About 80-90% of land plants are colonized by a specific group of fungi (largely Glomerocycota) that form a symbiotic relationship with plants, known together as arbuscular mycorrhiza. This plant-fungus symbiosis is an ancient partnership that may have been an important factor in enabling plants to colonize land. The plant supplies the fungus carbon in the form of sugars and lipids while the external network of fungal hyphae harvests and delivers phosphorous, nitrogen, and other micronutrients to the plant. In addition, the fungus also confers resistance to both drought and pathogen attack. There is an intricate series of two-way communications as the colonizing fungus “talks” to individual cell types in its path toward a specific cell type where it will branch to facilitate nutrient exchange.
However, when nitrogen or phosphorous become somewhat more available, the plant will put an abrupt halt to colonization (P inhibition). Yet crop varieties that retain mycorrhizal symbionts longer in moderately rich soils could significantly reduce phosphorous and nitrogen inputs, reducing costs and greenhouse gas emissions. Recent research indicates that one key to fine tuning the P inhibition threshold is understanding how specific plant cells change their end of the “conversation” during P-inhibition. In our project, the lab will use its expertise to characterize individual plant cell responses to the symbiont using single-cell RNA-seq techniques, live microscopy, and CRISPR mediated perturbations to test genetic models. The project will use millet, Setaria, as a model system for crops like corn, sorghum, and rice. The goal of the project is finding variants that could greatly lower nitrogen and phosphorous inputs and increase the overall health of crops by keeping their helpful symbionts in agriculture.