From function to omics: endophytic Beauveria bassiana promotes maize growth by activating phytohormone signaling pathways under elevated carbon dioxide.

BACKGROUND: Several entomopathogenic fungal (EPF) species can colonise and establish symbiotic relationships with plants as endophytes, which affects crop growth under elevated carbon dioxide (eCO₂) concentrations. However, how EPF facilitates eCO2 in plants is poorly understood, especially at the transcriptional and metabolic levels. Here, the authors used transcriptomics and metabolomics to examine the effects of a widely used EPF, Beauveria bassiana, on maize growth under eCO2, and how it regulated enzyme activity and endogenous hormone metabolism. RESULTS: Beauveria bassiana colonisation significantly enhanced maize growth across CO₂ concentrations. Key effects include: 39.64% greater leaf area than controls at ambient CO₂ during S3. Significant developmental divergence in leaf area between S3-S4 under eCO₂, 11.8% higher 100-grain weight in eCO₂+Bb vs. eCO₂ alone. Concurrent increases in stress-responsive enzymes and hormones aligned with omics-revealed activation of primary metabolic pathways (ZMA01100) and secondary metabolite biosynthesis pathways (ZMA01110). CONCLUSIONS: These findings suggested that B. bassiana colonization modulates plant growth under eCO2 by regulating the expression of related genes, and in turn, enzyme activity and hormone metabolism. The findings of the present study offered a theoretical foundation for elucidating the interactions between EPFs and plants under climate change.