<p>Prokaryotes are continually exposed to variations in their environment. Survival in unstable milieu requires a wide range of transcriptional regulators (TRs) that respond to specific environmental and cellular signals by modulating gene expression and provide an appropriate physiological response to external stimuli. These adaptive responses to environmental signals are mostly mediated by TRs from one of two families: the single or the two component signal transduction systems (1CSTS; 2CSTS). In this thesis the structural analysis of two 1CSTS – DntR and NikR − are presented. One study was carried out to try to develop a bacterial biosensor for synthetic dinitrotulenes compounds, the other to characterise the Ni-sensing mechanism that contributes to the acid adaptation of the human pathogen<i> Helicobacter pylori.</i> DntR belongs to the LysR family and the crystal structures obtained have allowed the proposal a model of the interaction of DntR with salicylate inducer as well as giving insights into the signal propagation mechanism in LysR-type transcription factors (<b>paper I</b>). DntR mutant crystal structures combined with the modelling of DntR-2,4-dnt interactions led to the design of a DntR mutant that has a limited response to 2,4-dnt in a whole cell biosensor system (<b>paper 2</b>). Crystal structures of apo-NikR from <i>H. pylori </i>(HpNikR) and of Ni-bound intermediary states of the protein were obtained. The latter have helped in unravelling the Ni incorporation and selectivity mechanisms of NikRs and have shown a strong cooperativity between conformational changes in the Ni binding domain with movements of the DNA binding domain (<b>paper 3</b>). Biochemical studies and comparisons of the HpNikR crystal structures with those of NikR homologues strongly suggest that HpNikR has evolved different surface properties (<b>paper 4</b>) and a new mode of DNA binding. </p>

Prokaryotes are continually exposed to variations in their environment. Survival in unstable milieu requires a wide range of transcriptional regulators (TRs) that respond to specific environmental and cellular signals by modulating gene expression and provide an appropriate physiological response to external stimuli. These adaptive responses to environmental signals are mostly mediated by TRs from one of two families: the single or the two component signal transduction systems (1CSTS; 2CSTS). In this thesis the structural analysis of two 1CSTS – DntR and NikR − are presented. One study was carried out to try to develop a bacterial biosensor for synthetic dinitrotulenes compounds, the other to characterise the Ni-sensing mechanism that contributes to the acid adaptation of the human pathogen Helicobacter pylori. DntR belongs to the LysR family and the crystal structures obtained have allowed the proposal a model of the interaction of DntR with salicylate inducer as well as giving insights into the signal propagation mechanism in LysR-type transcription factors (<b>paper I</b>). DntR mutant crystal structures combined with the modelling of DntR-2,4-dnt interactions led to the design of a DntR mutant that has a limited response to 2,4-dnt in a whole cell biosensor system (<b>paper 2</b>). Crystal structures of apo-NikR from H. pylori (HpNikR) and of Ni-bound intermediary states of the protein were obtained. The latter have helped in unravelling the Ni incorporation and selectivity mechanisms of NikRs and have shown a strong cooperativity between conformational changes in the Ni binding domain with movements of the DNA binding domain (<b>paper 3</b>). Biochemical studies and comparisons of the HpNikR crystal structures with those of NikR homologues strongly suggest that HpNikR has evolved different surface properties (<b>paper 4</b>) and a new mode of DNA binding.

