@entity2340 auxotrophic mutants in XXXX : inactivation of the trpC gene by cotransformation mutagenesis.

@entity526 @entity2340 @entity11150 @entity3456
@entity11150 @entity2340 auxotrophic mutants have been isolated after UV irradiation of conidiospores. The mutants belong to two different complementation groups, trpA and trpB, which complement each other in heterokaryons. Neither of the mutations could be complemented with the cloned A. @entity3456 trpC gene. To obtain A. @entity3456 trpC mutants in a direct way, gene inactivation by cotransformation was performed. For this purpose an in-frame gene fusion between the A. @entity3456 trpC and @entity526 lacZ genes was constructed and shown to be functionally expressed after introduction into A. @entity3456 by cotransformation with the pyrA gene as selective marker. Among the beta-galactosidase expressing cotransformants, obtained with either circular or linearized vectors, no trpC mutants were detected, even after enrichment. Such mutants, however, could be obtained by cotransformation of A. @entity3456 with specific fragments of the fusion gene. Biochemical analysis of the cotransformants indicated that in nearly all cases the fusion gene had replaced the wild-type trpC gene. Genetic analysis showed that the trpC mutation is not linked to any of the A. @entity3456 loci described so far. The trpC mutants can be complemented by the cloned A. @entity3456 trpC gene as well as by the A. nidulans trpC gene.
