An efficient transformation system of taxol-producing endophytic fungus EFY-21 (Ozonium sp.)

EFY-21 (Ozonium sp.) is a newly isolated taxol-producing endophytic fungus from Taxus chinensis var. mairei. In this study, an efficient PEG-mediated transformation of EFY-21 was established and conditions for transformation were evaluated. By the optimized enzyme system, mycelium age, digesting temperature and time, over 7 x 10(7) ml protoplasts were obtained and protoplast regeneration frequency was more than 6%. Plasmid pV2 containing the hygromycin-B phosphotransferase gene driven by a fungal promoter (trpC) was used to transform EFY-21 and 50% PEG with 20 mM Ca2+ was found to be suitable for the transformation. Southern blot analysis revealed that the transforming DNA was successfully integrated into the EFY-21 genome. By the optimized procedure, over two transformants per mu g DNA could be obtained. The establishment of efficient transformation system of taxol-producing endophytic fungus enables us to improve taxol production of the fungus by engineering the taxol biosynthetic pathway genes in the future.