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Resistência de Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) a fipronil: Padronização de bioensaios in vitro, detecção de resistência em populações de campo e avaliação sobre resistência cruzada com outras drogas.; Resistance of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) to fipronil standardization of in vitro bioassays, detection of resistance in field populations and evaluation of cross-resistance with other drugs.

Janer, Eleonor Adega Castro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 02/12/2010 PT
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65.5%
Para o sucesso das estratégias de manejo de Rhipicephalus (Boophilus) microplus (carrapato bovino) são necessários testes práticos, econômicos e confiáveis que possam detectar a presença de fenótipos resistentes a drogas em suas populações. O fipronil é um acaricida de uso relativamente recente não havendo testes padronizados para o diagnóstico de resistência do carrapato à molécula. No presente trabalho, foram padronizados bioensaios in vitro para esta finalidade: Teste de Imersão de Adultas, Teste de Imersão de Larvas e Teste de Pacote com Larvas. Os testes foram aplicados e, de forma inédita, populações resistentes foram diagnosticadas tanto no Brasil quanto no Uruguai. Ensaios com inibidores enzimáticos não evidenciaram participação importante de enzimas detoxificadoras no mecanismo de resistência. Foi demonstrada reação cruzada entre fipronil e lindano, não verificada para ivermectina. Em algumas situações, foi observado interferência do controle químico de pragas agrícolas no desenvolvimento de resistência dos carrapatos.; For the success of the strategies for the management of Rhipicephalus (Boophilus) microplus (cattle tick), practical, economical and reliable tests are needed to detect the presence of drug-resistant phenotypes in their populations. Fipronil is a relatively new acaricide with no standardized tests for the diagnosis of tick resistance to this molecule. In this study...

Estabelecimento de um patossistema modelo e análise da interação molecular planta-patógeno entre Eucalyptus grandis e Puccinia psidii Winter por meio da técnica de RNA-Seq.; Establishment of a model pathosystem and analysis of the molecular plant-pathogen interaction between Eucalyptus grandis and Puccinia psidii Winter

Leite, Thiago Falda
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 17/05/2012 PT
Relevância na Pesquisa
85.47%
Mais de 20 milhões de hectares em todo o mundo são atualmente destinados a plantações de Eucalyptus, sendo que o Brasil possui a segunda maior área. No ano de 2007 a rede internacional EUCAGEN, liderada pelo Brasil, África do Sul e Estados Unidos, surgiu com o objetivo de colaboração para a pesquisa genômica do eucalipto. A árvore escolhida para o sequenciamento (Brasuz) foi fornecida pelo Brasil e em 2011 as primeiras sequências foram disponibilizadas. Em todas as fases de seu desenvolvimento, o eucalipto está sob o constante ataque de patógenos, destacando-se a ferrugem, causada pelo Basideomiceto Puccinia psidii Winter como a mais importante doença em regiões tropicais. A doença vem se espalhando rapidamente pelo mundo e recentemente foi relatada na Austrália, centro de origem do eucalipto. Com o objetivo de estudar o mecanismo molecular da interação plantapatógeno entre Eucalyptus grandis e Puccinia psidii, estabeleceu-se um patossistema modelo composto por um isolado monopustular do fungo e plantas resistente e susceptível provenientes de uma progênie de meios irmãos da planta Brasuz. O desenvolvimento do patógeno nos genótipos selecionados foi analisado por meio de microscopia de luz e de epifluorescência...

Mechanism of resistance and presence of different resistance genes to Ramularia areola in two cotton genotypes

Zandoná,Carla; Novaes,Tanara G.; Nunes,Maria Paula; Almeida,Wilson P.; Aguiar,Paulo H.; Morello,Camilo L.; Shuster,Ivan; Mehta,Yeshwant R.
Fonte: Sociedade Brasileira de Fitopatologia Publicador: Sociedade Brasileira de Fitopatologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
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Earlier studies showed that the resistance of cotton genotype FMT 02102996 to Ramularia areola is governed by one dominant gene. More recently, the resistance of another genotype CNPA BA 2003-2059 to R. areola was detected under field and glasshouse conditions. Present investigation was conducted to verify the mechanism of resistance of the genotype CNPA BA 2003-2059 and to find out if the resistance of these two genotypes is governed by the same or by different genes. Segregating plant populations derived from the cross between the resistant genotype CNPA BA 2003-2059 and the susceptible genotype FMT 701, the back cross populations, as well as those derived from the cross between the two resistant genotypes were evaluated for disease severity by artificial inoculations under glasshouse conditions. The ratio of plants segregating for resistance and susceptibility was studied by χ2 test. The results indicated that the resistance to R. areola in genotype CNPA BA 2003-2059 is governed by one dominant gene and that the resistance in each one of the resistant genotypes is governed by a different dominant gene. These results may assist the local breeding programs aimed at pyramiding resistance genes to this pathogen and may form the basis for genetic mapping of resistance genes.

