Harnessing mechanisms for plant carbon delivery to symbiotic soil fungi for sustainable food production

The arbuscular mycorrhizal (AM) symbiosis between plants and symbiotic soil fungi confers key nutritional benefits to plants: AM fungi increase plant productivity by up to 30% by improving mineral nutrient uptake from the soil. In exchange for these nutrients, plants transfer more than one gigaton of photosynthetically fixed carbon each year to the AM fungal network in the soil. This carbon transfer has a major impact not just on plant and fungal physiology, but also on the global carbon cycle. My previous work identified a molecular pathway in plant roots that is activated during fungal colonization of root cells and transfers fixed carbon to AM fungi in the form of lipids. This finding represents a breakthrough in the field of AM symbiosis as we were able to describe, for the first time, how and in which form carbon is delivered to AM fungi. My discovery unlocks an opportunity: I propose to engineer the model crop rice to maximise carbon delivery to the fungal mycelium by exploiting the mechanisms underpinning carbon allocation to AM fungi. This approach could lead to enhanced nutrient uptake by promoting the symbiotic association, thereby reducing the need for synthetic fertilizer. Moreover, it also has the potential to increase carbon sequestration and soil fertility. However, it is currently unknown how plant carbon metabolism is altered at a whole plant level to increase carbon flux to the fungal mycelium, and how plants control the amount of carbon allocated to AM fungi. To achieve this ambitious aim, I will exploit the recent technological advances in genetics, carbon tracing, and single cell transcriptomics to map the carbon allocation pathway from leaves to roots and to AM fungi at single cell resolution (aim 1) and identify the genetic and transcriptional regulators of this pathway (aim 2). These insights, along with established knowledge, will be used to maximise carbon delivery from crop plants to the fungal mycelium in the soil (aim 3).