Exploring the root-associated microbiome of the resurrection plant Myrothamnus flabellifolia

Aims and background: The resurrection plant Myrothamnus flabellifolia tolerates complete desiccation and is a great model for studying how plants cope with extreme drought. Root-associated microbes play a major role in stress tolerance and are an attractive target for enhancing drought tolerance in staple crops. However, how these dynamics play out under the most extreme water limitation remains underexplored. This study aimed to identify bacterial and fungal communities that tolerate extreme drought stress in the bulk soil, rhizosphere, and endosphere of M. flabellifolia. Methods: High-throughput amplicon sequencing was used to characterise the microbial communities associated with M. flabellifolia. Results: The bacterial phyla that were most abundant across all compartments were Acidobacteriota, Actinobacteriota, Chloroflexota, Planctomycetota, and Pseudomonadota, while the most abundant fungal phyla were Ascomycota and Basidiomycota. Although the bulk soil hosted multiple beneficial root-associated microbes, the rhizosphere compartment showed the highest functional diversity of bacteria and fungi. In contrast, the endosphere exhibited a low abundance and diversity of microbes. These findings share consistent with the theory that M. flabellifolia recruits soil microbes from the bulk to the rhizosphere and finally to the endosphere. It is possible that these microbes could promote drought tolerance in associated plant tissues. Conclusion: We find that compartments act as the major driver of microbial diversity, but the soil physicochemical factors also influence microbial composition. These results suggest that the root-associated microbiome of M. flabellifolia is highly structured and may aid in plant function.