Rhizobacteria-priming improves common bean seeds germination under different abiotic stresses through improving hydrolysis and antioxidant enzymes kinetics parameters

Abstract

Bio-priming is a proven method for enhancing seed germination in stressful environments. Researchers have thoroughly explored its impact on enzyme activity during seed germination under diverse environmental stresses. Yet, there is limited knowledge about how bio-priming specifically influences enzyme kinetics. Understanding these kinetic changes could offer valuable insights into the metabolic adjustments and regulatory mechanisms employed by seeds to withstand stress. From this perspective, this study aims to investigate the effects of bio-priming with rhizobacteria on changes in hydrolysis enzymes (amylase and phytase) and antioxidant enzymes (superoxide dismutase and catalase) kinetics in germinated common bean seeds under different abiotic stresses. Two groups of common bean seeds germinated: the first consisted of dry seeds (non-primed), and the second was primed with Bacillus velezensis (bio-primed) under no-stress, drought, salinity, and lead acetate conditions. After 72 h of germination, the germination percentage was recorded. The germinated seeds underwent the extraction and purification of hydrolysis enzymes (amylase and phytase) and antioxidant enzymes (superoxide dismutase and catalase). The kinetic parameters (Michael constant, maximum velocity, turnover number, specificity constant, and catalytic efficiency) for each enzyme were determined. Bio-priming significantly improved common bean germination by enhancing the activity of hydrolysis enzymes and antioxidant enzymes. Enzyme kinetics changes significantly under stress, which indicates that there are differences in the enzyme configuration under stress that induce compounds that can inhibit enzyme activity by increasing the Km and decreasing the Vmax and the enzyme turnover Kcat. On the other hand, bio-priming significantly improved the catalytic efficiency of enzymes by decreasing the Km, increasing the Vmax, and increasing the enzyme turnover (Kcat) under both no-stress and stress conditions.