Made available in DSpace on 2014-06-11T19:28:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-03-26Bitstream added on 2014-06-13T19:15:56Z : No. of bitstreams: 1 frasnelli_sct_me_arafo.pdf: 758242 bytes, checksum: fc10d5e79dcb4b386aacc5d2776f572c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Diabetes mellitus se caracteriza pelo acúmulo de produtos finais da glicação avançada (AGEs) que ativam seu receptor RAGE. Entre as complicações associadas ao diabetes está a modulação da resposta imune, evidenciada pela maior susceptibilidade à infecção em diabéticos. O sistema imune percebe e reaje aos microrganismos por meio de receptores de padrões moleculares (receptores semelhantes à Toll, TLRs). Lipopolissacarídeo da parede celular (LPS) é um dos principais fatores de virulência de microrganismos Gramnegativos e é reconhecido principalmente por TLR4. A hipótese deste trabalho é que a ativação de RAGE e TLR4 por seus ligantes pode resultar em efeito sinérgico na modulação da proliferação, morte celular e expressão de citocinas inflamatórias por células mononucleares do sangue periférico (PBMC). Foram selecionados 7 indivíduos não diabéticos e 6 indivíduos portadores de diabetes tipo 2 para coleta de PBMCs. Estas células foram estimuladas com LPS bacteriano e BSA glicado, isoladamente e combinados, na presença e na ausência de inibidores dos receptores RAGE e TLR4. Proliferação e morte celular foram avaliadas por contagem direta em hemocitômetro e citometria de fluxo, respectivamente. A expressão de citocinas e quimiocinas inflamatórias foi avaliada por RT-qPCR, enquanto a modulação do padrão de resposta imune adaptativa foi estudada por meio de citometria de fluxo. Os resultados mostram 18 18 que PBMCs de pacientes portadores de diabetes tendem a ser mais resistentes à indução de morte celular. De um modo geral, a inibição dos receptores RAGE e TLR4 não interfere na atividade metabólica e viabilidade celular em diabéticos e não diabéticos. A expressão gênica de CCL3 e CCR5 não foi regulada pelos receptores RAGE e TLR, sendo discretamente mais elevada em pacientes não diabéticos. A expressão de TNF-α e IL-10 foi regulada... / Diabetes mellitus is characterized by the progressive accumulation of advanced glycation end-products (AGEs), which bind and activate their membrane-bound receptor (RAGE) on a variety of target cells. Modulation of the immune response is one of the diabetes-associated complications and is reflected on the increased susceptibility of diabetes patients to infections and sepsis. The immune system senses and reacts to microorganisms by pattern-recognition receptors, such as Toll-like receptors (TLRs). Bacterial lipopolysaccharide (LPS) is a major virulence factor of Gram-negative microorganisms, which is recognized mainly by TLR4. The hypothesis of this study is that of a synergism between activated TLR4 and RAGE that modulates the response of cells of innate and adaptive immunity in the circulation (peripheral blood monocytic cells, PBMCs). PBMCs were collected from 13 volunteers (7 with type 2 diabetes and 6 systemically-healthy controls). The cells were stimulated with bacterial LPS and glycated bovine serum albumin (AGE-BSA), both independently and in association. To study the role of TLR4 and RAGE signaling, these stimulations were performed in the presence and absence of specific inhibitors of RAGE and TLR4. We used direct counting in a hemocytometer and flow cytometry, respectively, to assess cell proliferation and 20 20 death. The expression of selected cytokines and receptors was studied by RTqPCR, whereas the effect of these stimuli on the modulation of T helper-type response was determined by flow cytometry. We observed increased cell survival in PBMCs from diabetic patients. Inhibition of RAGE and TLR4 had no marked effect on cell proliferation, metabolic activity and survival. Gene expression of CCL3 (MIP-1alpha) and CCR5 was discretely higher in PBMCs from non-diabetic patients and was not affected by RAGE or TLR4 signaling... (Complete abstract click electronic access below)

Orientador: Carlos Rossa Junior / Coorientador: Silvana Regina Perez Orrico / Banca: José Eduardo Cezar Sampaio / Banca: Sandra Helena Penha de Oliveira / Resumo: Diabetes mellitus se caracteriza pelo acúmulo de produtos finais da glicação avançada (AGEs) que ativam seu receptor RAGE. Entre as complicações associadas ao diabetes está a modulação da resposta imune, evidenciada pela maior susceptibilidade à infecção em diabéticos. O sistema imune percebe e reaje aos microrganismos por meio de receptores de padrões moleculares (receptores semelhantes à Toll, TLRs). Lipopolissacarídeo da parede celular (LPS) é um dos principais fatores de virulência de microrganismos Gramnegativos e é reconhecido principalmente por TLR4. A hipótese deste trabalho é que a ativação de RAGE e TLR4 por seus ligantes pode resultar em efeito sinérgico na modulação da proliferação, morte celular e expressão de citocinas inflamatórias por células mononucleares do sangue periférico (PBMC). Foram selecionados 7 indivíduos não diabéticos e 6 indivíduos portadores de diabetes tipo 2 para coleta de PBMCs. Estas células foram estimuladas com LPS bacteriano e BSA glicado, isoladamente e combinados, na presença e na ausência de inibidores dos receptores RAGE e TLR4. Proliferação e morte celular foram avaliadas por contagem direta em hemocitômetro e citometria de fluxo, respectivamente. A expressão de citocinas e quimiocinas inflamatórias foi avaliada por RT-qPCR, enquanto a modulação do padrão de resposta imune adaptativa foi estudada por meio de citometria de fluxo. Os resultados mostram 18 18 que PBMCs de pacientes portadores de diabetes tendem a ser mais resistentes à indução de morte celular. De um modo geral, a inibição dos receptores RAGE e TLR4 não interfere na atividade metabólica e viabilidade celular em diabéticos e não diabéticos. A expressão gênica de CCL3 e CCR5 não foi regulada pelos receptores RAGE e TLR, sendo discretamente mais elevada em pacientes não diabéticos. A expressão de TNF-α e IL-10 foi regulada... (Resumo completo, clicar acesso eletr^ônico abaixo) / Abstract: Diabetes mellitus is characterized by the progressive accumulation of advanced glycation end-products (AGEs), which bind and activate their membrane-bound receptor (RAGE) on a variety of target cells. Modulation of the immune response is one of the diabetes-associated complications and is reflected on the increased susceptibility of diabetes patients to infections and sepsis. The immune system senses and reacts to microorganisms by pattern-recognition receptors, such as Toll-like receptors (TLRs). Bacterial lipopolysaccharide (LPS) is a major virulence factor of Gram-negative microorganisms, which is recognized mainly by TLR4. The hypothesis of this study is that of a synergism between activated TLR4 and RAGE that modulates the response of cells of innate and adaptive immunity in the circulation (peripheral blood monocytic cells, PBMCs). PBMCs were collected from 13 volunteers (7 with type 2 diabetes and 6 systemically-healthy controls). The cells were stimulated with bacterial LPS and glycated bovine serum albumin (AGE-BSA), both independently and in association. To study the role of TLR4 and RAGE signaling, these stimulations were performed in the presence and absence of specific inhibitors of RAGE and TLR4. We used direct counting in a hemocytometer and flow cytometry, respectively, to assess cell proliferation and 20 20 death. The expression of selected cytokines and receptors was studied by RTqPCR, whereas the effect of these stimuli on the modulation of T helper-type response was determined by flow cytometry. We observed increased cell survival in PBMCs from diabetic patients. Inhibition of RAGE and TLR4 had no marked effect on cell proliferation, metabolic activity and survival. Gene expression of CCL3 (MIP-1alpha) and CCR5 was discretely higher in PBMCs from non-diabetic patients and was not affected by RAGE or TLR4 signaling... (Complete abstract click electronic access below) / Mestre

Background: There is need for judicious use of immunosuppression in patients with active lupus nephritis (LN), however this is guided by renal biopsy which is invasive and not freely available in most centres. Novel urinary biomarkers such as monocyte chemoattractant protein-1 (MCP-1) and tumour necrosis factor-like weak inducer of apoptosis (TWEAK) are secreted in the kidney and may be useful for predicting histological class, monitoring flares and assessing response to therapy. We assessed the utility of urinary MCP-1 (uMCP-1) and TWEAK (uTWEAK) in predicting renal histological findings, disease flares and treatment response 6 months following initiation of treatment for LN in newly biopsied patients. Methods: We recruited consenting patients with active LN confirmed on kidney biopsy. Relevant baseline demographic, biochemical and histological information was collected from the patients. ELISA methods were used to assess uMCP-1 and uTWEAK at baseline and at 6 months after completion of induction therapy. Results: There were 14 females and 6 male patients with a mean age of 29.8 ± 10.7 years, 60% were of mixed ancestry, 70% had proliferative LN. There was no association between uMCP-1 and uTWEAK and histological features (LN class, activity index, chronicity index and interstitial fibrosis). At 6 months, 6 patients were lost to follow-up and of the remaining 14, 12 (85%) attained remission (partial remission (n = 7) or complete remission (n = 5)). Both biomarkers were elevated in patients with active disease and significantly declined amongst those attaining remission, p = 0.018 and p = 0.015 respectively. However, for those not attaining remission, no association was found for both biomarkers (p >0.05). Conclusion: Our study did not show correlation between uMCP-1 and uTWEAK with histological features of LN. However, both biomarkers were elevated in patients with active disease and correlated with the remission status at the end of induction phase of treatment.

