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991.
Genetic diversity and differentiation in Portuguese cattle breeds using microsatellites 总被引:1,自引:0,他引:1
Genotype data from 30 microsatellites were used to assess genetic diversity and relationships among 10 native Portuguese cattle breeds, American Charolais and the Brazilian Caracú. Hardy–Weinberg equilibrium was observed for all loci/population combinations except for five loci in Brava de Lide and one locus in Alentejana that exhibited heterozygote deficiency. Estimates of average observed and expected heterozygosities, total number of alleles (TNA) per breed and mean number of alleles (MNA) per locus/population were obtained. A total of 390 alleles were detected. TNA among Iberian cattle ranged from 170 to 237 and MNA ranged from 5.67 to 8.07. The highest observed heterozygosities were found in the Caracú, Maronesa, Garvonesa and Arouquesa and the lowest in Brava de Lide and Mirandesa. Estimation of population subdivision using Wright's FST index showed that the average proportion of genetic variation explained by breed differences was 9%. Neighbour‐joining phylogenetic trees based on DA distances showed that the genetic relationships of present‐day Portuguese native breeds are consistent with historical origins in the Brown Concave (Arouquesa, Mirandesa, Marinhoa) and Red Convex (Mertolenga, Alentejana, Garvonesa, Minhota) evolutionary groups. The Iberian Black Orthoide group, represented by Brava de Lide and Maronesa, and the Barrosã breed appeared to be more closely related to the Brown Concave group but may represent a separate lineage. The Caracú breed was not found to be closely associated with any of the native Portuguese breeds. 相似文献
992.
As part of our efforts to characterize Na,K-ATPase isoforms in salmonid fish, we investigated the linkage arrangement of genes coding for the alpha and beta-subunits of the enzyme complex in the tetraploid-derived genome of the rainbow trout (Oncorhynchus mykiss). Genetic markers were developed from four of five previously characterized alpha-subunit isoforms (alpha1b, alpha1c, alpha2 and alpha3) and four expressed sequence tags derived from yet undescribed beta-subunit isoforms (beta1a, beta1b, beta3a and beta3b). Sex-specific linkage analysis of polymorphic loci in a reference meiotic panel revealed that Na,K-ATPase genes are generally dispersed throughout the rainbow trout genome. A notable exception was the colocalization of two alpha-subunit genes and one beta-subunit gene on linkage group RT-12, which may thus share a conserved orthologous segment with linkage group 1 in zebrafish (Danio rerio). Consistent with previously reported homeologous relationships among the chromosomes of the rainbow trout, primers designed from the alpha3-isoform detected a pair of duplicated genes on linkage groups RT-27 and RT-31. Similarly, the evolutionary conservation of homeologous regions on linkage groups RT-12 and RT-16 was further supported by the map localization of gene duplicates for the beta1b isoform. The detection of homeologs within each gene family also raises the possibility that novel isoforms may be discovered as functional duplicates. 相似文献
993.
Sargent DJ Geibel M Hawkins JA Wilkinson MJ Battey NH Simpson DW 《Annals of botany》2004,94(6):787-796
BACKGROUND AND AIMS: The aims of this investigation were to highlight the qualitative and quantitative diversity apparent between nine diploid Fragaria species and produce interspecific populations segregating for a large number of morphological characters suitable for quantitative trait loci analysis. METHODS: A qualitative comparison of eight described diploid Fragaria species was performed and measurements were taken of 23 morphological traits from 19 accessions including eight described species and one previously undescribed species. A principal components analysis was performed on 14 mathematically unrelated traits from these accessions, which partitioned the species accessions into distinct morphological groups. Interspecific crosses were performed with accessions of species that displayed significant quantitative divergence and, from these, populations that should segregate for a range of quantitative traits were raised. KEY RESULTS: Significant differences between species were observed for all 23 morphological traits quantified and three distinct groups of species accessions were observed after the principal components analysis. Interspecific crosses were performed between these groups, and F2 and backcross populations were raised that should segregate for a range of morphological characters. In addition, the study highlighted a number of distinctive morphological characters in many of the species studied. CONCLUSIONS: Diploid Fragaria species are morphologically diverse, yet remain highly interfertile, making the group an ideal model for the study of the genetic basis of phenotypic differences between species through map-based investigation using quantitative trait loci. The segregating interspecific populations raised will be ideal for such investigations and could also provide insights into the nature and extent of genome evolution within this group. 相似文献
994.
