24-Epibrassinolide Reduces Drought-Induced Oxidative Stress by Modulating the Antioxidant System and Respiration in Wheat Seedlings

Abstract

Brassinosteroids (BRs) represent a group of plant signaling molecules with a steroidal skeleton that play an essential role in plant adaptation to different environmental stresses, including drought. In this work, the effect of pretreatment with 0.4 µM 24-epibrassinolide (EBR) on the oxidant/antioxidant system in 4-day-old wheat seedlings (Triticum aestivum L.) was studied under moderate drought stress simulated by 12% polyethylene glycol 6000 (PEG). It was revealed that EBR-pretreatment had a protective effect on wheat plants as evidenced by the maintenance of their growth rate, as well as the reduction in lipid peroxidation and electrolyte leakage from plant tissues under drought conditions. This effect was likely due to the ability of EBR to reduce the stress-induced accumulation of reactive oxygen species (ROS) and modulate the activity of antioxidant enzymes. Meanwhile, EBR pretreatment enhanced proline accumulation and increased the barrier properties of the cell walls in seedlings by accelerating the lignin deposition. Moreover, the ability of EBR to prevent a drought-caused increase in the intensity of the total dark respiration and the capacity of alternative respiration contributes significantly to the antistress action of this hormone.

Effects of Lactone- and Ketone-Brassinosteroids of the 28-Homobrassinolide Series on Barley Plants under Water Deficit

“…Proline accumulation in droughtstressed plants has been observed many times previously [56,57]. BR treatment of plants is also known to stimulate proline accumulation under water deficit [13,15,20]. At the same time, we showed that pretreatment of barley plants with BRs followed by drought partially reduced stress-induced proline accumulation, despite the fact that in this case there was stimulation of P5CS1 gene expression of proline synthesis and inhibition of its degradation gene expression (Table 4).…”

“…Pretreatment of plants with HBL slightly (by 20%) stimulated TBARS accumulation, while HCS, on the contrary, relieved the drought-induced increase in TBARS content (Figure 3), i.e., at the level of the lipid peroxidation process, lactone-and ketone-containing BRs had opposite effects on plants under drought conditions. Pretreatment of wheat plants with 24-epibrassinolide followed by PEG6000-induced water deficit also resulted in a reduction in lipid peroxidation and electrolyte leakage from tissues [15]. Pretreatment of barley plants with HCS followed by drought increased SOD activity sevenfold, had no effect on catalase activity, and slightly decreased peroxidase activity relative to water deficit.…”

“…To increase plant resistance to the action of damaging factors, hormonal treatment is carried out during or before the action of the stressor [13][14][15]. Recently, short-term pretreatment of seeds or plants with phytohormones that initiate a priming state has attracted much interest [16,17].…”