Pisolithus tinctorius extract affects the root system architecture through compound production with auxin-like activity in Arabidopsis thaliana.

Abstract Pisolithus tinctorius is an ectomycorrhizal fungus that has been used worldwide as an inoculant to promote the growth and health of plant roots of forest importance. P. tinctorius has capacity to form symbiosis which mycorrhizal plants through the production of phytohormones, indole-3-acetic acid (IAA) the main auxin produced by these ectomycorrhizal fungi modulating root system architecture by inducing lateral root formation and root hair elongation in host plants of tree forest. However, the inoculant or compounds produced by P. tinctorius have not been evaluated in non-mycorrhizal plants. In the present study, we evaluated the effects of crude extracts of the P. tinctorius (CEPt) culture supernatant using Arabidopsis thaliana as plant model system to elucidate the molecular mechanisms of plant growth in non-host plant. Our results suggest that the crude extract of the supernatant produced by P. tinctorius has the ability to induce plant growth and root system architecture in Arabidopsis seedlings through the production of compounds with auxin-like activity, inducing the expression of DR5::uidA and BA3::uidA Arabidopsis line reporter of auxin responses and required an intact auxin signaling pathway, to modulate the plant growth in Arabidopsis seedlings.