Genome scans of DNA variability in humans reveal evidence for selective sweeps outside of Africa 总被引:17,自引:0,他引:17
The last 50,000-150,000 years of human history have been characterized by rapid demographic expansions and the colonization of novel environments outside of sub-Saharan Africa. Mass migrations outside the ancestral species range likely entailed many new selection pressures, suggesting that genetic adaptation to local environmental conditions may have been more prevalent in colonizing populations outside of sub-Saharan Africa. Here we report a test of this hypothesis using genome-wide patterns of DNA polymorphism. We conducted a multilocus scan of microsatellite variability to identify regions of the human genome that may have been subject to continent-specific hitchhiking events. Using published polymorphism data for a total of 624 autosomal loci in multiple populations of humans, we used coalescent simulations to identify candidate loci for geographically restricted selective sweeps. We identified a total of 13 loci that appeared as outliers in replicated population comparisons involving different reference samples for Africa. A disproportionate number of these loci exhibited reduced levels of relative variability in non-African populations alone, suggesting that recent episodes of positive selection have been more prevalent outside of sub-Saharan Africa. 相似文献
995.
Effect of light on the organogenic ability of garlic roots using a one-step in vitro system 总被引:3,自引:0,他引:3
A simple and efficient garlic in vitro shoot regeneration protocol has been developed. This system uses axenic root tips cultivated from the beginning in the presence of light and does not require any change or refreshing of the original medium during the entire process. The application of light from the beginning of the culture process did not affect the callus formation rate but did significantly improve the explant regeneration ability. In a 2-month period it was possible to obtain up to 250 shoots per gram of callus.Abbreviations
BAP:
6-Benzylaminopurine
-
2,4-D:
2,4-Dichlorophenoxyacetic acid
-
NAA:
-Naphthaleneacetic acid
Communicated by L. Peña 相似文献
996.
Productivity variations and seasonal fluctuations of cardenolides have been studied in 10 natural populations of Digitalis obscura distributed in three bioclimatic belts. Main cardenolides in D. obscura plants are those of the series A and such predominance (ca. 80-85%) over the series B metabolites is independent of the population studied or the degree of maturity of the leaves. Primary glycosides represent ca. 50-60% of total cardenolides; this percentage did not vary among populations or with the leaf age but increased in summer and decreased in winter. A correlation analysis between plant biomass and cardenolide content showed a positive relationship of these parameters, which, according to the bioclimatic distribution of the populations, suggests that certain environmental conditions may cause marked decreases in plant biomass together with a reduction in productivity. Cardenolide contents changed in the timecourse of the four seasons as a multiple response to distinct plant and/or environmental factors. The lowest production was recorded in May, followed by a fast cardenolide accumulation in summer, a decreasing phase in autumn, and a stationary phase in winter. We also analysed the seasonal expression of the gene encoding the progesterone 5beta-reductase, enzyme producing the required 5beta-configured intermediaries of cardenolides. A fragment of the isolated partial genomic sequence was used as a probe for Northern analysis to study the seasonal gene expression in selected populations. The expression pattern showed increasing levels from February to July and a further reduction in autumn, although harmful climatic conditions seems to induce overexpression of this gene. 相似文献
997.
