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An attempt was made to transform Alternaria alternata protoplasts using a plasmid vector, pDH25, bearing the Escherichia coli hygromycin B (Hy) phosphotransferase gene (hph) under the control of the Aspergillus nidulans trpC promoter. Transformants arose on a selective medium containing 100 μg Hy/ml. There were two types of transformants, forming large and small colonies on the selective medium. Transformation with one μg of the vector produced an average of 4.5 large colonies and 600 small ones. In large-colony transformants, the vector often integrated into the recipient chromosome in the form of highly rearranged tandem arrays. To increase transformation efficiency, fragments of the highly repetitive ribosomal RNA gene cluster (rDNA) of A. alternata were used to construct four new vectors for homologous recombination system. Use of these vectors gave higher transformation efficiency than the original plasmid. The best vector, pDH25r1a, gave rise to large-colony transformants at a frequency 20 times higher than pDH25. Transformation events in A. alternata with pDH25r1a occured by homologous recombination as a single crossover between the plasmid-borne rDNA segment and its homologue in the chromosome, often giving rise to tandemly repeated vector DNA.  相似文献   
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Rhizobial symbiosis is known to increase the nitrogen availability in the rhizosphere of legumes. Therefore, it has been hypothesized that other plants’ roots should forage towards legume neighbours, but avoid non-legume neighbours. Yet, root distribution responding to legume plants as opposed to non-legumes has not yet been rigorously tested and might well be subject to integration of multiple environmental cues.In this study, wedevised an outdoor mesocosm experiment to examine root distributions of the two plant species Pilosella officinarum and Arenaria serpyllifolia in a two-factorial design. While one factor was ‘neighbour identity’, where plants were exposed to different legume or non-legume neighbours, the other factor was ‘nitrogen supply’. In the latter the nutrient-poor soil was supplemented with either nitrogen-free or with nitrogen-containing fertilizer.Unexpectedly, of all treatments that included a legume neighbour (eight different species or factor combinations), we found merely one case of root aggregation towards a legume neighbour (P. officinarum towards Medicago minima under nitrogen-fertilized conditions). In this very treatment, also P. officinarum root–shoot allocation was strongly increased, indicating that neighbour recognition is coupled with a contesting strategy.Considering the various response modes of the tested species towards the different legume and non-legume neighbours, we can conclude that roots integrate information on neighbour identity and resource availability in a complex manner. Especially the integration of neighbour identity in root decisions must be a vital aptitude for plants to cope with their complex biotic and abiotic environment in the field.  相似文献   
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Using filtration enrichment techniques, an Aspergillus terreus arginine auxotrophic strain which contains a mutation that abolishes ornithine transcarbamylase (OTCase) activity has been isolated. This mutant has been genetically transformed with the cloned Aspergillus nidulans OTCase gene. Prototrophic transformants arose at a frequency of about 50 transformants per microgram of plasmid DNA. Southern blot analysis of DNA from the transformants showed that the transforming DNA was ectopically integrated at different locations in the A. terreus genome, often in multiple tandem copies. The transformants were phenotypically stable for several mitotic divisions and retained their capacity to produce extracellular enzymes.  相似文献   
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Yield of the clonal plant Glechoma hederacea was compared at different spatial scales, in heterogeneous and homogeneous environments providing the same amount of nutrients. For the heterogeneous treatments, environments were created with different patch sizes and different degrees of contrast in nutrient concentration between patches of different quality. Total clone yield differed by almost 2.5-fold across treatments, being highest in environments with large patches and high contrast, lowest in environments with small patches and high contrast, and intermediate under homogeneous conditions. Compared with plants in homogeneous conditions, there were significant increases or decreases in yield at all scales of measurement in many of the heterogeneous treatments. These effects on yield reflected a combination of local responses to growing conditions and modification of these responses due to physiological integration with other parts of the plant growing in contrasting conditions, supporting the proposal of de Kroon et al. (2005 New Phytol 166:73–82). The results show that plant yield at all scales is strongly dependent on environmental context, and that maximum yield can only be realized under a limited range of heterogeneous conditions.  相似文献   
6.
