RESUMO
BACKGROUND: Genetic interactions within hybrids influence their overall fitness. Understanding the details of these interactions can improve our understanding of speciation. One experimental approach is to investigate deviations from Mendelian expectations (segregation distortion) in the inheritance of mapped genetic markers. In this study, we used the copepod Tigriopus californicus, a species which exhibits high genetic divergence between populations and a general pattern of reduced fitness in F2 interpopulation hybrids. Previous studies have implicated both nuclear-cytoplasmic and nuclear-nuclear interactions in causing this fitness reduction. We identified and mapped population-diagnostic single nucleotide polymorphisms (SNPs) and used these to examine segregation distortion across the genome within F2 hybrids. RESULTS: We generated a linkage map which included 45 newly elucidated SNPs and 8 population-diagnostic microsatellites used in previous studies. The map, the first available for the Copepoda, was estimated to cover 75% of the genome and included markers on all 12 T. californicus chromosomes. We observed little segregation distortion in newly hatched F2 hybrid larvae (fewer than 10% of markers at p < 0.05), but strikingly higher distortion in F2 hybrid adult males (45% of markers at p < 0.05). Hence, segregation distortion was primarily caused by selection against particular genetic combinations which acted between hatching and maturity. Distorted markers were not distributed randomly across the genome but clustered on particular chromosomes. In contrast to other studies in this species we found little evidence for cytonuclear coadaptation. Instead, different linkage groups exhibited markedly different patterns of distortion, which appear to have been influenced by nuclear-nuclear epistatic interactions and may also reflect genetic load carried within the parental lines. CONCLUSION: Adult male F2 hybrids between two populations of T. californius exhibit dramatic segregation distortion across the genome. Distorted loci are clustered within specific linkage groups, and the direction of distortion differs between chromosomes. This segregation distortion is due to selection acting between hatching and adulthood.
Assuntos
Copépodes/genética , Hibridização Genética , Padrões de Herança , Polimorfismo de Nucleotídeo Único , Animais , Núcleo Celular/genética , Mapeamento Cromossômico/métodos , Cromossomos/genética , Cruzamentos Genéticos , Feminino , Biblioteca Gênica , Loci Gênicos , Genoma , Genótipo , Larva/genética , Masculino , Repetições de Microssatélites , Mitocôndrias/genética , Seleção Genética , Comportamento Sexual AnimalRESUMO
A qualidade microbiológica de produtos vegetais constitui atributo essencial para seu desempenho adequado. Neste estudo, foram avaliadas 27 amostras de três espécies vegetais: ginko biloba (Ginkgo biloba), cáscara sagrada (Rhamnus purshiana) e sene (Cassiaangustifolia). O método utilizado foi o de semeadura em profundidade (pour plate) e foram realizadas contagens em placas de Petri com meios seletivos e pesquisa de microrganismos específicos, de acordo com a Organização Mundial da Saúde (OMS). A contaminação bacterianavariou de 0,5 x 101 a 9,0 x 104 unidades formadoras de colônia (UFC)/g, estando todas as amostras em conformidade com a OMS e 5 (18,5 por cento), acima dos limites permitidos pela Farmacopéia Brasileira (FB). A contaminação fúngica variou de 0,5 x 101 a 8,45 x 104 UFC/g, com 6 (22,2 por cento) amostras acima dos limites da OMS e 9 (33,3 por cento) acima dos limites da FB. Foi confirmada a presença de Escherichia coli em 2 (7,4 por cento) amostras e Staphylococcus aureus em 6 (22,2 por cento). Considerando as recomendações da OMS, 22,2 por cento das matérias-primas analisadas foram consideradas insatisfatórias para o consumo e, de acordo com a FB, 37 das amostras apresentaram populações bacterianase fúngicas acima do tolerável, ou continham bactérias não aceitas. Os resultados apontam para a necessidade de controle microbiológico mais rigoroso das drogas vegetais.
The microbiological quality of vegetal products constitutes one of the essential attributes for its adequate performance. In this study, 27 vegetal raw material samples of three species, Ginkgo biloba, Rhamnus purshiana and Cassia angustifolia, were evaluated.The method utilized was pour plate plating and colony counts in Petri dishes with selective medium and investigation of specific microorganism were carried out in accordance with the World Health Organization (WHO). Bacterial contamination varied from 0.5 x 101 to 9.0 x 104 colony-forming units (CFU)/g, all samples in accordance with WHO and 5 (18.5 percent), above the limits allowed by the Brazilian Pharmacopoeia(FB). Fungal contamination varied from 0.5 x 101 to 8.45 x 104 CFU/g, with 6 (22.2 percent) samples above of the limits of WHO and 9 (33.3 percent) above of the limits of the FB. Presence of Escherichia coli in 2 (7.4 percent) and Staphylococcus aureus in 6 (22.2 percent) was confirmed.Considering the recommendations of WHO, 22.2 percent of the analyzed raw materials were considered unsatisfactory for consumption, and, inaccordance with the FB, 37 percent of the samples presented bacterial and fungal populations either above the tolerated or contained unaccepted bacteria. The results point out to the need for more rigorous microbiological control of herbal drugs.
