Arbuscular mycorrhizal fungi (AMF) form one of the most widespread symbiotic relationships on Earth. These soil fungi partner with the roots of most land plants, exchanging nutrients they gather from the soil for carbohydrates and fats from their plant hosts. Because AMF can connect with multiple plant species at once, and a single plant can host multiple fungi, they create extensive underground networks called common mycorrhizal networks (CMNs). These networks help maintain soil health, support plant growth, shape plant communities, and store carbon in their mycelia. Becasue of that they are commonly used as organic biofertilizers across the globe.
Despite their ecological and commercial importance, the genetic mechanisms governing the reproduction of these fungi (believed to be asexual organisms) and the connectivity of their underground networks remain unknown. Their networks facilitate large-scale nutrient transfer, but their efficiency varies depending on genetic makeup and structure, but due to their peculiar cell organization and genetic makeup these processes are not clearly understood. AMF possess multinucleate hyphae, meaning that thousands of nuclei coexist within a single continuous cell. Previously, these nuclei were thought to be genetically diverse, challenging the concept of AMF as true individuals. However, recent findings reveal a strict genetic organization: AMF can contain either genetically identical nuclei, or in some rare occasions they contain two nuclear population of unique genetic makeup (two genomes in a cell).
Despite these important recent advances, fundamental questions remain:
• How is genetic diversity generated in AMF?
• Can this variation exist without sexual reproduction?
• How does nuclear diversity impact network stability, nutrient exchange, and in a larger scale ecosystem processes?
How nuclei mix in AMF has significant ecological and agricultural implications. If nuclear competition leads to the exclusion of certain nucleotypes, network connectivity may be disrupted, affecting nutrient flow, plant community composition, and carbon sequestration. Conversely, nuclear cooperation could enhance network stability and resilience. By providing detailed insights into AMF nuclear interaction, we challenge long-standing assumptions about AMF asexuality and the presumed benefits of network connectivity for fungi and plants, reshaping understanding of their reproductive biology and network dynamics. This work opens new possibilities for optimizing mycorrhizal applications in agriculture, potentially improving crop resilience and nutrient uptake. Additionally, by reevaluating the functionality of common mycorrhizal networks, this work can help clarify how AMF shape plant communities and ecosystem dynamics, informing strategies to enhance soil fertility and carbon sequestration for more sustainable land management.
