A phosphate starvation response-centered network regulates mycorrhizal symbiosis

To secure phosphorus (P) from soil, most land plants use a direct phosphate uptake pathway via root hairs and epidermis and an indirect phosphate uptake pathway via mycorrhizal symbiosis. The interaction between these two pathways is unclear. Here, we mapped a network between transcription factors and mycorrhizal symbiosis-related genes using Y1H. Intriguingly, this gene regulatory network is governed by the conserved P-sensing pathway, centered on phosphate starvation response (PHR) transcription factors. PHRs are required for mycorrhizal symbiosis and regulate symbiosis-related genes via the P1BS motif. SPX-domain proteins suppress OsPHR2-mediated induction of symbiosis-related genes and inhibit mycorrhizal infection. In contrast, plants overexpressing OsPHR2 show improved mycorrhizal infection and are partially resistant to P-mediated inhibition of symbiosis. Functional analyses of network nodes revealed co-regulation of hormonal signaling and mycorrhizal symbiosis. This network deciphers extensive regulation of mycorrhizal symbiosis by endogenous and exogenous signals and highlights co-option of the P-sensing pathway for mycorrhizal symbiosis. [Display omitted] •A new map of the rice mycorrhizal symbiosis transcriptional regulatory network•PHR-centered network controls arbuscular mycorrhizal symbiosis•Phosphate regulates mycorrhizal symbiosis via the SPX-PHR-centered network•Co-option of the conserved P-sensing pathway for mycorrhizal symbiosis An interconnected network of 266 transcription factors and promoters of 47 mycorrhiza-related genes highlights a PHR-centered arbuscular mycorrhizal symbiosis transcriptional regulatory network in rice, which connects the indirect mycorrhizal phosphate uptake pathway with the direct phosphate uptake pathway.