Phytomelatonin: An Emerging Signal Molecule Responding to Abiotic Stress

doi:10.13560/j.cnki.biotech.bull.1985.2023-0880

Abstract

Abstract:

Compared with other five traditional hormones, the identification of melatonin（MT）was done in only two decades. MT is an emerging plant hormone, which is a pleiotropic signaling molecule with multiple physiological functions in organisms. In plants, MT is called phytomelatonin, which is not only involved in the regulation of seed germination, root system architecture, stomatal movement, biological rhythm, flowering, and senescence, but also in the response of plants to biotic and abiotic stresses by activating the activities of antioxidant system, scavenging ROS, followed by reducing osmotic stress, oxidative stress, protein denaturation, and cell damage caused by biotic and abiotic stress, thus plants respond to biotic and abiotic stresses. Based on the latest research progress of MT metabolism in plant and its response to abiotic stress, the anabolism and catabolism of MT in plants are summarized. The plant resistance to high temperature, low temperature, drought, salt, heavy metals, ultraviolet radiation and waterlogging is improved ultimately under stress by MT directly removing ROS and/or triggering the signal transduction pathway, up-regulating resistance related gene expression, and then activating the vitality of osmoregulation system and antioxidant system, promoting the synthesis of stress protein and secondary metabolic substances, stable photosynthesis and carbon metabolism, and thus reducing the accumulation of ROS and cell oxidative damage. This paper lays the theoretical foundation for understanding the metabolism, physiological function, and cellular signal transduction of MT in plants, and point out the future research directions.

Key words: phytomelatonin, abiotic stress, antioxidant system, osmoregulation system, stress tolerance

ZHOU Hong-dan, LUO Xiao-ping, TU Mi-xue, LI Zhong-guang. Phytomelatonin: An Emerging Signal Molecule Responding to Abiotic Stress[J]. Biotechnology Bulletin, 2024, 40(3): 41-51.

Figures/Tables 2

Fig. 1 Biosynthetic pathway of melatonin in plants Phytomelatonin（MT）can be biosynthesized in chloroplasts, cytosol, and mitochondria of the plant cells by at least four steps, five pathways, and six key enzymes. SKM: Shikimic acid. Trp: Tryptophan. TDC: Tryptophan decarboxylase. TPH: Tryptophan hydroxylase. COMT: Caffeic acid O-methyltransferase. ASMT: N-acetylserotonin methyltransferase. TAM: Tryptamine. 5HT: 5-hydroxytryptophan. SER: Serotonin; 5MT: 5-methoxytryptamine. T5H: Tryptophan-5-hydroxylase. SNAT: Serotonin N-acetyltransferase. NAS: N-acetylserotonin. ENP: Enzymatic, non-enzymatic, and pseudoenzymatic reaction. AFMK: N1-acetyl-N2-formyl-5-methoxykynuramine

Fig. 2 Role of phytomelatonin in plant response to abiotic stress Melatonin（MT）signaling be triggered in plants by high temperature, low temperature, drought, salt, flooding, heavy metal, and ultraviolet-B（UV-B）stress, which in turn respond to these stresses via two signaling pathways. ROS: Reactive oxygen species; Ca2+: calcium ion; NO: nitric oxide; H2S: hydrogen sulfide; ABA: abscisic acid; GA: gibberelin; JA: jasmonic acid; PA: polyamine; Pro: proline; SS: soluble sugar; SP: soluble proteins; HSP: heat shock proteins; LEA: late embryogenesis abundant; SOD: superoxide dismutase; APX: ascorbate peroxidase; GSH: glutathione.（↑）and（↓）indicate increase and decrease, respectively

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