1. A plant which expresses a chimeric protein, said chimeric protein comprising a transcription factor fused to a repressor domain sequence that converts said transcription factor into a transcription repressor, wherein said transcription factor is a protein comprising the amino acid sequence of SEQ ID NO: 4, or a protein comprising the amino acid sequence of SEQ ID NO: 4 but in which 1-20 amino acids have been deleted, substituted, added or inserted, and wherein the seeds of said plant exhibit an increase in weight, an increase in amount of fat and oil, or an increase in fat and oil content, in comparison to a wild-type plant not expressing said chimeric protein.