Abstract

DNA methylation has been referred as an important player in plant genomic responses to environmental stresses but correlations between the methylome plasticity and specific traits of interest are still far from being understood. In this study, we inspected global DNA methylation levels in salt tolerant and sensitive rice varieties upon salt stress imposition. Global DNA methylation was quantified using the 5-methylcytosine (5mC) antibody and an ELISA-based technique, which is an affordable and quite pioneer assay in plants, and in situ imaging of methylation sites in interphase nuclei of tissue sections. Variations of global DNA methylation levels in response to salt stress were tissue- and genotype-dependent. We show a connection between a higher ability of DNA methylation adjustment levels and salt stress tolerance. The salt-tolerant rice variety Pokkali was remarkable in its ability to quickly relax DNA methylation in response to salt stress. In spite of the same tendency for reduction of global methylation under salinity, in the salt-sensitive rice variety IR29 such reduction was not statistically supported. In ‘Pokkali’, the salt stress-induced demethylation may be linked to active demethylation due to increased expression of DNA demethylases under salt stress. In ‘IR29’, the induction of both DNA demethylases and methyltransferases may explain the lower plasticity of DNA methylation. We further show that mutations for epigenetic regulators affected specific phenotypic parameters related to salinity tolerance, such as the root length and biomass. This work emphasizes the role of differential methylome flexibility between salt tolerant and salt sensitive rice varieties as an important player in salt stress tolerance, reinforcing the need to better understand the connection between epigenetic networks and plant responses to environmental stresses.

Highlights

  • Soil salinity is a major environmental constraint to crop production with negative impacts on growth rates, tillering and seed production [1]

  • We evaluated global DNA methylation levels in distinct tissues of salt tolerant and sensitive rice varieties upon salt stress imposition

  • Global DNA methylation levels were quantified by the ELISA-based technique assay

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Summary

Introduction

Soil salinity is a major environmental constraint to crop production with negative impacts on growth rates, tillering and seed production [1]. Salinity tolerance is a quantitative trait controlled by multiple genes [3] which can be involved in signal transduction, ion transportation, metabolic pathways and transcription regulation [4]. Epigenetic mechanisms such as DNA methylation, histone modifications, nucleosome positioning and small non-coding RNAs, act in coordination to influence chromatin structure and gene expression [5,6,7,8]. This work focused in evaluating global DNA methylation levels in rice varieties with contrasting behaviors in response to salt stress. Mutations of epigenetic modulators affected specific phenotypic parameters related to salinity tolerance such as root length and biomass

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