Electrophoretic characterization of Aspergillus nidulans strains with chromosomal duplications

Pulsed-field gel electrophoresis was used to characterize strains of Asperg illus nidulans with a chromosomal duplication Dp(I-II). Morphologically det eriorated and improved Variants of these strains were also analyzed. The el ectrophoretic karyotype demonstrated that in two duplicated strains (A and B) the 4.2 Mb band, which corresponds to chromosome II, was absent and a ne w band was observed. Hybridization studies using the uapA (chromosome I) an d wA (chromosome II) genes demonstrated that the new band corresponded to c hromosome II plus the duplicated segment of chromosome I. The size of the c hromosomal duplication was approximately 1.0 Mb. Analysis of the chromosoma l bands of a morphologically improved strain showed that the duplicated seg ment of chromosome I was completely lost. The morphologically deteriorated variants V9 and V17 had the same karyotype as the duplicated strains. Howev er, the deteriorated variant V5 lost part of chromosome I and had a rearran gement involving chromosome V. This rearrangement may have resulted from th e mutagenic treatment used to obtain the genetic markers. Pulsed-field gel electrophoresis was found to be an excellent tool for locating chromosomal rearrangements.