Polyphenol oxidases (PPOs) are copper metalloproteins which play a critical role in producing various derivatives of polyphenolic compounds. These enzymes are encoded in the nuclear genome and subsequently transported into the plastid. A partial cDNA clone encoding polyphenol oxidase was isolated from immature sweet persimmon leaves. Using two degenerate primers, a single band of PCR product was produced by the toughdown PCR method. In sequence analysis, this clone (define SPO; 1381 bp) revealed high similarities to the previously reported plant PPO genes. Moreover, this SPO clone was comprised of copper A and copper B-binding sites and a histidine-rich region, indicating that this clone contained the key conserved elements of PPO. To characterize thespatial and temporal expression of PPO, total RNAs were extracted from leaf and fruit peel tissues at different developmental stages. In northern analysis, transcripts of PPO were detected in all the samples tested, but the strongest expression levels were dtected in mature fruit peels and leaves. Expression of PPO was inhibited in the transitional stage from chloroplast to chromoplast. In addition, the expression of PPO was highly induced in wounded immature fruit peel tissues.