Transcriptional responses of Paxillus involutus driven by phosphate availability and ectomycorrhizal symbiosis with Pinus Sylvestris

An artificial system was developed to grow the ectomycorrhizal basidiomycete P. involutus in symbiosis with its host tree P. sylvestris at different Pi concentrations. RNA-seq analysis was performed on P. involutus hyphae growing under Pi-limiting conditions, either in symbiosis or alone.We show that Pi starvation and ectomycorrhizal symbiosis have an independent effect on P. involutus transcriptome. Notably, low Pi availability induces expression of seven newly-identified putative high-affinity Pi transporter genes, while reducing expression of putative organic acid transporter ones. Additionally, low Pi availability induces a close transcriptional interplay between P and N metabolism. GTP-related signalling was found to have a positive effect in the maintenance of ectomycorrhizal symbiosis, whereas multiple putative cytochrome P450 genes were found to be down-regulated, unlike arbuscular mycorrhizal fungi.