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  • Title: Co-transformation with autonomously-replicating helper plasmids facilitates gene cloning from an Aspergillus nidulans gene library.
    Author: Gems DH, Clutterbuck AJ.
    Journal: Curr Genet; 1993 Dec; 24(6):520-4. PubMed ID: 8299174.
    Abstract:
    Autonomously-replicating, marker-less "helper" plasmids were added to transformations of Aspergillus nidulans with plasmids which normally transform by chromosomal integration. This resulted in as much as a 200-fold increase in transformation efficiency. Recovery of autonomously-replicating plasmid co-integrates indicated that co-transformation involves recombination between integrating and helper plasmids, which occurs at a high frequency. Increasing DNA sequence-homology between pairs of plasmids used in simultaneous transformations enhanced co-transformation efficiency. Using helper plasmids and an A. nidulans gene library in a normally-integrating vector, the genes adC and adD were cloned as part of such a co-integrate. In effect, the addition of helper plasmid converts an integrating into an autonomously-replicating gene library in vivo.
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