Eucommia ulmoides adapts to drought stress by recruiting rhizosphere microbes to upregulate specific functions

Abstract

Drought stress is a key factor limiting crop growth and production. Although a variety of crops can improve their survival and drought resistance as a result of interactions with their rhizosphere microbiota, the mechanisms related to plant–rhizosphere microbiota interactions under drought stress are not fully understood, especially regarding the mechanisms in habitats with droughts. Here, the molecular mechanisms involving the E. ulmoides rhizosphere microbiota in response to drought stress were systematically analyzed using pot experiments, metagenomic sequencing, and assessment of plant physiological indexes. The results showed that the composition and co-occurrence patterns of the E. ulmoides rhizosphere microbiota were altered under drought stress, and the phylogenetic diversity of the core microbes was increased. Moreover, Betaproteobacteria and Opitutae were significantly enriched in the rhizosphere and their relative abundances were significantly correlated with the levels of superoxide dismutase (SOD) and soluble sugar (SS) in E. ulmoides. Kyoto Encyclopedia of Genes and Genomes (KEGG) functional analysis showed that two-component system, biosynthesis of amino acids, ABC transporters, and ribosome became more abundant in the rhizosphere under drought stress, and were significantly correlated with SOD and SS levels. Similarly, genes encoding Carbohydrate Active Enzymes (CAZymes) activities that auxiliary activities and glycosyl transferases became more abundant and were significantly correlated with SOD and SS levels. In conclusion, the relative abundances of KEGG functions and CAZymes classes in the E. ulmoides rhizosphere microbiota were altered by enrichment of Betaproteobacteria and Opitutae, which in turn affected the host physiological indexes to improve the host’s adaptability to drought. These findings are of great significance for improving plant drought tolerance in order to increase sustainable crop production.