Root Ion flux and transcriptomic analyses reveal the response mechanisms of Gleditsia sinensis seedlings to salt stress

Abstract

Abstract Gleditsia sinensis Lam. is a widely distributed tree species in China characterized by its remarkable tolerance to barrenness and salinity, making it a valuable candidate for the ecological restoration of saline-alkali lands. Understanding its ion regulatory mechanisms is a prerequisite for salt tolerance evaluation and molecular breeding. However, the molecular mechanisms coordinating root ion fluxes and overall defense strategies in G. sinensis under salt stress remain largely unclear. In this study, we investigated the root ion flux characteristics and underlying molecular mechanisms of hydroponic G. sinensis seedlings under 100 mmol·L⁻¹ NaCl stress using non-invasive micro-test technology (NMT) and transcriptomic sequencing. The results demonstrated that while salt stress induced substantial Na⁺ accumulation, roots actively responded by promoting Na⁺ efflux and H⁺ influx in the elongation zone. Transcriptomic analysis revealed that seedlings adopted a “growth-defense trade-off” strategy. By down-regulating energy-intensive metabolic pathways, the seedlings reallocated limited energy to significantly up-regulate key ion transporters, including AHA11 , AKT1 , and SKOR . This transcriptional reprogramming established a transmembrane proton gradient that drove effective Na⁺ efflux and maintained intracellular K⁺ homeostasis. These findings provide a theoretical basis and genetic resources for targeted molecular breeding of G. sinensis in saline environments.