Cloning and assignment of linkage group loci to a karyotypic map of the filamentous fungusAspergillus flavus

Abstract

The purpose of this study was to develop a karyotypic map of A. flavus and assign parasexually defined linkage groups to chromosomes. Seven A. flavus chromosomal bands, ranging in size from 2.3 to 7.0 megabases were separated by clamped homogeneous electric field gel electrophoresis. Polyethylene glycol-mediated transformation of A. flavus with a wildtype cosmid genomic library was used to complement seven strains having auxotrophic mutations in genes mapped to six of the eight linkage groups. DNA from cosmids complementing each of these seven mapped auxotrophic genes was used to make linkage group-specific probes. Hybridization of these probes to chromosomal separations allowed us to assign six linkage groups (I, II, IV, VI, VII, VIII) to five chromosomal bands. In addition, five previously cloned but unmapped genes were located on this karyotypic map and thus assigned to their corresponding linkage groups, i.e., benA, rDNA, pyrG, aflR and adhl to groups I, II, II, VII, and IV or VIII, respectively. This karyotypic map will provide linkage group mapping of most cloned genes without parasexual analysis.