Mechanisms of Epichloë bromicola to Promote Plant Growth and Its Potential Application for Coix lacryma-jobi L. Cultivation.

Endophytic fungi play important roles in regulating plant growth and development and usually used as a promising strategy to enhance the biosynthesis of host valuable secondary metabolite, but the underlying growth-promoting mechanisms are only partly understood. In this study, the wild-type Arabidopsis thaliana seedlings co-cultured with fungal endophyte Epichloë bromicola showed auxin (IAA)-stimulated phenotypes, and the growth-promoting effects caused by E. bromicola were further verified by the experiments of spatially separated co-culture and fungal extract treatment. IAA was detected and identified in the extract of E. bromicola culture by LC-HRMS/MS, whereas 2,3-butanediol was confirmed to be the predominant volatile active compound in the diethyl ether and ethyl acetate extracts by GC-MS. Further study observed that IAA-related genes including synthesis key enzyme genes (CYP79B2, CYP79B3, NIT1, TAA1 and YUCCA1) and controlling polar transport genes (AUX1, BIG, EIR1, AXR3 and ARF1), were highly expressed at different periods after E. bromicola inoculation. More importantly, the introduction of fungal endophyte E. bromicola could effectively promote the growth and accumulation of coixol in Coix under soil conditions. Our study showed that endophytic fungus E. bromicola might be considered as a potential inoculant for improving medicinal plant growth.

An endophytic fungus Schizophyllum commune isolated from Panax ginseng enhances hairy roots growth and ginsenoside biosynthesis.

Using endophytic fungal elicitors to increase the accumulation of valuable secondary metabolites in plant tissue culture is an effective biotechnology strategy. In this study, a collection of 56 strains of endophytic fungi were isolated from different organs of cultivated Panax ginseng, of which seven strains can be symbiotically co-cultured with the hairy roots of P. ginseng. Further experiments observed that strain 3R-2, identified as endophytic fungus Schizophyllum commune, can not only infect hairy roots but also promote the accumulation of specific ginsenosides. This was further verified because S. commune colonization significantly affected the overall metabolic profile of ginseng hairy roots. By comparing the effects of S. commune mycelia and its mycelia extract (EM) on ginsenoside production in P. ginseng hairy roots, the EM was confirmed to be a relatively better stimulus elicitor. Additionally, the introduction of EM elicitor can significantly enhance the expressions of key enzyme genes of pgHMGR, pgSS, pgSE, and pgSD involved in the biosynthetic pathway of ginsenosides, which was deemed the most relevant factor for promoting ginsenosides production during the elicitation period. In conclusion, this study is the first to show that the EM of endophytic fungus S. commune can be considered as an effective endophytic fungal elicitor for increasing the biosynthesis of ginsenosides in hairy root cultures of P. ginseng.