pncA Mutations as a Major Mechanism of Pyrazinamide Resistance in Mycobacterium tuberculosis: Spread of a Monoresistant Strain in Quebec, Canada

Cheng, Shao-Ji; Thibert, Louise; Sanchez, Tracy; Heifets, Leonid; Zhang, Ying
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /03/2000 EN
Relevância na Pesquisa
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Pyrazinamide (PZA) is an important first-line tuberculosis drug that is part of the currently used short-course tuberculosis chemotherapy. PZA is a prodrug that has to be converted to the active form pyrazinoic acid by pyrazinamidase (PZase) activity, encoded by the pncA gene of Mycobacterium tuberculosis, and loss of PZase activity is associated with PZA resistance. To further define the genetic basis of PZA resistance and determine the frequency of PZA-resistant strains having pncA mutations, we sequenced the pncA gene from a panel of 59 PZA-resistant clinical isolates from Canada, the United States, and Korea. Two strains that did not contain pncA mutations and had positive PZase turned out to be falsely resistant. Three PZase-negative strains (MIC, >900 μg of PZA per ml) and one PZase-positive strain (strain 9739) (MIC, >300 μg of PZA per ml) did not have pncA mutations. The remaining 53 of the 57 PZA-resistant isolates had pncA mutations, confirming that pncA mutation is the major mechanism of PZA resistance. Various new and diverse mutations were found in the pncA gene. Interestingly, 20 PZA-monoresistant strains and 1 multidrug-resistant isolate from Quebec, Canada, all had the same pncA mutation profile, consisting of an 8-nucleotide deletion and an amino acid substitution of Arg140→Ser. Strain typing indicated that these strains are highly related and share almost identical IS6110 patterns. These data strongly suggest the spread of a PZA-monoresistant strain...

Resistance to Macrolides in Streptococcus pyogenes in France in Pediatric Patients

Bingen, Edouard; Fitoussi, Frederic; Doit, Catherine; Cohen, Robert; Tanna, Asha; George, Robert; Loukil, Chawki; Brahimi, Naima; Le Thomas, Isabelle; Deforche, Dominique
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2000 EN
Relevância na Pesquisa
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A total of 1,500 recent throat isolates of Streptococcus pyogenes collected between 1996 and 1999 from children throughout France were tested for their susceptibility to erythromycin, azithromycin, josamycin, clindamycin, and streptogramin B. The erythromycin-resistant isolates were further studied for their genetic mechanism of resistance, by means of PCR. The clonality of these strains was also investigated by means of serotyping and ribotyping. In all, 6.2% of the strains were erythromycin resistant, and 3.4 and 2.8% expressed the constitutive MLSB and M resistance phenotypes and harbored the ermB and mefA genes, respectively; ermTR was recovered from one isolate which also harbored the ermB gene. Ten serotypes and 8 ribotypes were identified, but we identified 17 strains by combining serotyping with ribotyping. Among the eight ribotypes, the mefA gene was recovered from six clusters, one being predominant, while the ermB gene was recovered from four clusters, of which two were predominant.

MECHANISM OF RESISTANCE TO ACTINOMYCIN IN BACILLUS SUBTILIS

Polsinelli, M.; Ciferri, O.; Cassani, G.; Albertini, A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1964 EN
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Polsinelli, M. (University of Pavia, Pavia, Italy), O. Ciferri, G. Cassani, and A. Albertini. Mechanism of resistance to actinomycin in Bacillus subtilis. J. Bacteriol. 88:1567–1572. 1964.—Strains of Bacillus subtilis were rendered resistant to actinomycin D by serial transfer in increasing concentrations of the drug. Resistance to the antibiotic appeared to be due to an altered cell-wall permeability, because the resistant strains did not take up actinomycin. No evidence was found for the presence of an enzyme(s) degrading actinomycin. Deoxyribonucleic acid (DNA) extracted from the actinomycin-resistant strains was found to bind actinomycin to the same extent as the DNA extracted from susceptible strains. The genetic nature of the resistance to actinomycin was demonstrated by means of transformation. Resistant strains appeared to have almost completely lost their transformability, as well as the tendency to autolyze.

