Effects of cycloheximide, actinomycin D and ethylene on the increase and subsequent decrease in acid invertase activity in wounded sweet potato

In wounded sweet potato root tissue, the mechanisms of the increaseand subsequent decrease of acid invertase activity were examinedin compariosn with phenylalanine ammonia lyase (PAL) and peroxidaseactivities. The increase in acid invertase and PAL activitiesin response to wounding was inhibited by both cycloheximideand actinomycin D. However, the increase in peroxidase activitywas inhibited by cycloheximide but was not inhibited by actinomycinD, which repressed RNA synthesis 60 to 70%. The increase inacid invertase activity was supressed by ethylene, while PALand peroxidase activities were stimulated. The results of cycloheximideco-treatment suggest that the fluctuation in enzyme activitiesby ethylene treatment involves de nove protein synthesis. Further,the effect of ethylene on enzyme activities was under competitionby carbon dioxide. The decrease in acid invertase activity atthe late stage of incubation was stimulated by cycloheximidetreatment, but that of PAL activty was prevented. The resultssuggest the existence of different inactivating systems betweenacid invertase and PAL. ¹ This paper constitutes Part 117 in the Series "The PhytopathologicalChemistry of Sweet Potato with Black Rot and Injury". (Received September 2, 1974; )