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21.
Background
The (almost) universality of the genetic code is one of the most intriguing properties of cellular life. Nevertheless, several variants of the standard genetic code have been observed, which differ in one or several of 64 codon assignments and occur mainly in mitochondrial genomes and in nuclear genomes of some bacterial and eukaryotic parasites. These variants are usually considered to be the result of non-adaptive evolution. It has been shown that the standard genetic code is preferential to randomly assembled codes for its ability to reduce the effects of errors in protein translation. 相似文献22.
Fogel GB Porto VW Weekes DG Fogel DB Griffey RH McNeil JA Lesnik E Ecker DJ Sampath R 《Nucleic acids research》2002,30(23):5310-5317
23.
Debora Franceschini Paola Del Porto Silvia Piconese Emanuele Trella Daniele Accapezzato Marino Paroli Stefania Morrone Enza Piccolella Enea Spada Alfonso Mele John Sidney Alessandro Sette Vincenzo Barnaba 《PLoS pathogens》2012,8(6)
Caspase-dependent cleavage of antigens associated with apoptotic cells plays a prominent role in the generation of CD8+ T cell responses in various infectious diseases. We found that the emergence of a large population of autoreactive CD8+ T effector cells specific for apoptotic T cell-associated self-epitopes exceeds the antiviral responses in patients with acute hepatitis C virus infection. Importantly, they endow mixed polyfunctional type-1, type-2 and type-17 responses and correlate with the chronic progression of infection. This evolution is related to the selection of autoreactive CD8+ T cells with higher T cell receptor avidity, whereas those with lower avidity undergo prompt contraction in patients who clear infection. These findings demonstrate a previously undescribed strict link between the emergence of high frequencies of mixed autoreactive CD8+ T cells producing a broad array of cytokines (IFN-γ, IL-17, IL-4, IL-2…) and the progression toward chronic disease in a human model of acute infection. 相似文献
24.
Carepo MS Azevedo JS Porto JI Bentes-Sousa AR Batista Jda S Silva AL Schneider MP 《Genetics and molecular research : GMR》2004,3(1):181-194
Chromobacterium violaceum is a Gram-negative bacterium found in a wide variety of tropical and subtropical ecosystems. The complete genome sequence of C. violaceum ATCC 12472 is now available, and it has considerable biotechnological potential for various applications, such as environmental detoxification, as well as medical and agricultural use. We examined the biotechnological potential of C. violaceum for environmental detoxification. Three operons, comprising the ars operon, involved in arsenic resistance, the cyn operon, involved in cyanate detoxification, and the hcn operon, encoding a cyanase, responsible for biogenic production of cyanide, as well as an open reading frame, encoding an acid dehalogenase, were analyzed in detail. Probable catalytic mechanisms for the enzymes were determined, based on amino acid sequence comparisons and on published structural information for these types of proteins. 相似文献
25.
Cytogenetic studies were conducted on five piranha species belonging to the genus Serrasalmus, subfamily Serrasalminae (Serrasalmus altispinis, S. compressus, S. elongatus, S. manuelli, and S. spilopleura). All the species were collected in the Amazon basin: confluence of Negro and Solimõoes Rivers (CatalãoLake), Solimões River (Marchantaria Island – Camaleão Lake), Uatumã River (Hydroelectric Power Station of Balbina), and Pitinga River (Hydroelectric Power Station of Pitinga). All the five species possess 2n = 60 chromosomes with 5–12 subtelo- and acrocentric chromosomes bearing nucleolar organizer regions. A proximal C-band positive heterochromatin block was evident on the long arms of a medium-sized metacentric chromosome pair in all the analized species, thus making it a cytogenetic marker for the genus. It is hypothesized that 2n = 60 chromosomes represents a derived feature in terms of the chromosomal evolution of piranhas because the basal lineages possess 2n = 62. Both Robertsonian centric fusion and non-Robertsonian rearragements such as pericentric inversions seem implicated in the chromosomal evolution of this group. 相似文献
26.
