Review about melatonin effects on postharvest of fruits and vegetables

Melatonin is a ubiquitous molecule distributed in nature and not only plays an important role in animals and humans but also has extensive functions in plants, such as delaying senescence, exerting antioxidant effects, regulating growth and development, and facilitating plant adaption to stress conditions. Endogenous melatonin is widespread in fruits and vegetables and plays prominent roles in the ripening and post-harvest process of fruits and vegetables. Exogenous application of melatonin removes excess reactive oxygen species from post-harvest fruits and vegetables by increasing antioxidant enzymes, non-enzymatic antioxidants, and enzymes related to oxidized protein repair. Moreover, exogenous application of melatonin can increase endogenous melatonin to augment its effects on various physiological processes. Many previous reports have demonstrated that application of exogenous melatonin improves the post-harvest preservation of fruits and vegetables. Although overproduction of melatonin in plants via transgenic approaches could be a potential means for improving the post-harvest preservation of fruits and vegetables, efforts to increase endogenous melatonin in plants are limited. In this review, we summarize the recent progress revealing the role and action mechanisms of melatonin in post-harvest fruits and vegetables and provide future directions for the utilization of melatonin to improve the post-harvest preservation of fruits and vegetables.Index of the paper?1 Introduction2 Contents Of Endogenous Melatonin21 Melatonin In Post-Harvest Fruits22 Melatonin In Post-Harvest Vegetables3 Application Of Exogenous Melatonin31 Application In Post-Harvest Fruits32 Application In Post-Harvest Vegetables4 Mechanisms Of Exogenous Melatonin Functions In Post-Harvest Fruits And Vegetables41 Exogenous Melatonin Increases Antioxidant Enzymes For Scavenging ROS42 Exogenous Melatonin Induces Non-Enzymatic Antioxidants43 Exogenous Melatonin Increases Oxidative Protein Repair-Related Enzymes44 Relationship Between Exogenous Melatonin and Hormones in Post-Harvest Stage44 Exogenous Melatonin Activates the ?-Aminobutyric Acid (GABA) Shunt Pathway45 Melatonin Acts As a Signal Molecule5 Conclusions And Future Prospects The figure is Figure 1 of the original paper - Model of exogenous melatonin-mediated post-harvest preservation mechanism in fruits and vegetables. (1) Blue lines and arrows indicate ROS elimination pathway. Melatonin acts psrimarily as a powerful free radical scavenger by increasing the content of antioxidant enzymes, non-enzymatic antioxidants, and the enzymes related to oxidative protein repair, removing excess active oxygen from post-harvest fruits and vegetables, and promoting GABA shunt pathway. Subsequently, the content of hydroxyl radicals and hydrogen peroxide decreases, the degree of membrane lipid peroxidation is reduced, thus protecting cells from oxidative damage and prolonging the shelf-life. (2) Green lines and arrows indicate pathogen response dependent pathway. Exogenous melatonin increases the levels of JA and SA, triggers plant pathogen responses, increases pathogen resistance, and extends the shelf life. (3) Orange lines and arrows indicate post-harvest decay of fruits and vegetables. Diseases or senescence of post-harvest fruits and vegetables produce lots of ROS, lead to lipid peroxidation, and cause post-harvest decay. Red arrows indicate increased levels of each component.? SourcesMelatonin Is a Potential Target for Improving Post-Harvest Preservation of Fruits and VegetablesTao Xu1,2*, Yao Chen1 and Hunseung Kang3*1Key Lab of Phylogeny and Comparative Genomics of the Jiangsu Province, Institute of Integrative Plant Biology, School of Life Sciences, Jiangsu Normal University, Xuzhou, China2Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States3Department of Applied Biology, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, South KoreaFront. Plant Sci., 30 October 2019?https://www.frontiersin.org/articles/10.3389/fpls.2019.01388/full