Modifications of wound-induced changes in phenylalanine ammonia-lyase activity in potato tuber tissue

Abstract

Potato tuber parencyma discs that are incubated in vitro in darkness at 20°C exhibit a ‘wounding time course’ where phenylalanine ammonia-lyase (PAL; E.C.4.3.1.5) activity peaks 24 h after excision and then declines to a stable plateau level. In contrast, if the discs are restored to the tuber environment immediately after excision, by a process of placing them inside a ‘host’ tuber, PAL activity remains at a constant low level for at least 48 h. When these discs are transferred from their host tuber to in vitro incubation, PAL activity immediately rises and follows a time course in which there are now two peaks within 48 h. Although the particular timing of the peaks is dependent on the length of the in situ preincubation, this pattern is established after only 4 h in situ. Both peaks are sensitive to actinomycin D and cycloheximide, which also abolish the low basal PAL activity.