Disclosed is a gene having a novel function of increasing or decreasing the productivity of a substance, particularly the content of an oil or fat in a seed.A chemiric protein, which is a fusion of a transcription factor comprising a protein that comprises the amino acid sequence depicted in any one even-numbered sequence selected from SEQ ID NO:1 to SEQ ID NO:158 and a functional peptide capable of converting a transcription factor into a transcription inhibition factor, is allowed to be expressed in a plant.