Mechanism Analysis of Sugar Metabolism Regulation in the Dynamic Response of Common Bean ( Phaseolus vulgaris L.) Leaves to Alkaline Salt Stress

Increasing soil salinization in the Songnen Plain region, Northeast China, has hindered common bean (Phaseolus vulgaris L.) cultivation. The specific regulatory mechanisms of sugar metabolism in common bean leaves under alkaline salt stress remain unclear. To address this research gap, in China's Songnen Plain, we subjected the high-yielding and multi-resistant granular bean variety "Qingyun 1" seedlings to stress treatments at 0, 24, and 48 h time points. Alkaline salt stress was simulated by applying 100 mM NaHCO₃ and Na₂CO₃ mixed at a 9:1 M ratio. With prolonged treatment time, common bean leaves gradually wilted and yellowed. Stomatal conductance, total chlorophyll, and carotenoids significantly decreased by 16.45%-75.77%. Superoxide dismutase, peroxidase, and catalase activities and malondialdehyde and H₂O₂ contents significantly increased by 42.04%-91.36%, all reaching extremely significant levels (p < 0.01). Under progressive photosynthesis inhibition, the dynamic regulatory network of sugar metabolism helped sustain common bean leaf responses to alkaline salt stress. Integration of the dynamic changes in the activities of hexokinase (HK), α-galactosidase (galA), and 6-phosphofructokinase with the levels of sugars resulted in persistently suppressed HK phosphorylation, enhancing galA activity accelerated stachyose and raffinose metabolism and Suc and Fru release promotion in the leaves under alkaline salt stress. This ensured sustained high SS concentrations, ultimately providing plants with additional energy and carbon sources. Thus, the key genes encoding galA could be important candidates for exploring alkaline salt stress response mechanisms in common bean. These findings provide insights and theoretical support for breeding new alkaline salt-tolerant common bean varieties.