Role\nof Vertical Transmission of Shoot Endophytes\nin Root-Associated Microbiome Assembly and Heavy Metal Hyperaccumulation\nin <i>Sedum alfredii</i>

The transmission\nmode of shoot-associated endophytes in hyperaccumulators\nand their roles in root microbiome assembly and heavy metal accumulation\nremain unclear. Using 16S rRNA gene profiling, we investigated the\nvertical transmission of shoot-associated endophytes in relation to\ngrowth and Cd/Zn accumulation of <i>Sedum alfredii</i> (<i>Crassulaceae</i>). Endophytes were transmitted from shoot cuttings\nto the rhizocompartment of new plants in both sterilized (γ-irradiated)\nand native soils. Vertical transmission was far more efficient in\nthe sterile soil, and the transmitted endophytes have become a dominant\ncomponent of the newly established root-associated microbiome. Based\non 16S rRNA genes, the vertically transmitted taxa were identified\nas the families of Streptomycetaceae, Nocardioidaceae, Pseudonocardiaceae,\nand Rhizobiaceae. Abundances of Streptomycetaceae, Nocardioidaceae,\nand Pseudonocardiaceae were strongly correlated with increased shoot\nbiomass and total Cd/Zn accumulation. Inoculation of <i>S. alfredii</i> with the synthetic bacterial community sharing the same phylogenetic\nrelatedness with the vertically transmitted endophytes resulted in\nsignificant improvements in plant biomass, root morphology, and Cd/Zn\naccumulation. Our results demonstrate that successful vertical transmission\nof endophytes from shoots of <i>S. alfredii</i> to its rhizocompartments\nis possible, particularly in soils with attenuated microbiomes. Furthermore,\nthe endophyte-derived microbiome plays an important role in metal\nhyperaccumulation.