DNA immunization, inoculation with an antigen-expressing plasmid DNA, is a new method for generating an antigen-specific immune response. At the time these investigations began, very little was known about the immune response produced by DNA vaccines. Thus, the first aim of our studies was to perform a detailed examination of the antibody response generated by DNA immunization with an influenza hemagglutinin (HA)-expressing DNA in BALB/c mice. Using several different routes and methods of DNA immunization, we observed a number of findings. Although all three forms of DNA immunization elicited strong anti-HA antibody responses, i.m. and i.d. saline DNA immunization required approximately 100 times more DNA than a gene gun DNA immunization to raise an equivalent titer of anti-HA antibody. Indeed, as little as one inoculation and one boost by gene gun of 0.0004 μg of DNA produced a measurable antibody response in 50% of mice. Unexpectedly, we found the isotype of the antibody response differed among groups of mice immunized by different forms of DNA immunization. Intramuscular and i.d. saline DNA immunization produced predominantly an IgG2a anti-HA antibody response, whereas gene gun DNA immunization elicited mostly an IgG1 anti-HA antibody response. Considering that IgG2a and IgG1 antibody isotypes were known to correlate with Th1 and Th2 immune responses, respectively, we analyzed the type of immune responses produced by i.m., i.d., and gene gun DNA immunization. We found that i.m. and i.d. saline DNA immunization produced a Th1 predominant cellular immune response. In contrast, gene gun DNA immunization produced a Th2 cellular immune response. The differences in the type of immune responses were found to be due to the method of DNA immunization, and not due to the route of DNA inoculation. A gene gun DNA immunization of muscle produced the same IgG1, Th2 immune response as a gene gun DNA immunization of skin, while a saline DNA immunization of muscle and skin produced mostly an IgG2a, Th1 immune response. Each method of DNA immunization created good memory Th cell responses. The type of immune response created by an initial DNA immunization remained fixed even after multiple boosts with the identical method of DNA immunization, following a boost with the alternative method of DNA immunization, or after a viral challenge. The differentiation of naive Th cells into Th1 or Th2 cells depends on a variety of factors. We performed many experiments to elucidate which factors played a role in the generation of Th1 or Th2 immune responses following saline DNA immunization and gene gun DNA immunization. DNA dose response studies revealed the use of different doses of DNA between groups of saline DNA and gene gun DNA immunized mice did not account for the differentiation of distinct Th cell subsets. Cytokine production inducible by a number of factors inherently associated with either saline DNA or gene gun DNA immunization did not affect Th differentiation. For instance, contamination of plasmid DNA with lipopolysaccharide did not account for differences in the immune response. Immunostimulatory CpG sequences did not affect Th differentiation following DNA immunization, but they did enhance the IgG2a antibody response to coinoculated HA protein. Finally, cotransfection of IFNγ or IL-4 expressing plasmids with an HA-expressing plasmid by gene gun inoculation or as a saline DNA injection did not shift the type of immune response in a Th1 or Th2 direction, respectively. Thus, it appeared that increased cytokine stimulation was not responsible for selective Th subset differentiation. One factor related to the method of DNA immunization did seem to correlate with Th1 differentiation. Deposition of plasmid DNA extracellulary by saline DNA injections (as opposed to intracellular DNA delivery by gene gun) may have stimulated Th1 immune responses. Manipulating a gene gun DNA immunization to deliver DNA to the dermis (and thus extracellularly) shifted the immune response from that of a Th2 type to a mixed Th1/Th2 type. Furthermore, evidence was gathered demonstrating that pDNA can interact with cell surface molecules and that specific sequences in pDNA can act as a ligand and bind to molecules. Taken together, our data led us to propose a new model for Th1 differentiation following saline DNA immunization. We believe extracellular pDNA binds to an APC cell surface molecule which activates the cell. The activated APC preferentially stimulates naive Th cells to differentiate into Th1 cells. Finally, studies using a variety of mice differing in their genetic backgound and MHC genotype demonstrated the generality of our findings regarding i.m. saline DNA inoculations of an HA-expressing pDNA. Saline DNA immunization produced IgG2a, Th1-predominant immune responses independent of the genetic background and MHC genotype of the mice. In contrast, the type of immune response elicited by a gene gun DNA immunization was dependent on the MHC genotype of mice. Thus the type of immune response produced by gene gun DNA immunization probably depends on the specific antigen (and its effect on MHC-peptide/TcR interaction and signaling) and is less likely due to any inherent feature associated with the process of gene gun DNA delivery.

