Accumulation of β-1,3-glucanase and chitinase isoforms, and salicylic acid in the DL-β-amino-n-butyric acid-induced resistance response of pepper stems toPhytophthora capsici

Abstract

Pepper (Capsicum annuumL.) plants sprayed with DL-β-amino-n-butyric acid (BABA) were protected againstPhytophthora capsiciinfection. BABA treatment induced the synthesis and accumulation of β-1,3-glucanases and chitinases in the stem tissues of pepper plants. Their accumulation was very pronounced in the stems challenge-inoculated withP. capsiciafter BABA treatment. Several β-1,3-glucanase and chitinase isoforms accumulated in BABA treatedP. capsici. When analysed by immunoblot of the denatured proteins, the 20 kDa β-1,3-glucanase and 32 kDa chitinase were found in pepper stems treated with BABA and/or infected byP. capsici. BABA treatment did not stimulate capsidiol production in pepper stems, but prior treatment led to high accumulation inP. capsici-infected ones. Unlike capsidiol production, BABA treatment triggered a dramatic increase in the endogenous levels of salicylic acid (SA) in pepper stems. The increase in endogenous SA was much pronounced inP. capsiciinfected stems after BABA treatment. In conclusion, the induction of resistance toP. capsiciin pepper plants by BABA treatment positively correlated with the accumulation of certain β-1,3-glucanase and chitinase isoforms, and SA. These results suggest strongly that SA may act as an endogenous signal responsible for activating particular components of resistance toP. capsiciand the induction of pathogenesis-related proteins such as β-1,3-glucanase and chitinase.