Transcript analysis of penicillin genes from Penicillium chrysogenum

Abstract

The presence of a transcriptional control simultaneously affecting the expression of the three penicillin biosynthetic genes, pcbAB, pcbC, and penDE (pen genes), was demonstrated in Penicillium chrysogenum. Using probes specific to each gene, it was observed that the highest level of expression of the pen genes occurred during exponential growth, in both the original ancestral strain (NRRL1951) and a high-penicillin producing strain P2. Expression also occurred in the presence of high concentrations of glucose, indicating that carbon catabolite repression was not directly involved in the regulation. Transcription of the pen genes appeared to cease as the growth rate decreased. Growth was limited in a fermenter by the rate of oxygen transfer. The phosphoglycerate kinase gene (pgk), used as a control, was strongly induced by the reduced oxygen levels, suggesting a stress-related response. By maintaining optimum growth conditions in fermenters, no induction of the pgk gene was observed whereas expression of the pen genes could be maintained. It was also possible to re-establish expression of the pen genes, after normal cessation, by the addition of cycloheximide to the culture medium.

Development of a Saccharomyces cerevisiae Strain with Enhanced Resistance to Phenolic Fermentation Inhibitors in Lignocellulose Hydrolysates by Heterologous Expression of Laccase

“…More recently, a slight increase (ratio, 1.3) in expression of PGK1 under anaerobic conditions compared to aerobic conditions was found by using glucose-limited chemostat cultures of S. cerevisiae (27). Moreover, the gene encoding phosphoglycerate kinase in Penicillium chrysogenum has previously been reported to be induced by decreased oxygen levels (19), and the same effect has been observed in mammalian cells (11,22). This possible explanation deserves to be investigated further, considering that heterologous proteins are often expressed in S. cerevisiae under control of the PGK1 promoter and under aerobic conditions.…”

Oxygen-regulated control elements in the phosphoglycerate kinase 1 and lactate dehydrogenase A genes: similarities with the erythropoietin 3' enhancer.

“…Substantial increase in PGK mRNA levels in an hypoxic environment has been found in Penicillium (30); levels of LDH mRNA increase in cereal roots in response to reduced oxygen tension (31); in bacteria, both glycolytic enzymes and the cytosolic form of LDH operative in fermentation can be induced under anaerobic conditions (32). Given that the ability to respond to changes in oxygen tension is fundamental and seems in the cases ofthe PGK and LDH genes to have been preserved in evolution, the possibility is raised that the oxygen-regulated control system first described in the context of Epo biology may not only act on a wide variety of genes in mammalian cells but also have an equivalent in more primitive species.…”

Biotechnical Genetics of Antibiotic Biosynthesis

“…In A. nidulans, an acvA transcript was observed in cells grown in fermentation medium but not in cells grown in minimal medium (MacCabe et al 1990). In P. chrysogenum, levels of acvA mRNA accumulated during a fermentation run and correlated with the production of penicillin (Renno et al 1992), suggesting that the acvA gene expression is, at least in part, regulated at the level of mRNA. reported the construction of translational fusions of the A. nidulans acvA and ipnA genes with different reporter genes.…”

“…acvA had four to seven times lower expression than did ipnA ). The expression of acvA fusion genes in A. nidulans as well as the appearance of acvA mRNA in P. chrysogenum was not temporally delayed to any great extent Renno et al 1992) (Sect. II.E.1).…”