The invention relates to a method for the stable expression of nucleic acids in transgenic plants, controlled by a parsley-ubiquitin promoter (PCUbi4-2). Said promoter, isolated from parsley (petroselinum crispum) exhibits in almost all transgenic plants an intensely constitutive expression in almost all vegetable tissue, including the seed. It also contains, among others, a potentially heat-shock inducible element (HSE). The invention also relates to nucleic acid constructs, vectors and transgenic plants and to the use of the latter for producing foodstuffs, animal feed, seeds, pharmaceuticals or fine chemicals.