College of Horticulture, Gansu Agricultural University, Lanzhou 730070, China.
College of Horticulture, Gansu Agricultural University, Lanzhou 730070, China.
Ecotoxicol Environ Saf. 2021 Jul 1;217:112248. doi: 10.1016/j.ecoenv.2021.112248. Epub 2021 Apr 23.
Melatonin (Mel), a powerful antioxidant that has the ability to regulate physiological and biochemical processes in plants under abiotic stresses. However, its roles in pesticide detoxification is poorly understood. Herein, selecting leaf spraying insecticide imidacloprid (IMD) as the model, we demonstrated the detoxification mechanism underlying root pretreatment of Mel on IMD in cucumber. IMD treatment affected the primary light conversion efficiency of photosystem II (Fv/Fm), reduced the quantum yield, and increased hydrogen peroxide and superoxide anions contents as well as the levels of membrane lipid peroxidation, indicating that excessive IMD treatment induces oxidative stress. Nonetheless, by increasing the appropriate levels of exogenous Mel, the photosynthesis of cucumber under IMD treatment reached the control levels, effectively removing reactive oxygen species. Furthermore, the content and ratio of ascorbate (AsA) and glutathione (GSH) were decreased under IMD treatment; Mel treatment enhanced the AsA/DHA and GSH/GSSG ratios, as well as the activities of MDHAR, DHAR and GR, suggesting that Mel could alleviate oxidative stress of cucumber treated with IMD by regulating the ascorbic acid-glutathione cycle. Importantly, IMD degradation rate and glutathione S-transferase (GST) activity increased after Mel treatment. The levels of transcripts encoding antioxidant enzymes GPX and GST (GST1,2 and 3) were also increased, indicating that Mel accelerated IMD degradation. These results suggest that Mel plays an important role in the detoxification of IMD by promoting GST activity and transcription and the AsA-GSH cycle, thus providing an approach for plants to reduce IMD residue through the plant's own detoxification mechanism.
褪黑素（Melatonin，Mel）是一种强大的抗氧化剂，能够调节植物在非生物胁迫下的生理和生化过程。然而，其在农药解毒中的作用尚不清楚。本研究选择叶片喷雾杀虫剂吡虫啉（Imidacloprid，IMD）为模型，研究了 Mel 对黄瓜中 IMD 根预处理的解毒机制。IMD 处理影响了光合作用系统 II 的原初光能转化效率（Fv/Fm），降低了量子产率，增加了过氧化氢和超氧阴离子的含量以及膜脂过氧化水平，表明过量的 IMD 处理会诱导氧化应激。然而，通过增加适当水平的外源 Mel，在 IMD 处理下黄瓜的光合作用达到对照水平，有效清除了活性氧。此外，IMD 处理降低了抗坏血酸（Ascorbic acid，AsA）和谷胱甘肽（Glutathione，GSH）的含量和比值；Mel 处理增强了 AsA/DHA 和 GSH/GSSG 的比值以及 MDHAR、DHAR 和 GR 的活性，表明 Mel 可以通过调节抗坏血酸-谷胱甘肽循环来缓解 IMD 处理对黄瓜的氧化应激。重要的是，Mel 处理后 IMD 的降解率和谷胱甘肽 S-转移酶（Glutathione S-transferase，GST）活性增加。编码抗氧化酶 GPX 和 GST（GST1、2 和 3）的转录本水平也增加，表明 Mel 加速了 IMD 的降解。这些结果表明，Mel 通过促进 GST 活性和转录以及 AsA-GSH 循环在 IMD 的解毒中发挥重要作用，从而为植物通过自身解毒机制降低 IMD 残留提供了一种方法。
