Characterization of inl + transformants of Neurospora crassa obtained with a recombinant cosmid-pool

Summary We constructed a Neurospora crassa gene library in a cosmid vector and used the cosmid-pool DNA to transform an inl, rg Neurospora crassa strain to inositol prototrophy. The inl⁺ colonies obtained in this experiment proved to be integrative type transformants. Genetic analysis revealed that the integration event occurred at or near the inl locus. In one of the transformants the inl⁺ trait exhibited mitotic and meiotic instability. In hybridization experiments free plasmids were detected in the F₁ progeny of the transformants. We were able to recover eleven different plasmids from the F₁ progeny of the transformants. None of these plasmids proved to carry a functional copy of the inl⁺ gene as judged by its transforming ability. Possible explanations for the observed phenomena are discussed.