Plasmodesmal-associated membrane beta-1,3-glucanase involved in plasmodesmal callose degradation and functions in the gating of plasmodesmata. Hydrolysis of (1->3)-beta-D-glucosidic linkages in (1->3)-beta-D-glucans. Highly expressed in flowers and siliques. By infection with the cucumber mosaic virus (CMV). Belongs to the glycosyl hydrolase 17 family.