Genomic profiling and assessment of the plant growth-enhancing traits in the novel actinomycete, Plantactinospora soli sp. nov.

Strain KLBMP 9567^T, 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 9567^T within the genus <i>Plantactinospora</i>, alongside its close relatives <i>Plantactinospora veratri</i> NEAU-FHS4^T and <i>Plantactinospora sonchi</i> NEAU-QY2^T, both sharing 98.6% sequence similarity. However, KLBMP 9567^T demonstrated low digital DNA-DNA hybridization values with <i>P. veratri</i> NEAU-FHS4^T and <i>P. sonchi</i> NEAU-QY2^T, 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 9567^T contained <i>meso</i>-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 9567^T is recognized as a new species within the <i>Plantactinospora</i> genus, named <i>Plantactinospora soli</i> sp. nov., with the type strain KLBMP 9567^T (= CGMCC 4.7773^T = NBRC 115787^T). 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 9567^T 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 <i>Arabidopsis</i> 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 9567^T enhances plant growth.