quando foram determinados a altura (HP) e diâmetro do pseudocaule (DP), 2 número de... / The banana (Musa spp.) is a herbal plant and its fruit is one of most consumed in the world mainly in tropical countries, including Brazil. Banana crops are affected by many phytosanitary problems, caused by phytopathogenic fungi, insect pests and nematodes. Radopholus similis, Meloidogyne spp., Pratylenchus coffeae, Helicotylenchus, multicinctus and Rotylenchulus reniformis are widely distributed in the main producer regions causing expressive economic losses in bananas production. This work aimed to study the reaction of banana cv. Prata Anã to Meloidogyne incognita and M. javanica in soils with different fertilities. Artificial infestation was accomplished using initial different population levels (0, 2,000, 10,000 and 50,000 nematodes / plant) of M. incognita or M. javanica. For this, two experiments were carried out in a totally random design. Each plot was constituted of one plant / pot. The soils used in both experiments were: Soil 1: with a mix of sand-soilmanure (1:1:1), sandy texture and pH 7,0; soil 2: (standard), medium texture, pH 5,6 without NPK fertilizer; soil 3: soil 2 with pH fitted to 6,4; soil 4: soil 3 with NPK fertilizer and soil 5: soil 2 with NPK fertilizer. The inoculation was proceded one week after plants set up. The final evaluation was made at 135 days after inoculation, when the height plant (HP) and pseudosterm diameter (DP), leaves number (NF), nematodes number for root gram (NºN/gR), soil and root total nematode number (NTSR), reproductive factor (FR), root fresh weight (PFR) and dry shoot (PSA) were determined. However, with the purpose of determine the best evaluation time, the parameters plant height, pseudostem leaves number and pseudostem diameter were evaluated also at 27, 56, 89 and 119 days after the inoculation. There were not verified significant interactions between M. incognita population initial levels and soil fertility for the parameters... (Complete abstract, click electronic access below)

Orientadora: Maria Aparecida Pessôa da Cruz Centurion / Banca: João Carlos de Oliveira / Banca: Luiz Evaldo de Moura Pádua / Banca: Ivana Marino Bárbaro / Banca: Rita de Cássia Panizzi / Resumo: A antracnose é freqüentemente encontrada em feijão-fava na região nordeste do Brasil, porém é pouco estudada. Nesse sentido, objetivou-se caracterizar o agente causal da antracnose, determinar a reação de genótipos a Colletotrichum truncatum e investigar a viabilidade da utilização da técnica de folhas destacadas em estudos relacionados a essa doença. Isolados foram caracterizados em relação a aspectos morfoculturais quando cultivados em meios de cultura batata-dextrose-ágar (BDA) e feijão-dextrose-ágar (FDA), em temperaturas de 26, 28 e 30ºC e fotoperíodo de 12 horas. A patogenicidade dos isolados e a reação dos genótipos foram avaliadas em folhas destacadas e na planta. O comportamento dos genótipos foi avaliado em duas épocas, no período chuvoso (17 de abril a 02 de junho/2008) e período seco (13 de junho a 29 de julho/2008). O delineamento utilizado foi o inteiramente casualizado com cinco e quatro repetições para avaliação da patogenicidade e dos genótipos, respectivamente. As características morfológicas e culturais variaram de acordo com o isolado e condições de cultivo, porém, foram compatíveis com as descritas para a espécie C. truncatum. A patogenicidade foi comprovada, porém não foram detectadas diferenças significativas entre os isolados. Os primeiros sintomas da doença apareceram aos três dias após a inoculação em folhas destacadas e plantas. Os genótipos UFPI - 578, UFPI - 468 e UFPI - 26 foram suscetíveis a C. truncatum. Quando avaliados em folha destacada não diferiram estatisticamente entre si no nível de infecção, independente da época. Em planta e na ausência de chuva, UFPI - 26 apresentou o maior nível de infecção, enquanto UFPI - 578, o menor. A correlação positiva e significativa (P<0,0001) entre folha destacada e planta comprova a viabilidade do emprego da técnica de folhas destacadas em estudos relacionados a essa doença / Abstract: Anthracnose is often found in lima bean plantations in the northeast region of Brazil, however, has been little studied. In this sense, the goals were to characterize the causal agent of anthracnose, determine the reaction of genotypes to Colletotrichum truncatum and investigate the viability of using the technique of detached leaves in studies related to this disease. Isolates were characterized in relation to aspects morphocultural when grown in culture BDA and FDA, in temperatures of 