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Nitric Oxide Functions as a Key Mediator in Brassinosteroid-Enhanced Alkaline Tolerance in Cucumber
Wenjing Nie1, Peng Qiao1, Yinyu Gu1
1Shandong Engineering Research Center of Functional Crop Germplasm Innovation and Cultivation Utilization, Yantai Engineering Research Center for Plant Stem Cell Targeted Breeding, Shandong Institute of Sericulture, Yantai 264001, China.
Plants (Basel, Switzerland)
|November 13, 2025
Summary
Exogenous 2,4-epibrassinolide (EBR) and nitric oxide (NO) boost cucumber seedling tolerance to alkaline stress. NO acts downstream of EBR, mediating antioxidant defense, ion balance, and photosynthesis for enhanced plant resilience.
Area of Science:
- Plant Physiology
- Plant Stress Responses
- Biochemistry
Background:
- Alkaline stress, induced by NaHCO3, severely inhibits plant growth by causing sodium toxicity, reactive oxygen species (ROS) accumulation, and photosynthetic impairment.
- Exogenous application of 2,4-epibrassinolide (EBR) and nitric oxide (NO) are potential strategies to mitigate abiotic stress effects in plants.
Purpose of the Study:
- To investigate the individual and combined roles of EBR and NO in enhancing cucumber (Cucumis sativus L.) seedling tolerance to NaHCO3-induced alkaline stress.
- To elucidate the underlying molecular and physiological mechanisms by which EBR and NO confer stress tolerance.
Main Methods:
- Hydroponic cultivation of cucumber seedlings under NaHCO3-induced alkaline stress.
- Application of exogenous EBR and NO, along with pharmacological inhibitors (tungstate, L-NAME, cPTIO, brassinazole) and qRT-PCR analysis.
- Measurement of physiological parameters including ion content, ROS levels, antioxidant enzyme activities, photosynthetic efficiency, and organic acid accumulation.
Main Results:
- Both EBR and NO treatments significantly alleviated alkaline stress symptoms, improving plant performance by enhancing ROS scavenging, maintaining ionic homeostasis, and reducing sodium toxicity.
- EBR and NO stimulated key ion transporters (SOS1, NHX2) and aquaporins (PIP1;2, PIP2;4), increased vacuolar and plasma membrane H+-ATPase activities, and boosted citric and malic acid accumulation.
- Pharmacological experiments indicated that NO acts as a downstream signaling molecule of EBR, crucial for mediating the protective effects against alkaline stress.
Conclusions:
- Nitric oxide (NO) functions as a critical downstream mediator of 2,4-epibrassinolide (EBR) signaling in cucumber's response to alkaline stress.
- EBR and NO collectively enhance plant tolerance by coordinating antioxidant defense, ion homeostasis, aquaporin activity, and organic acid metabolism.
- This study highlights the synergistic potential of EBR and NO in improving crop resilience to challenging soil conditions.
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