Unlocking the microbiome of an extremophile plant: metagenomic insights into Calotropis procera's endo-rhizosphere communities.

This study explores the root-associated microbiome of Calotropis procera, a drought-adapted, invasive plant thriving in Brazil. We analyzed microbial communities from the root endosphere, rhizosphere, and adjacent soil in two contrasting ecosystems: Caatinga (semi-arid) and Restinga (coastal). Using 16S rDNA sequencing and shotgun metagenomics, we tested three hypotheses: (I) environmental specificity of the rhizospheric bacterial microbiome, (II) continuity of bacterial composition between bulk soil and rhizosphere, and (III) host-driven filtering of the endophytic microbiome. Despite differing soil conditions – more sodium in Restinga and higher organic carbon in Caatinga – microbial profiles in root compartments remained consistent. The root endosphere was enriched with stress-tolerant bacteria and novel archaea, while fungal genera included Fusarium and Puccinia. Results partially supported environmental specificity and showed moderate soil-rhizosphere continuity, with evidence of plant-mediated selection. Host filtering was evident for bacteria and fungi but not archaea. These data indicate a C. procera-mediated regulation of its root microbiome composition, whereby the plant may either selectively recruit specific taxa from prevalent soil microbial communities (e.g., through root exudates) or vertically transmit a conserved subset of its microbiome via seeds. Our study enhances understanding of the C. procera microbiome and its microbial interactions, identifying potential candidates for future biotechnological applications.