Three antibiotics were evaluated for their effects on the elimination of Agrobacterium tumefaciens during the genetic transformation of loblolly pine ( Pinus taeda L.) using mature zygotic embryos as targets. Agrobacterium tumefaciens strains, EHA105, GV3101, and LBA 4404, all harbouring the plasmid pCAMBIA1301, which carries the selectable marker gene, hygromycin phosphotransferase ( hpt) controlled by the cauliflower mosaic virus 35S promoter and terminator, and the uidA reporter gene (GUS) driven by the cauliflower mosaic virus 35S promoter and the terminator of nopaline synthase gene, were used in this study. Exposure to 350 mg l-1 carbenicillin, claforan, and timentin respectively for up to 6 weeks did not eliminate the Agrobacterium, while antibiotics at 500 mg l-1 eradicated them from the co-cultivated zygotic embryos. All three antibiotics increased callus growth and shoot regeneration at 350 and 500 mg l-1 each, but reduced callus growth and shoot regeneration at 650 mg l-1 when compared with controls. Putative transgenic calli were selected for continued proliferation and differentiation on 4.5 mg l-1 hygromycin-containing medium. Transformed calli and transgenic plants produced on a selection medium containing 4.5 mg l-1 hygromycin were confirmed by GUS histochemical assays, by polymerase chain reaction (PCR), and by Southern blot analysis. These results are useful for future studies on optimizing genetic transformation procedures in loblolly pine. 相似文献
998.
We aim at studying adaptation to genetic and environmental stress and its evolutionary implications at different levels of
biological organization. Stress influences cellular processes, individual physiology, genetic variation at the population
level, and the process of natural selection. To investigate these highly connected levels of stress effects, it is advisable
- if not critical - to integrate approaches from ecology, evolution, physiology, molecular biology and genetics. To investigate
the mechanisms of stress resistance, how resistance evolves, and what factors contribute to and constrain its evolution, we
use the well-defined model systems ofDrosophila species, representing both cosmopolitan species such asD. melanogaster with a known genome map, and more specialized and ecologically well described species such as the cactophilicD. buzzatii. Various climate-related stresses are used as model stresses including desiccation, starvation, cold and heat. Genetic stress
or genetic load is modelled by studying the consequences of inbreeding, the accumulation of (slightly) deleterious mutations,
hybridization or the loss of genetic variability. We present here a research plan and preliminary results combining various
approaches: molecular techniques such as microarrays, quantitative trait loci (QTL) analyses, quantitative PCR, ELISA or Western
blotting are combined with population studies of resistance to climatic and genetic stress in natural populations collected
across climatic gradients as well as in selection lines maintained in the laboratory. 相似文献
999.
Exploiting dendritic cells for cancer immunotherapy: genetic modification of dendritic cells 总被引:5,自引:0,他引:5
Dendritic cells (DCs) are pivotal regulators of immune reactivity and immune tolerance. The observation that DCs can recruit naive T cells has invigorated cancer immunology and led to the proposal of DCs as the basis for vaccines designed for the treatment of cancer. Designing effective strategies to load DCs with antigens is a challenging field of research. The successful realization of gene transfer to DCs will be highly dependent on the employed vector system. Here, we review various viral and non-viral gene transfer systems, and discuss their distinct characteristics and possible advantages and disadvantages in respect to their use in DC-based immunotherapy. 相似文献
1000.
Richard?MeilanEmail author Maurizio?Sabatti Caiping?Ma Elena?Kuzminsky 《Journal of Plant Biology》2004,47(1):52-56
Unlike herbaceous, annual crops, trees are not highly domesticated and, therefore, have wild relatives with which they are
interfertile. They are also long-lived perennials that produce copious amounts of pollen and seed, which are often disseminated
over considerable distances by the wind. Federal regulators have made it clear that before transgenic trees can be grown commercially
in the U.S., it will be necessary to develop a strategy to mitigate the risk of transgene spread into the environment. One
way to satisfy this requirement is to genetically engineer reproductive sterility. Because of its many useful attributes,
poplar has becomethe model tree species for research community. However, because of its relatively long juvenile period, the development of a
reliable sterility system for poplar is taking longer than expected. By having an early-flowering genotype of poplar, it will
be possible to make much faster progress in our efforts to develop a reliable transgene-confinement system. We have identified
a genotype ofPopulus alba that can be induced to flower within nine months of being regenerated. 相似文献