The establishment of Populus x Laccaria bicolor ectomycorrhiza requires the inactivation of MYC2 coordinated defense response with a key role for root terpene synthases
José Eduardo Marqués-Gálvez, J. E., Veronica Basso, Annegret Kohler, Kerrie Barry, Keykhosrow Keymanesh, Jenifer Johnson, Vasanth Singan, Igor V. Grigoriev, Rytas Vilgalys, Francis Martin, & Claire Veneault-Fourrey
14 September 2022, BioRxiv; https://doi.org/10.1101/2022.09.06.505662
The jasmonic acid (JA) signaling pathway plays an important role in the establishment of the ectomycorrhizal symbiosis (ECM) between Laccaria bicolor and poplar. We previously showed that the L. bicolor effector MiSSP7 induces the stabilization of the poplar JAZ6, a JA co-repressor protein that binds to Populus MYC2.1 and MYC2.2, orthologs of the Arabidopsis MYC2 transcription factor (TF), blocking their activity. Here we showed that both TFs play a central role in root colonization by L. bicolor mycelium, since their overexpression decreased the formation of the Hartig net, the hyphal network involved in symbiotic nutrient exchanges. By combining RNA sequencing and DNA Affinity Purification sequencing (DAP-seq) analysis, we identified a core set of JA-responsive genes directly activated by poplar MYC2.1 and MYC2.2, that need to be bypassed by the fungi to colonize root apoplastic spaces. These genes encode for other TFs, receptor-like kinases and many defense-related proteins, including terpene synthases (TPS). Monoterpenes produced by some of these TPS impact L. bicolor growth and ECM formation, suggesting a role for poplar root monoterpenes as negative regulators of in planta fungal growth and ECM symbiosis.
Marqués-Gálvez, J. E., Basso, V., Kohler, A., Barry, K., Keymanesh, K., Johnson, J., Singan, V., Grigoriev, I., Vilgalys, R., Martin, F., & Veneault-Fourrey, C. (2022). The establishment of Populus x Laccaria bicolor ectomycorrhiza requires the inactivation of MYC2 coordinated defense response with a key role for root terpene synthases. bioRxiv, 2022.2009.2006.505662. https://doi.org/10.1101/2022.09.06.505662.