Minisymposium 1: Cell Walls

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Abs # M0104: Cell wall degradation during programmed cell death in lace plant

Presenter:	Guanwardena, Arunika N       Contact Presenter
Authors	Guanwardena, Arunika N (A)   Greenwood, John S (B)   Nancy, Dengler G (A)
Affiliations:	(A): University of Toronto (B): University of Guelph

Perforation formation in the lace plant leaf is a unique and fascinating use of developmental PCD showing many similar characteristics of apoptosis in animal cells. In this system, discrete populations of cells undergo a disruption of cytoplasmic streaming, loss of anthocyanin, indicating that rupture of the tonoplast, DNA degradation and other cytoplasmic changes such as formation of vesicles, shrinkage and invagination of membrane and degradation of other organelles. At the same time, adjacent cells are unaffected by these processes and develop normally. Unlike many other forms of plant PCD, cell wall degradation a key event in lace plant PCD and is required for formation of the open perforations in the leaf blade. Based on SEM and TEM appearance, cell wall matrix is degraded first, followed by disruption of cellulose microfibrils. The pectin composition of cell wall is altered during PCD as indicated by alcian blue and JIM antibody staining. Gel diffusion assays showed enhanced cellulase and pectinase enzyme activities during perforation formation stages. During the later stages of perforation formation, the walls of cells at the periphery of the perforation become impregnated with suberin, as indicated by fluorol yellow 088 and sudan 7b staining. These modifications may protect these living cells surrounding the perforation from the activity of wall degradative enzymes during lace plant leaf development.