RESUMO
Toxoplasma gondii is a globally distributed protozoan parasite that can infect virtually all warm-blooded animals and humans. Despite the existence of a sexual phase in the life cycle, T. gondii has an unusual population structure dominated by three clonal lineages that predominate in North America and Europe, (Types I, II, and III). These lineages were founded by common ancestors approximately10,000 yr ago. The recent origin and widespread distribution of the clonal lineages is attributed to the circumvention of the sexual cycle by a new mode of transmission-asexual transmission between intermediate hosts. Asexual transmission appears to be multigenic and although the specific genes mediating this trait are unknown, it is predicted that all members of the clonal lineages should share the same alleles. Genetic mapping studies suggested that chromosome Ia was unusually monomorphic compared with the rest of the genome. To investigate this further, we sequenced chromosome Ia and chromosome Ib in the Type I strain, RH, and the Type II strain, ME49. Comparative genome analyses of the two chromosomal sequences revealed that the same copy of chromosome Ia was inherited in each lineage, whereas chromosome Ib maintained the same high frequency of between-strain polymorphism as the rest of the genome. Sampling of chromosome Ia sequence in seven additional representative strains from the three clonal lineages supports a monomorphic inheritance, which is unique within the genome. Taken together, our observations implicate a specific combination of alleles on chromosome Ia in the recent origin and widespread success of the clonal lineages of T. gondii.
Assuntos
Cromossomos , Evolução Molecular , Toxoplasma/genética , Animais , Cruzamentos Genéticos , Variação Genética , Genética Populacional , Padrões de Herança , Meiose , Dados de Sequência Molecular , Recombinação Genética , Toxoplasma/classificaçãoRESUMO
Theileria annulata and T. parva are closely related protozoan parasites that cause lymphoproliferative diseases of cattle. We sequenced the genome of T. annulata and compared it with that of T. parva to understand the mechanisms underlying transformation and tropism. Despite high conservation of gene sequences and synteny, the analysis reveals unequally expanded gene families and species-specific genes. We also identify divergent families of putative secreted polypeptides that may reduce immune recognition, candidate regulators of host-cell transformation, and a Theileria-specific protein domain [frequently associated in Theileria (FAINT)] present in a large number of secreted proteins.
Assuntos
Genoma de Protozoário , Proteínas de Protozoários/genética , Theileria annulata/genética , Theileria parva/genética , Motivos de Aminoácidos , Animais , Bovinos , Proliferação de Células , Mapeamento Cromossômico , Cromossomos/genética , Sequência Conservada , Genes de Protozoários , Estágios do Ciclo de Vida , Metabolismo dos Lipídeos , Linfócitos/citologia , Linfócitos/parasitologia , Dados de Sequência Molecular , Família Multigênica , Filogenia , Sinais Direcionadores de Proteínas/genética , Estrutura Terciária de Proteína , Proteoma , Proteínas de Protozoários/química , Proteínas de Protozoários/fisiologia , Análise de Sequência de DNA , Especificidade da Espécie , Sintenia , Telômero/genética , Theileria annulata/crescimento & desenvolvimento , Theileria annulata/imunologia , Theileria annulata/patogenicidade , Theileria parva/crescimento & desenvolvimento , Theileria parva/imunologia , Theileria parva/patogenicidadeRESUMO
Aspergillus fumigatus is the most ubiquitous opportunistic filamentous fungal pathogen of human. As an initial step toward sequencing the entire genome of A. fumigatus, which is estimated to be approximately 30 Mb in size, we have sequenced a 922 kb region, contained within 16 overlapping bacterial artificial chromosome (BAC) clones. Fifty-four percent of the DNA is predicted to be coding with 341 putative protein coding genes. Functional classification of the proteins showed the presence of a higher proportion of enzymes and membrane transporters when compared to those of Saccharomyces cerevisiae. In addition to the nitrate assimilation gene cluster, the quinate utilisation gene cluster is also present on this 922 kb genomic sequence. We observed large scale synteny between A. fumigatus and Aspergillus nidulans by comparing this sequence to the A. nidulans genetic map of linkage group VIII.
Assuntos
Aspergillus fumigatus/genética , Aspergillus fumigatus/metabolismo , Genoma Fúngico , Nitratos/metabolismo , Aspergillus nidulans/genética , Cromossomos Artificiais Bacterianos , DNA Fúngico/química , DNA Fúngico/isolamento & purificação , DNA Intergênico , Enzimas/genética , Enzimas/metabolismo , Proteínas Fúngicas/genética , Proteínas Fúngicas/fisiologia , Ordem dos Genes , Genômica , Íntrons , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/fisiologia , Dados de Sequência Molecular , Família Multigênica , Fases de Leitura Aberta , Ácido Quínico/metabolismo , Saccharomyces cerevisiae/genética , Análise de Sequência de DNA , SinteniaRESUMO
Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica are closely related Gram-negative beta-proteobacteria that colonize the respiratory tracts of mammals. B. pertussis is a strict human pathogen of recent evolutionary origin and is the primary etiologic agent of whooping cough. B. parapertussis can also cause whooping cough, and B. bronchiseptica causes chronic respiratory infections in a wide range of animals. We sequenced the genomes of B. bronchiseptica RB50 (5,338,400 bp; 5,007 predicted genes), B. parapertussis 12822 (4,773,551 bp; 4,404 genes) and B. pertussis Tohama I (4,086,186 bp; 3,816 genes). Our analysis indicates that B. parapertussis and B. pertussis are independent derivatives of B. bronchiseptica-like ancestors. During the evolution of these two host-restricted species there was large-scale gene loss and inactivation; host adaptation seems to be a consequence of loss, not gain, of function, and differences in virulence may be related to loss of regulatory or control functions.
Assuntos
Bordetella bronchiseptica/genética , Bordetella pertussis/genética , Bordetella/genética , Genoma Bacteriano , Sequência de Bases , Bordetella/metabolismo , Bordetella/patogenicidade , Bordetella bronchiseptica/metabolismo , Bordetella bronchiseptica/patogenicidade , Bordetella pertussis/metabolismo , Bordetella pertussis/patogenicidade , DNA Bacteriano , Dados de Sequência Molecular , Análise de Sequência de DNA , Especificidade da EspécieRESUMO
The entire 127,923-bp sequence of the toxin-encoding plasmid pBtoxis from Bacillus thuringiensis subsp. israelensis is presented and analyzed. In addition to the four known Cry and two known Cyt toxins, a third Cyt-type sequence was found with an additional C-terminal domain previously unseen in such proteins. Many plasmid-encoded genes could be involved in several functions other than toxin production. The most striking of these are several genes potentially affecting host sporulation and germination and a set of genes for the production and export of a peptide antibiotic.
