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Intracellular accommodation of bacteria, fungi, and oomycetes by plants analyzed using transmission electron microscopy

Summary

Scientists used high-powered electron microscopes to examine how plants host different microorganisms inside their cells. They found that whether the microorganism is a helpful nitrogen-fixing bacterium, a nutrient-exchanging fungus, or a disease-causing oomycete, plants always separate it from the rest of the cell with a special membrane. This study reveals fundamental similarities in how plants accommodate different types of microorganisms, despite the very different outcomes for the plant.

Background

Transmission electron microscopy (TEM) enables high-resolution imaging of intracellular plant-microbe interfaces at the ultrastructural level. Previous comparative analysis has postulated that all intracellular symbioses share common structural features including a plant-derived membrane separating the microorganism from the plant cytoplasm. This study uses TEM to examine and compare three different plant-microbe interactions.

Objective

To document and compare the structural interfaces of three intracellular plant-microbe interactions (nitrogen-fixing symbiosis, arbuscular mycorrhiza, and pathogenic oomycete infection) using consistent sample preparation and imaging protocols performed by the same researcher.

Results

Comparative ultrastructural analysis revealed common features across all three interactions: a plant-derived membrane (peribacteroid, periarbuscular, or extrahaustorial membrane) separating the accommodated microorganism from plant cytoplasm, and an intervening space containing enzymes, proteins, and other compounds. Structural differences were observed in membrane thickness, interface space composition, and microorganism organelles.

Conclusion

The study confirms that symbiotic and pathogenic plant-microbe interactions share fundamental structural similarities despite differences in plant hosts, tissue types, and microorganism kingdoms. All interactions feature living microorganisms hosted within living plant cells separated by plant-derived membranes, supporting the 25-year-old postulate of structural homology across intracellular plant-microbe accommodations.
  • Published in:PLoS Pathogens,
  • Study Type:Comparative Ultrastructural Analysis,
  • Source: PMID: 41428668, DOI: 10.1371/journal.ppat.1013780
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