Specific and conserved patterns of microbiota-structuring by maize benzoxazinoids in the field

Background: Plants influence their root and rhizosphere microbial communities through the secretion of root exudates. However, how specific classes of root exudate compounds impact the assembly of root-associated microbiotas is not well understood, especially not under realistic field conditions. Maize roots secrete benzoxazinoids (BXs), a class of indole-derived defense compounds, and thereby impact the assembly of their microbiota. Here, we investigated the broader impacts of BX exudation on root and rhizosphere microbiotas of adult maize plants grown under natural conditions at different field locations in Europe and the USA. We examined the microbiotas of BXproducing and multiple BX-defective lines in two genetic backgrounds across three soils with different properties. Results: Our analysis showed that BX secretion affected the community composition of the rhizosphere and root microbiota, with the most pronounced effects observed for root fungi. The impact of BX exudation was at least as strong as the genetic background, suggesting that BX exudation is a key trait by which maize structures its associated microbiota. BX-producing plants were not consistently enriching microbial lineages across the three field experiments. However, BX exudation consistently depleted Flavobacteriaceae and Comamonadaceae and enriched various potential plant pathogenic fungi in the roots across the different environments. Conclusions: These findings reveal that BXs have a selective impact on root and rhizosphere microbiota composition across oil relent conditions. Taken together, this study identifies the BX pathway as an interesting breeding target to manipulate plant-microbiome interactions.

Automated summary

The study revealed that benzoxazinoids (BXs) have a selective impact on the composition of root and rhizosphere microbiota in adult maize plants, with significant effects observed in root fungi. The impact of BX secretion is at least as strong as genetic background, indicating that BX exudation is a key trait in structuring maize-associated microbiota. Across different environments, BX exudation consistently depleted certain microbial lineages and enriched potential plant pathogenic fungi.