Publicly-accessible resources have promoted the advance of scientific discovery. The era of genomics and big data has brought the need for collaboration and data sharing in order to make effective use of this new knowledge. Here, we describe the web resources for cancer genomics research and rate them on the basis of the diversity of cancer types, sample size, omics data comprehensiveness, and user experience. The resources reviewed include data repository and analysis tools; and we hope such introduction will promote the awareness and facilitate the usage of these resources in the cancer research community.  相似文献   
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Pervasive migration of organellar DNA to the nucleus in plants   总被引:1,自引:0,他引:1  
A surprisingly large number of plant nuclear DNA sequences inferred to be remnants of chloroplast and mitochondrial DNA migration events were detected through computer-assisted database searches. Nineteen independent organellar DNA insertions, with a median size of 117 by (range of 38 to >785 bp), occur in the proximity of 15 nuclear genes. One fragment appears to have been passed through a RNA intermediate, based on the presence of an edited version of the mitochondrial gene in the nucleus. Tandemly arranged fragments from disparate regions of organellar genomes and from different organellar genomes indicate that the fragments joined together from an intracellular pool of RNA and/or DNA before they integrated into the nuclear genome. Comparisons of integrated sequences to genes lacking the insertions, as well as the occurrence of coligated fragments, support a model of random integration by end joining. All transferred sequences were found in noncoding regions, but the positioning of organellar-derived DNA in introns, as well as regions 5 and 3 to nuclear genes, suggests that the random integration of organellar DNA has the potential to influence gene expression patterns. A semiquantitative estimate was performed on the amount of organellar DNA being transferred and assimilated into the nucleus. Based on this database survey, we estimate that 3–7% of the plant nuclear genomic sequence files contain organellar-derived DNA. The timing and the magnitude of genetic flux to the nuclear genome suggest that random integration is a substantial and ongoing process for creating sequence variation.Correspondence to: J.L. Blanchard  相似文献   
9.
For two years (2002, 2003) selective feeding ecology of the common carp (Cyprinus carpio L.) has been studied in carp-integrated rice fields in Apatani Plateau of Arunachal Pradesh (India). Sampling strategy was based on the water depths in the fields and on the flood phases: early flood phase (June–July), mid flood phase (July–August), and late flood phase (September–October). In 2003 the water level was higher and therefore periphyton availability was better. This resulted in larger gut contents and better growth of the carp compared with 2002 when the water levels were lower. Gut contents analyses revealed a total of 60 food items of which 22 belonged to the Chlorophycea, 12 to the Cyanobacteria, 10 to the Bacillariophycea and 16 to several zooplankton taxa. With the progress of flood phases, the fish increased its feeding on periphyton food items; simultaneously, feeding on plankton items gradually declined. This was caused by the increasing periphyton availability on the rice-stems. Selective feeding on plankton and periphyton taxa was studied, selectivity changed with the flood phases. Periphytic Chlorophycea and Cyanobacteria, especially, were strongly positively selected. Generally, periphyton was the most important resource for the common carp in the rice fields.  相似文献   
10.
A unique transgenic mouse line has undergone transgene integration in a very precise fashion. The phenotype displayed by mice of the line followed the predicted inheritance patterns for X-linked transgene insertion which has been confirmed. In order to investigate the mechanism of integration the DNA sequence of the transgene and cellular junctions have been determined. A comparison between wild type and transgenic mutant sequences at the site of insertion revealed that there was no loss or rearrangement of cellular DNA upon integration of the transgene. The cellular sequences at the transgene 5 and 3 joins are contiguous in the wild type. The integrant exists as a head to tail tandem dimer with minimal loss of sequence compared with the injected monomer. Analysis of the site of insertion has revealed a 5 bp homology between the 5 end of the transgene and the cellular sequences. In addition, adjacent to the site of insertion within the cellular sequences, there are several sequence motifs implicated in recombination events including a clustering of strong consensus sites for DNA topoisomerase type I and a region of homology to the human minisatellite consensus core sequence, theEscherichia coli Chi site and the meiotic recombination hotspot within the E gene of the murine major histocompatibility complex. This clustering of features is likely to have been factorial in the integrity of the insertion event. A model depicting the mechanism of this precise integration is proposed.  相似文献   
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