Melatonin as a regulatory hub of plant hormone levels and action in stress situations

• Published in: Plant biology (Stuttgart, Germany) Germany), 2021-05, Vol.23 (S1), p.7-19
• Main Authors: Arnao, M. B., Hernández‐Ruiz, J., Hu, Y.
• Format: Article
• Language: English
• Subjects: Abiotic stress; Abscisic acid; Animal tissues; biostimulator; Biosynthesis; Brassinosteroids; Catabolism; Cytokinins; Gibberellins; Hormones; Jasmonic acid; Melatonin; Physiological responses; Phytohormones; plant growth; Plant hormones; Plant resources; Plant stress; plant tolerance; Polyamines; redox network; Salicylic acid; Stress response; stress signalling
• ISSN: 1435-8603; 1438-8677
• DOI: 10.1111/plb.13202

Melatonin, a molecule first discovered in animal tissues, plays an important role in multiple physiological responses as a possible plant master regulator. It mediates responses to different types of stress, both biotic and abiotic. Melatonin reduces the negative effects associated with stressors, improving the plant response by increasing plant stress tolerance. When plants respond to stress situations, they use up a large amount of plant resources through a set of perfectly synchronized actions. Responses mediated by melatonin use the plant’s hormones to, after adequate modulation, counteract and overcome the negative action of the stressor. In this paper, we review melatonin–plant hormone relationships. Factors that trigger the stress response and the central role of melatonin are analysed. An extensive analysis of current studies shows that melatonin modulates the metabolism of plant hormones (biosynthesis and catabolism), the rise or fall in their endogenous levels, the regulation of signalling elements and how melatonin affects the final response of auxin, gibberellins, cytokinins, abscisic acid, ethylene, salicylic acid, jasmonates, brassinosteroids, polyamines and strigolactones. Lastly, a general overview of melatonin’s actions and its regulatory role at a global level is provided and proposals for future research are made. Melatonin in plants regulates the levels of plant hormones through the up‐ or down‐expression of biosynthesis and catabolic genes and signaling elements.