By inhibiting the function of a transcription factor that promotes transcription of a gene associated with the amounts of lignin and cellulose, a plant in which the amounts of lignin and cellulose are reduced without reducing the amount of glucan is produced. In this plant, glucan in the obtained cell wall components is in the state of highly easily undergoing saccharification. In this plant, moreover, natural dehiscence of pods is suppressed. A method of inhibiting the transcription factor incl...