Agrobacterium-mediated transformation leads to improved gene replacement efficiency in Aspergillus awamori.

In this study, the efficiency of gene replacement in Aspergillus awamori between Agrobacterium-mediated transformation and CaCl2/PEG-mediated transformation was compared. For the genes, pyrG and gfaA, it was found that the homologous recombination frequencies obtained by Agrobacterium-mediated transformation were 3- to 6-fold higher than the frequencies obtained with CaCl2/PEG protoplast transformation. For the pyrG gene, it was found that Agrobacterium-mediated transformation allowed an efficient homologous recombination with shorter DNA flanks than CaCl2/PEG protoplast transformation. Finally, the addition of the dominant amdS marker as a second selection marker to the gene replacement cassette led to a further 2-fold enrichment in transformants with gene replacement events, resulting in a gene replacement frequency of 55%. Based on the data it can be concluded that Agrobacterium-mediated transformation is an efficient tool for gene replacement and that the amdS gene can be successfully used as a second selection marker to select transformants with putative gene replacement.