Alfredo Seiiti Urashima Tatiane de Fátima Mistura Lis Natali Rodrigues Porto Paige Dariel Austin Renee Silvia Arias 《Journal of Phytopathology》2020,168(10):581-590
The use of resistant genotypes is the preferred method to control orange rust of sugarcane (Saccharum spp) caused by Puccinia kuehnii. This approach has been adopted in Brazil but outbreaks of the disease on previously resistant varieties showed that the efficacy of this method is limited and requires a better understanding of pathogen diversity. Nevertheless, adequate molecular markers for examining pathogen diversity at population level are not available, which limits the success of orange rust control by genetic resistance. Therefore, two independent investigations were conducted to examine genetic diversity of P. kuehnii from São Paulo state, the most important sugarcane growing state of Brazil. First, simple-sequence repeat (SSR) markers were developed in the present work and genotypic diversity of orange rust isolates from different locations investigated. Second, phenotypic diversity was examined by the single-pustule inoculation technique on P. kuehnii isolates retrieved from three susceptible commercial sugarcane cultivars. A total of 96 SSR markers were generated and tested for this species. Subsequently, 29 isolates of P. kuehnii were fingerprinted with nine SSR markers to estimate the genotypic diversity by neighbour-joining and 3D principal coordinates. The 29 isolates of the pathogen clustered into four main groups, which were identified by three SSR markers (NPRL_PK_108a, NPRL_PK_162_spka and NPRL_PK_221_spka). Phenotypic data at 21 days after the single-pustule inoculation showed that P. kuehnii from highly susceptible commercial cultivars harboured a small proportion of variants capable of causing disease on resistant cultivars. A differential reaction was demonstrated for the most virulent variant in a repeated experiment confirming the existence of races within P. kuehnii in Brazil. 相似文献
27.
Luiz Fernando Freire Royes Patrícia Gabbi Leandro Rodrigo Ribeiro Iuri Domingues Della-Pace Fernanda Silva Rodrigues Ana Paula de Oliveira Ferreira Mauro Eduardo Porto da Silveira Junior Luís Roberto Hart da Silva Alan Barroso Araújo Grisólia Danielle Valente Braga Fernando Dobrachinski Anderson Manoel Herculano Oliveira da Silva Félix Alexandre Antunes Soares Sara Marchesan Ana Flavia Furian Mauro Schneider Oliveira Michele Rechia Fighera 《Amino acids》2016,48(6):1373-1389
28.
Genetic structure and evidence of anthropogenic effects on wild populations of two Neotropical catfishes: baselines for conservation 下载免费PDF全文
F. D. Do Prado R. Fernandez‐Cebrián F. Foresti C. Oliveira P. Martínez F. Porto‐Foresti 《Journal of fish biology》2018,92(1):55-72
Genetic diversity and structure of Pseudoplatystoma corruscans and P. reticulatum, large migratory South America catfishes, where overfishing and the construction of numerous dams in their feeding and reproducing areas are affecting their migratory processes negatively, were studied using microsatellites in samples from Paraguay (that comprises the Pantanal biome), and the upper and lower Paraná Basins. Genetic diversity was in accordance to that observed for other large migratory fishes, but the most geographically isolated populations of P. reticulatum and those P. corruscans subject to anthropogenic effects (stocking and dams) showed lower genetic diversity and evidences of bottlenecks compatible with low effective population size. Pseudoplatystoma reticulatum presented subtle genetic differentiation within the Paraguay area, especially between the edges of its distribution. Pseudoplatystoma corruscans, in this same area, presented a quite homogeneous but significant genetic break between the Paraguay and upper Paraná populations, apparently resulting from natural and historical isolation between the basins until recently. These data demonstrates that, although these Pseudoplatystoma spp. are abundant in the Pantanal area, anthropogenic events are leading to negative effects on their populations, particularly in the upper Paraná Basin. Genetic differentiation observed along each species distribution demands conservation actions to preserve each population's biodiversity. These results represent important genetic information using new microsatellite markers and the first genetic study of P. reticulatum covering this area of its native distribution. Data may also contribute to a better understanding of species migration patterns and to be used as a baseline for proper management. 相似文献
29.
30.
Mechanical clearing of understory vegetation is increasingly used in Euro-Mediterranean forests to reduce fire hazard, yet
its long-term consequences for biodiversity remain poorly understood. This study analysed the influence of time since understory
management and management frequency, on herbaceous species richness, cover and composition, functional richness and composition,
and richness and cover within functional groups (life and growth forms, dispersal strategy, clonality, and plant height),
using a chronosequence of cork oak (Quercus suber) stands spanning about 70 years. Overall species richness was virtually constant over time, but the richness of species with
annual life form and plasticity in height was much higher in recently and recurrently treated stands; the opposite was found
for perennial (mainly hemicryptophytes and chamaephytes), tussock-forming and clonal species richness, and functional richness.
Overall herbaceous cover and that of annual, semi-basal, non-clonal and plastic species (in height) were favoured by recent
and recurrent fuel treatments; cover by perennial (hemicryptophytes and chamaephytes), short basal, tussock-forming, and clonal
species tended to increase for >10–20 years after management, and declined with management frequency. There was a marked shift
in species and functional composition associated with time since understory management and management frequency. These findings
suggest that widespread fuel management at <10 year intervals may shift understory herb communities to early-successional
stages, impairing the persistence of species and functional groups recovering slowly after disturbance. Fuel management needs
to balance the dual goals of fire hazard reduction and biodiversity conservation, retaining undisturbed patches in landscapes
otherwise managed to reduce fuel accumulation. 相似文献