Strain KLBMP 9567T, an isolate from weathered soil, was identified as a new actinobacterial species through a comprehensive polyphasic approach. Phylogenetic evaluations relying on 16S rRNA gene sequence placed KLBMP 9567T within the genus Plantactinospora, alongside its close relatives Plantactinospora veratri NEAU-FHS4T and Plantactinospora sonchi NEAU-QY2T, both sharing 98.6% sequence similarity. However, KLBMP 9567T demonstrated low digital DNA–DNA hybridization values with P. veratri NEAU-FHS4T and P. sonchi NEAU-QY2T, recorded at 48.5 and 29.1%, respectively. Meanwhile, the average nucleotide identity values were correspondingly recorded at 91.1 and 83.1%. The cell wall of KLBMP 9567T contained meso-diaminopimelic acid, with xylose, mannose, glucose and galactose as diagnostic sugars. The diagnostic dominant phospholipids included diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol. Given phenotypic and genotypic data, KLBMP 9567T is recognized as a new species within the Plantactinospora genus, named Plantactinospora soli sp. nov., with the type strain KLBMP 9567T (= CGMCC 4.7773T = NBRC 115787T). Genome mining revealed genes associated with plant growth promotion, specifically those encoding enzymes for synthesizing plant hormones like indole acetic acid and gibberellic acid. Experimental validation demonstrated that KLBMP 9567T can produce significant quantities of indole acetic acid (20.6 mg l−1) and gibberellic acid (42.6 mg l−1). Moreover, co-culture with Arabidopsis showed marked growth enhancements: a 56.3% increase in lateral root proliferation, a 16.7% elongation in primary root length and a 44.8% boost in biomass accumulation. These findings underscore the strain’s potent plant growth-promoting attributes, providing profound insights into the mechanisms by which KLBMP 9567T enhances plant growth.
