Key message The endophytic fungus strain TH15 isolated from root of T. hemsleyanum secrets zearalenone and phytohormones (IAA, JA and SA), which have the effect on regulating root development of T. hemsleyanum. Tetrastigma hemsleyanum is a traditional Chinese herb plant. The endophytic fungus strain TH15 isolated from root of T. hemsleyanum has been reported to significantly promote the growth of T. hemsleyanum. In this study, we combined HPLC-MS and ELISA to analyze the composition of TH15's fermentation broth. We also explored the effects of zearalenone, a metabolite of strain TH15, on the growth of T. hemsleyanum seedlings and expansin gene expression in root. Metabolomic analysis revealed that TH15 metabolites contained 5 phytohormones [indole-3-acetic acid (IAA), methyl indole-3-acetate (MeIAA), jasmonic acid (JA), jasmonoyl-l-isoleucine (JA-ILE) and salicylic acid (SA)], amino acids, sugar and vitamins. ELISA test indicated that TH15 metabolites contained zearalenone (ZEN). Supplement 0.1-0.5 mg/L ZEN into the culture medium promoted the growth of seedlings of T. hemsleyanum. Besides, ZEN treatment significantly promoted expression of the expansin gene in the root of T. hemsleyanum. The endophytic fungus strain TH15 secretes phytohormones like IAA, JA and SA, as well as other metabolites like ZEN. TH15's growth-promoting effects are realized by these secreted molecules' coordinated action. The endophytic fungal metabolite ZEN participates in the regulation of T. hemsleyanum's growth, which is an important molecular mechanism for the plant growth-promoting effects of the endophytic fungi strain TH15.