26, 28 and 30ºC and photoperiod of 12 hours. The pathogenicity of the isolates and the reaction of the genotypes were evaluated in detached leaf and plant. The behavior of the genotypes were evaluated in two seasons, in the presence and absence of rain. The design was completely randomized to five and four replicates to evaluate the pathogenicity and genotypes, respectively. The cultural and morphological characteristics varied according with the isolates and conditions of the grown, but were compatible with those described for the species C. truncatum. The pathogenicity was proved no significant differences between the isolates. The first symptoms of the disease appeared to three days after inoculation in detached leaves and plants. The genotypes UFPI - 578, UFPI - 468 and UFPI - 26 were susceptible to C. truncatum. When evaluated in detached leaves did not differ significantly among themselves in the level of infection, independent of the season. In plants, UFPI - 26 was the most susceptible in season 2 with the highest level of infection, while the UFPI - 578 was the least susceptible. The positive and significant correlation (P <0.0001) between detached leaves and plant prove the viability of employment of detached leaves in studies related to this disease / Doutor

Submitted by Liliane Ferreira (ljuvencia30@gmail.com) on 2018-10-03T11:55:30Z No. of bitstreams: 2 Dissertação - Gracielle Teles Pádua - 2018.pdf: 3474471 bytes, checksum: 88584015e304fe0302aa7b1d209b5a74 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-10-04T10:24:46Z (GMT) No. of bitstreams: 2 Dissertação - Gracielle Teles Pádua - 2018.pdf: 3474471 bytes, checksum: 88584015e304fe0302aa7b1d209b5a74 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-10-04T10:24:46Z (GMT). No. of bitstreams: 2 Dissertação - Gracielle Teles Pádua - 2018.pdf: 3474471 bytes, checksum: 88584015e304fe0302aa7b1d209b5a74 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-08-31 / Escherichia coli (E. coli) occupies the 2nd place among microorganisms involved in outbreaks of DVA’s in Brazil and is among the 4 most important worldwide, due to its importance the purpose of the work was to verify the microbiological quality the presence of E. coli in products of animal origin. A total of 365 strains were isolated by means of trailing swabs of 154 carcasses of cattle, slaughtered in the municipality of Mineiros - GO. The incidence of E. coli in the samples collected was 81,65%.Of the isolates, 16 had the gene (eae), and none had genes (stx1, stx2). Therefore, their frequency in the carcasses was 9,74% (15/154). All 16 strains were tested for adhesion genes (ToxB, efa1), but none has these genes. They were also tested for motility where 100% (16/16) were positive and for hemolysis where a frequency of 37,5% (6/16) was obtained. Fifty strains were tested for antimicrobial resistance, and the antibiotics with the highest percentages of resistance among bacteria were Cephalotin with 82% (41/50), followed by Gentamicin and Amicacin with 26% (13/50) each. None of the samples showed production of the extended spectrum beta-lactamase enzyme. These results demonstrate the presence of EPEC multiresistant in bovine carcasses slaughtered in the municipality of Mineiros-GO. / A Escherichia coli (E. coli) ocupa o 2° lugar entre os microrganismos envolvidos em surtos de DVA’s no Brasil e está entre os 4 mais importantes a nível mundial, devido a sua importância o intuito do trabalho foi de verificar a qualidade microbiológica frente a presença de E. coli nos produtos de origem animal. Um total de 365 cepas foram isoladas por meio de suabes de arrasto de 154 carcaças de bovinos, abatidos no município de Mineiros – GO. A incidência de E. coli nas amostras coletadas foi de 81,65%. Das cepas isoladas, 16 possuíam o gene (eae), e nenhuma apresentou os genes (stx1, stx2). Portanto, a frequência destas nas carcaças foi de 9,74% (15/154). As 16 cepas foram testadas para os genes de adesão (ToxB, efa1), porém nenhuma apresentou os referidos genes. Também foram testadas para motilidade onde 100% (16/16) foram positivas, e para hemólise onde se obteve incidência de 37,5% (6/16). Quanto ao perfil de resistência a antimicrobianos foram testadas 50 cepas, e os antibióticos com maiores porcentagens de resistência entre as bactérias foram a Cefalotina com 82% (41/50), seguido pela Gentamicina e Amicacina com 26% (13/50) cada. Nenhuma das amostras apresentou a produção da enzima beta-lactamase de espectro estendido. Os resultados demonstram a presença de EPEC multirresistentes em carcaças de bovinos abatidos no município de Mineiros –GO.

