The Homocysteine S-Methyltransferase Family and Functional Analysis of <i>AhEXF4LS</i> Resistance to Bacterial Wilt in Peanut

The homocysteine S-methyltransferase (HMT) family plays a crucial role in plant metabolism and stress adaptation; however, its functional characteristics in peanuts and its association with biotic stress tolerance have not been thoroughly investigated. To bridge this knowledge gap, we identified 10 AhHMT family members that exhibit significant evolutionary conservation with HMT homologues from leguminous and solanaceous species. Collinearity analyses further revealed conserved synteny between AhHMTs and orthologs in wild peanut, <i>Arabidopsis thaliana</i>, soybean, and other plant species. Notably, <i>AhEXF4LS</i> was significantly upregulated following infection with <i>Ralstonia solanacearum</i> (<i>R. solanacearum</i>). Subcellular localization demonstrated that AhEXF4LS-YFP was localized in the cell nucleus. Importantly, in peanut roots overexpressing <i>AhEXF4LS</i>, colonization by <i>R. solanacearum</i> was significantly reduced, accompanied by substantial increases in reactive oxygen species accumulation and lignin deposition. These findings indicate that <i>AhEXF4LS</i> effectively counteracts <i>R. solanacearum</i> infection, offering a valuable genetic resource for the development of bacterial wilt-resistant peanut cultivars.