Maize, and other plants, deploy both primary and species-specific, secondary metabolites to communicate with other organisms and cope with 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 health. However, the molecular mechanisms that coordinate these plant-microbe interactions remain elusive. We report that maize specialized diterpenoid metabolites with known antifungal bioactivities also influence rhizosphere bacterial communities. We show that antibiotic dolabralexin diterpenoids 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 isogenic 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. These findings suggest physiological functions of maize diterpenoids beyond known chemical defenses, including the assembly of the rhizosphere microbiome community.
Coauthors: Joseph Edwards – University of Texas;Katherine Louie – Joint Genome Institute;Benjamin Bowen – Joint Genome Institute;Trent Northen – Joint Genome Institute;Philipp Zerbe – UC Davis