The Endophytic Fungus Cyanodermella asteris Influences Growth of the Nonnatural Host Plant Arabidopsis thaliana

is a fungal endophyte from , a perennial plant from the northern part of Asia. Here, we demonstrated an interaction of with , Chinese cabbage, rapeseed, tomato, maize, or sunflower resulting in different phenotypes such as shorter main roots, massive lateral root growth, higher leaf and root biomass, and increased anthocyanin levels. In a variety of cocultivation assays, it was shown that these altered phenotypes are caused by fungal CO , volatile organic compounds, and soluble compounds, notably astins. Astins A, C, and G induced plant growth when they were individually included in the medium. In return, stimulates the fungal astin C production during cocultivation. Taken together, our results indicate a bilateral interaction between the fungus and the plant. A stress response in plants is induced by fungal metabolites while plant stress hormones induced astin C production of the fungus. Interestingly, our results not only show unidirectional influence of the fungus on the plant but also vice versa. The plant is able to influence growth and secondary metabolite production in the endophyte, even when both organisms do not live in close contact, suggesting the involvement of volatile compounds.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.