Figure 2.

Schematic presentation of the Differential Fluorescence Induction screen. Approximately 13,000 clones of the P. luminescens promoter-trap library, based on the reporter gene mcherry encoding the Red Fluorescent Protein mCherry, were analyzed for induced fluorescence in the presence of G. mellonella larvae homogenate. Positive clones were verified in triplicate before sequencing the DNA-fragment upstream of the reporter gene. When no native promoter was present within the DNA-fragment, a promoter motif search was performed. The P. luminescens genome was then searched for similar promoter motifs. DNA-sequences containing the predicted promoter motifs were cloned upstream of the reporter gene mcherry, and induction was analyzed after exposure of P. luminescens to insect homogenate (in vitro) or in viable G. mellonella larvae (in vivo).