Lotus japonicus VIH2 is an inositol pyrophosphate synthase that regulates arbuscular mycorrhiza

Plant yield is often maximized by the extensive use of mineral fertilizers, which, however, has severe environmental consequences. Phosphate is particularly problematic as it represents a globally limited resource, and its runoff and soil erosion threaten open water bodies. Many crops engage in arbuscular mycorrhizal (AM) symbiosis with nutrient-acquiring fungi, aiding in the uptake of phosphate and other mineral nutrients. However, AM colonization is strongly reduced under high soil phosphate levels. A mechanistic understanding of phosphate sensing, phosphate starvation responses, and their connection to AM remains incomplete. Here, we show that, in Lotus japonicus, low-abundant, energy-rich inositol pyrophosphates act as important regulatory signals of AM, orchestrating the cross-talk between phosphate starvation responses, nutrient acquisition, and plant root endosymbiosis. These findings hold promise for breeding nutrient-efficient crops.