Chitinase and β‐1,3‐glucanase activities in chickpea (Cicer arietinum). Induction of different isoenzymes in response to wounding and ethephon

Chitinase and β‐1,3‐glucanase activities were assayed in roots, stems and leaves of 12‐day‐old chickpea (Cicer arietinum L.) plants. While glucanase activity was higher in roots than in the aerial parts of the plant, leaves had higher Chitinase activity. Both glucanase and chitinase activities were induced in roots and stems in response to wounding (excision into 1‐cm pieces), with activity increasing 6 h after treatment, reaching a maximum between 24 and 48 h, and thereafter remaining nearly constant up to 72 h. Ethephon treatment also induced β‐1,3‐glucanase and chitinase activities in stems but not in roots. Both enzymes occurred in root and stem tissues as a complex mixture of isoenzymes. At least four different peaks with glucanase and chitinase activities could be resolved by gel filtration chromatography on Sephacryl S‐200 and chromatofocusing on PBE 94 (pH 4–7). Following ammonium sulfate precipitation and ion exchange on CM‐ and DEAE‐Trisacryl, three β‐1,3‐glucanase and chitinase fractions, referred to as basic, neutral and acidic, were separated on the basis of their chromatographic behaviour. Most of the total protein (75%) of stem extracts was found in the acidic fraction, whereas the major glucanase (53%) and chitinase (62%) activities were in the basic and neutral fractions, respectively. While wounding resulted in an increase in the neutral glucanase and chitinase activities, the activities of the acidic fractions were promoted by ethephon.