Integrated physiological, transcriptomic and metabolomic analysis revealed heterosis for cadmium tolerance in maize

Heterosis describes superior performance of F₁ hybrids over parents in yield and stress tolerance, yet its role in Cd tolerance remains poorly characterized in maize. This study integrated physiological, transcriptomic, and metabolomic analyses for the hybrid Zhengdan958 (ZD958) and its parents under cadmium (Cd) stress. Compared to parental lines, ZD958 consistently exhibited superior morphological traits (e.g., plant height, root biomass) and significantly enhanced elevated catalase (CAT) activity under Cd stress. Mid-parent heterosis (MPH) for key traits ranged from 2.73 % to 25.90 %, confirming robust hybrid vigor under Cd exposure. Transcriptomic analysis identified 904 unique differentially expressed genes (DEGs) in ZD958 under Cd stress, with weighted gene co-expression network analysis (WGCNA) revealing two key modules. Metabolomic analysis identified 902 metabolites, and the differentially accumulated metabolites in ZD958 primarily enriched in phenylpropanoid biosynthesis, glycerophospholipid metabolism, and glycosylphosphatidylinositol-anchor biosynthesis. Analysis of non-additive expression (NAE) genes identified one gene under both conditions, which was also specifically down-regulated in ZD958 under Cd stress. Analysis of allele-specific expression (ASE) genes revealed 12 genetically over-dominant genes in ZD958. Integrated multi-omics analysis highlighted the critical roles of phenylpropanoid biosynthesis and starch and sucrose metabolism in the heterosis of ZD958 to Cd stress. Our findings provide novel insights into how phenylpropanoid biosynthesis and starch/sucrose metabolism mediate heterosis for Cd tolerance.