Root exudate-microbe interactions mediated by Oceanobacillus picturae and stachyose promote cadmium tolerance in...

Cadmium (Cd) is a toxic heavy metal that poses serious risks to human health and the ecological environment. Perilla frutescens (L.) Britt. has important medicinal and culinary value, yet its seedlings are highly sensitive to cadmium exposure. Carbohydrates, which mediate key aspects of plant-microbe interactions, play an essential role in recruiting rhizosphere microbiota. In this study, we examined how inoculation with Oceanobacillus picturae alleviates cadmium toxicity by secreting carbohydrate metabolites that reshape the rhizosphere microbial community of perilla. Inoculation markedly reduced cadmium-induced root damage, increasing fresh and dry plant weights by 2.3-fold and 1.1-fold, and enhancing root length by 14% compared with the control. In addition, root exudate profiles showed clear changes following inoculation. Metabolomic analyses revealed that stachyose was a key exudate enriched under stress conditions and acted synergistically with Azospirillum brasilense and Acinetobacter pittii to enhance perilla growth and cadmium tolerance. These findings demonstrate that perilla recruits specific plant growth-promoting rhizobacteria through stachyose-mediated chemical signaling in response to cadmium stress. This work advances our understanding of plant-microbe interactions under heavy metal stress and provides a foundation for microbiome-based phytoremediation technologies. It also offers practical value for developing sustainable agricultural practices and supporting ecological conservation.