Genomic and functional characterization of quorum sensing and plant growth-promoting traits in Pseudomonas sp. P77

Eucommia ulmoides is a valuable medicinal and economic tree species whose seedling establishment is often constrained by slow early growth and vulnerability to stress. Plant growth-promoting bacteria (PGPB) represent sustainable alternatives to chemical inputs; however, PGPB associated with E. ulmoides and the genetic basis underlying their plant growth-promoting activities remain underexplored. An N -acyl-homoserine lactone (AHL)-producing isolate, designated Pseudomonas sp. P77, was obtained from the root tissues of E. ulmoides . Functional assays showed that the strain displayed diverse plant growth-promoting characteristics, including phosphate and potassium solubilization, indole-3-acetic acid (IAA) production, and biofilm-forming capacity. UPLC–MS/MS analysis identified multiple AHLs in P77 culture samples, with C6-HSL, C8-HSL, and 3-oxo-C10-HSL among the major detected compounds. Inoculation with P77 significantly promoted the growth of E. ulmoides seedlings, as reflected by increased biomass, and was accompanied by enhanced antioxidant enzyme activities. Whole-genome sequencing generated a high-quality complete circular chromosome of 7.10 Mb with a GC content of 61.25% and an average sequencing coverage of 165.92×. Genome annotation identified genes encoding LuxI- and LuxR-family homologs potentially involved in AHL-mediated quorum sensing (QS), along with numerous genes potentially associated with plant growth-promoting traits. AntiSMASH analysis further predicted 25 biosynthetic gene clusters (BGCs), including those potentially involved in the biosynthesis of pyoverdine, hydrogen cyanide, and other bioactive secondary metabolites. Phenotypic and genomic analyses indicate that Pseudomonas sp. P77 exhibits plant growth-promoting traits, nutrient-mobilizing activities, and biofilm-forming ability, as well as genetic potential for AHL-mediated QS. These findings provide a genomic basis for the development of P77 as a microbial inoculant for E. ulmoides nursery production and a valuable resource for future strain improvement.