Listening to plant's Esperanto via root exudates: reprogramming the functional expression of plant growth-promoting rhizobacteria.

Rhizomicrobiome plays important roles in plant growth and health, contributing to the sustainable development of agriculture. Plants recruit and assemble the rhizomicrobiome to satisfy their functional requirements, which is widely recognized as the 'cry for help' theory, but the intrinsic mechanisms are still limited. In this study, we revealed a novel mechanism by which plants reprogram the functional expression of inhabited rhizobacteria, in addition to the de novo recruitment of soil microbes, to satisfy different functional requirements as plants grow. This might be an efficient and low-cost strategy and a substantial extension to the rhizomicrobiome recruitment theory. We found that the plant regulated the sequential expression of genes related to biocontrol and plant growth promotion in two well-studied rhizobacteria Bacillus velezensis SQR9 and Pseudomonas protegens CHA0 through root exudate succession across the plant developmental stages. Sixteen key chemicals in root exudates were identified to significantly regulate the rhizobacterial functional gene expression by high-throughput qPCR. This study not only deepens our understanding of the interaction between the plant-rhizosphere microbiome, but also provides a novel strategy to regulate and balance the different functional expression of the rhizomicrobiome to improve plant health and growth.