Murine malaria: genetic control of resistance to Plasmodium chabaudi.

Stevenson, M M; Lyanga, J J; Skamene, E
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1982 EN
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Strain variation in the level of resistance to malaria was investigated in inbred strains of mice after infection with Plasmodium chabaudi. When infected intraperitoneally with 10(6) P. chabaudi-parasitized erythrocytes, mice of 11 inbred strains could be separated into two groups by using survival time as the criterion; C57BL/6J, C57L/J, DBA/2J, CBA/J, and B10.A/SgSn mice were found to be resistant to P. chabaudi, whereas A/J, DBA/1J, BALB/c, C3H/HeJ, AKR/J, and SJL/J mice were susceptible. An examination of F1 hybrids revealed that resistance was dominant over susceptibility. A segregation analysis of backcross and F2 progeny derived from susceptible A/J and resistant B10.A/SgSn parental mice suggested that host resistance in this strain combination was genetically controlled by a single, dominant, non-H-2-linked gene. Inheritance of resistance was autosomal, but expression of the trait was influenced by the sex of the host, female mice being more resistant than male mice. Phenotypic expression of the resistance gene was apparent within 6 days of infection as a significant difference between resistant and susceptible mice in the level of parasitemia. A preliminary analysis of the mechanism of resistance showed that compared with susceptible A/J mice...

Genetic control of murine resistance to Toxoplasma gondii.

Williams, D M; Grumet, F C; Remington, J S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1978 EN
Relevância na Pesquisa
65.57%
The genetics of murine susceptibility to Toxoplasma gondii was investigated in inbred mice and their F1 and F2 offspring. Among four strains of congenic mice of the B10 background, those with H-2a/a and H-2b/b genotypes were more susceptible than were those with H-2d/d and H-2k/k genotypes. Breeding studies utilizing three of these strains demonstrated linkage between the H-2a allele and greater susceptibility. These data suggest the existence of an H-2-linked gene affecting susceptibility to T. gondii. In challenge of recombinant inbred mice derived from C57Bl/6J (high susceptibility) and BALB/c (low susceptibility) strains, lines BE, BJ, and BK were more susceptible than lines BD, BG, BH, and BI. These data are consistent with the existence of a second disease susceptibility gene linked to the H-13 locus. F1 offspring of the C57B1/6J X B10.D2 mice were significantly less susceptible than either parent. This phenotypic complementary suggests the presence of more than one genetic mechanism of resistance to T. gondii. From these combined data, we conclude that (i) susceptibility to T. gondii in mice is affected by at least two genes, (ii) one of the genes is linked to the H-2 and one to the H-13 locus, and (iii) more than a single mechanism of resistance must be considered to explain the observed genetic controls of susceptibility.

Digital karyotyping identifies thymidylate synthase amplification as a mechanism of resistance to 5-fluorouracil in metastatic colorectal cancer patients

Wang, Tian-Li; Diaz, Luis A.; Romans, Katharine; Bardelli, Alberto; Saha, Saurabh; Galizia, Gennaro; Choti, Michael; Donehower, Ross; Parmigiani, Giovanni; Shih, Ie-Ming; Iacobuzio-Donahue, Christine; Kinzler, Kenneth W.; Vogelstein, Bert; Lengauer, Chris
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
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Resistance to chemotherapy is a major cause of mortality in advanced cancer patients. In this study, digital karyotyping was used to search for genomic alterations in liver metastases that were clinically resistant to 5-fluorouracil (5-FU). In two of four patients, we identified amplification of an ≈100-kb region on 18p11.32 that was of particular interest because it contained the gene encoding thymidylate synthase (TYMS), a molecular target of 5-FU. Analysis of TYMS by fluorescence in situ hybridization identified TYMS gene amplification in 23% of 31 5-FU-treated cancers, whereas no amplification was observed in metastases of patients that had not been treated with 5-FU. Patients with metastases containing TYMS amplification had a substantially shorter median survival (329 days) than those without amplification (1,021 days, P <0.01). These data suggest that genetic amplification of TYMS is a major mechanism of 5-FU resistance in vivo and have important implications for the management of colorectal cancer patients with recurrent disease.

