A Systematic Review of Melatonin in Plants: An Example of Evolution of Literature

Abstract

Melatonin (N-acetyl-5-methoxy-tryptamine) is a mammalian neurohormone, antioxidant and signaling molecule that was first discovered in plants in 1995. The first studies investigated plant melatonin from a human perspective quantifying melatonin in foods and medicinal plants and questioning whether its presence could explain the activity of some plants as medicines. Starting with these first handful of studies in the late 1990s, plant melatonin research has blossomed into a vibrant and active area of investigation and melatonin has been found to play critical roles in mediating plant responses and development at every stage of the plant life cycle from pollen and embryo development through seed germination, vegetative growth and stress response. Here we have utilized a systematic approach in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) protocols to reduce bias in our assessment of the literature and provide an overview of the current state of melatonin research in plants, covering 1995–2021. This review provides an overview of the biosynthesis and metabolism of melatonin as well as identifying key themes including: abiotic stress responses, root development, light responses, interkingdom communication, phytohormone and plant signaling. Additionally, potential biases in the literature are investigated and a birefringence in the literature between researchers from plant and medical based which has helped to shape the current state of melatonin research. Several exciting new opportunities for future areas of melatonin research are also identified including investigation of non-crop and non-medicinal species as well as characterization of melatonin signaling networks in plants.

Compression principle and Zipf’s Law of brevity in infochemical communication

“…By contrast, the parallel study of ubiquitous substances in many species and ecosystems may be essential to understanding inter-kingdom communication (e.g. melatonin case in [69]).…”

Distinct GmASMTs are involved in regulating transcription factors and signalling cross-talk across embryo development, biotic, and abiotic stress in soybean

“…Melatonin (MEL) was first reported in plants and is widely distributed in vegetative and reproductive tissue ( Dubbels et al, 1995 ; Hattori et al, 1995 ). They play an important role in circadian rhythm, biochemical and physiological processes in plants ( Murch and Erland, 2021 ). They act as effective signalling and bioactive molecule associated with plants tolerance against abiotic and biotic stresses ( Tan et al, 2019 ; Qari et al, 2022 ).…”

Exogenous melatonin enhances the growth and production of bioactive metabolites in Lemna aequinoctialis culture by modulating metabolic and lipidomic profiles

“…Melatonin has multiple functions in plants. As an amphiphilic molecule, melatonin is ubiquitous in all intracellular plant compartments [ 12 ], and was reported to play key roles in various plant responses and development [ 13 ]. Recently, melatonin was suggested as a plant hormone when the first phytomelatonin receptor, CAND2/PMTR1, in Arabidopsis thaliana , which governs stomatal closure in response to stress, was discovered [ 14 ].…”

“…Furthermore, it increases the efficiency of the electron transport chain by scavenging ROS and RNS produced in the mitochondria and reducing the loss of glutathione and protein damage [ 22 ]. Melatonin also protects plants from various abiotic and biotic stresses, such as acid rain, cold, drought, pathogens, infections, heavy metals, herbicides, salinity, and high temperature [ 23 – 27 ], and stabilizes the photosynthetic network under light and temperature stress conditions [ 13 , 28 – 30 ].…”