FIGURE 4.

Expression of rhodomycin methylesterase gene in G001 results in the production of N,N-dimethyldaunorubicin. (A) Schematic representation of the relevant genotype of the strains used in this experiment, with heterologous genes indicated by a diagonal striped pattern. (B) LC-MS analysis of crude extracts of G001, MAG304 and MAG305 cultivated in E1 medium. Extracted ion chromatograms showing the mass peaks [M + H]⁺ of compounds 3–7 and 9–12. (C) Schematic representation of the proposed biosynthetic pathway for N,N-dimethyldoxorubicin (12). Introduction of the 15-methylesterase gene rdmC from the rhodomycin BGC resulted in the production of N,N-dimethyl-13-deoxydaunorubicin (9) and N,N-dimethyl-13-dihydrodaunorubicin (10). A minor peak was detected for N,N-dimethyldaunorubicin (11), but N,N-dimethyldoxorubicin (12) could not be detected.