by Li Pok Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 94-114). / Abstracts in English and Chinese. / Acknowledgements --- p.I / Abbreviations --- p.II / Abstract --- p.V / 摘要 --- p.VIII / Publications --- p.XI / Table of contents --- p.XII / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Human Th lymphocytes and their immunopathogenic roles --- p.1 / Chapter 1.1.1 --- Characteristics of Th lymphocytes --- p.1 / Chapter 1.1.2 --- Migration and activation --- p.1 / Chapter 1.1.3 --- Th cell differentiation --- p.2 / Chapter 1.1.4 --- Pathological roles --- p.4 / Chapter 1.2 --- Cytokines as modulator in Th lymphocyte activation --- p.6 / Chapter 1.2.1 --- IL-18 --- p.6 / Chapter 1.2.2 --- IL-25 --- p.7 / Chapter 1.3 --- Surface marker expression in Th lymphocytes --- p.8 / Chapter 1.3.1 --- Adhesion molecules --- p.8 / Chapter 1.3.2 --- Cytokine and chemokine receptors --- p.9 / Chapter 1.3.3 --- Costimulatory molecules --- p.11 / Chapter 1.4 --- Cytokine and chemokine release from Th lymphocytes / Chapter 1.4.1 --- Thl cytokines --- p.13 / Chapter 1.4.2 --- Th2 cytokines --- p.14 / Chapter 1.4.3 --- Chemokines --- p.15 / Chapter 1.5 --- Intracellular signaling pathways in Th lymphocytes --- p.19 / Chapter 1.5.1 --- p38 MAPK pathway --- p.19 / Chapter 1.5.2 --- ERK pathway --- p.20 / Chapter 1.5.3 --- JNK pathway --- p.20 / Chapter 1.5.4 --- NF- k B pathway --- p.21 / Chapter 1.6 --- Pharmacological intervention of signaling pathways --- p.22 / Chapter 1.7 --- Aims and scope of the study --- p.24 / Chapter Chapter 2 --- Materials and Methods / Chapter 2.1 --- Materials --- p.26 / Chapter 2.1.1 --- Blood samples --- p.26 / Chapter 2.1.2 --- Media and reagents for cell culture --- p.26 / Chapter 2.1.3 --- Antibodies for costimulation of Th cells --- p.28 / Chapter 2.1.4 --- Recombinant human cytokines --- p.28 / Chapter 2.1.5 --- "Signaling pathway inhibitors: SB203580, PD98035, SP600125 and BAY117082" --- p.28 / Chapter 2.1.6 --- Monoclonal antibodies and reagents for immunofluorescent staining --- p.29 / Chapter 2.1.7 --- Reagents and buffers for the purification of human Th lymphocytes --- p.31 / Chapter 2.1.8 --- Reagents and buffers for protein array --- p.32 / Chapter 2.1.9 --- Reagents and buffers for Thl/2 cytokine and chemokine detection --- p.32 / Chapter 2.1.10 --- Reagents and buffers for protein extraction --- p.32 / Chapter 2.1.11 --- Reagents and buffers for SDS-polyacrylamide gel electrophoresis --- p.33 / Chapter 2.1.12 --- Reagents and buffers for Western blot analysis --- p.35 / Chapter 2.1.13 --- Reagents and buffers for non-radioactive electromobility shift assay (EMSA) --- p.37 / Chapter 2.1.14 --- Reagents and buffers for cell viability and proliferation assay --- p.39 / Chapter 2.1.15 --- Reagent kit for endotoxin level assay --- p.39 / Chapter 2.1.16 --- Other reagent kits --- p.40 / Chapter 2.2 --- Methods --- p.41 / Chapter 2.2.1 --- Purification of human Th lymphocytes and cell culture --- p.41 / Chapter 2.2.2 --- Measurement of total and allergen-specific IgE concentrations --- p.41 / Chapter 2.2.3 --- Immunophenotyping of cells by flow cytometry --- p.42 / Chapter 2.2.4 --- Protein array --- p.42 / Chapter 2.2.5 --- Quantitative analysis of cytokines and chemokines by flow cytometry --- p.43 / Chapter 2.2.6 --- Quantitative analysis of IFN-γ by ELISA --- p.43 / Chapter 2.2.7 --- SDS-PAGE --- p.44 / Chapter 2.2.8 --- Western blot analysis --- p.44 / Chapter 