Plasma membrane proteomics reveals mechanism of low potassium tolerance in two contrasting maize genotypes.

Potassium (K) deficiency is a major constraint on plant growth and crop productivity. To elucidate the genotypic mechanisms underlying maize adaptation to K deficiency, we comprehensively compared the physiological responses and 8-plex iTRAQ (4 biological replicates) based plasma membrane (PM) proteomes of two maize genotypes with contrasting K efficiency. Under low-K conditions, the K-efficient genotype (K-ef) maintained greater growth and root vitality and exhibited significantly higher K concentration and accumulation than the K inefficient genotype (K-inef). Quantitative plasma membrane (PM) proteomic analysis revealed 52 differentially accumulated proteins (DAPs) in K-ef (29 upregulated and 23 downregulated) and 49 DAPs in K-inef (38 upregulated, and 11 downregulated). These DAPs were involved in transport, signal transduction, lipid metabolism, cellular structure, and redox/defense. Integrating the physiological and proteomic data revealed that K-ef may adopt an "energy-saving" strategy by prioritizing K+ transport, redox defense, and Ca2+ signaling, whereas K-inef falls into an energy-wasting strategy and indiscriminate stress response. Our study provides valuable insights into physiological and molecular mechanisms underlying low K stress in maize roots and providing a basis to further study K nutrition in other crop species.