Ginsenoside Rb1 inhibits root growth by targeting mitochondrial complex III and SOD2 to dysregulate redox homeostasis in <i>Panax quinquefolius</i>

Abstract Continuous cropping obstacles seriously constrained the replanting and yield of Panax quinquefolius while the autotoxic allelochemical ginsenosides are the major factor leading to continuous cropping obstacles. Here, we elucidate the autotoxic molecular mechanism of ginsenoside Rb1 using P. quinquefolius adventitious roots and callus, together with Arabidopsis thaliana. Thermal proteome profiling identified six putative targets of Rb1, among which mitochondrial cytochrome b–c1 complex subunit 6 (QCR6) of mitochondrial complex III and manganese superoxide dismutase (SOD2) were verified as primary effectors. Rb1 directly binds to QCR6 and SOD2 to modulate ROS homeostasis, thereby inducing sulfenylation changes of redox-sensitive proteins such as PRDX and GAPDH. Functional assays in PqSOD2 overexpression and knockdown lines, as well as A. thaliana sod2 mutants, demonstrated that SOD2 is indispensable for Rb1-mediated redox regulation and root development. Altered SOD2 levels triggered transcriptional reprogramming of root growth-related genes. Metabolomic analyses further revealed Rb1-induced accumulation of oxalic acid, which suppressed root branching. Collectively, these results uncover a redox signaling cascade in which Rb1 targets complex III and SOD2, propagates ROS signals, and orchestrates downstream oxidative post-translational modifications, transcriptional responses, and metabolic shifts to inhibit root growth, resulting in continuous cropping obstacles.