Effects of gamma irradiation on the plasma membrane of suspension-cultured apple cells. Rapid irreversible inhibition of H+-ATPase activity.
Dong, C. Z.; Montillet, J. L.; Triantaphylides, C.;
Physiologia Plantarum Year: 1994 Vol: 90 Issue: 2 Pages: 307-312 Ref: 31 ref.
1994
บทคัดย่อ
ABSTRACT :
The effects of ionizing radiation, used in postharvest treatment of fruits and vegetables, were investigated on cultured apple cells (cv. Royal Red). Irradiation (2 kGy) induced an increase of passive ion effluxes from cells and a decrease of cell capacity to regulate external pH. These alterations were probably due to effects on plasma membrane structure and function and were further investigated by studying the effects of irradiation on plasma membrane H+-ATPase activity. Plasma membrane-enriched vesicles were prepared and the H+-ATPase activity was characterized. Irradiation of the vesicles induced a dose-dependent inhibition of H+-ATPase activity. The loss of enzyme activity was immediate, even at low doses (0.5 kGy), and was not reversed by the addition of 2 mM dithiothreitol. This inhibition may be the result of an irreversible oxidation of enzyme sulphydryl moieties and/or the result of changes induced within the lipid bilayer affecting the membrane-enzyme interactions. Further analysis o
f the H-ATPase activity was carried out on vesicles obtained from irradiated cells confirming the previous results. In vivo recovery of activity was not observed within 5 h following the treatment, thus explaining the decrease of cell capacity to regulate external pH. This rapid irreversible inhibition of the plasma membrane H+-ATPase must be considered as one of the most important primary biochemical events occurring in irradiated plant material.