FIG. 2.

Relative expression levels of the key genes of penicillin biosynthesis as a function of the genomic copy number of the penicillin cluster. Expression of pcbAB (closed squares), pcbC (closed triangles), penDE (open squares), and phl (open triangles). Transcript levels were normalized with the γ-actin gene, and the expression level in the single-copy strain DS47274 was set at 12.5% to relate to the 8-fold-increased copy number of the P. chrysogenum DS17690 strain. Because of the experimental error in the determination of the expression level in the single-copy strain, the maximum expression levels may scale beyond 100%.