The Tag:PH(PLCδ-Unk) entry in FlyBase represents a pleckstrin homology domain, where it is known that the domain originated from a PLCδ gene and that it binds specifically to phosphatidylinositol 4,5-bisphosphate, but the species and/or gene of origin are unknown. The Tag:PH(PLCδ-Unk) tag can be used to monitor the distribution of phosphatidylinositol 4,5-bisphosphate within a cell, if fused to an appropriate reporter protein, or to target a tagged protein to a particular subcellular localization via phosphatidylinositol 4,5-bisphosphate binding.