“Salicylic acid enhances thermotolerance and antioxidant defense in Trigonella foenum graecum L. under heat stress”

Plants possess various defense mechanisms to cope with genotoxic and environmental challenges, with high temperatures posing a significant threat due to global warming. In this investigation, ten-day-old Trigonella foenum-graecum (fenugreek) seedlings were cultivated in a controlled environment chamber with conditions set at 70-80% relative humidity, a day/night cycle of 25/18 °C, and a photosynthetically active radiation (PAR) of 1000 μmol m^-2 s^-1. Other groups of seedlings were subjected to temperatures of 30, 35, or 40 °C. Our research aimed to investigate the relationship between temperature intensity, duration, growth responses, physiological and metabolic activities, and the stress alleviation by salicylic acid. The results demonstrated that high temperatures significantly reduced plant growth, membrane stability, while increasing proline and protein content, as well as electrolyte leakage in the leaves. The most pronounced results were observed when exposed to 40 °C for 24 h. Salicylic acid completely mitigated the negative impacts of high-temperature stress when it was applied at 40 °C for 24 h. We utilized two-dimensional electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to examine proteins across three groups: control plants, stressed plants, and plants subjected to salicylic acid treatment. Our results revealed that, among the proteins influenced by high-temperature stress, 12 displayed the most significant differences in regulation. These stress-responsive proteins played roles in signal transduction, stress defense, detoxification, amino acid metabolism, protein metabolism (including translation, processing, and degradation), photosynthesis, carbohydrate metabolism, and energy pathways. These proteins may hold practical implications for diverse biological activities. In conclusion, salicylic acid treatment enhanced thermotolerance in fenugreek plants, although further investigation is required at the genome level to elucidate the mechanism of salicylic acid action under heat stress.