Mycelial dynamics in arbuscular mycorrhizal fungi.

Arbuscular mycorrhizal fungi (AMF), similar to other filamentous fungi, develop extensive hyphal networks collectively known as mycelia. AMF mycelia are complemented by a variety of specialized structures such as spores, vesicles, and auxiliary cells, which together form integrated and functionally diverse AMF networks. AMF mycelia have long been conceptually fragmented, with research disproportionately focusing on the intraradical phase and especially on intraradical structures such as arbuscules, while usually neglecting the extraradical mycelial phase. Moreover, they are often examined from a plant-centric perspective, where they are usually viewed as mediators of nutrient transfer to host roots. However, AMF mycelia are now increasingly recognized as a crucial component of AMF integrated networks with complex structural, physiological, and ecological dynamics. To encourage broader investigation into this underexplored domain, I synthesize both recent advances and historically overlooked findings on mycelial morphogenesis, growth strategies, resilience, cellular coordination mechanisms, and inter-mycelial interactions. By reframing the mycelium as a single, responsive, and functionally central unit of AMF biology, I propose novel mechanisms that may shape mycelial function, highlight methodological opportunities, and suggest key open questions that must be addressed to fully understand how these hyphal networks function across scales.