An object of the present invention is to explore, isolate, and identify a dwarfing gene by activation tagging. The present invention provides a gene encoding a protein of the following (a) or (b): (a) a protein consisting of the amino acid sequence represented by any of SEQ ID NOs: 2, 4, 6, and 8; or (b) a protein consisting of an amino acid sequence derived from the amino acid sequence represented by any of SEQ ID NOs: 2, 4, 6, and 8 with the deletion, substitution, or addition of one or several amino acids and having the activity of dwarfing a plant body.