Isolates with Low-Level Vancomycin Resistance Associated with Persistent Methicillin-Resistant Staphylococcus aureus Bacteremia

Howden, Benjamin P.; Johnson, Paul D. R.; Ward, Peter B.; Stinear, Timothy P.; Davies, John K.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2006 EN
Relevância na Pesquisa
75.55%
Low-level vancomycin-resistant Staphylococcus aureus (vancomycin-intermediate S. aureus [VISA] and heterogenous VISA [hVISA]) is increasingly reported and leads to glycopeptide treatment failure. Various phenotypic features have been reported for these isolates, but the genetic changes leading to hVISA and VISA have yet to be clearly determined. We assessed phenotypic, antibiotic resistance, and genomic changes by using genomic DNA microarray comparison and sequencing of selected loci in five pairs of clinical hVISA/VISA strains and the initial methicillin-resistant Staphylococcus aureus (MRSA) isolates obtained prior to vancomycin therapy. The isolates were from adult patients in Australia and New Zealand who had persistent MRSA bacteremia (>7 days) while receiving vancomycin therapy. In all cases, the initial isolates were found to be fully vancomycin-susceptible Staphylococcus aureus (VSSA). The hVISA/VISA phenotype was associated with increased cell wall thickness, reduced autolytic activity in four of five hVISA/VISA strains, and a striking reduction in biofilm formation compared to the parent strains in all pairs. All five pairs appeared to be isogenic, and genomic DNA microarray comparison suggested that major genetic changes are not required for the development of the resistant phenotype in these strains. No sequence differences were found in the agr locus or the tcaRA genes for any pair...

Mechanism of Resistance to Bacillus thuringiensis Toxin Cry1Ac in a Greenhouse Population of the Cabbage Looper, Trichoplusia ni▿

Wang, Ping; Zhao, Jian-Zhou; Rodrigo-Simón, Ana; Kain, Wendy; Janmaat, Alida F.; Shelton, Anthony M.; Ferré, Juan; Myers, Judith
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
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The cabbage looper, Trichoplusia ni, is one of only two insect species that have evolved resistance to Bacillus thuringiensis in agricultural situations. The trait of resistance to B. thuringiensis toxin Cry1Ac from a greenhouse-evolved resistant population of T. ni was introgressed into a highly inbred susceptible laboratory strain. The resulting introgression strain, GLEN-Cry1Ac-BCS, and its nearly isogenic susceptible strain were subjected to comparative genetic and biochemical studies to determine the mechanism of resistance. Results showed that midgut proteases, hemolymph melanization activity, and midgut esterase were not altered in the GLEN-Cry1Ac-BCS strain. The pattern of cross-resistance of the GLEN-Cry1Ac-BCS strain to 11 B. thuringiensis Cry toxins showed a correlation of the resistance with the Cry1Ab/Cry1Ac binding site in T. ni. This cross-resistance pattern is different from that found in a previously reported laboratory-selected Cry1Ab-resistant T. ni strain, evidently indicating that the greenhouse-evolved resistance involves a mechanism different from the laboratory-selected resistance. Determination of specific binding of B. thuringiensis toxins Cry1Ab and Cry1Ac to the midgut brush border membranes confirmed the loss of midgut binding to Cry1Ab and Cry1Ac in the resistant larvae. The loss of midgut binding to Cry1Ab/Cry1Ac is inherited as a recessive trait...

