EVIDENCE FOR A ROLE OF BETA-1,3-GLUCANASE IN DICOT SEED-GERMINATION

Class I beta-1,3-glucanases are antifungal vacuolar proteins implicate d in plant defense that show developmental, hormonal, and pathogenesis -related regulation. The expression was studied in germinating tobacco seeds of a chimeric P-glucuronidase (GUS) reporter gene fused to 1.6 kb of the 5' flanking sequence of the tobacco class I beta-1,3-glucana se B (GLB) promoter. Histological staining for GUS activity showed tha t expression of the GLB promoter is highly localized in a specific zon e of the endosperm in germinating seeds. The temporal and spatial patt erns of GUS and beta-1,3-glucanase activity found, suggest a novel fun ction for class I beta-1,3-glucanases during seed germination in a dic otyledonous plant.