2.2.9 --- EMSA / gel shift assay --- p.45 / Chapter 2.2.10 --- MTT assay --- p.46 / Chapter 2.2.11 --- Cell proliferation assay --- p.46 / Chapter 2.2.12 --- Endotoxin level assay --- p.47 / Chapter 2.2.13 --- Statistical analysis --- p.47 / Chapter Chapter 3 --- Results / Chapter 3.1 --- Effects of IL-18 and IL-25 on the induction of Thl/2 cytokine and chemokine release from costimulated Th lymphocytes --- p.48 / Chapter 3.1.1 --- IL-18 and IL-25 could up-regulate the protein expression of cytokines and chemokines --- p.48 / Chapter 3.1.2 --- IL-18 but not IL-25 induced the release of IFN-γ and TNF-α --- p.48 / Chapter 3.1.3 --- "IL-18 and IL-25 induced the release of IL-5, IL-6 and IL-10" --- p.49 / Chapter 3.1.4 --- "IL-18 induced the release of IP-10, MIG, RANTES, MlP-lα and IL-8" --- p.49 / Chapter 3.1.5 --- "IL-25 induced the release of IP-10, MIG and RANTES" --- p.49 / Chapter 3.1.6 --- IL-18 and IL-25 did not enhance the proliferation of costimulated Th cells --- p.49 / Chapter 3.2 --- "Effects of IL-18 and IL-25 on the activation of p38 MAPK, ERK, JNK and NF- k B" --- p.58 / Chapter 3.2.1 --- "Costimulation with or without IL-18 and IL-25 could activate p38 MAPK, ERK and JNK" --- p.58 / Chapter 3.2.2 --- Costimulation with or without IL-18 and IL-25 could induce NF- k B activity --- p.58 / Chapter 3.3 --- Effects of inhibitors on the IL-18 and IL-25-induced release of Thl/2 cytokines and chemokines --- p.63 / Chapter 3.3.1 --- "Optimal dosage of SB203580, PD98035, SP600125 and BAY117082" --- p.63 / Chapter 3.3.2 --- "SB203580, PD98035 and BAY 117082 but not SP600125 suppressed the IL-18 and IL-25-induced release of Thl/2 cytokines" --- p.63 / Chapter 3.3.3 --- SP600125 suppressed the IL-18 and IL-25-induced release of chemokines --- p.64 / Chapter 3.4 --- Effects of inhibitors on the cell surface expression of IL-18 and IL-25 receptors --- p.72 / Chapter 3.4.1 --- "SB203580, PD98035, BAY 117082 but not SP600125 could suppress IL-18 receptor on costimulated Th cells" --- p.72 / Chapter 3.4.2 --- "SB203580, SP600125, PD98035 and BAY 117082 could not suppress IL-25 receptor on costimulated Th cells" --- p.72 / Chapter 3.5 --- Effects of costimulation on the expression of cell surface markers on Th lymphocytes --- p.75 / Chapter Chapter 4 --- Discussion / Chapter 4.1 --- Effects of IL-18 and IL-25 on the release of Th1/2 cytokines and chemokines --- p.80 / Chapter 4.2 --- "Regulation of Thl/2 cytokines and chemokines through intracellular p38 MAPK, ERK, JNKand NF-kB" --- p.83 / Chapter 4.3 --- Effects of costimulation on different surface markers in Th cells --- p.87 / Chapter 4.4 --- Concluding remarks and future perspectives --- p.90 / References --- p.94

Chez le maïs, la création de nouvelles variétés repose largement sur la technologie des plantes Haploïdes Doublées. Celle-ci s’appuie sur l’utilisation du pollen de lignées particulières, dites «inductrices d’haploïdes», qui déclenchent un processus de gynogenèse in vivo. Ce mécanisme permet la production d’embryons haploïdes contenant uniquement les informations génétiques maternelles. Après doublement des stocks chromosomiques des plantules haploïdes générées, il est possible d’obtenir des lignées fixées en seulement quelques générations, réduisant ainsi considérablement les schémas de sélection. Bien que les déterminismes génétiques à l’origine de la gynogenèse in vivo soient restés énigmatiques pendant près de soixante ans, nos