It is intended to provide for a polycistronic expression pattern in a plant used as a host. The present invention provides a polynucleotide which comprises the following DNA (a) or (b) and functions as an IRES (internal ribosome entry site) in a plant: (a) DNA of the nucleotide sequence represented by SEQ ID NO: 1, 2, 3, or 4; or (b) DNA of a nucleotide sequence derived from the nucleotide sequence represented by SEQ ID NO: 1, 2, 3, or 4 by the substitution, deletion, addition, and insertion of one or more bases and having a function of positively regulating the translation of a nucleic acid located downstream thereof.