Abstract
N-acetyl-5-methoxytryptamine (Melatonin), as a crucial messenger in plants, functions in adjusting biological rhythms, stress tolerance, plant growth and development. Several studies have shown the retardation effect of exogenous melatonin treatment on plant growth and development. However, the in vivo role of melatonin in regulating plant leaf growth and the underlying mechanism are still unclear. In this study, we found that high concentration of melatonin suppressed leaf growth in Arabidopsis by reducing both cell size and cell number. Further kinetic analysis of the fifth leaves showed that melatonin remarkably inhibited cell division rate. Additionally, flow cytometic analysis indicated that melatonin negatively regulated endoreduplication during leaf development. Consistently, the expression analysis revealed that melatonin regulated the transcriptional levels of key genes of cell cycle and ribosome. Taken together, this study suggests that high concentration of melatonin negatively regulated the leaf growth and development in Arabidopsis, through modulation of endoreduplication and the transcripts of cell cycle and ribosomal key genes.
Highlights
N-acetyl-5-methoxytryptamine (Melatonin), as an endogenous biomolecule first discovered in the pineal gland of cow [1], was later found to be extensively in almost all living organisms, including plants [2,3,4,5,6]
To investigate the effect of melatonin on leaf growth in Arabidopsis, WT (Col-0) seeds were firstly germinated for one day on 1/2 MS (Murashige & Skoog) media to alleviate the effect of melatonin on seeds germination; the germinated seeds were transferred onto new 1/2 MS media with different concentrations of melatonin and cultured for another six days
We found that high concentration of melatonin suppressed the cell proliferation and endoreduplication, and the expression of related key genes in leaf growth might contribute to this issue
Summary
N-acetyl-5-methoxytryptamine (Melatonin), as an endogenous biomolecule first discovered in the pineal gland of cow [1], was later found to be extensively in almost all living organisms, including plants [2,3,4,5,6]. Cell proliferation and expansion are two different but interconnected events that are necessary for the process of leaf growth. Only changes on level of cell proliferation or cell expansion will not certainly alter the leaf size because of the compensation effect caused by reduced cell proliferation and the DNA ploidy increase resulted from endoreduplication [38,48]. Wild-type Arabidopsis (WT, Columbia-0 ecotype) were treated with various concentrations of melatonin, and the results showed that high concentration of melatonin dramatically suppressed leaf growth by reducing the cell number and cell size. Further comprehensive analyses suggested that melatonin might regulate the leaf growth by inhibiting cell proliferation and endoreduplication
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