[Energy metabolism in wheat root cells under modification of plasma membrane permeability by antibiotic nystatin].

This paper reports changes in ion transport and energy metabolism of plant cells during short- and long-term expositions, resp., to antibiotic nystatin, which is known to specifically bind with plasma membrane sterols to form channels. The excised roots of 5 days old wheat seedlings were used as a model system in this research. It has been shown that treatment of excised roots with nystatin leads to activation of energy metabolism expressed as an increase of respiration and heat production by root cells. Furthermore, in the presence of nystatin increased pH of incubation medium, plasma membrane depolarization and a significant loss of potassium ions were observed. Nystatin-induced stimulation of respiration was prevented by malonate, an inhibitor of succinate dehydrogenase, electron acceptor dichlorophenolindophenol, and AgNO3, an inhibitor of H(+)-ATPase. Based on the data obtained it can be suggested that nystatin-induced stimulation of respiration is related to electron transport activation via mitochondrial respiratory chain, and is connected with activation of plasmalemma proton pump. Moreover, nystatin-induced increase of oxygen consumption was prevented by cerulenin, an inhibitor of fatty acid and sterol synthesis. This indicates that additional sterols and phospholipids may be synthesized in root cells to "heal" nystatin-caused damage of plasma membrane. A supposed chain of events of cell response to nystatin action may by as following: formation of nystatin channels-influx of protons--depolarization of plasmalemma-efflux of potassium ions-disturbance of ion homeostasis--activation of H(+)-ATPase work-increase in energy "requests" for H(+)-ATPase function--increase in the rate of oxygen consumption and heat production. The increased energy production under the action of nystatin, may provide the work of proton pump and synthesis of sterols and phospholipids, which are necessary for membrane regeneration.

[Respiration of wheat roots during inhibition of phospholipase A2 by 4-bromphenacylbromide]. / Dykhanie kornei pshenitsy pri ingibirovanii fosfolipazy A2 4-bromfenatsilbromidom.

Dependence of oxygen consumption by wheat root cells on the activity of phospholipase A2 (PLA2) was studied. The treatment of excised roots with 4-bromophenacile bromide (BPB), a specific inhibitor of PLA2, caused a decrease in the content of free fatty acids (FFA) and in oxygen consumption of root cells. The latter was prevented by exogenous application of a mixture of FFA. A similar inhibitory effect was caused by BPB after the activation of root respiration by 2,4-dinitrophenol (DNP). These data suggest that FFA may be involved in the regulation of respiration through the formation of succinate. This is supported by the fact of reduction of DNP-induced stimulation of oxygen consumption by malonate, known to be an inhibitor of succinate dehydrogenase, and by stimulation of respiration by exogenous application of succinate.