Elevated methionine improves the nutritional quality of seeds and alters epigenetic landscapes in Arabidopsis

Title : Elevated methionine improves the nutritional quality of seeds and alters epigenetic landscapes in Arabidopsis

Abstract:

The key methionine biosynthetic enzyme cystathionine γ-synthase (CGS) was expressed under the control of the seed-specific phaseolin promoter in Arabidopsis, tobacco, and soybean. This led to a marked accumulation of amino acids and sugars in seeds, resulting in significantly elevated levels of protein and starch, which are important for nutritional value (Cohen et al. 2014). These metabolites are hypothesized to originate from leaf-derived translocation. Transcriptome profiling of Arabidopsis leaves revealed increased expression of genes involved in DNA methylation and chromatin remodelling. Since methionine is the precursor of S-adenosylmethionine (SAM)—the primary methyl donor for DNA and histone methylation, its elevated levels are expected to influence the epigenome (Girija et al. 2023). While low SAM levels have been associated with DNA hypomethylation, the consequences of increased Met/SAM remain poorly understood. To explore this, we analysed the mto1 mutant, which accumulates high methionine and SAM due to a mutation in CGS. Whole-genome bisulfide sequencing (WGBS) revealed widespread hypermethylation, particularly in non-CG contexts (CHG, CHH) within pericentromeric heterochromatin. Although gene body methylation (gbM) was also altered, it showed only a weak association with gene expression changes. Downregulation of transposable element-associated genes (TEGs) and stress-responsive genes suggests that elevated methionine/SAM suppresses genome plasticity by silencing TEs. Genes in sulphur assimilation and aspartate family pathways, which contribute to methionine biosynthesis, were downregulated, while methionine catabolic genes were upregulated. Overall, these findings establish a mechanistic link between methionine metabolism, the sulphur assimilation pathway, epigenetic regulation, and nutrient allocation, highlighting the influence of sulphur metabolic status on the plant epigenome and genome stability.

Biography:

Rachel Amir's lab focuses on improving the nutritional value of plants by increasing levels of essential amino acids, especially methionine, which is often limiting and reduces plant nutritional quality. Recently, a link has been shown between methionine, the precursor to S-adenosylmethionine, a contributor of plant methyl groups, and epigenetic changes that affect gene expression and growth. We have about 100 publications. Rachel is a full professor and the dean of the Faculty of Life Sciences at Tel Hai University.