Specific amino acids identified in root exudates promote sugarcane growth by enhancing Klebsiella variicola DX120E colonization and modulating rhizosphere bacterial community

Root exudates play a crucial role in regulating microbial interactions within the plant rhizosphere, thereby influencing plant growth. However, whether and how specific exudates affect plant-microbe interactions remains to be further investigated. This study explored non-targeted metabolomics, 16S rRNA gene sequencing, and physiological assays to investigate the metabolite-mediated interactions between Klebsiella variicola DX120E and sugarcane ( Saccharum spp. hybrids) root exudates. The initial metabolomic analysis revealed that DX120E inoculation significantly altered the exudate profile, primarily enriching amino acids. Therefore, we further investigated the specific physiological roles of these identified amino acids. Both exudates and amino acids markedly enhanced bacterial chemotaxis, biofilm formation, exopolysaccharide secretion, cellulase activity, and colonization-related genes (e.g. , ecpA ). Consequently, inoculating with DX120E, followed by root exudate or amino acid application, significantly increased sugarcane plant height, chlorophyll content, activity of key nitrogen metabolism enzymes, net photosynthetic rate, biomass, and rhizosphere soil nutrient availability. Analysis of the soil microbiome revealed that inoculation with DX120E, in conjunction with amino acid supplementation, significantly enriched the relative abundance of beneficial microbial groups in the rhizosphere soil, including taxa at the phylum level (e.g., Actinobacteria) and the genus level (e.g., Bacillus and other nitrogen-fixing bacteria). Furthermore, growth-promoting metabolic pathways, including the biosynthesis of siderophore group nonribosomal peptides, were enhanced. Overall, sugarcane root exudates, particularly amino acids, mediate the interaction with strain DX120E, synergistically enhancing host plant growth. These findings provide theoretical insights and practical strategies for developing sustainable crop growth. • DX120E inoculation reprograms sugarcane root exudates by enriching amino acids. • Amino acids trigger DX120E chemotaxis, biofilm formation, and root colonization. • DX120E and amino acids synergistically enrich beneficial microbes and enhance siderophore synthesis. • Coupling DX120E with amino acids significantly boosts sugarcane growth.