MYCOLab Ai Logo - gold and army green

Cell wall remodeling in a fungal pathogen is required for hyphal growth into microspaces

Summary

Researchers discovered how fungi squeeze through tiny spaces inside plant tissues to cause disease. They found that fungi need to soften and remodel their cell walls to reduce their width and fit through spaces that are much narrower than normal fungal filaments. This ability to change shape is critical for the fungus to invade and colonize plants, ultimately causing wilting diseases in crops like tomatoes.

Background

Fusarium oxysporum is a major plant pathogen causing vascular wilt diseases on over a hundred crops. During infection, fungal hyphae must traverse extremely narrow spaces between plant cells such as apoplastic spaces and plasmodesmata. The mechanisms underlying hyphal plasticity during growth into these confined microspaces are poorly understood.

Objective

This study investigated the genetic and cellular mechanisms required for hyphal growth through extremely narrow 1 µm channels using isogenic mutants of F. oxysporum. The researchers tested whether conserved MAPK pathways involved in invasive growth, cell wall integrity, and osmotic stress response are necessary for hyphal passage through microspaces.

Results

The Mpk1 cell wall integrity MAPK cascade was essential for hyphal growth through microchannels, while invasive growth and hyperosmolarity response pathways were dispensable. Cell wall remodeling mutants showed inability to reduce hyphal diameter within channels and increased chitin and glucan content was reduced in hyphae growing within microchannels. High extracellular osmolarity rescued the channel passage defects by reducing turgor pressure.

Conclusion

Cell wall remodeling and the Mpk1 MAPK pathway are critical for hyphal growth into microspaces, while invasive growth pathways contribute independently to pathogenicity. Both morphogenetic processes—cell wall-dependent entry into microspaces and invasive growth—are essential for plant infection but governed by distinct cellular pathways.
  • Published in:mBio,
  • Study Type:Experimental Research,
  • Source: 10.1128/mbio.01184-25, PMID: 40586248
Scroll to Top