Intrachromosomal recombination between direct repeats in Penicillium chrysogenum: gene conversion and deletion events

Recombination between direct repeats has been studied in Penicillium chryso genum using strain TD7-88 (lys(-) pyr(+)), which contains two inactive copi es of the lys2 gene separated by 4.5 kb of DNA (including the pyrG gene) in its genome. Gene conversion leading to products with the lys(+) pyr(+) phe notype was observed at a frequency of 1 in 3.2 x 10(3) viable spores. Two t ypes of deletion events giving rise to lys(+) pyr(-) and lys(-) pyr(-) phen otypes were obtained with different frequencies. Southern analysis revealed that gene conversion occurs mainly as a result of crossing over events tha t remove the BamHI frameshift mutation present in one of the repeats. In ly s(-) pyr(-) recombinants, the deletion events do not affect the frameshift mutation in the BamHI site, while lys(+) pyr(-) recombinants showed repair of the BamHI frameshift mutation and the genotype of the parental non-disru pted strain was restored. In summary, deletion events in P. chrysogenum ten d to favor the restoration of the phenotype and genotype characteristic of the parental non-disrupted strain.