College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China; Provincial Center for Bio-Pesticide Engineering, Yangling, Shaanxi 712100, China.
Institute of Nuclear Technology and Biotechnology, Xinjiang Academy of Agricultural Sciences, Key Laboratory of Crop Ecophysiology and Fanning System in Desert Oasis Region, Ministry of Agricultural and Rural Affairs, Urumqi 830091, China.
Pestic Biochem Physiol. 2023 Aug;194:105512. doi: 10.1016/j.pestbp.2023.105512. Epub 2023 Jun 29.
The main component of orange peel essential oil is limonene. Limonene is a natural active monoterpene with multiple functions, such as antibacterial, antiseptic and antitumor activity, and has important development value in agriculture. This study found that limonene exhibited excellent anti-tobacco mosaic virus (TMV) bioactivity, with results showing that its protection activity, inactivation activity, and curative activity at 800 μg/mL were 84.93%, 59.28%, and 58.89%, respectively-significantly higher than those of chito-oligosaccharides. A direct effect of limonene on TMV particles was not observed, but limonene triggered the hypersensitive response (HR) in tobacco. Further determination of the induction activity of limonene against TMV demonstrated that it displayed good induction activity at 800 μg/mL, with a value of 60.59%. The results of physiological and biochemical experiments showed that at different treatment days, 800 μg/mL limonene induced the enhancement of defense enzymes activity in tobacco, including of SOD, CAT, POD, and PAL, which respectively increased by 3.2, 4.67, 4.12, and 2.33 times compared with the control (POD and SOD activities reached highest on the seventh day, and PAL and CAT activities reached highest on the fifth day). Limonene also enhanced the relative expression levels of pathogenesis related (PR) genes, including NPR1, PR1, and PR5, which were upregulated 3.84-fold, 1.86-fold and 1.71-fold, respectively. Limonene induced the accumulation of salicylic acid (SA), and increased the relative expression levels of genes related to SA biosynthesis (PAL) and reactive oxygen species (ROS) burst (RBOHB), which respectively increased by 2.76 times and 4.23 times higher than the control. Systemic acquired resistance (SAR) is an important plant immune defense against pathogen infection. The observed accumulation of SA, the enhancement of defense enzymes activity and the high-level expression of defense-related genes suggested that limonene may induce resistance to TMV in tobacco by activating SAR mediated by the SA signaling pathway. Furthermore, the experimental results demonstrated that the expression level of the chlorophyll biosynthesis gene POR1 was increased 1.72-fold compared to the control in tobacco treated with 800 μg/mL limonene, indicating that limonene treatment may increase chlorophyll content in tobacco. The results of pot experiment showed that 800 μg/mL limonene induced plant resistance against Sclerotinia sclerotiorum (33.33%), Phytophthora capsici (54.55%), Botrytis cinerea (50.00%). The bioassay results indicated that limonene provided broad-spectrum and long-lasting resistance to pathogen infection. Therefore, limonene has good development and utilization value, and is expected to be developed into a new botanical-derived anti-virus agent and plant immunity activator in addition to insecticides and fungicides.
橙皮精油的主要成分是柠檬烯。柠檬烯是一种具有多种功能的天然活性单萜烯，具有抗菌、防腐和抗肿瘤活性，在农业中有重要的开发价值。本研究发现柠檬烯对烟草花叶病毒（TMV）表现出优异的生物活性，结果表明其保护活性、失活活性和 800μg/mL 的治疗活性分别为 84.93%、59.28%和 58.89%，显著高于壳寡糖。未观察到柠檬烯对 TMV 颗粒的直接作用，但柠檬烯引发了烟草中的过敏反应（HR）。进一步测定柠檬烯对 TMV 的诱导活性表明，其在 800μg/mL 时表现出良好的诱导活性，值为 60.59%。生理生化实验结果表明，在不同处理天数下，800μg/mL 柠檬烯诱导烟草防御酶活性增强，包括 SOD、CAT、POD 和 PAL，分别比对照增加了 3.2、4.67、4.12 和 2.33 倍（POD 和 SOD 活性在第 7 天达到最高，PAL 和 CAT 活性在第 5 天达到最高）。柠檬烯还增强了与发病机制相关（PR）基因的相对表达水平，包括 NPR1、PR1 和 PR5，分别上调了 3.84 倍、1.86 倍和 1.71 倍。柠檬烯诱导水杨酸（SA）的积累，并增加与 SA 生物合成（PAL）和活性氧（ROS）爆发（RBOHB）相关的基因的相对表达水平，分别比对照高 2.76 倍和 4.23 倍。系统获得性抗性（SAR）是植物对病原体感染的重要免疫防御机制。观察到 SA 的积累、防御酶活性的增强以及防御相关基因的高水平表达表明，柠檬烯可能通过激活 SA 信号通路介导的 SAR 诱导烟草对 TMV 的抗性。此外，实验结果表明，用 800μg/mL 柠檬烯处理烟草后，叶绿素生物合成基因 POR1 的表达水平比对照增加了 1.72 倍，表明柠檬烯处理可能会增加烟草中的叶绿素含量。盆栽试验结果表明，800μg/mL 柠檬烯诱导植物对核盘菌（33.33%）、辣椒疫霉（54.55%）和灰葡萄孢（50.00%）的抗性。生物测定结果表明，柠檬烯对病原体感染提供了广谱和持久的抗性。因此，柠檬烯具有良好的开发利用价值，有望开发成为除杀虫剂和杀菌剂之外的新型植物源性抗病毒剂和植物免疫激活剂。
