Embryonic developmental protein (PubMed:2598266, PubMed:10072776). The lateral or ventral identity of a cell depends upon the concentration of this protein in its nucleus during the blastoderm stage (PubMed:2598266). A morphogenetic protein that specifically binds to the kappa B-related consensus sequence 5'-GRGAAAANCC-3', located in the enhancer region of zygotic genes such as Zen, Twist, Snail and Decapentaplegic. Mediates an immune response in larvae (PubMed:10072776). Part of a signaling pathway involving NF-kappa-B and Toll-related receptors, that functions in the apoptosis of unfit cells during cell competition (PubMed:25477468). May be part of a NF-kappa-B and Tollo signaling cascade that regulates development of the peripheral nervous system (PubMed:18000549). Interacts with tamo via the nuclear localization signal (PubMed:12653959). Interacts with emb, a component of the nuclear export complex (PubMed:14638854, PubMed:17032737). In ventral regions it is first cytoplasmic, then the protein is relocalized in the nucleus (PubMed:2598266). Its nuclear localization is essential to its function as a morphogen (PubMed:2598266). In dorsal regions it remains cytoplasmic (PubMed:2598266). Tamo negatively regulates nuclear import of dl (PubMed:12653959). Emb is responsible for export of dl from the nucleus (PubMed:14638854). Nuclear localization is enhanced upon microbial infection (PubMed:17032737). In unchallenged larvae, expression of both isoforms is seen in fat body and gut (isoform A is more abundant). After immune challenge levels of both isoforms are enhanced. Isoform A is expressed maternally and both isoforms are expressed zygotically from 6-9 hours embryos through to adulthood. Nuclear localization signal at positions 335-340.