Orientador: Anete Pereira de Souza / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-18T01:20:36Z (GMT). No. of bitstreams: 1 Schneider_DilaineRoseSilva_D.pdf: 11263694 bytes, checksum: 808a3a965f6f47fb9c2108a4c971b122 (MD5) Previous issue date: 2010 / Resumo: A brusone do arroz (rice blast disease) causada pelo ascomiceto fitopatógeno Magnaporthe grisea continua a ter um enorme impacto nas culturas de arroz (Oryza sativa) no Brasil e no mundo. PWL2, uma proteína efetora, é um conhecido produto de um gene AVR (avirulência). O gene PWL2 impede que o fungo infecte weeping lovegrass (Eragrostis curvula). Neste trabalho nós identificamos em uma linhagem de M. grisea um gene que produz uma proteína diferente de PWL2, denominada PWL2D. A seqüência do gene PWL2D tem duas bases que diferem do gene PWL2, as quais produzem alterações nos resíduos de 90 e 142 da proteína. A alteração do resíduo 90 (de D90 para N90) é fundamental para a avirulência. Neste trabalho foram efetuadas a clonagem do gene PWL2D no vetor pET32-Xa/LIC, a expressão em Escherichia coli e a avaliação da estrutura de PWL2D por técnicas espectroscópicas. A proteína PWL2D fusionada à cauda TRX é propensa a agregação, e sua solubilidade é melhorada quando super-expressa sem o seu peptídeo-sinal original. Os resultados estruturais obtidos indicam que a proteína PWL2D possivelmente é intrinsecamente desordenada. Foi elaborado um modelo para a resistência/susceptibilidade do hospedeiro à M. grisea considerando a atuação de PWL2D como uma proteína intrinsecamente desordenada. Os resultados obtidos deverão facilitar a análise estrutural de PWL2D e podem contribuir para a compreensão da função do gene nas interações fungo / planta. Oito diferentes genes de M. grisea, além de PWL2D, foram também estudados neste trabalho. Dentre estes, destacam-se o gene que produz a xilanase XYL5 e seu domínio catalítico, o gene que codifica a chaperona ABC1 e seus dois domínios funcionais, e o gene que codifica a trealase PTH9, sendo todos estes relacionados à patogenicidade do fungo M. grisea. A xilanase XYL5 (EC 3.2.1.8) e seu domínio catalítico conservado (XYL5/DOM) foram fusionados à Maltose Binding Protein (MBP) ou à tiorredoxina (TRX) e expressas em E. coli. A produção de proteína solúvel e ativa foi influenciada pelo tipo de fusão. Os extratos solúveis contendo as proteínas de fusão MBP-XYL5 e MBP-XYL5/DOM apresentaram atividade xilanolítica em relação ao controle. Entretanto, durante o processo de purificação, a atividade foi perdida. Assim, obteve-se pela primeira vez o gene de patogenicidade XYL5 de M. grisea expresso com sucesso em E. coli e sua atividade enzimática xilanolítica foi demonstrada. Não foi possível expressar a chaperona ABC1 na forma solúvel nos sistemas de expressão utilizados, e a sequência gênica referente à trealase PTH9 - por mostrar a presença de introns após o seqüenciamento do gene amplificado na linhagem de M. grisea em estudo, mostrou-se inadequado para a sua expressão protéica no sistema de expressão procariótico utilizado durante a realização deste trabalho / Abstract: The rice blast disease caused by the ascomycete phytopathogen Magnaporthe grisea continues to have a huge impact on crops of rice (Oryza sativa) in Brazil and worldwide. PWL2, an effector protein, is a product of an AVR (avirulence) gene . The gene PWL2 prevents fungus from infecting weeping lovegrass (Eragrostis curvula). In this work we identified in a strain of M. grisea a gene that produces a protein different from PWL2, called PWL2D. The gene sequence PWL2D has two bases that differ from PWL2 gene, which produce changes in residues 90 and 142 of the protein. The change of residue 90 (from D90 to N90) is critical to avirulence. In this work it was realized the cloning of the gene in the vector PWL2D pET32-Xa/LIC, the expression in Escherichia coli and the assessment of PWL2D structure by spectroscopic techniques. The protein fused to the tag PWL2D TRX is prone to aggregation, and its solubility is improved when overexpressed without its original signal peptide. The structural results obtained indicate that possibly the protein PWL2D is intrinsically disordered. A model for the resistance/susceptibility of the host to M. grisea was developed considering the performance of PWL2D as an intrinsically disordered protein. The results should facilitate structural analysis of PWL2D and may contribute to the understanding of gene function in the interactions fungus/plant. Eight different genes of M. grisea, besides PWL2D, were also studied in this work. Among these, stands out the gene that produces xylanase XYL5 and its catalytic domain, the gene that codify the chaperone ABC1 and its two functional domains, and the gene that codify the trehalase PTH9, all them being related to the pathogenicity of the fungus M. grisea. The xylanase XYL5 (EC 3.2.1.8) and its retained catalytic domain (XYL5/DOM) were fused to the solubilizing proteins (MBP) or thioredoxin (TRX) and expressed into E. coli. The production of soluble and active protein was influenced by the type of fusion. The soluble extracts containing the fusion proteins MBP- XYL5 and MBP-XYL5/DOM showed xylanolytic activity compared to the control. However, during the purification process, the activity was lost. Thus, we obtained for the first time the gene pathogenicity XYL5 M. grisea expressed successfully in E. coli and its enzymatic xylanolytic activity was demonstrated. It was not possible to express the chaperone ABC1 in soluble form in the expression systems used, and the gene sequence related to trehalase PTH9 - by showing the presence of introns after the sequencing of the gene amplified in the strain of M. grisea under study, rendered inadequate for its protein expression in the prokaryotic system used during the realization of this work / Doutorado / Genetica de Microorganismos / Doutor em Genetica e Biologia Molecular