Bioactive Diterpenoids Impact the Composition of the Root-Associated Microbiome in Maize (Zea mays)
Abstract Background : Plants deploy both primary and species-specific, specialized metabolites to communicate with other organisms and adapt to environmental challenges. This includes interactions with soil-dwelling microbial communities, where plants may exchange sugars for important nutrients and protection against environmental perturbations, directly benefitting plant fitness. However, the molecular mechanisms underlying these plant-microbe interactions often remain elusive. Results : In this study, we report that maize ( Zea mays ) specialized diterpenoid metabolites with known antifungal bioactivities also influence rhizosphere bacterial communities. Metabolite profiling showed that dolabralexins, antibiotic diterpenoids that are highly abundant in roots of some maize varieties, can be exuded from the roots. Comparative 16S rRNA gene sequencing determined the bacterial community composition of the maize mutant Zman2 ( anther ear 2 ), which is deficient in dolabralexins and closely related bioactive kauralexin diterpenoids. Under well-watered conditions, the Zman2 rhizosphere microbiome differed significantly from the wild-type sibling with the most significant changes observed for Alphaproteobacteria of the order Sphingomonadales. By contrast, there was no difference in the microbiome composition between the mutant and wild-type was observed under drought stress. Metabolomics analyses support that these differences are attributed to the diterpenoid deficiency of the Zman2 mutant, rather than other metabolome alterations. Conclusions : Together, these findings support physiological functions of maize diterpenoids beyond known chemical defenses, including the assembly of the rhizosphere microbiome.