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Cellular anatomy of arbuscular mycorrhizal fungi

Summary

This comprehensive review explains the unique cellular structure of arbuscular mycorrhizal fungi, which form vast underground networks connecting plants to soil nutrients. These fungi are remarkable because their hyphae lack internal walls, allowing nutrients and organelles to flow freely throughout their continuous cytoplasm. By synthesizing current knowledge about how these fungi are organized and function at the cellular level, the authors highlight how this organization enables the complex nutrient exchange that supports plant growth and ecosystem health worldwide.

Background

Arbuscular mycorrhizal (AM) fungi are ancient plant mutualists that form multinucleate, open-pipe mycelial networks and are ubiquitous across terrestrial ecosystems. These fungi play crucial roles in ecosystem functioning by supporting plant growth, mediating ecosystem diversity, and contributing to carbon cycling. Despite their ecological significance, the cellular biology of AM fungi remains underexplored due to challenges in culturing, genetic transformation, and microscopy techniques.

Objective

This review synthesizes current knowledge on AM fungal cellular structure and organization across three levels: the hypha and its anatomy, hyphal networks and network-level cellular dynamics, and AM fungal spores. The authors aim to identify critical knowledge gaps and propose directions for future research to advance understanding of fundamental AM fungal cell biology and its contributions to ecosystem health.

Results

The review reveals that AM fungal hyphae have multilayered cell walls with varying chitin and glucan compositions across developmental stages and species. Nuclei and organelles including mitochondria, vacuoles, lipid droplets, and Golgi bodies are distributed throughout the continuous cytoplasm. The hyphal network exhibits remarkable morphological diversity with specialized structures including arbuscules, branching absorbing structures, and runner hyphae, with variation in hyphal anastomosis frequencies across species.

Conclusion

Understanding AM fungal cellular organization is essential for predicting symbiotic trade dynamics with plants and ecosystem functioning. The authors highlight critical knowledge gaps regarding obscure organelles, cytoskeletal dynamics, actin filaments, and organelle positioning, and propose that combining fluorescent probes, antibody methods, live-cell imaging, and single-molecule FISH techniques could resolve previously unknown aspects of AM fungal biology.
  • Published in:Current Biology,
  • Study Type:Review,
  • Source: PMID: 40494310
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