The present invention relates to a promoter directing high levels of expression of a gene in plant storage roots, derived from the sweet potato MADS-box gene, a vector directing high levels of expression of a gene in plant storage roots comprising the same and a transient assay method expressing a foreign gene transiently in plant storage roots using the same vector. The promoter according to the present invention can induce high levels of expression particularly in plant storage roots. Therefore the present invention is very useful for the development of transgenic plants to produce valuable materials in large quantities in plant storage roots.