Expression levels of UPC2 across the 55 cultivation conditions. The colored matrix is a schematic representation of the settings of the ten cultivation parameters over the 55 conditions. The colored lanes indicate the cultivation parameters that are employed to order the experiments, in this case, aeration type and limiting element. The applied regression model was able to explain 71% of the variance in the expression of this gene. The model selected one significant single effect, i.e. aeration type, and two significant combinatorial effects, i.e. aeration type anaerobic together with limiting element zinc and the usage of proline or asparagine as nitrogen source. The reconstructed expression pattern based on these three effects is indicated by the shaded area.