Comprehensive Genome Analysis on the Novel Species Sphingomonas panacis DCY99 T Reveals Insights into Iron Tolerance of Ginseng.

Plant growth-promoting rhizobacteria play vital roles not only in plant growth, but also in reducing biotic/abiotic stress. Sphingomonas panacis DCY99 ^T is isolated from soil and root of Panax ginseng with rusty root disease, characterized by raised reddish-brown root and this is seriously affects ginseng cultivation. To investigate the relationship between 159 sequenced Sphingomonas strains, pan-genome analysis was carried out, which suggested genomic diversity of the Sphingomonas genus. Comparative analysis of S. panacis DCY99 ^T with Sphingomonas sp. LK11 revealed plant growth-promoting potential of S. panacis DCY99 ^T through indole acetic acid production, phosphate solubilizing, and antifungal abilities. Detailed genomic analysis has shown that S. panacis DCY99 ^T contain various heavy metals resistance genes in its genome and the plasmid. Functional analysis with Sphingomonas paucimobilis EPA505 predicted that S. panacis DCY99 ^T possess genes for degradation of polyaromatic hydrocarbon and phenolic compounds in rusty-ginseng root. Interestingly, when primed ginseng with S . panacis DCY99 ^T during high concentration of iron exposure, iron stress of ginseng was suppressed. In order to detect S. panacis DCY99 ^T in soil, biomarker was designed using spt gene. This study brings new insights into the role of S . panacis DCY99 ^T as a microbial inoculant to protect ginseng plants against rusty root disease.