PJB-2023-342
RESTORATION OF THE THYLAKOID MEMBRANE FUNCTIONAL STATE USING THE COMPOSITION OF SAPONINS FROM THE MEDICINAL PLANT GLYCYRRHIZA GLABRA UNDER COLD STRESS
RENA GANIYEVA
Abstract
The chloroplast membrane is under the constant effect of external factors (temperature, light, nutrition, etc.) resulting in certain changes in the state of the structure. Low temperatures are known to contribute to a decrease in the fluidity of the lipid phase of the membrane. Metabolites of cell lipid metabolism, in turn, can facilitate the mobility of protein components. Modifying these conditions, we used the incubation of Triticum aestivum L. seedlings at a low temperature (4°C) for various periods as a hardening effect of membrane lipids in vivo. Adding a fraction of saponins, natural detergents, isolated from the medicinal plant Glycyrrhiza glabra into the nutrient solution provoked a change in the state of the thylakoid membrane. Under these conditions, the nature of the change in the delayed chlorophyll a fluorescence and the state of the pigments in the light-harvesting antenna were studied in vivo using the absorption spectra. It was shown that in wheat seedlings untreated with saponins, after 4 hours of cold stress, the activity of the electron transport chain in the PSII decreases, which is associated with the blocking of electron transfer in the QB region. Longer cold stress contributed to the restoration of these changes. The maximum change in the compositions of photosynthetic pigments occurred after 48 hours of cold stress. The introduction of saponins into the nutrient solution was shown to prevent changes in the reactions in the electron transport chain of PSII, which correlated with the restoration of the pigment pool in the light-harvesting antenna. The latter is probably associated with an adaptive increase in membrane stability. The corrective effect of the saponin fraction is possible due to the dilution of the lipid components of the thylakoid membrane, and the transition of the membrane from a quasicrystalline to a liquid state. Restoration of membrane fluidity activates the work of proteins - electron carriers in the PSII electron transport chain and stabilizes the light-harvesting pigment complex.
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