# Temporal Dynamics of Gene Expression and Metabolic Rewiring in Wild Barley (Hordeum spontaneum) Under Salt Stress

## TL;DR

This study explores how wild barley adapts to high salt levels by changing its gene activity and metabolism, offering insights for developing salt-tolerant crops.

## Contribution

The paper reveals a coordinated network of metabolic and redox pathways activated in wild barley under salt stress.

## Key findings

- 140 genes were dynamically upregulated across 19 metabolic pathways under salt stress.
- Key metabolic nodes like acetyl-CoA and ubiquinone helped stabilize membranes and manage redox balance.
- Increased lipid biosynthesis and antioxidant pathways improved cellular resilience to salinity.

## Abstract

This study investigates the adaptive mechanisms that enable a single wild barley (Hordeum spontaneum) accession to withstand extreme salinity. Salt stress reshapes plant metabolism and gene expression, offering targets for breeding salt-tolerant cereals. A time-course RNA-Seq experiment was conducted on leaves exposed to 500 mM NaCl, followed by differential expression and functional annotations to characterize transcriptomic responses. Transcriptomic profiling identified 140 dynamically upregulated genes distributed across 19 interconnected metabolic pathways, with phased activation of oxidative phosphorylation, nitrogen assimilation, lipid remodeling, and glutathione metabolism. Central metabolic nodes, including acetyl-CoA, hexadecanoyl-CoA, and ubiquinone, coordinated bioenergetic output, membrane stabilization, and redox homeostasis. Ribose-5-phosphate and ribulose-5-phosphate linked glycolysis and the pentose phosphate pathway, supplying NADPH for antioxidant defense and nucleotide repair, while riboflavin derived from Ru5P enhanced flavoprotein activity. In parallel, glucose and fructose-6-phosphate supported osmotic adjustment and glycolytic flux, and increased sterol and cuticular lipid biosynthesis, including cholesterol-like compounds, reinforced membrane integrity and calcium signaling. Glutathione and N-acetyl-glutamate together mitigated oxidative stress and modulated polyamine metabolism, strengthening cellular resilience under salt stress. These findings outline a coordinated network of metabolic and redox pathways that can guide the engineering of salt-tolerant cereals for sustainable production in saline agroecosystems.