Exogenous Melatonin Improves Plant Iron Deficiency Tolerance via Increased Accumulation of Polyamine-Mediated Nitric Oxide.

Cheng Zhou,Jianfei Wang,Zhongyou Ma,Jian Zhu,Zhi Liu,Lin Zhu

doi:10.3390/ijms17111777

Abstract

Melatonin has recently been demonstrated to play important roles in the regulation of plant growth, development, and abiotic and biotic stress responses. However, the possible involvement of melatonin in Fe deficiency responses and the underlying mechanisms remained elusive in Arabidopsis thaliana. In this study, Fe deficiency quickly induced melatonin synthesis in Arabidopsis plants. Exogenous melatonin significantly increased the soluble Fe content of shoots and roots, and decreased the levels of root cell wall Fe bound to pectin and hemicellulose, thus alleviating Fe deficiency-induced chlorosis. Intriguingly, melatonin treatments induced a significant increase of nitric oxide (NO) accumulation in roots of Fe-deficient plants, but not in those of polyamine-deficient (adc2-1 and d-arginine-treated) plants. Moreover, the melatonin-alleviated leaf chlorosis was blocked in the polyamine- and NO-deficient (nia1nia2noa1 and c-PTIO-treated) plants, and the melatonin-induced Fe remobilization was largely inhibited. In addition, the expression of some Fe acquisition-related genes, including FIT1, FRO2, and IRT1 were significantly up-regulated by melatonin treatments, whereas the enhanced expression of these genes was obviously suppressed in the polyamine- and NO-deficient plants. Collectively, our results provide evidence to support the view that melatonin can increase the tolerance of plants to Fe deficiency in a process dependent on the polyamine-induced NO production under Fe-deficient conditions.

Highlights

Since the first identification of melatonin (N-acetyl-5-methoxytryptamine) from the borine pineal gland [1], considerable efforts have been made to unravel its roles in living organisms, including animals and plants
Melatonin treatments enhance the tolerance of harvested peach fruits to chilling stress, which is associated with the increased polyamine content [42]. These findings indicate that melatonin regulates plant abiotic stress responses, possibly involving polyamine-mediated nitric oxide (NO) accumulation
This study indicated that melatonin regulated Fe deficiency responses and promoted Fe remobilization from the cell wall via induction of polyamine-mediated NO accumulation

Summary

Introduction

Since the first identification of melatonin (N-acetyl-5-methoxytryptamine) from the borine pineal gland [1], considerable efforts have been made to unravel its roles in living organisms, including animals and plants. Melatonin is involved in regulating diverse physiological processes, such as biorhythms, seasonal reproduction, antioxidant functions, and immune stimulation [2,3,4]. Plants are frequently subjected to various biotic or abiotic stresses. It has recently been reported that melatonin can increase the resistance of plants to biotic stress via the salicylic acid (SA)- and nitric oxide (NO)-mediated signaling pathways [14,15]. Whether melatonin is involved in the regulation of plant iron (Fe) deficiency responses and the underlying mechanisms are poorly known to date

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Discussion

Conclusion