Lecanicillium attenuatum endophytically colonizes Phaseolus vulgaris, influencing plant growth and defense through modulation of gene expression and metabolic pathways

Entomopathogenic fungi, in addition to their obvious pathogenicity to insects, can also colonize the plant rhizosphere and internal tissues, antagonize diseases and pests, promote plant growth, and thereby play multiple ecological roles in nature. Exploring and utilizing the defense mechanism of entomopathogenic fungi that induce plant resistance through colonization will help enhance the application value of entomopathogenic fungi in agricultural ecosystems. Previous studies have shown that L. attenuatum can induce resistance in P. vulgaris plants against the pest Frankliniella occidentalis . However, the related mechanisms require further investigation. This study demonstrates that L. attenuatum successfully colonizes P. vulgaris via root irrigation and exerts a moderate growth-promoting effect, as manifested by concurrent increases in plant height, chlorophyll content, biomass accumulation, and root development. Compared with the control group, the plant height, chlorophyll content, and biomass of P. vulgaris plants inoculated with L. attenuatum significantly increased by 10.9%, 10.8%, and 20.8%. Additionally, integrated transcriptomic and metabolomic analyses revealed that genes related to auxin, phenylpropanoid, and flavonoid biosynthesis were upregulated in P. vulgaris plants inoculated with L. attenuatum , and flavonoid metabolites were also upregulated. Notably, defense-related gene expression exhibited a tissue-specific regulatory pattern, specifically manifested as significant upregulation of jasmonic acid pathway genes in root tissues, whereas salicylic acid pathway genes were significantly upregulated in distal leaf tissues. L. attenuatum successfully colonizes P. vulgaris via root irrigation and establishes a symbiotic relationship, promoting plant growth and inducing tissue-specific defense priming, thereby providing novel strategic avenues for biological control of plant diseases and stress adaptation research.