Description
Innate immune responses rely on expression of potent effector molecules, such as antimicrobial peptides, which have the capability to kill invading microorganisms. The presence and recognition of microbial components triggers several signaling pathways, such as the Toll and IMD pathways, which in turn activate NF-kB/Rel transcription factors to induce transcription of a large number of immune system genes. Not much is known how these genes are kept silent in healthy flies in the presence of commensal microorganisms, and how the expression of immune defense genes is turned off. We found that several immune defense genes are constitutively active in nub[1] mutants, indicating that the POU domain transcription factor Pdm1/Nubbin may act as a repressor of immune gene expression.