School of Biology, Food and Environment, Hefei University, Hefei 230601, China.
State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei 230036, China.
Int J Mol Sci. 2021 Oct 28;22(21):11704. doi: 10.3390/ijms222111704.
Cadmium (Cd) is one of the most injurious heavy metals, affecting plant growth and development. Melatonin (-acetyl-5-methoxytryptamine) was discovered in plants in 1995, and it is since known to act as a multifunctional molecule to alleviate abiotic and biotic stresses, especially Cd stress. Endogenously triggered or exogenously applied melatonin re-establishes the redox homeostasis by the improvement of the antioxidant defense system. It can also affect the Cd transportation and sequestration by regulating the transcripts of genes related to the major metal transport system, as well as the increase in glutathione (GSH) and phytochelatins (PCs). Melatonin activates several downstream signals, such as nitric oxide (NO), hydrogen peroxide (HO), and salicylic acid (SA), which are required for plant Cd tolerance. Similar to the physiological functions of NO, hydrogen sulfide (HS) is also involved in the abiotic stress-related processes in plants. Moreover, exogenous melatonin induces HS generation in plants under salinity or heat stress. However, the involvement of HS action in melatonin-induced Cd tolerance is still largely unknown. In this review, we summarize the progresses in various physiological and molecular mechanisms regulated by melatonin in plants under Cd stress. The complex interactions between melatonin and HS in acquisition of Cd stress tolerance are also discussed.
镉（Cd）是最具危害性的重金属之一，会影响植物的生长和发育。褪黑素（N-乙酰-5-甲氧基色胺）于 1995 年在植物中被发现，此后被认为是一种多功能分子，可以缓解非生物和生物胁迫，特别是 Cd 胁迫。内源性触发或外源性施加的褪黑素通过改善抗氧化防御系统来重新建立氧化还原稳态。它还可以通过调节与主要金属转运系统相关的基因的转录本，以及增加谷胱甘肽 (GSH) 和植物螯合肽 (PCs)，来影响 Cd 的运输和螯合。褪黑素激活几种下游信号，如一氧化氮 (NO)、过氧化氢 (HO) 和水杨酸 (SA)，这些信号是植物 Cd 耐受所必需的。与 NO 的生理功能类似，硫化氢 (HS) 也参与植物的非生物胁迫相关过程。此外，外源褪黑素在盐度或热胁迫下诱导植物中 HS 的产生。然而，HS 作用在褪黑素诱导的 Cd 耐受中的参与在很大程度上仍然未知。在这篇综述中，我们总结了褪黑素在 Cd 胁迫下调节植物各种生理和分子机制的进展。还讨论了褪黑素和 HS 在获得 Cd 胁迫耐受性方面的复杂相互作用。
