Microbiome and metabolome dynamics in phloem and rhizosphere of Pinus tabuliformis against Dendroctonus valens infestation.

Microbial communities play essential roles in mediating plant defenses against insect pests. However, how host-associated microbiota and metabolites jointly respond to bark beetle infestation remains largely unexplored. Here, we integrated microbiome and metabolome profiling to elucidate how Pinus tabuliformis regulates its phloem and rhizosphere responses under varying levels of Dendroctonus valens infestation. Both bacterial and fungal diversity, as well as the relative abundance of dominant taxa such as Erwinia and Pseudoxanthomonas, shifted significantly with infestation intensity. Concurrently, key plant defense metabolites-including terpenoids, jasmonates, and polyphenols-were markedly elevated. Pathway enrichment analysis indicated that the phloem was characterized by enhanced phenylpropanoid and flavonoid biosynthesis, whereas the rhizosphere soil accumulated terpenoids and polyketides, implicating both compartments in resistance modulation. In the phloem, differential bacterial and fungal taxa displayed distinct positive and negative correlations with phenylpropanoid intermediates and downstream derivatives, while in the rhizosphere, bacteria from Bacillota and fungi such as Candida and Ogataea were strongly linked to diterpenoids, sesquiterpenoids, flavonoids, and indole derivatives. These findings demonstrate that P. tabuliformis mounts a compartment-specific, microbiome-associated metabolic response to D. valens infestation, providing new insights into the ecological roles of symbiotic microbiota in plant defense and offering a mechanistic foundation for microbe-based pest management strategies.