In Blepharisma japonicum, conjugation is initiated by the conjugation-inducing substances, gamone 1 and gamone 2. Gamone 2 has been identified as an amino acid derivative in 1973. On the other hand, gamone 1 is a glycoprotein and amino acid sequences have been revealed only recently by us. We now analyze the expression of gamone 1 and the conjugation-inducing mechanism triggered by gamones. Gamone 1 was transcribed specifically in mating type I cells, but not in type II cells. Cells in the immaturity period did not transcribe gamone 1 gene until they reach mature (30~40 fissions after conjugation). Well-fed mature cells did not transcribe gamone 1 and they started transcribing it in the stationally phase. Transcription was greatly increased when type I cells were stimulated by gamone 2. These results indicate that the expression of gamone 1 is strictly regulated by internal and external factors in the transcriptional level. We have sequenced the 5’ flanking region of gamone 1 gene and revealed TATA-box and PSE (proximal sequence element) upstream from the transcription initiation site. Several genes have been identified from the subtraction between the conjugation-induced cells and non-induced cells. The expression system of gamone 1 in E. coli has been constructed recently.