Metagenomic and metabolomic profiling of rhizosphere microbiome adaptation to irrigation gradients in Camellia oil trees

The industrial cultivation of Camellia oil tree, a key woody oil species, has faced substantial challenges due to escalating extreme weather events in recent years. To investigate rhizosphere adaptations to irrigation regimes, three-year-old saplings were subjected to four evapotranspiration (ET)-based treatments: 50 % ET (I50), 75 % ET (I75), 100 % ET (I100), and natural rainfall (Control). Soil available nutrients (dissolved organic nitrogen, ammonium nitrogen, available phosphorus) and enzyme activities (urease, phytase, acid phosphatase, β-glucosidase, leucine aminopeptidase) were significantly lower under I100 than under I50. Metagenomic and untargeted metabolomic analyses revealed rhizosphere responses to these treatments. Shannon diversity index at phylum and genus levels were significantly higher in I50 and I75 than in I100. Relative abundances of Pseudomonadota, Acidobacteriota, Actinomycetota, and Bacteroidota increased in I50 and I75 but decreased in I100. Reduced irrigation elevated soil nitrogen (N) and phosphorus (P) cycling gene abundance. Differentially abundant metabolites were predominantly enriched in amino acid biosynthesis pathways. Integrated analysis demonstrated a positive correlation between L-glutamate e and N/P cycling genes, alongside significant negative correlations with soil and leaf water content. In summary, under irrigation deficit, Camellia oil tree roots exhibited increased L-glutamate levels alongside enriched Acidobacteriota, Actinomycetota, Chloroflexota, and Planctomycetota, collectively enhancing soil N and P cycling. These findings advance irrigation strategy optimization for drought resilience and deepen understanding of plant-environment interactions in perennial crops. • Full irrigation boosts Camellia oil tree fruit yield by 72 %–156 %. • Full irrigation cut rhizosphere soil DON & NH + 4 -N by 37–57 %. • Full irrigation cut rhizosphere soil enzymes by 6–79 %. • Deficit irrigation boosted N/P-cycle genes by 142–180 %. • Deficit irrigation boosts glutamate (17–40 %) and is linked to N/P cycle genes.