Altered expression of the steroid bioconverting pathway in pAN 7-1 transformants of Cochliobolus lunatus.

The filamentous fungus C. lunatus converts progesterone mainly to its 11 beta-hydroxy derivative. C. lunatus transformed with the plasmid pAN 7-1, which contains the E. coli hph gene expressed under the control of the A. nidulans gpd and trpC expression signals, lacks this activity, but exhibits acetyl side chain degradation of progesterone through the reaction scheme progesterone----20 beta-hydroxy-progesterone----delta 4-androstene-3,17-dione---- testolactone + testosterone. The main part of this metabolic pathway is not expressed in the non-transformed strain. It was determined that the site-specific integration of the plasmid into the genome directly influences the expression of genes involved in the bioconversion of steroids.