Differential Induction and Accumulation of β‐1,3‐Glucanase and Chitinase Isoforms in the Intercellular Space and Leaf Tissues of Pepper by Xanthomonas campestris pv. vesicatoria Infection

Abstract

AbstractThe virulent strain Ds 1 of Xanthomonas campestris pv. vesicatoria multiplied in pepper (cv. Hanbyul) leaves better than did the avirulent strain 81–23, which formed localized necrosis at the onset of pathogenesis. Infection of pepper leaves by X. campestris pv. vesicatoria induced the synthesis and accumulation of β‐1,3‐glucanase and chitinase in the intercellular space and leaf tissue of pepper plants. In the uninoculated controls, the two hydrolases remained at a very low level. High levels of the two enzymes were found in an incompatible interaction of pepper leaves with X. campestris pv. vesicatoria. In particular, chitinase activity in the intercellular washing fluids (IWF) was higher in the incompatible than in the compatible interactions. The direct detection of acidic β‐1,3‐glucanases on 10% native PAGE gels revealed only two isoform bands (Ga 1 and Ga 2). Isoelectric focusing identified two acidic β‐1,3‐glucanase isoforms with pl 5.0 and 5.2, and four basic isoforms with pl 7.1, 7.4, 7.9, and 8.8 in the IWF and extracts of infected leaf tissues. Some of the isoforms disappeared during pathogenesis and the others appeared during symptom expression. The acidic chitinase isoforms (Ca 1, Ca 2, and Ca 3) were located primarily in the intercellular spaces. Synthesis of high levels of the acidic isoform Ca 3 in infected pepper leaves was seen. Several basis chitinase isoforms accumulated only in diseased leaf tissue, and especially more in the incompatible than the compatible interaction. By using isoelectric focusing, the three acidic and seven basic chitinase isoforms in the IWF and leaf extracts were detected on chitin overlay gels.