Modulation of Elicitor-Induced Chitinase and β-1,3-Glucanase Activity by Hormones in <italic>Phaseolus vulgaris</italic>

Abstract

Chitinase and β-1 ,3-glucanase induction in Phaseolus vulgaris by cell wall elicitor from Col-letotrichum lindemuthianum has been studied together with the effects of the hormones IAA and ethylene. Chitinase and β-1, 3-glucanase increased in response to the elicitor in the resistant cultivar, Kievit, but not in the susceptible cultivar, Pinto. However, both activities increased in both cultivars in response to hormones in the absence of elicitor; elicitor did not augment this response in cv. Kievit. Aminoethoxyvinyl glycine (AVG) abolished all responses except those obtained by the application of ethylene. Of other hydrolases tested, only β -galactosidase was induced by elicitor; this was similar for both cultivars but hormones were without effect. Evidence suggests that both chitinase and β-l ,3-glucanase are located within the cell rather than in the intercellular space. It is concluded that chitinase and β;-l,3-glucanase are coordinately synthesized as a defence response since they hydrolyse complementary linkages in pathogen derived polysac-charides. Regulation of the induction of the two enzymes is primarily due to ethylene and the lack of response in the compatible reaction appears to arise from an inability to synthesize ‘ stress ’ ethylene.