Endophytes and mycorrhiza; out of sight, but not out of smell

MARINA, OMACINI; ESTEBAN, FIORENZA JUAN; MINAS, ALEXIA; FERNANDEZ PATRICIA CARINA

Congreso; Holobiont; 2022

Herbivory is a complex relationship that requires an understanding of the interaction among plants, herbivores, and their symbionts. Most cool season grasses are simultaneously associated with asexual endophytic fungi of the genus Epichloë and arbuscular mycorrhizal fungi (AMF). Here, we demonstrate these endophytes and AMF can be linked with the fungus cultivated by leaf-cutting ants through plant chemistry. We performed a greenhouse experiment to identify and quantify the volatile organic compounds (VOCs) emitted Lolium multiflorum with contrasting levels of association with the endophyte Epichloë occultans. They were sown in pots with sterilized soil inoculated or not with AMF. Our results showed that symbiosis with this endophyte only increased the total amount of VOCs released by plants inoculated with AMF. The green leaf volatile Z3-Hexenylacetate (Z3-HAC) was the main compound collected and its emission was three times higher in plants with high level of association with both types of symbionts than with a low level of one of them. Considering that leaf-cutting ants reject plants if they are unsuitable for their symbiotic fungus, we also extracted samples of Leucoagaricus gongylophorus from colonies of Acromyrmex ambiguous and exposed them to the volatile Z3-HAC or only to mineral oil in petri dishes for 6 weeks. We showed that this green leaf volatile affected the growth of the ant fungal symbiont. This study reveals a novel mechanism by which leaf and root symbionts can protect their shared host, mediating multiple ecological interactions. Besides, it provides an update on recent insights into the induction and perception of plant green leaf volatiles by mutualistic fungi.