ABSTRACT
Taxa-4(5),11(12)-diene is the precursor for paclitaxel biosynthesis. The diterpenoid paclitaxel (marketed as Taxol), a plant secondary metabolite isolated from yew, is an effective drug widely used in the treatment of numerous cancers. However, further application of taxol has been restricted due to its low yield in plants and the difficulties in extraction. To increase the intact isoprene flux, we constructed the fusion gene plasmid pBgGGTS and individual cassette plasmid pBgGGgTS to enhance the expression levels of geranylgeranyl diphosphate synthase gene (ggpps) and a taxadiene synthase gene (ts) in Coprinopsis cinerea. These two plasmids were separately transformed into C. cinerea LT2 strain, resulting in several putative transformants. Putative transformants were determined by PCR technique, indicating that 5 out of 13 putative transformants transformed by pBgGGTS and 6 out of 13 putative transformants transformed by pBgGGgTS, respectively. Additionally, the Southern blotting analysis of these 10 transformants confirmed that both ggpps and ts gene were stably integrated into the genome of C. cinerea. Crude extracts from each of the transformants were analyzed. There is no difference in the mycelium extracts among the wild-type LT2 and two types of transformants. However, analysis of culture filtrates indicated that an additional GC peak was found at the retention time of 16.762 min which was absent in the wild type control. The mass fragmentation pattern of this peak had the same diagnostic ions with taxa-4(5),11(12)-diene. According to peak area, the amounts of taxa-4(5),11(12)-diene in each fermented broth were 44 ng/L (transformed with pBgGGgTS) and 30 ng/L (transformed with pBgGGTS), respectively. In conclusion, co-expression of the ggpps and ts gene could increase the taxadiene production in C. cinerea.