Permeability of the Plasma Membrane for Propidium Iodide and Destruction of Cell Nuclei in the Epidermis of Pea Leaves: The Effect of Polyelectrolytes and Detergents

Abstract

Damage to the plasma membrane (PM) of cells in pea leaf epidermis determined by its permeability to propidium iodide (PI), which binds to DNA of cell nuclei, and programmed cell death (PCD) detected by the destruction of cell nuclei were investigated. PM of the epidermal cells in the isolated epidermis was permeable to PI (it stained their nuclei). PM of the guard cells did not allow PI to pass through. KCN, an inducer of PCD, caused the destruction of both epidermal and guard cell nuclei. KCN-induced destruction of guard cell nuclei was accompanied by the penetration of PI into the cells. The polycation chitosan at a concentration of 0.1 mg/mL caused the destruction of the epidermal cell nuclei, but the permeability of the guard cell PM for PI staining their nuclei was induced at a concentration of 1 mg/mL. Other polycations (cytochrome c, polylysine, polyethylenimine, and protamine) also caused staining of the guard cell nuclei by PI. Polyanions (polyacrylic acid, dextran, and heparin) initiated the destruction of cell nuclei, which was accompanied by the penetration of PI into cells. Detergents Triton X-100 and lauryldimethylamine-N-oxide produced the permeability of the guard cell PM for PI and prevented the destruction of the nuclei that was induced by KCN. Treatment of the epidermis with Triton X-100 (for 2 h with its subsequent washing) increased the destruction of the guard cell nuclei that was caused by KCN. Polycations polyethyleneimine and protamine were prevented, while chitosan, cytochrome c, and polylysine, on the contrary, enhanced KCN-induced destruction of the guard cell nuclei. The obtained data shows that the destruction of cell nuclei upon induction of cell death with KCN or polyanions is accompanied by damage to PM (producing its permeability for PI). Damage to PM caused by detergents or polycations prior to cell treatment by KCN can prevent or, on the contrary, intensify the destruction of cell nuclei.