Similar Genetic Basis of Resistance to Bt Toxin Cry1Ac in Boll-Selected and Diet-Selected Strains of Pink Bollworm

Fabrick, Jeffrey A.; Tabashnik, Bruce E.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 18/04/2012 EN
Relevância na Pesquisa
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Genetically engineered cotton and corn plants producing insecticidal Bacillus thuringiensis (Bt) toxins kill some key insect pests. Yet, evolution of resistance by pests threatens long-term insect control by these transgenic Bt crops. We compared the genetic basis of resistance to Bt toxin Cry1Ac in two independently derived, laboratory-selected strains of a major cotton pest, the pink bollworm (Pectinophora gossypiella [Saunders]). The Arizona pooled resistant strain (AZP-R) was started with pink bollworm from 10 field populations and selected with Cry1Ac in diet. The Bt4R resistant strain was started with a long-term susceptible laboratory strain and selected first with Bt cotton bolls and later with Cry1Ac in diet. Previous work showed that AZP-R had three recessive mutations (r1, r2, and r3) in the pink bollworm cadherin gene (PgCad1) linked with resistance to Cry1Ac and Bt cotton producing Cry1Ac. Here we report that inheritance of resistance to a diagnostic concentration of Cry1Ac was recessive in Bt4R. In interstrain complementation tests for allelism, F1 progeny from crosses between AZP-R and Bt4R were resistant to Cry1Ac, indicating a shared resistance locus in the two strains. Molecular analysis of the Bt4R cadherin gene identified a novel 15-bp deletion (r4) predicted to cause the loss of five amino acids upstream of the Cry1Ac-binding region of the cadherin protein. Four recessive mutations in PgCad1 are now implicated in resistance in five different strains...

Genetic Basis for In Vitro and In Vivo Resistance to Lincosamides, Streptogramins A, and Pleuromutilins (LSAP Phenotype) in Enterococcus faecium

Isnard, Christophe; Malbruny, Brigitte; Leclercq, Roland; Cattoir, Vincent
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2013 EN
Relevância na Pesquisa
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As opposed to Enterococcus faecalis, which is intrinsically resistant to lincosamides, streptogramins A, and pleuromutilins (LSAP phenotype) by production of the ABC protein Lsa(A), Enterococcus faecium is naturally susceptible. Since this phenotype may be selected for in vivo by quinupristin-dalfopristin (Q-D), the aim of this study was to investigate the molecular mechanism of acquired LSAP resistance in E. faecium. Six LSAP-resistant in vitro mutants of E. faecium HM1070 as well as three different pairs of clinical isolates (pre- and postexposure to Q-D) were studied. The full genome sequence of an in vitro mutant (E. faecium UCN90B) was determined by using 454 sequencing technology and was compared with that of the parental strain. Single-nucleotide replacement was carried out to confirm the role of this mutation. By comparative genomic analysis, a point mutation was found within a 1,503-bp gene coding for an ABC homologue showing 66% amino acid identity with Lsa(A). This mutation (C1349T) led to an amino acid substitution (Thr450Ile). An identical mutation was identified in all in vitro and in vivo resistant strains but was not present in susceptible strains. The wild-type allele was named eat(A) (for Enterococcus ABC transporter)...

Herceptin Resistance Database for Understanding Mechanism of Resistance in Breast Cancer Patients

Ahmad, Sahil; Gupta, Sudheer; Kumar, Rahul; Varshney, Grish C.; Raghava, Gajendra P. S.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 27/03/2014 EN
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Monoclonal antibody Trastuzumab/Herceptin is considered as frontline therapy for Her2-positive breast cancer patients. However, it is not effective against several patients due to acquired or de novo resistance. In last one decade, several assays have been performed to understand the mechanism of Herceptin resistance with/without supplementary drugs. This manuscript describes a database HerceptinR, developed for understanding the mechanism of resistance at genetic level. HerceptinR maintains information about 2500 assays performed against various breast cancer cell lines (BCCs), for improving sensitivity of Herceptin with or without supplementary drugs. In order to understand Herceptin resistance at genetic level, we integrated genomic data of BCCs that include expression, mutations and copy number variations in different cell lines. HerceptinR will play a vital role in i) designing biomarkers to identify patients eligible for Herceptin treatment and ii) identification of appropriate supplementary drug for a particular patient. HerceptinR is available at http://crdd.osdd.net/raghava/herceptinr/.

