TISSUE-SPECIFICITY AND INDUCTION OF CLASS-I, CLASS-II AND CLASS-III CHITINASES IN BARLEY (HORDEUM-VULGARE)

Barley (Hordeum vulgare L.) chitinases (EC 3.2.1.14) were found to be-distributed and induced in highly tissue specific patterns. Out of 6 chitinases investigated 3 were present in leaves and only a class II chitinase (molecular mass 24 846+/-5 Da, pI greater than or equal to 9.8) was markedly induced in leaves heavily infected with powdery mildew(Erysiphe graminis f.sp. hordei). The class Ti chitinase and a novel class III chitinase (molecular mass 30 kDa, pI greater than or equal to 9.8) were found in intercellular washing fluid of leaves, suggesting extracellular deposition. Neither of these two proteins were induced after infiltration of sodium salicylate (2 mM, pH 6.5) or nickel chloride (2 mM). The class III chitinase showed exochitinase activity in addition to endochitinase activity. No grain specific chitinases were found in leaves after any of the stresses applied. In contrast, 3 grain specific chitinases and one of the leaf chitinases were found in in vitro cultures.