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

Recombination between direct repeats has been studied in Penicillium chrysogenum using strain TD7-88 (lys(-) pyr(+)), which contains two inactive copies 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(+) phenotype was observed at a frequency of 1 in 3.2 x 10(3) viable spores. Two types of deletion events giving rise to lys(+) pyr(-) and lys(-) pyr(-) phenotypes were obtained with different frequencies. Southern analysis revealed that gene conversion occurs mainly as a result of crossing over events that remove the BamHI frameshift mutation present in one of the repeats. In lys(-) 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-disrupted strain was restored. In summary, deletion events in P. chrysogenum tend to favor the restoration of the phenotype and genotype characteristic of the parental non-disrupted strain.