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  • 1
    Electronic Resource
    Electronic Resource
    Mitotic stability of transforming DNA is determined by its chromosomal configuration in the fungus Cochliobolus heterostrophus (1991)
    Springer
    Current genetics 19 (1991), S. 227-233 
    Details
    ISSN: 1432-0983
    Keywords: Cochliobolus ; Transformation ; DNA instability ; Homologous recombination ; Ectopic integration ; DNA methylation ; Plant disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cochliobolus heterostrophus was transformed with a plasmid (pH1S) containing a bacterial gene (hygB), which confers resistance to the antibiotic hygromycin B when under control of an 838-bp fragment of promoter 1 from C. heterostrophus. The plasmid integrated at either homologous (52% single copy, 33% tandemly repeated copies) or ectopic (4% single copy, 11% tandemly repeated copies) sites on different chromosomes, resulting in four distinct configurations of integrated DNA. All four configurations were highly stable during mitotic growth; virtually no loss of integrated DNA was detected after five subcultures on nonselective medium or after seven cycles of pathogenesis on maize, the normal host of this fungus. However, deletion of integrated DNA was detected after eight or more disease cycles. The frequency of deletion depended on the configuration of the recombinant chromosome. A single copy of pH1S integrated at an homologous site was flanked by direct repeats of the target sequence and was least stable; up to 50% of the population lacked integrated DNA after 12 disease cycles. A single copy integrated at an ectopic site had no repeated DNA directly associated with it and was the most stable; no deletions were detected after 12 disease cycles. Tandemly repeated copies of pH1S integrated at either homologous or ectopic sites appeared to have intermediate stability; 2–18% of each population lost at least one copy after 12 disease cycles, although in no case were all copies deleted. Cytosine residues of integrated DNA were methylated during mitotic growth, but this had no apparent effect on the expression of hygB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336491
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  • 2
    Electronic Resource
    Electronic Resource
    Variable electrophoretic karyotypes of members of Aspergillus Section Flavi (1992)
    Springer
    Current genetics 21 (1992), S. 371-375 
    Details
    ISSN: 1432-0983
    Keywords: Electrophoretic karyotyping ; Aspergillus Section Flavi ; Chromosome length polymorphisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Contour-clamped homogeneous electric field gel electrophoresis was used to establish karyotypes for fungi of Aspergillus Section Flavi. Under identical electrophoretic conditions, five to eight chromosomal bands were separated in Aspergillus flavus isolates and five to seven chromosomal bands in A. parasiticus isolates. Each distinct chromosomal band contained one or more chromosomes. Other members of Aspergillus Section Flavi (A. oryzae, A. sojae, and A. tamarii) had similar karyotypes to those of A. flavus and A. parasiticus. A related species, A. versicolor, showed six chromosomal bands. With the exception of small chromosomes present in some isolates, the estimated sizes of chromosomes for all six species range from approximately 3.0 to ≥7.0 Mb. It is likely that all isolates of these species contain the same number of large (〉3 Mb) chromosomes; however, not all of the chromosomal bands could be resolved into separate chromosomes for each isolate due to chromosome length polymorphisms. This variability, observed in A. flavus and A. parasiticus, generated unique chromosomal band patterns within these species. The total genome sizes of these fungi were at least as large as those reported for A. nidulans and A. niger (31–38.5 Mb). Conserved genes were mapped to analogous chromosomes of A. flavus and A. parasiticus by gene hybridization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351697
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    Paper (German National Licenses)
    Fulltext
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