Transcriptional Response of Virus-Infected Cassava and Identification of Putative Sources of Resistance for Cassava Brown Streak Disease

Maruthi, M. N.; Bouvaine, Sophie; Tufan, Hale A.; Mohammed, Ibrahim U.; Hillocks, Rory J.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 20/05/2014 EN
Relevância na Pesquisa
65.49%
Cassava (Manihot esculenta) is a major food staple in sub-Saharan Africa, which is severely affected by cassava brown streak disease (CBSD). The aim of this study was to identify resistance for CBSD as well as to understand the mechanism of putative resistance for providing effective control for the disease. Three cassava varieties; Kaleso, Kiroba and Albert were inoculated with cassava brown streak viruses by grafting and also using the natural insect vector the whitefly, Bemisia tabaci. Kaleso expressed mild or no disease symptoms and supported low concentrations of viruses, which is a characteristic of resistant plants. In comparison, Kiroba expressed severe leaf but milder root symptoms, while Albert was susceptible with severe symptoms both on leaves and roots. Real-time PCR was used to estimate virus concentrations in cassava varieties. Virus quantities were higher in Kiroba and Albert compared to Kaleso. The Illumina RNA-sequencing was used to further understand the genetic basis of resistance. More than 700 genes were uniquely overexpressed in Kaleso in response to virus infection compared to Albert. Surprisingly, none of them were similar to known resistant gene orthologs. Some of the overexpressed genes, however, belonged to the hormone signalling pathways and secondary metabolites...

Will a Global Subsidy of Artemisinin-Based Combination Treatment (ACT) for Malaria Delay the Emergence of Resistance and Save Lives?

Laxminarayan, Ramanan; Over, Mead; Smith, David L.
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
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Artemisinin-based combination treatments (ACTs) are seen as an important tool in the global effort to roll back malaria. With rapidly increasing parasite resistance to chloroquine in many parts of the world, there is greater international recognition of the need for both a different antimalarial and a coordinated malaria treatment strategy to ensure that resistance does not needlessly cut short the useful therapeutic life of any successor drug to chloroquine. The effectiveness of antimalarial drugs is a global public good, of particular value in malarious regions that also are among the most economically impoverished parts of the world. Inappropriate drug use in neighboring countries reduces the incentive of any given country to deploy drug regimens that may be rapidly undermined by resistance originating outside their borders. Therefore, a case can be made for globally coordinated action to protect the effectiveness of these valuable drugs. Translating this case to one for a global subsidy is not straightforward. On the one hand, in the absence of such a subsidy to ensure that ACTs are comparably priced to monotherapies, increasing monotherapy of artemisinin and other antimalarials that would be used along with artemisinin in ACT will hasten the demise of this drug. On the other hand...

Evolved glyphosate resistance in plants: Biochemical and genetic basis of resistance

Powles, S.; Preston, C.
Fonte: Weed Sci Soc Amer Publicador: Weed Sci Soc Amer
Tipo: Artigo de Revista Científica
Publicado em //2006 EN
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Resistance to the herbicide glyphosate is currently known in at least eight weed species from many countries. Some populations of goosegrass from Malaysia, rigid ryegrass from Australia, and Italian ryegrass from Chile exhibit target site–based resistance to glyphosate through changes at amino acid 106 of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene. Mutations change amino acid 106 from proline to either serine or threonine, conferring an EPSPS weakly resistant to glyphosate. The moderate level of resistance is sufficient for commercial failure of the herbicide to control these plants in the field. Conversely, a nontarget site resistance mechanism has been documented in glyphosate-resistant populations of horseweed and rigid ryegrass from the United States and Australia, respectively. In these resistant plants, there is reduced translocation of glyphosate to meristematic tissues. Both of these mechanisms are inherited as a single, nuclear gene trait. Although at present only two glyphosate-resistance mechanisms are known, it is likely that other mechanisms will become evident. The already very large and still increasing reliance on glyphosate in many parts of the world will inevitably result in more glyphosate-resistant weeds...

Genetic mapping of Bt-toxin binding proteins in a Cry1A-toxin resistant strain of diamondback moth Plutella xylostella

