MARKED INDUCTION OF BASIC CHITINASE IN PUMPKIN IN RESPONSE TO WOUNDING

The activity and immunoreactive protein of basic chitinase in various tissues of pumpkin (Cucurbita spp.) were investigated. The activity and immunoreactive protein of chitinase in fruit tissues were about twice those in leaf and stem tissues, and were barely detectable in seeds. Chitinase activity gradually increased during germination of pumpkin seeds. The activity and immunoreactive protein of chitinase rapidly increased during callus formation from pumpkin fruit tissue slices. However, they also increased during incubation of tissue slices in the absence of 2,4-D. Thus, chitinase activity after incubation of tissue slices for four days was about 150 times that in fresh tissues. Furthermore, immunocytochemical analyses, by a tissue printing method, showed that the immunoreactive protein of a basic chitinase in pumpkin fruit tissues increased during incubation of the tissue slices and was abundant on the epidermal side of fruit tissue slice. Thus, chitinase induction during callus formation may not be caused by the effect of 2,4-D, but by a wounding response.