Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agriculture, Hainan University, Haikou, China.
Department of Cellular and Structural Biology, The University of Texas Health Science Center, San Antonio, TX, USA.
J Pineal Res. 2015 Aug;59(1):102-8. doi: 10.1111/jpi.12244. Epub 2015 May 26.
Melatonin (N-acetyl-5-methoxytryptamine) is a naturally occurring small molecule, serving as important secondary messenger in the response of plants to various biotic and abiotic stresses. However, the interactions between melatonin and other important molecules in the plant stress response, especially in plant immunity, are largely unknown. In this study, we found that both melatonin and nitric oxide (NO) levels in Arabidopsis leaves were significantly induced by bacterial pathogen (Pst DC3000) infection. The elevated NO production was caused by melatonin as melatonin application enhanced endogenous NO level with great efficacy. Moreover, both melatonin and NO conferred improved disease resistance against Pseudomonas syringe pv. tomato (Pst) DC3000 infection in Arabidopsis. NO scavenger significantly suppressed the rise of NO which was induced by exogenous application of melatonin. As a result, the beneficial effects of melatonin on the expression of salicylic acid (SA)-related genes and disease resistance against bacterial pathogen infection were jeopardized by use of a NO scavenger. Consistently, melatonin application significantly lost its effect on the innate immunity against P. syringe pv. tomato (Pst) DC3000 infection in NO-deficient mutants of Arabidopsis. The results indicate that melatonin-induced NO production is responsible for innate immunity response of Arabidopsis against Pst DC3000 infection.
褪黑素（N-乙酰-5-甲氧基色胺）是一种天然存在的小分子，作为植物对各种生物和非生物胁迫反应的重要第二信使。然而，褪黑素与植物应激反应中其他重要分子之间的相互作用，特别是在植物免疫中，很大程度上是未知的。在这项研究中，我们发现细菌病原体（Pst DC3000）感染显著诱导拟南芥叶片中的褪黑素和一氧化氮（NO）水平。NO 的产生增加是由褪黑素引起的，因为褪黑素应用非常有效地增强了内源性 NO 水平。此外，褪黑素和 NO 都赋予了拟南芥对 Pseudomonas syringe pv. tomato (Pst) DC3000 感染的更好的抗病性。NO 清除剂显著抑制了外源褪黑素应用诱导的 NO 的上升。结果，NO 清除剂的使用危及了褪黑素对水杨酸（SA）相关基因表达和对细菌病原体感染的抗病性的有益影响。一致地，在拟南芥的 NO 缺陷突变体中，褪黑素的应用显著丧失了其对 P. syringe pv. tomato (Pst) DC3000 感染的先天免疫的作用。结果表明，褪黑素诱导的 NO 产生是拟南芥对 Pst DC3000 感染的先天免疫反应的原因。
