DIFFERENTIAL INDUCTION AND ACCUMULATION OF BETA-1,3-GLUCANASE AND CHITINASE ISOFORMS IN THE INTERCELLULAR SPACE AND LEAF TISSUES OF PEPPER BY XANTHOMONAS-CAMPESTRIS PV VESICATORIA INFECTION

The virulent strain Ds 1 of Xanthomonas campestris pv. vesicatoria mul tiplied in pepper (cv. Hanbyul) leaves better than did the avirulent s train 81-23, which formed localized necrosis at the onset of pathogene sis. Infection of pepper leaves by X. campestris pv. vesicatoria induc ed the synthesis and accumulation of beta-1,3-glucanase and chitinase in the intercellular space and leaf tissue of pepper plants. In the un inoculated controls. the two hydrolases remained at a very low level. High levels of the two enzymes were found in an incompatible interacti on of pepper leaves with X. campestris pv. vesicatoria. In particular, chitinase activity in the intercellular washing fluids (IWF) was high er in the incompatible than in the compatible interactions. The direct detection of acidic beta-1,3-glucanases on 10% native PAGE gels revea led only two isoform bands (Ga 1 and Ga 2). Isoelectric focusing ident ified two acidic beta-1,3-glucanase isoforms with pI 5.0 and 5.2, and four basic isoforms with pI 7.1, 7.4, 7.9, and 8.8 in the IWF and extr acts of infected leaf tissues. Some of the isoforms disappeared during pathogenesis and the others appeared during symptom expression. The a cidic chitinase isoforms (Ca 1: Ca 2, and Ca 3) were located primarily in the intercellular spaces. Synthesis of high levels of the acidic i soform Ca 3 in infected pepper leaves was seen. Several basis chitinas e isoforms accumulated only in diseased leaf tissue, and especially mo re in the incompatible than the compatible interaction. By using isoel ectric focusing, the three acidic and seven basic chitinase isoforms i n the IWF and leaf extracts were detected on chitin overlay gels.