ENERGY METABOLISM IN WHEAT ROOT CELLS UNDER MODIFICATION OF PLASMA MEMBRANE PERMEABILITY BY ANTIBIOTIC
NYSTATIN
L. Kh. Gordon,1 Y. N. Valitova, T. I. Ogorodnicova, D. F. Rakhmatullina,
A. Y. Alyabyev, N. L. Loseva, A. N. Tsentsevitsky, N. F. Ruban
Institute of Biochemistry and Biophysics RAS, Kazan';
1 e-mail: gordon@mail.knc.ru
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
Í+-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 Í+-ATPase work - increase in energy "requests" for Í+-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.
Key words: wheat root, energy exchange, oxygen consumption, heat production, protons, potassium ions, inhibitory
analysis
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