Physiological and Transcriptomic Analyses of Salt Stress Response in Peanut Seedling

Soil salinization is a major constraint on peanut production. Here, we characterized the physiological and transcriptomic responses of peanut (Arachis hypogaea L.) seedlings exposed to 200 mM NaCl. Salt stress markedly inhibited plant growth, elevated the Na+/K+ ratio, and induced oxidative stress, as reflected by increased contents of malondialdehyde, hydrogen peroxide, and superoxide anion, along with damaged chloroplast ultrastructure and reduced chlorophyll content and Fv/Fm. Transcriptomic analysis of roots at 0, 3, 6, 12, and 24 h post-treatment identified 4332 differentially expressed genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that phenylpropanoid and flavonoid biosynthesis, glutathione metabolism, and mitogen-activated protein kinase signaling pathways were significantly activated. Weighted gene co-expression network analysis (WGCNA) revealed that the salmon and yellow modules were strongly correlated with physiological traits and identified a key co-expressed gene pair involving AhbHLH162 and AhGST. Numerous transcription factors from the ERF, MYB, bHLH, NAC, and WRKY families were differentially expressed, underscoring their roles in salt tolerance. These findings provide insights into the molecular basis of salt tolerance in peanut and offer candidate targets for genetic improvement.