Jiang, W.B., Dept. Postharvest Sci. Fresh Produce, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel, Department of Food Science, China Agricultural University, 100094 Beijing, China
Lers, A., Dept. Postharvest Sci. Fresh Produce, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Lomaniec, E., Dept. Postharvest Sci. Fresh Produce, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Aharoni, N., Dept. Postharvest Sci. Fresh Produce, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel

During leaf senescence protein degradation is enhanced. In order to obtain information on the enzymes involved in this process, a study was initiated to identify and characterize proteases whose activity is elevated in artificially senescing parsley leaves. A 70-kDa serine protease (EC 3.4.21) was identified by an activity gel assay. This protease activity, which is low in young leaves, was found to increase considerably in parallel to the advance of senescence and the reduction in the protein content of the leaves. A high correlation between the progress of senescence and the increase in the activity of the 70 kDa serine protease was demonstrated. Treatments with CO2 or gibberellic acid, which retard senescence, reduced the protease's activity, whereas acceleration of senescence with ethylene enhanced it.