Baxter, S.; Zhao, J.Z.; Shelton, A.; Vogel, H.; Heckel, D.
Fonte: Pergamon-Elsevier Science Ltd Publicador: Pergamon-Elsevier Science Ltd
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
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A major mechanism of resistance to Bacillus thuringiensis (Bt) toxins in Lepidoptera is a reduction of toxin binding to sites in the midgut membrane. Genetic studies of three different species have shown that mutations in a candidate Bt receptor, a 12-cadherin-domain protein, confer Cry1A toxin resistance. Despite a similar resistance profile in a fourth lepidopteran species, Plutella xylostella, we have previously shown that the cadherin orthologue maps to a different linkage group (LG8) than Cry1Ac resistance (LG22). Here we tested the hypothesis that mutations in other genes encoding candidate Bt-binding targets could be responsible for Bt resistance, by mapping eight aminopeptidases, an alkaline phosphatase (ALP), an intestinal mucin, and a P252 glycoprotein with respect to the 29 AFLP marked linkage groups in a P. xylostella cross segregating for Cry1Ac resistance. A homologue of the Caenorhabditis elegans Bt resistance gene bre-2 was also mapped. None of the genes analysed were on the same chromosome containing the Cry1Ac resistance locus, eliminating them as candidate resistance genes in the parental resistant strain SC1. Although this finding excludes cis-acting mutations in these genes as causing resistance in this strain...

Análises da resistência genética à tospovirus e potyvirus em acessos de Solanum (secção lycopersicon); Genetic analysis of resistance to tospovirus and potyvirus in access of Solanum (section lycopersicon)

Oliveira, Renata Maria de
Fonte: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Agronomia (EAEA); Escola de Agronomia e Engenharia de Alimentos - EAEA (RG) Publicador: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Agronomia (EAEA); Escola de Agronomia e Engenharia de Alimentos - EAEA (RG)
Tipo: Dissertação Formato: application/pdf
POR
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Tomato is one of the most cultivated vegetables worldwide, and this is an important factor in their vulnerability to attack by pests and diseases, which contribute to the decrease in production and affects the quality of the fruit. Among diseases affecting tomato production, the ones caused by viruses are of the utmost importance, which are more difficult to control, highlighting those caused by species of the genus Tospovirus, which can cause losses of up to 100 %. The tospoviruses are responsible for the disease known as 'tomato spotted wilt' and are transmitted by thrips. In Brazil, four species of tospoviruses occur in tomato: Tomato spotted wilt virus (TSWV), Tomato chlorotic spot virus (TCSV), Groundnut ringspot virus (GRSV) and Chrysanthemum stem necrosis virus (CSNV), with a greater incidence of GRSV. The first TSWV resistance gene identified was the Sw-5, which is effective against all species of tospoviruses infecting tomato and is widely used in breeding programs for this reason, because the resistance gene presents a dominant trait. Sources of resistance were found in other wild accessions of the species S. chilense, S. habrochaites, S. pimpinellifolium, S. corneliomuelleri and S. lycopersicum, showing promising results as sources of resistance for use in breeding programs. To identify a source of tospovirus resistance in wild accessions of the Germplasm Bank of Embrapa Hortaliças...

Variable Sensitivity to Bacterial Methionyl-tRNA Synthetase Inhibitors Reveals Subpopulations of Streptococcus pneumoniae with Two Distinct Methionyl-tRNA Synthetase Genes

Gentry, Daniel R.; Ingraham, Karen A.; Stanhope, Michael J.; Rittenhouse, Stephen; Jarvest, Richard L.; O'Hanlon, Peter J.; Brown, James R.; Holmes, David J.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2003 EN
Relevância na Pesquisa
65.46%
As reported previously (J. R. Jarvest et al., J. Med. Chem. 45:1952-1962, 2002), potent inhibitors (at nanomolar concentrations) of Staphylococcus aureus methionyl-tRNA synthetase (MetS; encoded by metS1) have been derived from a high-throughput screening assay hit. Optimized compounds showed excellent activities against staphylococcal and enterococcal pathogens. We report on the bimodal susceptibilities of S. pneumoniae strains, a significant fraction of which was found to be resistant (MIC, ≥8 mg/liter) to these inhibitors. Using molecular genetic techniques, we have found that the mechanism of resistance is the presence of a second, distantly related MetS enzyme, MetS2, encoded by metS2. We present evidence that the metS2 gene is necessary and sufficient for resistance to MetS inhibitors. PCR analysis for the presence of metS2 among a large sample (n = 315) of S. pneumoniae isolates revealed that it is widespread geographically and chronologically, occurring at a frequency of about 46%. All isolates tested also contained the metS1 gene. Searches of public sequence databases revealed that S. pneumoniae MetS2 was most similar to MetS in Bacillus anthracis, followed by MetS in various non-gram-positive bacterial, archaeal, and eukaryotic species...