WGCNA identifies key genes involved in methyl jasmonate-mediated tolerance to mercury stress in maize (Zea mays L.)

Methyl jasmonate (MeJA) plays a pivotal role in regulating plant responses to abiotic stress. However, the mechanisms by which MeJA modulates maize (Zea mays L.) tolerance to mercury (Hg) stress and the key genes involved remain poorly understood. In this study, seedlings of the maize cultivar “Longrui 999” were subjected to filter paper-based treatment of 45 mg/L HgCl₂ (Hg) or 45 mg/L HgCl₂ + 75 μmol/L MeJA (Hg + MeJA), with 100 mL solution added to each container and 50 mL of distilled water supplied daily to maintain a stable concentration. Hg stress significantly inhibited seedling growth and photosynthetic capacity, whereas MeJA application alleviated these inhibitory effects. Weighted gene co-expression network analysis (WGCNA) of transcriptomic data identified two modules associated with Hg2⁺ + MeJA treatment (MEbrown and MEblue). KEGG and GO enrichment analyses revealed that the MEbrown module primarily reflects activation of detoxification and transport processes, while MEblue genes were predominantly involved in photosynthesis-related pathways and functions. Hub genes in MEbrown (UGT71K, DTX40, LOX1.5, AGAL1, RAMDAZC7, and At1g03400) and MEblue (CFBP, AS1, MDH1, PSBR, ABCG22, and PLGG) were further identified as key regulators. These results provide molecular evidence for the role of MeJA in mitigating Hg-induced stress and identify candidate genes that may contribute to Hg tolerance in maize, warranting further validation in breeding-related studies.