travaux ont permis le clonage positionnel et l’identification du gène majeur causal de l’induction d’haploïdes. Ce gène, exprimé spécifiquement dans les grains de pollen, code pour une phospholipase A2, nommée NOT LIKE DAD (NLD). Il s’avère que chez l’ensemble des lignées inductrices le gène NLD présente une insertion de quatre paires de bases, conduisant à la formation d’une protéine tronquée responsable de la gynogenèse in vivo. Cette mutation n’entraine pas un défaut spatial ou temporel de l’expression du gène mais une délocalisation de la protéine. La protéine sauvage localise au niveau de l’unité mâle germinative, sur la membrane d’origine végétative entourant les deux cellules spermatiques, alors que la protéine tronquée perd cette localisation. Des approches pharmacologiques et de mutagenèses dirigées ont permis de révéler un adressage de NLD à la membrane grâce à des ancrages lipidiques et des interactions électrostatiques entre la membrane et la protéine. En parallèle, il a pu être observé que la troncation de NLD, en plus de conduire à la formation d’haploïdes maternels, entraînait de nombreux phénotypes de grains anormaux. Le génotypage des produits de fécondations (albumens et embryons) résultant de croisements avec des lignées inductrices ont permis de mettre en évidence l’existence d’anomalies chromosomiques paternelles, pouvant expliquer ces différents phénotypes de grains anormaux. L’ensemble de ces résultats indiquent que la phospholipase NLD intacte est nécessaire pour le bon déroulement de la reproduction sexuée. / In maize, plant breeding mainly relies on double haploid technology. The main principle of this technology is the use of special lines called “inducer lines”, which induce in vivo gynogenesis. This mechanism allows haploid embryos production which only contain maternal genetics information. After chromosome doubling of the haploid seedlings, it is possible to obtain fixed lines in only few generations, thus considerably reducing breeding cycles. Although genetic determinants behind in vivo gynogenesis remained enigmatic for nearly sixty years, our work allowed the positional cloning and the identification of the major gene controlling haploid induction. This gene, specifically expressed in pollen grain, encodes for a phospholipase A2 called NOT LIKE DAD (NLD). It turns out that in all the inducer lines the NLD gene has a 4-bp insertion, leading to the formation of a truncated protein responsible for gynogenesis in vivo. This mutation did not result in a spatial or temporal defect in the expression of the gene but in the delocalization of the protein. The wild type protein localizes at the male germ unit on the vegetative membrane surrounding the two sperm cells, while the truncated protein loses this location. Pharmacological and mutagenic approaches revealed that NLD is targeted to the membrane through lipid anchoring and electrostatic interactions between membrane and protein. In parallel, it has been observed that the truncation of NLD; in addition to leading to the formation of maternal haploids; led to many pleiotropic phenotypes of abnormal kernels. The genotyping of fertilization products (endosperms and embryos), shows the existence of paternal chromosomal anomalies, which can explain these different phenotypes of abnormal kernels. All these results indicate that the intact NLD phospholipase is therefore necessary for the proper course of sexual reproduction.

