Evidence for a role of β‐1,3‐glucanase in dicot seed germination

Class I β‐1,3‐glucanases are antifungal vacuolar proteins implicated in plant defense that show developmental, hormonal, and pathogenesis‐related regulation. The expression was studied in germinating tobacco seeds of a chimeric β‐glucuronidase (GUS) reporter gene fused to 1.6 kb of the 5′ flanking sequence of the tobacco class I β‐1,3‐glucanase B (GLB) promoter. Histological staining for GUS activity showed that expression of the GLB promoter is highly localized in a specific zone of the endosperm in germinating seeds. The temporal and spatial patterns of GUS and β‐1,3‐glucanase activity found, suggest a novel function for class I β‐1,3‐glucanases during seed germination in a dicotyledonous plant.