High Na + concentrations trigger severe environmental problems, further restraining crop yield and deteriorating produce quality. Our study observed that salt stress severely inhibits the growth of garlic by decreasing shoot height (19.95-26.55%), leaf width (24.00-29.63%), and pseudostem development (7.49-17.39%), while inducing oxidative damage by increasing ROS (O 2 · − up to 6909.62 μg/g/min FW) and lipid peroxidation induced oxidative damage. Pseudomonas sp . UW4 treatment significantly increased biomass (12.61%-70.55% of fresh weight) and root vigor (91.67% on the 5th day), photosynthetic pigments and soluble protein and soluble sugar contents. Strain UW4 markedly elevated the activities of SOD, POD, CAT, APX and GR, with the most prominent promoting effects on POD activity and the contents of the AsA-GSH system. Metabolomic analyses showed that strain UW4 up regulated abscisic acid (ABA) transduction and IAA content. Transcriptome analysis identified differential expression analysis (DEGs) mainly enriched for ABA signaling (ko04075) and auxin biosynthesis (ko00380). Strain UW4 coordinated hormone signaling regulation and osmoregulation by activating ABA signaling through the up regulation of protein phosphatase 2C (PP2C) and the down regulation of pyrabactin resistance 1-like proteins (PYLs) , also increasing the endogenous indole acetic acid (IAA) concentration. Weighted correlation network analysis (WGCNA) combined the PYLs associated modules ethylene responsive element binding protein (EREBP) and teosinte branched 1/cycloidea/proliferating cell factor 21 (TCP21) and the PP2C -enriched module to reduce oxidative stress. PP2C enriched modules homeodomain-leucine zipper and ABRE binding factors ( HD-ZIP, ABF ) to stress acclimation, and these key transcription factors are actively involved in brassinosteroid and ABA signaling. AsPP2C localized to the nucleus and cytoplasm in tobacco and Arabidopsis cells. YFP-AtPP2C Col overexpression lines exhibited significant salt tolerance, while UW4 further enhanced the salt resistance of these overexpression lines. Strain UW4 also markedly downregulated the expression level of the ACO gene in garlic under salt stress, which further verified its biological functions. These results demonstrate that strain UW4 enhances garlic salt tolerance by modulating ABA-dependent ROS scavenging and hormone homeostasis. It provides an effective microbial strategy for saline farmland remediation, and this eco-friendly strain is suitable for application in sodium-stressed soils to ensure safe crop production.
Wang et al. (Mon,) studied this question.