Submitted by Mario BC (mario@bc.ufrpe.br) on 2016-08-30T12:44:49Z No. of bitstreams: 1 Nayara Cristina de Magalhaes Sousa.pdf: 439589 bytes, checksum: a4ec46c7aaf9d641d8236704ff4a86e1 (MD5) / Made available in DSpace on 2016-08-30T12:44:49Z (GMT). No. of bitstreams: 1 Nayara Cristina de Magalhaes Sousa.pdf: 439589 bytes, checksum: a4ec46c7aaf9d641d8236704ff4a86e1 (MD5) Previous issue date: 2015-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / An increasing use of products that triggers herbivores insects resistance induction and plant pathogens or that promote the strengthening of the plants after the emergence of begomovirose. Thus, this study aimed to evaluate the action of fertilizers and biofertilizers inducer acibenzolar - S - methyl (ASM) on mortality and B. tabaci adult behavior and its reflection in tomato disease. Nine products were tested as potential inducers of resistance, the standard insecticide thiamethoxam + lambda-cyhalothrin + 0.5% mineral oil, and the control which consisted only of water. To evaluate the insect mortality were used leaf discs of bean-to-pig. The citrus extract (Sumo K®) had action on insects from 24 hours and caused the highest cumulative mortality of adult whitefly (87.45%). In the interaction of cultivar with inductors on mortality of whitefly the citrus extract (Sumo K®) caused cumulative mortality exceeds 80% in 48 hours of exposure of insects, significantly different from the other products. In the evaluation of resistance induction treatments Sumo K® and Bion® promoted the reduction in the incidence and severity of begomovirose the plant, however, only the mixture insecticide presented desired results. Held adult preference test free choice. There was no significant difference between treatments, only plants sprayed with insecticides were less infested. Thus, we conclude that the use of Sumo-K and Bion in tomato options would be compatible with other control tactics aimed at management of whitefly and begomovírose. / É crescente o uso de produtos que desencadeiam a indução de resistência a insetos herbívoros e a fitopatógenos ou que propiciam o revigoramento das plantas após o surgimento da begomovirose. Com isso, o presente estudo teve como objetivo avaliar a ação de fertilizantes organominerais e do indutor acilbenzolar – S – metil (ASM) na mortalidade e no comportamento de adultos de B. tabaci e seu reflexo na doença em tomateiro. Foram testados nove produtos como possíveis indutores de resistência, o inseticida padrão tiametoxam+lambda-cialotrina+óleo mineral a 0,5%, além da testemunha que consistiu apenas de água. Para avaliação da mortalidade do inseto foram utilizados discos foliares de feijão-de-porco. O extrato cítrico (Sumo k®) apresentou ação sobre os insetos a partir de 24 horas e causou a maior mortalidade acumulada de adultos da mosca-branca (87,45%). Na interação da cultivar com os indutores sobre a mortalidade da mosca-branca o extrato cítrico (Sumo K®) ocasionou mortalidade acumulada superior a 80% em 48h de exposição dos insetos, diferindo significativamente dos demais produtos. Na avaliação da indução de resistência os tratamentos Sumo K e Bion promoveram a redução na incidência e severidade da begomovirose na planta, porém, somente a mistura inseticida apresentou resultados desejados. Realizou-se teste de preferência de adultos com chance de escolha. Não houve diferença significativa entre os tratamentos, somente plantas pulverizadas com o inseticida foram menos infestadas. Desta forma, é possível concluir que o emprego de Sumo-K e Bion na cultura do tomateiro seriam opções compatíveis com outras táticas de controle visando o manejo da mosca-branca e da begomovírose.

The NF-κB family of transcription factors can be activated through canonical (classical) or non-canonical (alternative) signalling pathways, which are regulated by the redundant ubiquitin ligases, cellular inhibitor of apoptosis 1 and 2 (cIAP1 and cIAP2). While the canonical NF-κB pathway is needed for myoblast proliferation, it is inactivated during myoblast differentiation. However, the non-canonical NF-κB pathway is a major factor in promoting myoblast fusion, which is crucial to the processes of myogenesis and muscle repair. Ablation of cIAP1 levels through a chemical antagonist such as a SMAC- mimetic compound (SMC) activates non-canonical signalling to enhance myogenesis. The cytokine TNF-like weak inducer of apoptosis (TWEAK) has also been shown to activate primarily the alternative NF-κB pathway when signalling through its receptor Fn14. Here I show that alternative NF-κB signalling activity, stimulated by the addition of TWEAK or loss of cIAP1, can promote myogenesis. I also demonstrate that TWEAK is an endogenous myokine produced by myoblasts to promote their own differentiation, and suggest that targeting the alternative NF-κB pathway, with SMAC-mimetics or recombinant TWEAK for example, would be of therapeutic value in the repair and regeneration of muscle for various myopathies.