Abstract
DNA methylation and demethylation precisely and effectively modulate gene expression during plant growth and development and in response to stress. However, expression profiles of genes involved in DNA methylation and demethylation during plant development and their responses to phytohormone treatments remain largely unknown. We characterized the spatiotemporal expression patterns of genes involved in de novo methylation, methyl maintenance, and active demethylation in roots, shoots, and reproductive organs using β-glucuronidase (GUS) reporter lines. Promoters of DNA demethylases were generally more highly active at the mature root tissues, whereas the promoters of genes involved in DNA methylation were more highly active at fast-growing root tissues. The promoter activity also implies that methylation status in shoot apex, leaf primordia, floral organs, and developing embryos is under tight equilibrium through the activity of genes involved in DNA methylation and demethylation. The promoter activity of DNA methylation and demethylation-related genes in response to various phytohormone treatments revealed that phytohormones can alter DNA methylation status in specific and redundant ways. Overall, our results illustrate that DNA methylation and demethylation pathways act synergistically and antagonistically in various tissues and in response to phytohormone treatments and point to the existence of hormone-linked methylome regulation mechanisms that may contribute to tissue differentiation and development.
Highlights
Epigenetic mechanisms coordinate the expression of thousands of genes in a heritable yet flexible manner, without changing the underlying DNA sequence [1]
In order to better understand the connection between DNA methylation and phytohormones, we assessed the spatiotemporal expression patterns of genes involved in DNA methylation and demethylation in roots and shoots in response to treatment of six phytohormones: auxin (AUX), cytokinin (CK), gibberellic acid (GA), ethylene (ET), abscisic acid (ABA), and salicylic acid (SA)
In order to assess the spatial and temporal expression patterns of genes involved in DNA methylation and demethylation in various plant tissues and organs, a number of transgenic GUS reporter lines were generated
Summary
Epigenetic mechanisms coordinate the expression of thousands of genes in a heritable yet flexible manner, without changing the underlying DNA sequence [1]. DNA methylation, along with histone modifications, chromatin remodeling, and non-coding small RNAs (sRNAs) constitute the highly dynamic and interconnected epigenome, which contributes to the regulation of gene expression during plant development and stress response [2,3,4,5,6,7,8,9]. DNA methylation is generally regarded as a repressive mark of gene expression. DNA methylation in the promoter of protein coding and microRNA genes has been generally shown to cause transcriptional repression, recent reports point to a possible role of DNA methylation in gene transcriptional activation [3,10,11,12,13]. The functional role of DNA methylation in gene body regions, remains largely unknown even though recent studies associate DNA methylation levels and patterns with gene expression and splicing efficiency [14,15,16]
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