Adaptive Changes in the ∆5-Sterol Profile Triticum aestivum L. in Drought Conditions

A study was conducted on changes in the content of free ∆5-sterols and their esters in Triticum aestivum L. wheat leaves of contrasting varieties: Buryatskaya ostistaya (drought-resistant) and Diamant 2 (drought-sensitive) under conditions of prolonged drought (1, 4, 7, and 10 days of water deficit). A variety of sterol profile responses were found in the studied varieties. The drought-resistant variety Buryatskaya ostistaya demonstrated greater resistance to stress, maintaining a more stable content of total ∆5-sterols and increasing the level of β-sitosterol on day 7 of drought (in the fraction of free sterols from 1432.4 to 1737.4 μg/g dry weight and in the fraction of their esters from 213.3 to 420.3 μg/g dry weight), which indicates more effective adaptation mechanisms. The Diamant 2 variety showed a sharp decrease in free sterols on days 1 and 4 of stress (by 57 and 14%, respectively) and the activity of enzymes in the fraction of bound sterols involved in their synthesis. Both varieties were characterized by constant ratios of 24-methylsterols/24-ethylsterols and stigmasterol/β-sitosterol in the free sterol fraction. This work highlights the importance of sterols in plants’ drought-tolerance mechanisms. Further studies are needed to examine the roles of not only free but also conjugated sterols in plant adaptation to abiotic stress.