Reconfiguration of the root and shoot metabolome in trees by arbuscular and ectomycorrhizal associations

Mengxue Xia, Vidya Suseela and Nishanth Tharayil, Dept. Plant & Environmental Sciences, Clemson University, Clemson, SC, M. Luke McCormack, Plant and Microbial Biology, Univ. of Minnesota, St, Paul, MN, Peter G. Kennedy, Plant and Microbial Biology, University of Minnesota, St Paul, MN

Background/Question/Methods
The knowledge of how arbuscular- (AM) and ecto- mycorrhizas (EcM) affect plant chemistry is essential for unveiling their respective roles in ecosystem biogeochemical processes and plant functions. However, direct comparison of plant chemical responses to AM and EcM is still lacking. Here we investigated chemical traits that have been linked with litter decomposition (e.g., lignin, condensed tannins, nitrogen), along the in-depth leaf and root metabolomes across four tree species each inoculated by multiple AM or EcM fungi.
Results/Conclusions
Concentrations of tissue components that are associate with litter recalcitrance (e.g., lignin and condensed tannins) were decreased or unaffected by both types of mycorrhizal associations. Furthermore, significant mycorrhizal impacts on plant metabolomes was characterized by profound shifts of polyphenolic profile across AM and EcM, yet AM tended to have a larger-scale influence by affecting more metabolites. In particular, a subset of highly responsive compounds (e.g., sugar alcohols and flavon-3-ols) shared a common pattern in their responses across AM and EcM, highlighting their essential role in tree-mycorrhizal interactions. However, the metabolic responses in AM roots that suggest an enhanced resistance to oxidative pressure did not occur in the two EcM hosts. This study represents an early step to compare plant biochemical adjustments across AM and EcM associations. Our results provide novel insights at the metabolite level on chemical processes involved in tree-mycorrhizal interactions across AM and EcM, and highlight critical metabolites in these interactions.