RESUMEN
Ticks transmit more pathogens to humans and animals than any other arthropod. We describe the 2.1 Gbp nuclear genome of the tick, Ixodes scapularis (Say), which vectors pathogens that cause Lyme disease, human granulocytic anaplasmosis, babesiosis and other diseases. The large genome reflects accumulation of repetitive DNA, new lineages of retro-transposons, and gene architecture patterns resembling ancient metazoans rather than pancrustaceans. Annotation of scaffolds representing â¼57% of the genome, reveals 20,486 protein-coding genes and expansions of gene families associated with tick-host interactions. We report insights from genome analyses into parasitic processes unique to ticks, including host 'questing', prolonged feeding, cuticle synthesis, blood meal concentration, novel methods of haemoglobin digestion, haem detoxification, vitellogenesis and prolonged off-host survival. We identify proteins associated with the agent of human granulocytic anaplasmosis, an emerging disease, and the encephalitis-causing Langat virus, and a population structure correlated to life-history traits and transmission of the Lyme disease agent.
Asunto(s)
Anaplasma phagocytophilum , Vectores Arácnidos/genética , Genoma/genética , Ixodes/genética , Canales Iónicos Activados por Ligandos/genética , Animales , Perfilación de la Expresión Génica , Genómica , Enfermedad de Lyme/transmisión , Oocitos , Xenopus laevisRESUMEN
BACKGROUND: The genome of Anopheles gambiae, the major vector of malaria, was sequenced and assembled in 2002. This initial genome assembly and analysis made available to the scientific community was complicated by the presence of assembly issues, such as scaffolds with no chromosomal location, no sequence data for the Y chromosome, haplotype polymorphisms resulting in two different genome assemblies in limited regions and contaminating bacterial DNA. RESULTS: Polytene chromosome in situ hybridization with cDNA clones was used to place 15 unmapped scaffolds (sizes totaling 5.34 Mbp) in the pericentromeric regions of the chromosomes and oriented a further 9 scaffolds. Additional analysis by in situ hybridization of bacterial artificial chromosome (BAC) clones placed 1.32 Mbp (5 scaffolds) in the physical gaps between scaffolds on euchromatic parts of the chromosomes. The Y chromosome sequence information (0.18 Mbp) remains highly incomplete and fragmented among 55 short scaffolds. Analysis of BAC end sequences showed that 22 inter-scaffold gaps were spanned by BAC clones. Unmapped scaffolds were also aligned to the chromosome assemblies in silico, identifying regions totaling 8.18 Mbp (144 scaffolds) that are probably represented in the genome project by two alternative assemblies. An additional 3.53 Mbp of alternative assembly was identified within mapped scaffolds. Scaffolds comprising 1.97 Mbp (679 small scaffolds) were identified as probably derived from contaminating bacterial DNA. In total, about 33% of previously unmapped sequences were placed on the chromosomes. CONCLUSION: This study has used new approaches to improve the physical map and assembly of the A. gambiae genome.
Asunto(s)
Anopheles/genética , Genoma de los Insectos/genética , Mapeo Físico de Cromosoma , Animales , Bacterias/genética , Centrómero/genética , Cromosomas/genética , Eucromatina/genética , Polimorfismo Genético , Especificidad de la EspecieRESUMEN
Genome information resources such as Ensembl manage and present DNA sequence and annotation arising from genome projects. Recent developments in the Ensembl system include access to inter-species comparisons at both the genomic and protein sequence levels and improvements to the display of polymorphism data. Users can now display their own data in the context of other annotation. In addition, a fast and flexible data retrieval system, EnsMart, has been developed.