Implicated in the defense of plants against pathogens (Probable). Not involved in plasmodesmal callose degradation and in the gating of plasmodesmata during tobamovirus infection (PubMed:23656331). Hydrolysis of (1->3)-beta-D-glucosidic linkages in (1->3)-beta-D-glucans. Exported in the apoplast and secreted to the cell wall under treatment with salicylic acid (SA). By 2,6-dichloroisonicotinic acid (INA) and salicylic acid (possibly an endogenous signal for acquired resistance). Strongly induced by infection with the bacterial pathogen P.syringae pv. tomato DC3000 (PubMed:1392589). Induced by infection with avirulent and virulent strains of P.syringae pv. maculicola (PubMed:1824335). Induced by infection with the turnip vein clearing virus (TVCV) and cucumber mosaic virus (CMV) (PubMed:23656331). Belongs to the glycosyl hydrolase 17 family.