Abstract
Caenorhabditis elegans, a free-living nematode model, secretes neuropeptides, but the ecological roles of its peptide exudates in regulating rhizosphere microbial activity remain largely unexplored. We identified six short peptides (P1, P9, P19, P20, P25, and P26) from C. elegans exudates that significantly enhanced indole-3-acetic acid (IAA) production by the plant growth-promoting bacterium Arthrobacter pascens ZZ21. These peptides were heat-labile and proteinase K-sensitive but unaffected by DNase I or RNase A, confirming their proteinaceous (peptide) nature rather than nucleic acid origin. The retention of bioactivity in n-butanol extracts further supported their hydrophilic, peptide-like properties. LC-MS/MS identified 30 linear peptides, including the six bioactive ones, which exhibited distinct dose-dependent effects, suggesting diverse regulatory mechanisms. Despite their relatively low abundance, these peptides strongly promoted IAA production in the bacterial culture system across multiple concentrations. These findings reveal an unrecognized mechanism whereby free-living nematodes regulate rhizobacterial metabolism via secreted peptides, offering new insights into nematode-mediated chemical signaling. Therefore, this study advances understanding of plant-microbe-nematode interactions and highlights strategies for manipulating rhizosphere microbiota in sustainable agriculture.