Marker and promoter effects on heterologous expression in Aspergillus nidulans
2006
Lubertozzi, David | Keasling, Jay D.
To study the effects of selection marker, promoter type, and copy number on heterologous expression in Aspergillus nidulans, strains were constructed with single- and multicopy plasmid integrations bearing a reporter gene (lacZ) under the control of either an inducible (alcA) or constitutive (gpdA) promoter and one of three Aspergillus nutritional marker genes (argB, trpC, or niaD). β-Galactosidase activity in the transformants varied over three orders of magnitude, with the majority of levels in the range of 5×10³–1×10⁴ U/mg. Significant differences in mean expression levels were found when comparing single-copy transformants with the same promoter but a different marker. Transformants with the argB marker had the highest average expression, ∼threefold over the trpC or niaD clones. For each promoter, maximal expression for the set was seen in the range of the single-copy clones, implying that increasing the copy number does not reliably increase expression in Aspergillus.
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