Determination of lipid ordering in chloroplast microdomains of wheat leaves under soil drought conditions

The degree of lipid matrix ordering in the chloroplast microdomains of leaves from two wheat cultivars – a drought-tolerant Buryatskaya Ostistaya and a moisture-sensitive Diamant 2 – was studied under control conditions and under prolonged water deficit (10 days). Lipid ordering was assessed based on generalized polarization values obtained using the Laurdan lipophilic probe. Stress intensity was evaluated according to the level of reactive oxygen species. Under control conditions, both cultivars showed an increase in the generalized polarization values in rafts of zone 1 (R1). In contrast, in rafts of zone 2 (R2), this parameter remained unchanged in the drought-tolerant cultivar, whereas in the moisture-sensitive cultivar it decreased on days 4 and 10 relative to day 1. Under drought conditions, the generalized polarization values in R1 of the tolerant cultivar decreased on days 4 and 10. A decrease in generalized polarization was also observed in R2, with the most pronounced reduction occurring on day 4. An increase in the generalized polarization values was observed in the microdomains of both zones in Diamant 2, except on day 7, when a decrease in microviscosity was recorded. Hence, the microviscosity changes detected in the lipids of the studied microdomains, under both control and stress conditions, suggest that chloroplast membrane microdomains in wheat leaves may not only be involved in cellular responses to stress, but may also participate in other physiological and biochemical processes.