SABATH methyltransferase can methylate small-molecule metabolites of plants to generate different products, and it plays a crucial role in plant growth and development as well as stress response. In this study, 13 SABATH genes distributed on five chromosomes of cucumbers were identified, and the synergistic effects among their domains, gene structures, conserved motifs, phylogenetic relationships, collinearity analysis, cis-acting elements, expression patterns, and plant growth-promoting rhizosphere bacteria (PGPR) were analyzed. The gene structure and conserved motifs of the same group of CsSABATH have similar intron numbers and conserved motifs. We detected 10 cis-elements in the promoter of the CsSABATH gene, indicating that they may be involved in different signaling pathways. qRT-PCR revealed the tissue-specific, drought and salt stress-responsive expression of the SABATH gene in cucumbers. Furthermore, we also verified that the expression level of CsaV3_6G046510 after inoculation with PGPR-GD17 bacteria under drought and salt stress was significantly lower than normal drought and salt dress, indicating that this gene may respond to PGPR and in abiotic stress play an important role. This study provides valuable insights into the molecular characteristics and evolutionary history of the SABATH gene family in cucumbers, laying a foundation for further analysis of the function of the CsSABATH gene in cucumbers.

To elucidate the cooperative regulatory mechanisms underlying Paraburkholderia sp. GD17-mediated salt tolerance in cucumber plants. Hydroponically grown cucumber plants were inoculated with GD17 and subsequently subjected to NaCl treatment. Physiological, biochemical parameters, as well as gene expression profiles, were comprehensively analyzed. GD17 inoculation significantly improved plant growth, developmental performance, and salinity tolerance. Under salt stress, GD17-inoculated plants exhibited higher leaf nutrient contents compared to non-inoculated controls, particularly an elevated K⁺/Na⁺ ratio, which was closely associated with the upregulated expression of Na⁺ extrusion-related genes. A substantial increase in proline content and the corresponding biosynthesis-related gene expression indicated that enhanced osmoprotectant synthesis played a critical role in GD17-conferred salt tolerance. Phytohormone levels and their signaling-related gene expression were also significantly upregulated in GD17-inoculated plants under salt stress. Moreover, transcription factor gene expression was markedly increased in GD17-treated plants following salt exposure. GD17 inoculation alleviated salt-induced photosynthetic inhibition, as demonstrated by improved photosynthetic efficiency and reduced suppression of photosynthesis-related gene expression. Transcriptional profiling further revealed that starch degradation, photorespiration, and the pentose phosphate pathway were crucial for GD17-mediated salt tolerance. Reduced oxidative damage, driven by enhanced antioxidative activity, further contributed to the observed protective mechanisms. This study demonstrates that the application of Paraburkholderia sp. GD17 concurrently enhances cucumber growth and salinity tolerance, effectively resolving the trade-off between growth and defense. Multi-level analyses provided comprehensive mechanistic insights into these synergistic effects.