Developmental and Structural Section
Gunawardena, Arunika H.L.A.N. , Greenwood, John S. , Dengler, Nancy G. .
Cell wall degradation during leaf perforation development in lace plant.
LACE plant, Aponogeton madagascariensis, undergoes a highly unusual form of leaf morphogenesis, in which an initially simple leaf shape secondarily adopts a complex shape through the formation of perforations as the leaves expand. Discrete patches of cells located equidistantly between the longitudinal and transverse veins undergo programmed cell death. Cell death is initiated at the center of the patch and progresses outwards, ceasing at about five cell layers from the vascular tissue. The cell death process involves tonoplast rupture, alteration of cytoplasmic streaming, DNA degradation, and ultimately, collapse and death of the cytoplasm. Unlike perforation formation in the only distantly related Monstera, walls of most of the dying cells in the patch are degraded and the perforation is ripped open as the leaf expands. Alcian blue and ruthenium red staining, as well as immunolocalization of pectin epitopes, suggest that the walls of the dying cells are initially rich in pectin. Scanning and transmission electron microscopy observations indicate that the wall matrix degrades first, leaving a fibrillar network that stains for cellulose. Gel assays indicate that pectinases are active throughout perforation development, while cellulose activity is restricted to early stages of perforation formation. Sudan and Fluorol yellow staining provide histochemical evidence for the presence of suberin in the cell walls at the periphery of the perforation, perhaps indicating a wall modification that protects adjacent cells from wall degradation.
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1 - University of Toronto, Department of Botany, Toronto, Ontario, M5S 1A1, Canada
2 - University of Guelph, Department of Botany, Guelph, Ontario, N1G 2W1, Canada
3 - University of Toronto, Department of Botany, 25 Willcocks Street, Toronto, Ontario, M5S 3B2, Canada
programmed cell death
Presentation Type: Oral Paper:Papers for Sections
Location: 303/Bell Memorial Union
Date: Wednesday, August 2nd, 2006
Time: 8:30 AM