An apple polyphenol oxidase cDNA is up-regulated in wounded tissues.

A full-length cDNA clone encoding apple (Malus domesticus) polyphenol oxidase (PPO) was isolated from a fruit peel cDNA library. Southern analysis indicated that apple PPO is encoded by a divergent multigene family. By northern analysis, PPO mRNA was only detected in a fruit sample taken one week after full bloom. PPO mRNA accumulated in wounded tissues, and also in peel tissue showing the symptoms of superficial scald, a post-harvest disorder. The induction of PPO mRNA provides the first evidence for transcriptional control of PPO expression after wounding or the manifestation of a physiological disorder.