An appropriate increase in the transcription of Aspergillus nidulans uvsC improved gene targeting efficiency.

Gene targeting to knock out the activity of specific genes has become important due to recent progress in genomics research. But this technique is still unavailable for many organisms, including economically important microorganisms, due to the high background of ectopic integration during genetic transformation. Strategies to improve targeting efficiency have included manipulating the expression of genes that are involved in homologous recombination. In this study, transcription of Aspergillus nidulans uvsC was elevated using the promoter sequences of the glyceraldehyde-3-phosphate dehydrogenase and Taka-amylase A genes from A. nidulans and A. oryzea respectively. Although a several-fold increase in the efficiency of targeting was observed at 3 loci, mycelial growth was suppressed in strains that had higher levels of uvsC transcription. These results suggest that uvsC is a rate-limiting factor in gene targeting, and that the increased efficiency of this targeting is hindered by a negative effect of increased transcription on cell proliferation.