The purpose of the present invention is to provide technology for identifying a 5' UTR having excellent translation ability while taking into account 5' UTR variants in monocotyledons, providing a DNA molecule that codes for the 5' UTR, and efficiently producing a recombinant protein in the monocotyledons. It is possible to efficiently produce a recombinant protein in a monocotyledon by using a nucleic acid structure in a polynucleotide that codes for a foreign protein, said structure comprising a base sequence among the base sequences shown in sequences 1-4 and linking to a 5' UTR or a variant thereof.