Critical roles of the activation of ethylene pathway genes mediated by DNA demethylation in Arabidopsis hyperhydricity

Abstract

Hyperhydricity (HH) often occurs in plant tissue culture, seriously influencing the commercial micropropagation and genetic improvement. DNA methylation has been studied for its function in plant development and stress responses. However, its potential role in HH is unknown. In this study, we report the first comparative DNA methylome analysis of normal and hyperhydric Arabidopsis thaliana (L.) Heynh. seedlings using whole‐genome bisulfite sequencing (BS‐seq). We found that the global methylation level decreased in hyperhydric seedlings, and most of the differentially methylated genes were CHH hypomethylated genes. Moreover, the bisulfite sequencing results showed that hyperhydric seedlings displayed CHH demethylation patterns in the promoter of the ACS1 and ETR1 genes, resulting in upregulated expression of both genes and increased ethylene accumulation. Furthermore, hyperhydric seedling displayed reduced stomatal aperture accompanied by decreased water loss and increased phosphorylation of aquaporins accompanied by increased water uptake. While silver nitrate (AgNO3) prevented HH by maintained the degree of methylation in the promoter regions of ACS1 and ETR1 and downregulated the transcription of both genes. AgNO3 also reduced the content of ethylene together with the phosphorylation of aquaporins and water uptake. Taken together, this study suggested that DNA demethylation is a key switch that activates ethylene pathway genes to enable ethylene synthesis and signal transduction, which may subsequently influence aquaporin phosphorylation and stomatal aperture, eventually causing HH; thus, DNA demethylation plays a crucial role in HH. These results provide insights into the epigenetic regulation mechanism of HH and confirm the role of ethylene and AgNO3 in hyperhydricity control.

Hyperhydricity in Plant Tissue Culture

“…The hyperhydric seedlings displayed CHH context demethylation patterns in the promoters of genes for 1-aminocyclopropane-1-carboxylase synthase (ACS1) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO1), key enzymes in ethylene biosynthesis, resulting in upregulated expression of both genes and increased ethylene accumulation. Thus, DNA demethylation is a key switch in the activation of genes for ethylene biosynthesis to enable signal transduction, which may subsequently influence aquaporin phosphorylation and stomatal aperture, eventually causing hyperhydricity [ 65 ].…”

Methyl-Sensitive Amplification Polymorphism (MSAP) Analysis Provides Insights into the DNA Methylation Changes Underlying Adaptation to Low Temperature of Brassica rapa L.

“…Zhu et al [52] investigated anthocyanin enrichment in peaches during low-temperature storage and found that the higher transcript levels of anthocyanin synthase-related genes were associated with reduced methylation levels in their promoter regions. The promoter of the ACS1 and ETR1 genes in Arabidopsis hyperhydricity involved in the ethylene pathway displays CHH demethylation patterns, which consequently causes the upregulation of these two genes and increases ethylene enrichment [53]. In the current study, random sequencing of the cold-induced polymorphic DNA methylation bands revealed that some of these genes were highly homologous with the anti-freeze proteins endo-1,3-beta-glucosidase, VQ motif-containing protein 22 (VQ22), cysteine-rich receptor-like protein kinase 10 (CRK10), protein phosphatase 2C (PP2C), auxin-induced protein 15A (AUX15A), and glycine-rich RNA-binding protein 5 (GR-RBP5), of which the difference was most pronounced for VQ22 (Table 4).…”