Integrated Omic Analyses Reveal Module Networks Regulating Growth and Bioactive Component Synthesis of Sophora tonkinensis via Calcium Modulation

<i>Sophora tonkinensis</i> is a key medicinal plant endemic to the calcium-rich karst regions along the China-Vietnam border. This study investigated how calcium regulates the growth and biosynthesis of bioactive compounds in <i>S. tonkinensis</i> tissue culture seedlings by exposing them to a gradient of calcium concentrations. Our findings demonstrate that a moderate calcium level (T2, 2.99 mmol·L^-1) promoted root development, increasing root dry weight, and significantly elevated the content of matrine and oxymatrine. In contrast, a high calcium level (T4, 5.98 mmol·L^-1) inhibited root growth, reducing root length, but triggered a distinct metabolic shift, markedly increasing the accumulation of trifolirhizin and maackiain. Integrated transcriptomic, proteomic, and metabolomic analyses revealed that calcium exerts systemic regulation through multiple functional pathways. We identified four key signaling pathways-phytohormone, plant immunity, MAPK, and phospholipid signaling-as central hubs coordinating genetic information processing, vesicular transport, and metabolic reprogramming. These results provide valuable insights into the calcium-mediated regulatory networks and offer valuable targets for optimizing cultivation practices to enhance the yield of bioactive compounds in <i>S. tonkinensis</i>.