Roots secrete many photosynthates into the rhizosphere and these exudates are important interfaces for host-microbiome interactions. The aerial roots of many wild plants and cereal crops, such as maize and sorghum, can secrete large amounts of mucilage which is a specific type of root exudates.

A group of researchers from Xishuangbanna Tropical Botanical Garden (XTBG) has been investigating the interactions between root-zone microorganisms and plant root exudates, and how these microorganisms in turn influenced plant health and growth.

Their recent attention to the aerial root mucilagestudy has led to a novel model for studying the crucial interactions between functional metabolites and the probiotic microbiome, based on the aerial root mucilage probiotics system.

In this model, the researchers used three Poaceae monocotyledons and one Melastomataceae dicotyledon vine plant to identify the similarities and differences in metabolites and microbiome in the aerial root mucilage and underground rhizosphere.

The functional microbiome contains probiotics and gatekeeper microbes. These microbes either serve as diazotrophs or help maintain microbial homeostasis in the aerial root mucilage microhabitat.

The root exudates significantly affected the growth and function of rhizosphere microorganisms, especially for strains in the probiotic model, the XTBG team found.

Probiotics played an important role in maintaining the micro-ecological balance of the rhizosphere, providing a scientific basis for the development of new agricultural biotechnology strategies in the future, their study also showed.

The mucilage may contain functional attractor compounds and antimicrobials defense metabolites. Plants synthesized those functional compounds and secreted into the rhizosphere by root transporters. At the same time, the host used other element transporters to assimilate and absorb nutrients provided by rhizosphere functional microbiome.

The researchers suggested to use multi-omics approaches including genomics, transcriptomics, metabolomics, and microbiomics, combined with molecular biology experiments,for analyzing and verifying the interactions between host mucus metabolites and the microbiome.

The aerial root mucilage-functional microbiome study system will provide new insights into the mechanisms by which root exudates maintain microbial function and stability in the rhizosphere microenvironment.

“Managing and optimizing the rhizosphere microbial community will possibly improve plant health and productivity,” said PANG Zhiqiang, first author of the study.

The study was supported by the National Natural Science Foundation of China and the China Postdoctoral Science Foundation. Results of their study were published in The ISME Journal.