Physiological and Proteomic Analyses Reveal the Adaptive Mechanisms of Maize Genotypes Under Potassium Deficiency

Potassium (K) deficiency severely constrains maize productivity, yet the molecular mechanisms underlying genotypic differences in K tolerance remain poorly understood. A comparative physiological and iTRAQ-based quantitative proteomic analysis was conducted on two maize inbred lines with contrasting K-deficiency tolerance (Ktm, tolerant; Ksm, sensitive) following 3 days of K starvation (0 mM K), using roots as the primary analytical target. Physiological assessments revealed that under K deficiency, Ktm exhibited higher root vitality (Ktm decreased by 16.65% vs. Ksm by 31.54%) and larger root volume but lower electrolyte leakage compared with Ksm. Proteomic profiling identified 93 and 126 differentially abundant proteins (DAPs) in Ktm and Ksm, respectively. Integrative analysis indicated that Ktm responsed to K deprivation though coordinated downregulation of glycolytic enzymes, differential ROS accumulation with enhanced catalase (CAT) and peroxidase (POD) upregulation, and increased the abundances of cell wall-reinforcing proteins (dirigent proteins and cinnamyl alcohol dehydrogenase). In contrast, Ksm exhibited a less efficient stress response characterized by impaired ROS signaling, H₂O₂ accumulation, and compromised membrane permeability. These results suggested that under short-term K starvation, K tolerance in maize was associated more closely with the efficiency of metabolic reprogramming and ROS homeostasis than with differences in root K content. Our findings provide a mechanistic framework for understanding genotypic variation in K adaptation and identify candidate protein markers for breeding K-efficient maize varieties.