Defense against chitin-containing fungal pathogens. Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide (1->4)-beta-linkages in chitin and chitodextrins. Vacuolar and protoplast. Highest levels in younger leaves or stems segments and in older ones. Leaves and stems of intermediate age show a decreased expression. Appreciable amounts are also found in old root segments, and carpels. In response to infection, elicitor, ethylene, wounding. Belongs to the glycosyl hydrolase 19 family. Chitinase class I subfamily.